Note: Descriptions are shown in the official language in which they were submitted.
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OXYFLUORINATION
THIS INVENTION relates, broadly, to oxyfluorination. More particularly
the invention relates to a process for the oxyfluorination of a surface of a
solid to
activate it.
According to the invention, there is provided a process for the activation by
oxyfluorination of at least part of a surface of a solid, which process
includes
exposing, under selected conditions of temperature and pressure and for a
selected
reaction time, at least part of the surface of the material of the solid to an
oxyfluorinating atmosphere which is a gas/vapour mixture which includes at
least
one fluorine-containing gas which reacts with the material of the exposed
surface, at
least one oxygen-containing gas which reacts with the material of the exposed
surface, and water vapour, said gases in the oxyfluorinating atmosphere acting
to
oxyfluorinate the exposed surface, thereby to activate it, and the water
vapour acting
to enhance the activation of the exposed surface to enhance the amenability of
the
exposed surface to adhesive bonding to other materials, the process including
selecting the fluorine-containing gas from the group consisting of F2, XeF2,
CIF, CIF3,
BrF, BrF3, BrF5, IFS, OF2, O2F2 and mixtures of any two or more thereof.
By fluorine-containing gas is meant that each molecule of the gas
contains at least one fluorine atom, and the term oxygen-containing gas has a
corresponding meaning.
AMENDED SHEET
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In particular, the enhancement of the activation of the exposed surface
may act to enhance the amenability of the exposed surface to adhesive bonding
to
other materials. Such other materials include inks or pigments printed
thereon, coating
materials deposited thereon by metallization such as vapour phase
metallization, and in
particular glues and adhesives, ceramics and paints. Such other materials also
include
matrix materials such as concretes or other set cementitious materials or the
like,
reinforced by the solid having the activated surface in the reinforcement of
such matrix
materials by oxyfluorinated reinforcing materials, for example in the
production of
composite products.
Thus, for applications involving the formation of an adhesive bond
between two components, by bringing the components into contact with each
other
with one of the components being in a flowable or mouldable state and with the
other of
the components being in solid form and having a surface at least partly
activated by
oxyfluorination, and causing or allowing the flowable or mouldable component
to set or
cure in contact with the solid component, thereby to bond adhesively to the
solid
component to form an adhesive bond therebetween, the process of the present
invention acts to provide the solid component with a surface whose enhanced
activation in turn enhances adhesion of the set or cured component to the
solid
component, the surface activation of the solid component being effected prior
to
bringing the components into contact with each other.
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The process may include selecting the solid material which is subjected
to activation by oxyfluorination from the group consisting of polymeric
materials
having constituents which are confined to carbon and hydrogen, elastomeric
materials having constituents which are confined to carbon and hydrogen,
polymeric
materials having constituents which are not confined to carbon and hydrogen
and
which include, in addition to carbon and hydrogen, other atomic species as
constituents, elastomeric materials having constituents which are not confined
to
carbon and hydrogen and which include, in addition to carbon and hydrogen,
other
atomic species as constituents, carbon, glasses, metals, metalloids, wood,
leather,
cotton, wool, ceramics, asbestos and blends and mixtures thereof. It is
expected
that the enhanced bonding of the present invention will have substantial
utility in the
coating of polymeric and elastomeric substrates, particularly those which are
refractory
or resistant to coating. When the process is used to produce activated
polymeric or
elastomeric products which are intended for coating, the process may include
selecting the solid material which is subjected to activation by
oxyfluorination from
the group of materials consisting of polymeric materials, elastomeric
materials and
mixtures of any two or more thereof. The process may include selecting the
solid
material which is subjected to activation by oxyfluorination from the group of
such
materials having constituents which are confined to carbon and hydrogen, such
as
hydrocarbon polymers, or instead, the process may include selecting the solid
material which is subjected to activation by oxyfluorination from the group of
such
materials having constituents which are not confined to carbon and hydrogen
and
which include, in addition to carbon and hydrogen, other atomic species as
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constituents. Such polymeric materials and mixtures or blends thereof all
comprise
hydrogen atoms which can be replaced by fluorine atoms. Such polymers can be
used
for the mass production of motor-vehicle parts, such as bumpers or buffers, in
which
case it can be important and desirable to be able to coat them with durable
paint
coatings, which adhere strongly thereto. Similar considerations can
nevertheless also
apply to coating solid materials which are not of polymeric materials, but
which have
surfaces which can be activated by the activating atmosphere to receive
coatings, with ,
desirable adhesion thereto.
It is further expected that the products of the process of the present
invention will have substantial utility in the production of composite
materials, structures
and/or artifacts wherein a matrix such as a cementitious matrix is
strengthened or
reinforced by reinforcing material. In these cases the component in the
flowable s
mouldable state is typically a cementitious slurry which is caused or allowed
to set
and/or cure in contact with the solid component which acts as a reinforcing
component,
to form a set cementitious matrix which adhesively adheres by means of a
cementitious
bond to the reinforcing component so that the matrix is strengthened and
reinforced
thereby. Such cementitious matrices have, typically, a relatively low tensile
strength
and/or a relatively low fracture toughness, whereas the reinforcing materials
typically
have a relatively high tensile strength and/or fracture toughness. The
reinforcing
material will thus be solid at ambient temperatures and may comprise particles
such as
granules, or, in particular, fibres, and may be in the form of a polymeric
material, a
metal, carbon or a glass which is activated by the oxyfluorination.
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As indicated above, examples of polymeric materials contemplated for
activation by oxyfluorination by the process of the present invention include
polymers
which are polyhydrocarbons such as polypropylene, polyethylene, polystyrene,
polypentene, polybutadiene, or the like, consisting only of carbon and
hydrogen, and
mixtures or blends of two or more such polymers, which may be selected from
hydrocarbon homopolymers and copolymers such as block copolymers, random- or
statistical copolymers and graft copolymers, and from higher polymers such as
terpolymers, containing only carbon and hydrogen. Instead, the polymeric
materials
selected for activation by oxyfluorination may comprise polymers of olefins
which do
not only contain carbon and hydrogen. Furthermore, depending on their end use,
said
hydrocarbon polymers may be blended or mixed with application-specific
additives
which do not contain only carbon and hydrogen, and/or the hydrocarbon polymers
may
be blended or mixed with polymers of olefins which do not contain only carbon
and
hydrogen, but which contain other constituents, each of such polymer groups
again
optionally being homopolymers or copolymers such as block copolymers, random-
or
statistical copolymers, graft copolymers, or higher polymers such as
terpolymers, for
example polyamides (nylons), aramids (kevlars) or acrylonitrite butadiene
styrenes
(ABS polymers), one or more of which olefins is a polymer having a constituent
other
than carbon or hydrogen, provided that the polymer containing the application-
specific
additive or having a constituent other than carbon or hydrogen comprises
hydrogen
atoms which are replaceable by fluorine atoms, before activation thereof in
accordance
with the process of the present invention. Blends which are activated by
oxyfluorination
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may be formed by physically blending their constituents or by polymerizing
their
constituents together in a reactor. Whatever the nature of the polymer, it
should,
however, contain hydrogen surface atoms which are replaceable by fluorine
atoms and
preferably also by oxygen atoms during oxyfluorination of its surface.
When the enhanced bonding of the products of the process of the
present invention is utilized for the strengthening and reinforcement of a
cementitious
matrix, the reinforcing component material is conveniently a polypropylene or
a
polyethylene, such as an ultra-high mass polyethylene (UHMPE), or a higher
polymer
such as a nylon, a kevlar or an ABS polymer, or indeed a material other than a
polymer, but which has surfaces which can be activated by the activating
atmosphere
of the present process, examples being carbon and steels such as mild steel,
galvanized steel and stainless steel. When the enhanced bonding of the
products of
the process of the present invention is utilized for the coating of solid
components in
the form of polymers, the polymer is conveniently an olefinic polymer such as
a
polypropylene homopolymer, a high-density polyethylene (HDPE) or a reactor-
grade
thermoplastic olefin (RTPO).
