Note: Descriptions are shown in the official language in which they were submitted.
CA 02192946 2002-06-11
1
METHOD FOR THE PRODUCTION OF COMPOSITES
THIS INVENTION relates to a method of producing a composite material. In
particular, it relates to a method of producing such composite materials for
making structures
and/ or artifacts wherein a substrate is protected against corrosion and/or
permeation of
fluids by a surface cladding. It also relates to a method of producing such
composite
materials wherein one component is strengthened or reinforced by another
component. The
invention also relates to such composite materials, particularly when produced
by means of
said method.
According to the invention, there is provided a method of producing a
composite material, the method comprising:
subjecting a surface of a polyolefin component comprising a polyolefin
material to
surface activation thereof; and
adhesively securing together the polyolefin component and a substrate
component
selected from cementitious components and metal components, at the activated
surface of
the pofyolefin component,
the activation being by surface oxyfluorination activation by exposing the
polyolefin
component to an oxyfluorinating gas mixture at a pressure of 1 -500 kPa and at
a
temperature above OEC and below the melting point of the polyolefin material
of the
polyolefin component, the activation acting to incorporate fluorine and oxygen
into the
surface of the polyolefin component and the adhesively securing together of
the polyolefin
component and the substrate component being effected by means of an adhesive
composition, the method including the step, prior to the adhesive securing, of
subjecting the
activated surface of the polyolefin component to hydrolysis. to form
carboxylic acid groups
on the surface, which groups contribute to the activation of the surface, and
to said adhesion
thereof to the substrate.
By surface activation is meant that the surface of the polyolefin component is
brought into contact with a fluid in a fashion whereby atoms, molecules and/or
radicals
derived from the fluid are incorporated into the surface of the component.
The polyolefin component may act to protect the substrate component, the
polyolefin component forming a surface cladding for the substrate component.
The
CA 02192946 1996-12-13
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2
polyolefin surface cladding may protect the substrate component against
corrosion.
The polyolefin surface cladding may instead or in addition protect the
substrate
component against permeation of fluids, particularly when the latter is
cementitious.
The oxyfluorinating gas mixture may comprise at least 5% by volume of a
fluorine-containing gas and at least 5% by volume of oxygen, the gas mixture
being
at a pressure of at Least SKPa and at a temperature of at least 20°C.
Preferably said
gas mixture comprises 5 - 20% by volume of the fluorine-containing gas and 5 -
95% by volume of the oxygen, the gas mixture being at a pressure of 5 - 150KPa
and at a temperawre of 20 - 100°C.
More particularly, the surface activation may provide the activated polyolefln
component surface with a surface tension at 20°C of at least 40 mN/m,
the
polyolefin material being selected from polyethylenes, polypropylenes,
copolymers
of ethylene and propylene and blends of such polyoleflns, such as ethylene-
propylene
diene monomer elastomers. The polyoiefins used include unmodified or modified
polyolefins, eg those modified by containing ethyl vinyl acetate as an impact
modifier.
Any suitable method can be used to oxyfluorinate the surface of the
polyolefin component which is oxyfluorinated before it is adhesively secured
to the
cementitious or metal substrate component. Any suitable fluorinating process
may
be used for this purpose, suitably modified to provide for oxyfluorination,
for
example the fluorinating processes described in US Patenu Nos. US 3,647,b I 3;
US 3,862,284; US 3,865,615; US 4,020,223; US 4,081,574; US 4, I 42,032;
US 4,296,151; US 4,508, 781; US 4,53b,26b; US 4,557,945; US 4,764,405;
and US 4,869,859 as well as published European Patent Application
EPO 214 635, and South African Patents Nos. 85/9500 and 87/8240, describe
techniques which can be adapted for the oxyfluorination described hereunder.
AiviEfVG'v SHEET
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,:
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3
By oxyfluorination is meant that the surface is provided with fluorine and
oxygen substituenu, eg on -CH2 and/or -CH3 groups forming part of the surface.
The fluorinating gas mixture may be fluorine itself (F2), it may be a
fluorinated
noble gas such as XeF2, or it may be a fluorohalogen such as C1F3, BrFS, IFS
or the
like. The oxyfluorinating gas mixture will typically be one in which the
fluorine-
containing gas forms part of a mixture with one or more other gases, such as
oxides
of sulphur, oxides of nitrogen or oxides of carbon, halogens, interhalogens,
nitrogen,
oxygen or mixtures thereof, such as air, at least one of which other gases
will contain
oxygen. The proportion of the fluorine-containing gas in such gas mixture can
vary
within wide limits, the fluorine-containing gas forming eg 0,1-99,9% by volume
of
said mixture, typically forming 1 - 30% by volume thereof, although, as
indicated
above, particularly preferred gas mixtures include those comprising 5 - 20% by
volume of fluorinating gas such as F2 and 5 - 95% by volume oxygen (02 or 03).
As described in more detail hereunder, adhesively securing the activated
surface of the polyolefln component to the subsuate component may be effected
by
means of an adhesive composition comprising a thermosetting resin.
The oxyfluorination under the above process conditions will usually take place
in a reactor comprising a vacuum chamber with provision for feeding thereto
and
withdrawal therefrom of gases, pressure conuol, temperature control and
control of
the composition of gas mixtures therein, and the process will usually be
carried out
batchwise.