The process may include selecting the solid material which is subjected
to activation by oxyfluorination from the group of materials consisting of
carbon,
glasses, metals, metalloids and mixtures of any two or more thereof. In
particular,
the process may include selecting carbon as the solid material which is
subjected to
activation by oxyfluorination.
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Instead, the process may include selecting the solid material which is
subjected to activation by oxyfluorination from metals and metalloids which
are
members of the group consisting of mild steel, low carbon steel, stainless
steel, and
mixtures or alloys of any two or more thereof. In particular, the process may
thus
include selecting mild steel or low carbon steel as the solid material which
is
subjected to activation by oxyfluorination.
As will be appreciated and as indicated above, exposing the surFace of
the solid material to the oxyfluorinating atmosphere comprising the gas/vapour
mixture
of the present invention will be under conditions of temperature and pressure,
and for a
reaction time, selected to provide the exposed surface with desired properties
such as,
in particular, an enhanced amenability to adhesive bonding to other materials.
In
particular, the process may include selecting the fluorine-containing gas
which reacts
with the exposed surface from the group consisting of molecular fluorine (F~),
fluorinated noble gases, fluorohalogens, oxides of fluorine, and mixtures
of~any two
or more thereof. As indicated above, the fluorine-containing gas may be
molecular
fluorine (FZ) itself, or it may be made up of one or more other suitable
fluorine-
containing gaseous compounds, examples of which are fluorinated noble gases
such
as XeF2, or fluorohalogens such as CIF, CIF3, BrF, BrF3, BrFS, and IFS,
or oxides of fluorine such as OF2 or 02F~ so that, in other words, the
AMENDED SHEET
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oxyfluorinating atmosphere may include a fluorine-containing gaseous compound
selected from the group consisting of F2, XeF2, CIF, CIF3, BrF, BrF3, BrFS,
IFS, OF2 or
02F2 and mixtures of at least two such gases.
Furthermore, the process may include selecting the oxygen-containing
gas which reacts with the exposed surface from molecular oxygen (02) (such as
the
oxygen present in ambient air), ozone (03) and mixtures thereof. In other
words, the
oxygen-containing gas may be selected from the group of oxygen-containing
gaseous
compounds consisting of 02, 03 and mixtures thereof.
Optionally, the oxyfluorinating atmosphere may include, in addition to
any fluorine-containing gaseous compound, any oxygen-containing gaseous
compound and any further reactive gas, also at least one inert - or diluent
gas which is
inert to, and does not react with, the exposed solid material surface, such
gas being, for
example, helium, argon, carbon dioxide, or, in particular, molecular nitrogen
(N2).
Thus, broadly, the process may include diluting the oxyfluorinating atmosphere
with
a diluent gas which is inert to the exposed surface and inert to the other
constituents
of the oxyfluorinating atmosphere, and does not react therewith. For example,
the
oxyfluorinating atmosphere may be a mixture of fluorine gas and wet or moist
air
containing water vapour, which can more correctly be regarded as humid air,
the
atmosphere having, as constituents, F2, 02, N2, and water vapour. Thus, the
process
may include selecting the inert gas from the group consisting of nitrogen, the
noble
gases and mixtures of any two or more thereof. More particularly, the process
may
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gases and mixtures of any two or more thereof. More particularly, the process
may
include selecting the inert gas from the group consisting of helium, argon,
carbon
dioxide, molecular nitrogen (N2) and mixtures of any two or more thereof.
In particular, the process may include using, as the oxyfluorinating
atmosphere, a gas/vapour mixture of molecular fluorine (F2) molecular oxygen
(02)
and water vapour. In this case, the process may include diluting the
oxyfluorinating
atmosphere, using molecular nitrogen (N2) as a diluent.
If desired, the gas/vapour mixture may have its activity enhanced by
subjecting it to ultra-violet (UV) radiation. Thus, optionally, the process
may include
subjecting the oxyfluorinating atmosphere to ultra-violet radiation before the
exposing of the solid material to the oxyfluorinating atmosphere is ended. The
subjecting of the oxyfluorinating atmosphere to ultra-violet radiation may be
prior to
the exposing of the solid material to the oxyfluorinating atmosphere. Instead
or in
addition, the subjecting of the oxyfluorinating atmosphere to ultra-violet
radiation may
be during the exposing of the solid material to the oxyfluorinating
atmosphere.
The reaction conditions may vary between relatively broad limits. Thus
the process may include exposing the solid material to a said oxyfluorinating
atmosphere in which the fluorine-containing gas includes molecular fluorine
(F2) at a
partial pressure of 0.01 - 200 kPa. The exposing of the solid material to the
oxyfluorinating atmosphere may be for a period of 0.10 seconds - 10 hours, at
a
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total pressure of the oxyfluorinating atmosphere of 0.1 - 500 kPa with the
surface of
the solid material and the activating atmosphere at a temperature at which the
solid
material has a surface which is stable. By stable in this regard is meant that
the
surface shows no tendency to soften or melt at the temperature in question,
and no
tendency to char, decompose or disassociate. Preferably, the exposing of the
solid
material to the oxyfluorinating atmosphere is at a total pressure of 1 - 200
kPa, and
at a said temperature which is above 0°C, for a period of 0.1 seconds -
1 hour.
More particularly, the exposing of the solid material to the oxyfluorinating
atmosphere may be at a pressure 5 - 150 kPa and at a said temperature which is
20
- 100°C, for a period of 1 second - 10 minutes. In other words,
exposing the solid
surface to the oxyfluorinating atmosphere may be for a period of 0.10 seconds -
10
hours, e.g. 1 second - 1 hour, at a total pressure of the activating
atmosphere of 0.1
kPa - 500 Kpa, e.g. 1 kPa - 200 kPa, and at a temperature of the surface of
the solid
and of the oxyfluorinating atmosphere of above 0°C at which the
reinforcing
component is solid, e.g. 0°C up to the melting point of the solid, if
it melts rather than
charring or decomposing.
Furthermore, in the oxyfluorinating atmosphere, the fluorine-containing
gas may, as indicated above, have a partial pressure from as low as 0.01 kPa
up to as
high as 200 kPa, when the fluorine-containing gas is F2. Preferably the
partial
pressure, when the fluorine-containing gas is F2, is 0.1 - 10 kPa, more
preferably 1 - 5
kPa. Thus, the activation may be effected by exposing the solid surface to the
oxyfluorinating atmosphere at a pressure of 1 - 200 kPa, more preferably 5 -
150 kPa,
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and at a temperature above 0°C and below the melting or
charring/decomposition
temperature of the material of the solid, i.e. typically 20 -100°C.
Reaction times which
are short have been found to be feasible, for example 0.1 - 60 seconds,
typically 1 - 10
seconds or even 1 - 5 seconds.
In particular, the process may include exposing the solid material to a
said oxyfluorinating atmosphere which, in addition to its comprising a
fluorine-
containing gas, an oxygen-containing gas and water vapour, includes at least
one
further reactive constituent selected from the group consisting of halogens,
interhalogen compounds and mixture of any two or more thereof. In other words,
the
oxygenating atmosphere may, in addition to its comprising a fluorine-
containing gas,
an oxygen-containing gas, water vapour and any inert or diluent gas used,
contain also
at least one further reactive constituent selected from halogens other than
fluorine,
such as chlorine (C12), bromine (Br2) or indeed iodine (12) vapour, or
selected from
interhalogen compounds or mixtures thereof. The proportion of the fluorine-
containing
gas in the oxyfluorinating atmosphere can vary within wide limits. Thus, the
fluorine-
containing gas may form 0.1 - 99.0% by volume of said mixture, typically 1 -
30% by
volume thereof. Particularly preferred oxyfluorinating atmospheres include
those in
which the fluorine-containing gas such as F2 forms 5 - 20% by volume and
oxygen (02)
forms 5 - 95% by volume. The water vapour content of the oxyfluorinating
atmosphere
may be such that it has a relative humidity of 0.1 - 99%, preferably 30 - 90%,
e.g. 50 -
80%.
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Furthermore, the process may include exposing the solid material to a
said oxyfluorinating atmosphere having a fluorine-containing gas content of
0.1 -
99% by volume. In particular, the exposing of the solid material may be to a
said
oxyfluorinating atmosphere having a fluorine-containing gas content of 1 - 30%
by
volume. Preferably, the process may include exposing the solid material to a
said
oxyfluorinating atmosphere of which the fluorine-containing gas forms 5 - 20%
by
volume and the oxygen-containing gas forms 5 - 95% by volume. Furthermore, the
process may include exposing the solid material to an activating atmosphere
which
has a relative humidity of 0.1 - 99%, preferably 30 - 99%, and more preferably
50 -
80%.
Furthermore the process may include exposing the solid material to the
oxyfluorinating atmosphere until the surface concentration of fluorine of said
exposed
surface has been increased by at least 0.01 pgF/cm2. While the process may be
such as to provide the exposed solid surface with a relatively low surface
fluorine
concentration, e.g. in the range of 0.01 NgF/cm2 - 50 pgF/cm2, the process may
be
used to provide higher surface fluorine concentrations of above 50 NgF/cm2,
which are
obtainable, if desired.
In a particular embodiment, the fluorine-containing gas may be F2, being
present in the oxyfluorinating atmosphere at a partial pressure of 0.01 kPa -
200 kPa,
the exposing of the surface of the solid to the oxyfluorinating atmosphere
being such
as to provide the surface with a surface fluorine concentration of 0.01 - 50
NgF/cm2.
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Thus, the process may include exposing the solid material to the
oxyfluorinating
atmosphere until the surface concentration of fluorine of said exposed surface
has
been increased by 0.01 - 50 NgF/cm2.
In a particular embodiment, the process may include, prior to the
exposing of the solid material to the oxyfluorinating atmosphere, degreasing
the
exposed surface, for example by washing the solid with water and a detergent
followed
by rinsing it with water and then treating it with isopropanol or another
suitable organic
solvent such as those used in the motor trade for dislodging grease or oil.
The process may include exposing the solid material to the
oxyfluorinating atmosphere in a reaction chamber in a reaction vessel, the
process
including flushing the reaction chamber by means of the oxylfuorinating
atmosphere
prior to the exposing of the solid material to the oxyfluorinating atmosphere.
The
exposing of the solid surface to the activating atmosphere in the reaction
chamber or
the reaction vessel, which has been flushed by means of such oxyfluorinating
atmosphere, may be carried out on a continuous basis or on a batchwise basis.
If
carried out on a continuous basis, exposing the solid surface to the
atmosphere may
be effected in in-line fashion by continuously transporting the solid through
a reaction
chamber, which may be open-ended, containing the atmosphere, which atmosphere
may be replenished or continuously flushed through the reaction chamber at a
suitable
rate to maintain the desired concentrations of the reagent gases in the
atmosphere.
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The oxyfluorinating or activating atmosphere may, as indicated above and if
desired, be
subjected to UV radiation, during the exposure of the solid thereto.
Naturally, routine experimentation will be carried out with regard to the
various parameters such as oxyfluorinating or activating atmosphere
compositions and
pressures, reaction times, temperatures, or solid materials whose surfaces are
activated, and the fluorine- and oxygen surface concentrations achieved
thereon, to
achieve optimum, or at least acceptable, results, bearing practical and
economic
considerations in mind.
The invention extends also to an oxyfluorination product whenever
produced by the process of the present invention.
With regard to the coating of solid materials having surfaces activated by
the process of the present invention, applying the coating to the
oxyfluorinated surface
may be by painting e.g. spray-painting, the oxyfluorinated surface with one of
the
following paints:
a single-component base coat in an organic solvent; followed by
a clear two-component (top) coat in an organic solvent; or
a two-component pigmented top coat in an organic solvent or diluent.
A resin- and a hardener- (or catalyst) component of a two-component
polyurethane or
epoxy paint are typically contained in two separate containers. When the paint
is
required for spray painting the resin and the hardener are mixed in a
specified ratio and
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then thinned to a spraying viscosity. This paint mixture has a limited
lifetime, usually a
few hours. Single-component paints do not require or employ a hardener, and
only
need to be thinned to spraying viscosity.
With regard to the product of the process of the present invention, this
extends to a solid material such as polymeric material, whenever coated by a
coating
adhesively bonded thereto. The product of the process of the present invention
also
extends to a composite material, structure and/or artifact which comprises a
set matrix,
such as a cementitious matrix, strengthened or reinforced by reinforcing
material to
which the cementitious matrix is adhesively bonded, the matrix comprising a
settable,
e.g. cementitious, component which has set in contact with a reinforcing
component to
form a matrix in contact with a reinforcing material comprising said
reinforcing
component, which matrix adheres thereto, by means of an adhesive bond, the
reinforcing component having an oxyfluorinated surface to which the
cementitious
matrix adheres, the surface of the reinforcing component having been activated
and
oxyfluorinated in accordance with the process of the present invention.
The invention will now be described, by way of illustrative example, with
reference to the following Examples and with reference to the accompanying
diagrammatic drawings, in which:
Figure 1 shows a three-dimensional view of a test sample used for the fibre
pull-
out tests described hereunder with reference to Examples 1 and 2; and
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Figure 2 shows a diagrammatic flow/block diagram illustrating details of the
reactor employed for the coating aspect of the present invention.
REINFORCING OF MATRICES
EXAMPLE 1 - INVENTION
Monofilament polypropylene fibres were produced by direct extrusion to have a
rectangular cross-section nominally of 0.5mm x 1.3mm, the fibres having a
length of 40mm, a specific gravity of 0.91, a tensile strength of 120MPa and
an
elongation at break of 14%. The fibres were loaded under a humid ambient air
atmosphere into a vacuum reaction vessel and the vessel was evacuated down
to an absolute pressure of 15 kPa. The vessel was then Faded with a dry 20%
F2/80%N2 (by volume) gas mixture up to an absolute pressure of 45 kPa at a
temperature of 38°C, to form an oxyfluorinating atmosphere in
accordance with
the process of the present invention. The fibres had their surfaces activated
by
oxyfluorination by allowing them to remain exposed to and in contact with the
activating atmosphere in the vessel for 2.5 hours at 38°C, after which
the vessel
was flushed with ambient air. During this contact the surfaces of the
polypropylene fibres were activated by oxyfluorination, in the presence of
water
vapour, by oxygen from the air at 15 kPa remaining in the vessel after the
evacuation, and by fluorine from the F2/N2 gas mixture added to said air, the
water vapour also being derived from the air at 15 kPa remaining in the vessel
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after the evacuation. The water vapour provided the oxyfluorinating atmosphere
at 45 kPa with a relative humidity of approximately 18%.
EXAMPLE2-CONTROL
Example 1 was repeated except that the air at 15 kPa present in the vessel
before loading of the F2/N2 gas mixture was replaced by artificial dry air,
i.e. a
dry mixture of 21 % 02/79%N2 (by volume). This was effected by evacuation of
the vessel down to a hard vacuum at effectively zero pressure for purposes of
practical utility, followed in turn by loading of the 02/N2 mixture into the
vessel
and loading of the F2/N2 mixture into the vessel, to produce an essentially
dry
oxyfluorinating atmosphere containing negligible amounts of water vapour.
A highly flowable and readily castable and smoothable mortar slurry mix
was prepared by mixing together ordinary Portland cement with dried natural
river sand
and water, in a cement:wateraand mass ratio of 1:0.52:2. The river sand had a
maximum particle size in the range of about 2-4.7mm and an average particle
size in
the range of about 0.6-1.5mm. Mixing was effected manually until the mixture
was
substantially homogeneous. Fibre pull-out tests were then conducted on dumb-
bell-
shaped specimens, one of which is indicated by reference numeral 10 in Figure
1,
prepared by casting said mortar slurry mix when fresh into dumb-bell-shaped
polymethyl-methacrylate moulds. Each specimen had a thickness T of 20mm and a
maximum width W of 51 mm, and had a waist 12 which divided it into two lobed
parts
14. A plastics sheet 16 at the waist 12 separated the parts 14 from each other
to
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prevent bonding therebetween. One of the monofilament fibres, after surface
activation, was embedded at 20 in the specimen 10 to extend along the polar
axis 18 of
the specimen 10, with half (20mm) of its length embedded in each lobed part
14. The
specimen 10 was then allowed to set to form a set cementitious matrix in which
the
reinforcing component formed by the fibre 20 was embedded, adhesive
cementitious
bonding taking place between the fibre 20 and the matrix. The cast specimens
were
cured respectively for 7 and 28 days in water at a temperature of 21-25EC. The
strength of the adhesive interfacial shear bond between the fibre 20 and the
cementitious matrix was in each case measured using a tensile testing machine
equipped with a 500N transducer and a data-logging system, operating at a pull-
out
rate of 2mm/minute. The interfacial shear bond strength was calculated by
dividing the
maximum shear bond force attained by the bonding area of the fibre, i.e.:
Interfacial shear= maximum shear bond force
bond strength 2 x fibre length x (width + thickness)
The units of the shear bond force and length were selected so that the
interfacial
shear bond strength was obtained in MPa. The fibre pullout test results are
presented in the following table, Table 1, for fibres produced by both Example
1
and Example 2, and in each case after 7 and 28 days' curing time respectively,
five specimens being tested in each case.
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TABLE 1
Shear bond stren4th (MPa) Shear bond strength (MPa)
(7 days' curing ) ~_2.a days' curing)
0.40 0.33
0.49 0.45
Example 1 0.58 0.55
0.50 0.46
0.44 0.50
Average 0.48 Average 0.46
0.42 0.33
0.39 0.39
Example 2 0.48 0.38
0.35 0.40
0.37 0.44
Average 0.40 Average 0.39
From Table 1 it emerges that the average interfacial bond strengths of the
fibres
treated according to Example 1 (Invention) were 0.48MPa and 0.46MPa
respectively after 7 and 28 days' curing. The corresponding values for Example
2 (Control) were respectively 0.40MPa and 0.39MPa, respectively showing an
increase of 20% after 7 days' curing and of 18% after 28 days' curing,
compared
with the control.
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EXAMPLE 3 - INVENTION
Example 1 was repeated using polypropylene fibres which were formed from
fibrillated polypropylene tape produced by extrusion followed by a
fibrillation
process. The fibres had a nominal rectangular cross-sectional profile or
outline
of 0.097mm x 7.5mm, being 36mm in length, with a specific gravity of 0.91, a
tensile strength of 128MPa and an elongation at break of 5.3%.
EXAMPLE 4 - CONTROL
Example 2 was repeated using the fibrillated fibres of Example 3.
A proprietary cementitious mixture, Concor HT Wetcrete, obtained from
Concor Technicrete (Proprietary) Limited, of 13 Church Street, Crown
Industrial Area,
Johannesburg, South Africa was prepared to form a shotcrete mixture and was
admixed with fibrillated fibres whose surfaces had been activated in
accordance with
Examples 3 and 4 respectively.
The constituents of the mixture, including the aggregate and fibres, were
admixed until substantially homogeneous in a mechanical mixer which was
connected
to a spray nozzle by means of a peristaltic conveyor system. The proportion of
fibres
admixed with the shotcrete amounted to 9kg fibres/m3 shotcrete. As soon as the
mixture became homogeneous (i.e. after it was mixed for a period of about 4
minutes) it
was passed along the peristaltic conveyor system and sprayed through the spray
nozzle into a mould to spray-cast a square panel or slab having sides of 600mm
and a
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21
thickness of 100mm. After the spray casting, the panel or slab was left in the
mould
under ambient air for 3 days, after which the panel or plate was water-cured
for 25 days
before energy-absorption tests were conducted on the panel or plate.
The energy-absorption tests were carried out by supporting each panel
or plate along its 600mm edges while centre-point-loading was applied thereto
over a
central square area having sides of 100mm, respectively parallel to the 600mm
sides of
the panel or plate. The load was applied to the face of each panel or plate
opposite to
the direction from which the mixture arrived in the mould from the spray
nozzle, i.e. the
load was applied to the face of the panel or slab which, during the spray-
casting, had
rested on and abutted on the 600mm x 600mm floor of the mould which faced
upwardly, the spraying taking place downwardly from the spray nozzle into the
mould
and on to the floor.
The panel or slab containing the fibres whose surfaces had been surface-
activated in accordance with Example 3 was found to display a total energy
absorption
of 1096 joules(J), whereas the control panel or slab whose fibres had been
surface-
activated in accordance with Example 4 was found to display a total energy
absorption
of 688 J, i.e. the use of the activation atmosphere of Example 3 led to an
increase of
59% in energy absorption of the panel or slab, compared with Example 4.
Furthermore, while the load-bearing capacity over a deformation range of 5 -
25mm of
the latter panel or slab was found to decrease from 67kN, progressively to a
value of
7kN, i.e. by a factor of 9.6, the load-bearing capacity over the same
deformation range
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22
of the former was found to decrease at a slower rate from 54kN, progressively
over the
same deformation range to a value of 26kN, i.e. by a factor of only 2.1. Thus,
in
additon, the panel or slab containing fibres activated in accordance with
Example 3
(invention) had a 3.7 times higher residual load-bearing capacity than the
control panel
or slab whose fibres had been activated in accordance with Example 4.
COATING OF MATERIALS
With regard to Examples 5 - 10 set out hereunder, a reactor-grade
thermoplastic
olefin (RTPO)-SP 179-22 manufactured by Basell Polyolefins Company N.V.,
Woluwe Garden, Woluwedal 24, B-1932 Zaventem, Belgium, was used, except where
other polymers are specified. This RTPO consists of isotactic polypropylene
polymerized together with a reactor-made ethylene-propylene rubber (EPR).
Various oxyfluorination atmospheres were used. Degreasing of the
materials took place before oxyfluorination by first washing with water and a
detergent
before rinsing with water, followed in some cases by wiping with isopropanol.
In this
regard the Applicant has found that the nature of the detergent was not
critical, and a
number of household detergents were found to be suitable. The fluorination
took place
at room temperature, typically 25°C, for various periods of time. In
each case the
treated surface, after drying if necessary, was painted.
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In the tests whose results are set out in Tables 2, 3 and 4 hereunder, the
following paint was applied:-
A single-component polyurethane base coat in an organic solvent,
obtained from Herberts (France) S.A., B.P. 1025, 78205, Nantes, La Jolie,
Cedex,
France, was used as a pigmented base-coating paint with the trade designation
HERBERTS BN RG/PERSAN 777, RN 313.565 (Ref. No. FA 9211036) followed by a
two-component unpigmented clear coat paint with the trade designation VERNIS 2-
K
EC 510027 (Ref. No. 9213226/FA 9213227) and a hardener designated FA 9212586.
In each case two layers of base coat, each layer being at least 2 Nm thick and
the
thickness of the layers amounting in total to at most about 15 Nm thickness,
were
applied to the sample, followed by two layers of clear (top) coat, each of
about 15 - 40
Nm thickness. Each of the base coat layers was allowed to dry by leaving it
exposed to
air at room temperature for a period of 3 - 12 minutes, before the following
layer was
applied; and each layer was applied by spray-painting. The final layer was
allowed to
dry for 10 minutes and then baked at 80°C for 30 minutes. The final
layer was exposed
to the air at room temperature for a period of 3 days before the pull-off
tests were
performed.
In the tests whose results are set out in Tables 5 and 6 hereunder the
following paint was applied:-
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A two-component polyurethane pigmented topcoat obtained from Dulux AECI
Paints (Proprietary) Limited, ALRODE, 1451, Gauteng Province, South Africa.
This
white-pigmented topcoat paint with the trade designation DUCO DURATHANE K
Enamel Cathkin White/Wit (Ref. No. D 928-0025) and a hardener designated Slow
D
928-0809 were used. In each case four layers of the two-component topcoat were
applied, amounting to approximately 50pm in total thickness. After the
application of
each layer, a flash-off period of 3 - 12 minutes was allowed before the
following layer
was applied. The final layer was allowed to dry for 10 minutes. The final
layer was
exposed to the air at room temperature for a period of 3 days before the pull-
off tests
were performed.
Water contact angles were measured, using a Cahn DC A 322 instrument
obtained from MET Systems, 3 Gaiety Street, Robindale, Randburg, Gauteng
Province, South Africa. The advancing and receding angles were measured as
described in the Cahn DCA operating manual, using a stage speed of 50pm/s.
Adhesion of the paint to the sample was tested by adhesively securing metal-
backed test pads to the painted sample, using a cyanoacrylate adhesive
available from
Loctite (South Africa) (Proprietary) Limited under the trade designation of
LOCTITE 496
CYANOACRYLATE. Pull-off adhesion strength was tested in accordance with
International ISO Standard 4622-1978(E), using a 20 mm diameter test cylinder
adhesively secured to the painted surface using said Loctite 496. The test
cylinders
were pulled from the painted test samples by means of a tensile tester, the
force in
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Newtons (N) required to break the test assembly was recorded together with the
standard deviation. The breaking strength in megaPascals (MPa) is given by
F/314,
where F is the breaking force in Newtons, and the test cylinders were 20 mm in
diameter. The fracture surfaces were examined and the results were expressed
as the
percentage area and in terms of the site of the fracture, expressed in terms
of
adhesive-, cohesive- or adhesive/cohesive failure. In Tables 4 - 9 the
following scheme
was used to describe the site of fracture:
A - Cohesive failure of the sample material
A/B - Adhesive failure between sample material and first coat
B - Cohesive failure of first coat
B/C - Adhesive failure between first and second coats
-/Y - Adhesive failure between final coat and adhesive.
In Examples 5 - 10 a single-component paint is referred to as a 1-K paint, and
a
two-component paint is referred to as a 2-K paint.
~Yennoi ~ ~
Samples in the form of plates made of the RTPO SP 179-22 having dimensions
of 10cm x 10cm were exposed to an oxyfluorinating atmosphere at 25~C in a
reaction vessel after evacuating air from the vessel to a residual air
pressure of
25 kPa. The oxyfluorinating atmosphere was formed in the vessel at a total
pressure of 30 kPa. The charged vessel contained a gas/vapour mixture made
up of humid ambient air with a partial pressure of 25 kPa, and of an F2/N2 gas
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mixture at a partial pressure of 5 kPa, the F2/N2 mixture comprising 20% by
volume F2 and 80% by volume N 2. This gas mixture will be referred to
hereunder as 'SkPa 20% F2/N2/25kPa air mixture'. Oxyfluorinating times were
varied from a minimum of 5 seconds up to a maximum of 1 hour (3600
seconds), to obtain various different surface concentrations of fluorine on
the
treated surface. Two layers of Herberts BN RG Persan base coat were applied
followed by two layers of clear coat. The four layers had an approximate
thickness of 52pm. The painting took place after exposing the oxyfluorinated
samples for 24 hours at 25°C to humid ambient air to hydrolyse the
oxyfluorinated surfaces. The standard deviation measured during the evaluation
of the paint adhesion strength was about 1.4 MPa. Results are set forth in the
following table, Table 2.
TABLE 2
SP 179-22 material exposed at 25°C to 5 kPa 20% F2/N2/25 kPa air
mixture painted with Herberts Persan 1-K base coat/2-K clear coat, after
exposing the surface to humid ambient air for 24 h.
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OxyfluorinatingBreaking Nature Fluorine Water contact
time force of concentrationangle
(seconds) (MPa) failure (NgF/cmz) advance/
(%) recede ()
0 0 1 OOA/B 0 108,7/77,0
5,39 60A,40A/B2,9 92,1/51,7
4,84 80A,20A/B2,9 91,2/43,8
5,06 90A,10A/B3,0 75,5/34,2
60 6,59 100A 3,2 63,4/25,8
300 6,74 100A 3,8 56,5/19,9
900 6,25 80A,20A/B4,3 43,9/15,4
1800 6,54 100A 4,8 65,5/20,2
3600 6,64 80A,20A/B6,4 67,7/20,5
From Table 2 it is clear that excellent surface activation and paint adhesion
were obtained from a 5 second exposure time onwards and that no
decrease in the adhesion strength was observed for longer times, even after
1 hour of oxyfluorination. Although very little change in the amount of
surface- incorporated fluorine was observed, initial changes in the water
contact angle were sensitive measures for adequate activation. A
surprisingly small amount of fluorine was incorporated in the surface.
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EXAMPLE 6
Example 5 was repeated except that the painted samples were immersed in
water at 40°C for 10 days before the paint adhesion strength was
evaluated.
The standard deviation in the breaking force was about 2,0 MPa. Results
are set forth in the following table, Table 3:
TABLE 3
SP 179-22 material exposed at 25°C to 5 kPa 20% F2/N2/25 kPa air
mixture
painted with Herberts Persan 1-K base coat/2-K clear coat after 24 hours
exposure to air, followed by 10 days of immersion in water at 40°C.
Oxyfluorinating Breaking strength Nature of failure
time (MPa)
(seconds)
5,10 90A,1 OA/B
6,90 1 OOA
6,59 1 OOA
60 5,89 1 OOA
300 8,21 1 OOA
900 11,61 100-/Y
1800 7,97 100-/Y
3600 4, 38 1 OOA
From comparing the paint adhesion strength before water immersion (Table
2) to that after immersion (Table 3), it was clear that no decrease arising
from the immersion was observed. In fact, an increase was generally
observed.
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wnnnoi c ~
Using the same material, oxyfluorination and painting conditions as for
Example 5, but with an oxyfluorinating time of 10 seconds, the influence of
different partial pressures of fluorine was investigated. The results are
summarized in Table 4 hereunder.
From Table 4 one can deduce that a partial pressure of 1 kPa of F2
(SkPa 20% F2/N2/25kPa air mixture) is adequate to induce excellent
adhesion strength.
TABLE 4
Material SP 179-22 exposed at 25°C to various mixtures of F2/N2
and
air with the air at 25kPa and the F2/N2 at various different pressures for 10
seconds and then painted with Herberts Persan 1-K base coat/2-K clear coat
after exposure to air for 24 hours.
Pressure of 20% Breaking Nature of FailureWater Contact
F21N2 added to Strength (%) Angle ()
25kPa Air Mixture AdvancelRecede
(kPa) (MPa)
1 No adhesion No adhe Lion 100/72,9
2 No adhesion No adhesion 100/58,0
7,09 10A, 90A/B 64,8/30,5
6, 54 100-/Y 68, 7/29, 3
8,62 40A/B, 60-/Y 60,5/20,2
11,38 100-/Y 59,7/24,4
9,44 100-/Y 62,2/23,2
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EXAMPLE 8
As for Example 5, all SP 179-22 plate samples were oxyfluorinated for 10
seconds using 5 kPa 20% F2/N2/25kPa air mixture, at different temperatures.
The paint adhesion of the samples was evaluated after 10 days of water
immersion at 40°C. The results are summarised in Table 5. From Table 5
it
is clear that good adhesion was obtained over a wide oxyfluorination
temperature range, but that adhesion decreased substantially when
oxyfluorinating near the melting temperature (169°C) of the plastic
substrate.
Comparing the 70.3° contact angle at 150°C with that of
Table 2, it was to
have been expected that excellent adhesion would be achieved. This
indicates that contact angle changes are not sufficient to predict adequate
adhesion after water immersion.
TABLE 5
Material SP 179-22 oxyfluorinated at a number of different temperatures by
exposure to 5 kPa 20% FZ/N2/25kPa air mixture for 10 seconds and then
painted with Dulux Cathkin White after exposure to air for 24 hours.
OxyfluorinationBreaking Nature Fluorine Water contact
temperature strength of Concentration angle ()
(C) (MPa) failure (NgF/cm2) advance/recede
(%)
25 7,66 10A,90A/B2,7 63,0/34,6
50 9,24 10A,90-/Y2,9 60,8/34,1
100 7,60 50A,50A/B3,2 53,5/32,2
150 No adhesionNo adhesion2,9 70,3/37,1
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EXAMPLE 9
Using the same oxyfluorination conditions as for Example 5 but fixing
oxyfluorinating time at 10 seconds and using a 5 kPa 20% F2/N2/25 kPa air
mixture, an SP 179-22 sample was oxyfluorinated. Instead of waiting for 24
hours before painting, the sample was painted with Dulux Cathkin White
after exposure to the atmosphere, on the one hand, 600 seconds after
oxyfluorination, and, on the other hand, 7 months after fluorination. The
paint adhesion was evaluated after the painted sample was submerged for
days at 40°C in water - See Table 6, Samples Nos. 1 and 2 hereunder.
Comparing the adhesion strength with that of a sample painted after 24
hours after oxyfluorination (e.g. adhesion strength of 7,66 MPa at 25°C
in
Table 5) it is clear that paint adhesion strength was not influenced by the
hydrolysis time of the substrate before painting.
Painting the oxyfluorinated sample after 7 months of exposure to the
atmosphere had no detrimental effect on adhesion strength, as is apparent
from a comparison of the respective breaking strength values of 6.7 MPa
and 6.8 MPa, respectively of Sample 1 for 600 seconds and Sample 2 for 7
months in Table 6 hereunder. This result shows that surface oxyfluorination
can be regarded as permanent.
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To determine whether or not the paint adhesion strength deteriorates with
time, an SP 179-22 sample, Sample 3 in Table 6 hereunder, was
oxyfluorinated in the same fashion as for Samples 1 and 2. Sample 3 was
exposed to air for 24 hours after oxyfluorination, before being painted with
Herberts Persan 1-K base coat followed by a 2-K polyurethane clear coat
(see paint system (a) in Example 7 hereunder). After one year's exposure to
the laboratory atmosphere the paint adhesion strength was determined and
a value of 10.3 MPa was obtained (see Sample 3 in Table 6) indicating that
no loss in paint adhesion strength took place after one year. Indeed,
samples submerged for 3 months in water at 50°C, did not show any
decrease in paint adhesion strength.
TABLE 6
Material SP 179-22 exposed at 25°C to a 5 kPa 20% F2/N2/25
kPa air mixture for 10 seconds, and then painted with Dulux
Cathkin White and evaluated after different exposure times.
Sample Breaking Nature of failureFluorine Water contact
No strength (~) Concentzationangle ()
(MPa) (NgF/cm ) advance/recede
1 6,7 10A,90A/B 2,5 63,1/34,6
2 6,82 20A,50A/B, Not measuredNot measured
30-/Y
3 10,3 100-/Y Not measuredNot measured
~'~ Painted 10 minutes after surface oxyfluorination
~> Painted 7 months after surface oxyfluorination
~» Breaking strength evaluated one year after painting
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EXAMPLE 10
For this example a number of different polyolefin materials, known to be
difficult to paint, were oxyfluorinated and painted with a variety of
different
paints. The following substrates were oxyfluorinated:
(a) A reactor-grade polypropylene SP 179-22 manufactured by
Montell and obtained from Bruneal Plastics (Proprietary)
Limited, PO Box 289, Lonehill 2062, Gauteng Province;
(b) A block copolymer manufactured by Plastomark
(Proprietary) Limited of Highchem Park, 16th Road,
Midrand, Gauteng Province, Republic of South Africa;
(c) A polypropylene homopolymer from Polifin Limited,
PO Box 72, Modderfontein, 1645, Republic of South
Africa;
(d) A random or statistical polypropylene copolymer called
Stat from Plastomark (Proprietary) Limited;
(e) A high-density polyethylene (HDPE) manufactured by
BASF South Africa (Proprietary) Limited, 852, 16th
Street, Midrand (Designation Lupolen 526125).
(f) A linear low-density polyethylene manufactured by
Polyfin Limited (Rotational moulding grade 3185).
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Samples of these olefin materials were oxyfluorinated by
exposing them at 25°C to a partial pressure of 5 kPa 20%
F2/N2/25 kPa air mixture for 10 seconds and then painting them
after 24 hours exposure to air with the following paints by spray-
painting the surface to apply one of the following paint systems:
(a) A 1-K polyurethane base coat with the trade
designation Herberts BN RG Persan 777 RN (RN
313. 565) followed by a 2-K polyurethane clear
(top) coat with the trade designation VERNIS 2-K
EC 510027 (Ref. No. 9213226/FA 9213227) and
a hardener (Ref. No. FA 9212586).
(b) A 2-K topcoat with the trade designation DUCO
DURATHANE K ENAMEL Cathkin White (Ref.
No. D 928-0025) obtained from Dulux
(Proprietary) Limited, PO Box 911641, 117
Phillips Street, Rosslyn, Pretoria, Gauteng
Province.
(c) An Epoxy 2-K paint with the trade designation
Dulux Hi Chem Epoxi-Emalje Brilliant Green (Ref.
No. D 355-0221 ) and a hardener (Ref. No.
39490) obtained from Dulux (Proprietary) Limited.
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(d) A 1-K water-borne base coat (WBC), followed by
the 2-K clear coat mentioned in (a) above, from
Herberts.
(e) A 2-K soft-touch coat, trade designation Karl
Worwag, Woropur-Softfeellack Schwartz Nach
Matt (Ref. No. 64090) mit Hartner (Ref. No.
57859) obtained from Karl Worag Lack- and
Farbenfabrik GmbH & Co, Strohgan Strasse 28,
70435 Stuttgart, Germany.
(f) A 1-K primer trade designation Plascon 1-K A/Dry
H/Build Pri for P/Propyl. EPDM obtained from
Plascon (Herberts), PO Box 1594, Port Elizabeth
6000, Eastern Cape Province, Republic of South
Africa.
From Table 7 hereunder it can be seen that oxyfluorinations
((a)-(f)) generally led to improved paint- and primer adhesion
when compared to the adhesion of a primer on a surface that
had not been oxyfluorinated. Polymers containing propylene
(RTPO SP 179, block copolymer, homopolymer, and random
copolymer) showed better adhesion than those containing only
ethylene (HDPE, LLDPE). The adhesion of paints applied
directly to an oxyfluorinated surface was in most cases equal or
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36
better than the adhesion of primers on an oxyfluorinated
surface.
It should be noted that the water-based or water-borne base
coat (d) could be applied directly to the oxyfluorinated surface
without first applying a primer. Thus, the use of adhesion
promoters is not necessary when substrates are oxyfluorinated
before paint application. This can eliminate the cost of applying
expensive, environmentally unfriendly primer coats. This fact,
as well as the excellent adhesion obtained on an oxyfluorinated
sample with a water-borne base coat, can significantly reduce
painting costs and reduce health risks for workers applying
paints.
The soft-touch paint ((e) in Table 7) showed excellent adhesion
to polypropylene-containing polymers. Soft-touch paints are
generally applied to highly isotactic polypropylene block
copolymers used for the interior trims and dashboards of
motorcars. From Table 7 it can be seen that the adhesion of
the soft-touch paint was excellent on the block copolymer.
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m a a a a a a
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38
From the results in the Examples 5 - 10 it appears that the process of the
present
invention is capable of producing products with regard to which substantial
breaking forces
are required to break the bond between the oxyfluorinated surface of the
sample, and the
first or lowermost paint layer applied thereto. Typically failure takes place
either under the
oxyfluorinated surface, in the material of the sample, or at the outer surface
of the~p~nt, at
the interface between the paint and the adhesive. In none of the tests was
more than 40%
of the site of the failure made up of adhesive failure between the
oxyfluorinated sample
surface and the first or lowermost coat of paint. Furthermore in each of
Examples 5 - 10,
depending on the exposure times, results could be achieved where no such
adhesive
failure at the sample/paint interface took place.
In particular it is to be noted that the humid ambient air (usually between
30% and 70% relative humidity) of the SkPa 20% F2/N2/25kPa air mixture
employed in
Examples 5 - 10 contained sufficient humidity for the SkPa 20% F2/N2/25kPa air
mixture to
have a moisture content in terms of water vapour of 2 - 10 mgll.
Further tests, as set forth hereunder in Examples 11 - 13, were carried out to
compare dry oxyfluorination with oxyfluorination using the gas/vapour mixture
oxyfluorinating atmosphere of the present invention, containing water vapour.
In
Examples 11 - 13, the polypropylene homopolymer used was that listed under (c)
in
Example 10 above, and a rotational moulded linear low-density polyethylene
(LLDPE)
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39
obtained from Sasol Polymers, a division of Sasol Limited, Johannesburg, under
the trade
designation Reference LLDPE HR 486/06.
Sample preparation was done in accordance with that described above for
Examples 5 - 10 except that, instead of wiping with isopropanol, the samples
were left to
dry overnight. The paint used was the DUCO DURATHANE K ENAMEL Cathkin
White/Wit (Ref. No. D 928-0025) top coat paint/Slow D 928-0809 hardener
combination
from Dulux AECI Paints (Proprietary) Limited referred to above. When an epoxy
adhesive
is referred to in Examples 11 - 13 it is that available from Pratley
Manufacturing &
Engineering Company (Proprietary) Limited, Factoria, Krugersdorp, P.O. Box
3055,
Kenmare 1745 Gauteng Province, South Africa, under the trade designated
Pratley
Quickset White Epoxy Glue, which was used in accordance with the
manufacturer's
instructions. Adhesion was evaluated using the metal-backed test pads to
measure pull-
off and adhesion strength using a 20mm diameter test cylinder according to
International
ISO Standard 4622-1978(E) as described above. Samples in the form of 10cm x
10cm
plates of the polymers described in Examples 11 - 13 were exposed to various
oxyfluorinating gas/vapour mixtures according to the invention at 25°C
in a reaction vessel.
The atmospheric relative humidity of the ambient air used was 50 - 70% during
the course
of carrying out Examples 11 - 13.
The apparatus of Figure 2 was used to create a gas/vapour mixture as an
oxyfluorinating atmosphere having a desired relative humidity in a reaction
vessel.
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In particular a humid oxyfluorination atmosphere of about 75% relative
humidity and a dry oxyfluorination atmosphere of substantially 0% relative
humidity were
created.
In Figure 2, the apparatus employed is generally designated by reference
numeral 22. The apparatus comprised a reactor in the form of a stainless steel
reaction
vessel 24 shown provided with a lid 26 sealed by means of an O-ring 28. The
reaction
vessel 24 was provided with a heater jacket 30, and was connected via an
inlet/outlet
opening 32 in a lid 26 therefor, to a fluid flow line 34. The flow line 34 was
provided with a
pair of shut-off valves, respectively designated 36 and 38, joined together by
a flexible
metal bellows 40.
Flow line 34 branched from a manifold 42, to which were connected a
plurality of flow lines respectively designated 44, 46, 48 and 50.
Flow line 44 led to a vacuum pump 52, and was separated from the
remainder of the manifold 42 by a shut-off valve 54. Flow lines 46, 48 and 50
entered the
manifold 42 on the same side of the valve 54 as the flow line 34, i.e. remote
from the flow
line 44.
Flow line 46, provided with a regulating valve 56 was a supply line for a
mixture of F2/N2; and flow line 48, provided with a regulating valve 58 was a
dry synthetic
air supply line. In tum, the flow line 50 was provided with a shut-off valve
60 and a
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41
regulating valve in the form of an adjustable needle valve 62 and led to a gas-
wash bottle
64, containing water 66 and provided with an air inlet pipe 68. Finally, a
pressure
transducer 70 was shown connected to the manifold 42 by a pressure line 72.
In other words the reactor 24 was a stainless steel vessel sealed by the O-
ring 28. The temperature in the reactor was controlled by the !eater jacket
30. For
convenience valves 36 and 38 were joined by the flexible metal bellows 40. The
glass
gas-wash bottle 64 containing water 66 was used to humidify the air loaded
into the
fluorination reactor 24. Two valves 60, 62 were used at the point where the
humidified air
from the gas-wash bottle 64 was admitted to the manifold 42. Valve 62 was an
adjustable
needle valve that was set to deliver humidified air to the evacuated reactor
24 at a rate
which resulted in a level of humidity of at least 75% relative humidity. Valve
60 was a
shut-off valve, which was used to admit/shut-off the humid air flow into the
manifold 42 and
the reactor 24.
Vacuum pump 52 was connected to manifold 42 via the normally closed
valve 54 and was used to evacuate the manifold 42 and reactor 24 before each
run. The
pressure transducer 70 constantly measured the pressure in the manifold 42 and
reactor
24 of the apparatus 22 to control the steps of evacuation of the reactor 24
and subsequent
loading of gas components from flow lines 46, 48 and 50. Valve 58 admitted the
F2/N2
mixture via line 46 to the manifold 42 and was used to admit and regulate the
loading of
the F2/N2 mixture before the oxyfluorination process. During humid
oxyfluorination
air/water vapour mixture from gas-wash bottle 64 was loaded via the manifold
42 into the
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reactor 24 by opening valve 60 and adjusting valve 62 to achieve a desired
loading rate.
Instead, for dry oxyfluorination, dry synthetic air from a synthetic air
cylinder (not shown)
attached to supply line 48 using a flexible metal hose (also not shown) was
fed via its own
flow regulation valve (not shown) and valve 58 into the manifold 42. The
synthetic air was
purchased from Air Products (Proprietary) Limited, Kempton Park with the
following
specification:
a) Oxygen - 20 - 22% by volume
b) Nitrogen - the balance
c) Water - less than 2 ppm
HUMID OXYFLUORINATION PROCEDURE
In operation the temperature of the reactor 24 was regulated at about 1 -
2°C above ambient temperature by means of the heater jacket 30. The
actual recorded
temperatures during the test runs fluctuated between 25°C and
30°C. Initially valves 36,
38, 60, 54, 58 and 56 were closed and the test samples were loaded into the
open reactor
24. The lid 26 of the reactor 24 was then closed and sealed by means of O-ring
28.
Valves 54, 36 and 38 were then opened and the manifold 42 and reactor 24 of
the
apparatus 22 were evacuated to as low pressure as possible whereafter valve 54
was
closed. Valve 60 was then opened and humid air was admitted into the manifold
42 and
reactor 24 at a desired rate by means of needle valve 62 to allow air of about
75%.or more
relative humidity into the reactor 24 up to a specified pressure. Valve 60 was
then closed.
The F2/N2 mixture from line 46 was then admitted up to a specified pressure in
the
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manifold 42 and reactor 24, by slowly opening valve 56. Thereafter, valves 56,
38 and 36
were closed for the duration of the humid activation.
The test samples were left in contact with the gas mixtures for specified
periods of time. Valves 54, 38 and 36 were then opened and the gases in the
reactor 24
pumped off. Valve 54 was then closed and air from the atmosphere was admitted
to the
manifold 42 and reactor 24 by opening valve 60. When the pressure in the
manifold 42
and reactor 24 reached about 80kPa, valve 60 was closed and valve 54 was
opened to
allow pump 52 to pump air out of the manifold 42 and reactor 24. This cycle of
evacuation
and flushing with air was repeated three times in order to remove any residual
fluorine and
hydrofluoric acid from the reactor 24. Finally, air was allowed into the
reactor 24 through
valve 60 up to atmospheric pressure whereafter the lid was opened and the test
samples
removed from the reactor.
DRY OXYFLUORINATION PROCEDURE
The only difference between dry and humid oxyfluorination was the use of
dry synthetic air from the synthetic air bottle attached to line 48, instead
of humid air from
the gas-wash bottle 64. Special precautions were, however, taken in removing
any
moisture in the apparatus 22 therefrom, downstream of valve 60 before, during
and after
the dry oxyfluorination process.
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The temperature of the reactor was controlled as before. Valves 36, 38, 60,
54, 58 and 56 were closed as before. Thereafter the apparatus was evacuated,
followed
by flushing to a pressure of about 80 kPa with dry synthetic air from the air
supply
connected to line 48 by manipulating valves 54 and 58 in succession. This was
repeated
three times in order to remove any traces of water from the manifold 42 and
reactor 24.
Dry air was then bled into the manifold 42 and reactor 24 up to atmospheric
pressure,
before closing all valves and opening the reactor lid 26. Pre-dried test
samples were then
quickly loaded into reactor 24, whereafter the reactor lid 26 was replaced and
sealed with
O-ring 28. A sequence of three successive evacuations, each followed by
flushing with
synthetic dry air to about 80 kPa, of the manifold 42 and reactor 24 was
performed as
before, to remove all traces of moisture therefrom. Finally, dry synthetic air
was admitted
to the manifold 42 and reactor 24 up to a specified pressure via valve 58.
Valve 56 was
then slowly opened and F2/N2 mixture admitted to the manifold 42 and reactor
24 to a
specified partial pressure. Valves 56, 38 and 36 were then closed for the
duration of the
dry activation.
The test samples were left in contact with the oxyfluorination atmospheres
for specified periods of time. Valves 54, 38 and 36 were then opened and the
gases in the
reactor 24 and manifold 42 evacuated therefrom by pump 52. The manifold 42 and
reactor 24 were then flushed with synthetic dry air and evacuated three times
as before to
remove all residual fluorine and hydrofluoric acid. Finally, synthetic dry air
was allowed to
flush the reactor 24 through valve 58 up to atmospheric pressure whereafter
the lid 26 was
opened and the test samples were removed from reactor 24.
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EXAMPLE 11
Polypropylene homopolymer samples were cleaned and were subjected to
dry oxyfluorination in the absence of water vapour, and to humid
oxyfluorination in the
presence of water vapour. The samples subjected to dry oxyfluorination were
left for 24
hours in a silica gel-filled desiccator prior to oxyfluorination, whereas
those subjected to
humid oxyfluorination were equilibrated in a closed vessel with a relative
humidity of
,95% prior to oxyfluorination. All samples were oxyfluorinated for 10 seconds.
For the
dry oxyfluorination, samples were exposed to an oxyfluor-inating gas
atmosphere
consisting of a F2/N2 gas mixture at a pressure of 3kPa, the F2/N2 mixture
comprising 20%
by volume F2 and 80% by volume N2, and dry air consisting of an 02/N2 mixture
comprising 21 % by volume 02 and 79% N2 by volume, at a pressure of 25 kPa.
The total
reaction pressure was thus 28 kPa, and the atmosphere comprised 3 parts by
volume of
the F2/N2 mixture, mixed with 25 parts by volume of the 02/N2 mixture. For the
humid
oxyfluorination the atmosphere was the same, except that the dry air was
replaced by air
comprising 02 and N2 in the same 21:79 volume ratio, but of 75% relative
humidity. The
results are set forth in Table 8.
TABLE 8
2-K polyurethane paint adhesion strengths on dry- and humid oxyfluorinated
polypropylene samples. Samples were painted within 1 hour of oxyfluorination.
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Dry Oxyfluorination Humid Oxyfluorination
Breaking Nature of FailureBreaking Nature of Failure
Strength Strength (MPa)
(MPa)
9.88 100% A/B 13.62 90%-/Y, 10% A/B
13.82 100% -/Y 9.73 90%-/Y, 10% A/B
4.49 100% A/B 11.40 90%-/Y, 10% A/B
10.79 100% -/Y 12.18 ' 90%-/Y, 10% A/B
7.35 50% A/B, 50% - 13.79 100%-/Y
/Y
Mean Mean 12.1 1.7
9.3 3.5
It was noted that for the dry oxyfluorination the adhesive failure generally
occurred
between the polypropylene substrate and the paint coating, while for the humid
oxyfluorination the failure was between the paint coating and the adhesive,
indicating
superior paint adhesion to the substrate when humid oxyfluorination was
employed. This
was emphasised by the significant increase in average breaking strength from
9.26 MPa
to 12.14 MPa when dry oxyfluorination was replaced by humid oxyfluorination.
This was
coupled with a substantial decrease in standard deviation, suggesting that
humid
oxyfluorination is more homogeneous than dry oxyfluorination, leading to a
more reliable
activation of the substrate with the potential for better quality control. The
nature of the
failure for the humid oxyfluorination samples indicated that the A/B bond
strength was in
fact greater than the average value of 12.14 MPa. Further tests using ambient
air showed
that a drop from 75% or higher down to 65% relative humidity in the humid
oxyfluorination
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gave a mean breaking strength of 12.43 MPa, which compared favourably with the
12.14
MPa in Table 8 for 75% relative humidity.
EXAMPLE 12
Example 11 was repeated on rotational moulded linear low-density polyethylene,
with an increase of reaction time from 10 seconds to 3 minutes. Results are
set forth in
Table 9.
TABLE 9
2-K polyurethane paint adhesion strengths on dry - and humid oxyfluorinated
linear
low-density polyethylene.
Dry Oxyfluorination Humid Oxyfluorination
Breaking Nature of Breaking Natu-re of Failure
Strength Failure Strength (MPa)
(MPa)
0.93 100% A/B 3.05 100% A/B
1.91 100% A/B 7.07 100% A/B
0.78 100% A/B 5.80 100% A/B
1.26 100% A/B 3.81 100% A/B
5.86 100% A/B 3.92 100% A/B
Mean Mean 4.7 1.7
2.2 2.1
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With linear low-density polyethylene changing from the dry oxyfluorination to
the humid
oxyfluorination effectively doubled the breaking strength with a substantial
decrease in
standard deviation. In each case failure occurred between the polyethylene
substrate and
the paint coating. As with Example 11, the increase in breaking strength
achieved by
humid oxyfluorination was substantial.
EXAMPLE 13
Example 11 was repeated except that the paint coating of Example 11 was
replaced by a coating of Pratley Quickset White Epoxy Glue. Results are set
forth in Table
10.
TABLE 10
Pratley Quickset White Epoxy Glue adhesion strength on polypropylene
homopolymer.
Dry Oxyfluorination Humid Oxyfluorination
Breaking Nature of FailureBreaking StrengthNature of Failure
Strength (M Pa)
(MPa)
2.76 100% A/B 13.44 100% A
5.94 50% A/B, 50% 13.93 100% A
A/B
13.33 100% A 12.19 100% A
5.16 50% A/B, 50% 13.89 100% A
A
11.18 100% A
Mean Mean 13.3 0.8
7.07 4.4
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In Table 10 test results for certain samples were ignored and excluded because
of uneven
sample surfaces which rendered these test results unreliable. In Table 10 A/B
refers to
adhesive failure between the polypropylene substrate and the epoxy coating,
while A
refers to cohesive failure of the substrate. The results shown in Table 10
also confirm that
changing from dry oxyfluorination to humid oxyfluorination led to an
improvement of
breaking strength for adhesive coatings as well as more homogeneous surface
activation.
Here the epoxy coating also serves as the adhesive for securing the breaking
strength test
cylinder to the coating, so that no further adhesive is applied as in the case
of paint
coatings.
It is believed that the process of the present invention has broad
application to a wide variety of solid materials where surface activation,
particularly with
respect to achieving enhanced adhesion, plays a role. A broad spectrum of
materials is
known to benefit from dry fluorination or dry oxyfluorination in terms of
surface activation
or modification, which leads to varying degrees of improved adhesion to
flowable or
mouldable substances such as glues, dyes, paints, resins, epoxies and various
cementitious matrices. It is therefore expected that at least the same
spectrum of
materials is susceptible to enhanced surface activation or modification by
oxyfluorination in the presence of water vapour according to the present
invention, so as
further to improve their adhesion properties. Thus, it is believed that the
present
invention can in principle be extended to activation of materials such as
natural organic
substances including wood, leather, textiles such as cotton and wool, and also
to
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activation of inorganic substances such as metals or metalloids, ceramics,
glass,
asbestos and carbon. Enhanced activation, particularly with respect to
adhesion, is
thus expected to follow such oxyfluorination. In particular it is believed
that the
oxyfluorination of metal reinforcements in cementitious matrices may have the
effect of
ameliorating corrosion of the metal and thus reducing corrosion and cracking
in the
matrices.