When the polyolefln cladding component is in the form of a sheet, it may,
however, be treated in a roll-to-roll process using a flim fluotinator as the
reactor,
with similar oxyfluorination conditions to those described above with
reference to the
batch process. The absolute pressure in such reactor will typically be one
atmosphere, ~ 20 k1'a. The gas mixture composition may, as indicated above, be
such that it has a fluorine (F2) content is 5 - 20 % by volume , the remainder
being
made up of other reactive gases, or inert gases, eg N2. The proportion of said
other
AMENDEv ~HEE i
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CA 02192946 1996-12-13
4
gases in the mixture may be between 5 and 95 % by volume, the balance being
made up by an inert gas such as N2.
As indicated above, the surface oxyfluorination, may be such as to provide
the activated polyolefin component surface with a surface tension at
20° C of at
least 40 mN/m, preferably at least 45 mN/m.
The substrate component may be a cementitious component made of a
cementitious material such as cement, concrete, cementitious mortar or a
related
cement-containing material. The cementitious substrate component may be flat,
being cg a concrete wall or floor, or tubular, being cg a concrete pipe. The
substrate
component may instead be a metal component, such as mild steel component, and
may be tubular, being cg a pipe, although it may, instead be a box or
container-type
structure. Accordingly, the material of the substrate component may be
selected
from cement, concrete, cementitious mortar or mild steel, the thermosetting
resin
being selected from epoxy resins and polyester resins.
The polyolefin component, when used for cladding, may be of an
appropriate shape, depending on the shape of the substrate component. Thus,
the
polyolefln component may be a flat or curved sheet. When the substrate
component
is tubular, cg a pipe, the polyolefln component may be a pipe, a polyolefin
pipe
forming an external and/or internal cladding or lining for the cementitious or
metal
pipe, as the case may be.
The cladding or other poiyolefln component may be of polyethylene, such
as high density polyethylene (HDPE), polypropylene (PP), or copolymers of
ethylene
and propylene, such as ethylene-propylene-diene monomer elastomer (EPDM),
modified or unmodified, as indicated above, or blends of such polyolefins.
Adhesively securing the fluorinated surface of the polyolefin cladding
component to the cementitious or metal substrate component may be effected by
ANitNO~=v SHEET
1J~;.;W'-
CA 02192946 2005-04-12
using a suitable adhesive composition, such as a thermosetting resin as
indicated
above. The adhesive composition may comprise a curable settable thermosetting
resin, eg an epoxy resin or polyester resin. Suitable epoxy resin-based
adhesive
compositions are those available in South Africa as PRO-STRUCT 121 and
PRO-STRUCT 30/71 from Pro-Struct, a division of KayMac Limited. Suitable
polyester resin-based adhesive compositions are a polyester resin adhesive
paste
available in South Africa as FREE FIX 40/6345 from NCS Resins, a division of
Sentrachem Ltd, a resilient isophthalic polyester resin adhesive available in
South
Africa as GELCOATT"" 65 from said NCS Resins, and an isophthalic, non-
accelerated
resilient polyester resin adhesive available in South Africa as POLYLITET""
8130 from
said NCS Resins.
The invention extends to a composite material whenever produced in
accordance with the method of the invention.
The method includes the step, as indicated above and prior to the
adhesive securing, of subjecting the activated surface of the polyolefin
component to
hydrolysis, to enhance the adhesion of the fluorinated surface to the adhesive
composition. The hydrolysis is particularly effective when the adhesive
securing step
is by means of an epoxy adhesive composition. The hydrolysis may be effected
by
contacting the oxyfluorinated surface with water at an elevated temperature
for a
sufficient period of time, eg by immersing the polyolefin component in water
overnight
at 50°C, to hydrolyse any hydrolysable chemical groups on the
fluorinated surface of
the polyolefin component. Exposure of the oxyfluorinated surface to
atmospheric air
for extended periods of time should also result in full hydrolysis of the
oxyfluorinated
surface. In particular, the hydrolysis may be by contacting the activated
surface of the
polyolefin component with liquid water for a period of 2-6 hours.
The surface may be subjected to degreasing prior to oxyfluorination
thereof and/or after fluorination and prior to the adhesive securing of the
cladding
component to the cementitious or metal substrate component. Accordingly, the
surface may be subjected to degreasing prior to activation thereof.
Furthermore, the
surface may, after activation thereof and prior to the adhesive securing, be
subjected
to degreasing.
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6
Suitable degreasing agents used to degrease the surface may be selected from
trichloro-ethylene (TCE), acetone, ethanol, methyl ethyl ketone (MEK) and
xylene.
Water-soluble detergents can also be used. Naturally routine experimentation
will
be employed to determine which degreasing agents are compatible with the
surface
and with the resins employed in the process of the invention.
As indicated above, the polyolefin component may be secured to the
substrate component to form a surface cladding of the substrate component.
Furthermore, instead, the substrate component may be secured to the polyolefin
component to form a surface cladding of the polyolefin component.
0 Thus, instead of using the polyolefin component to protect the substrate
component, the substrate component may be used for strengthening and/or rein-
forcing the polyolefin component. The polyolefln component in this case may be
tubular or hollow cylindrical, eg circular or square in cross-section,
suitable for
containing and/or transporting a fluid. In particular, the polyolefin
component may
I 5 be a pipe or pipe fitting, or a tank, the metal reinforcing component
foaming an
external cladding or lining for the polyolefin pipe, pipe fitting or tank.
Typically in
this case, the polyolefin material of the polyolefin substrate component is
again
polyethylene, such as high density polyethylene (HDPE), polypropylene (PP), or
copolymers of ethylene and propylene, such as ethylene-propylene-diene monomer
20 elastomer (EPDM), modified or unmodified, or blends of such polyolefins.
The metal
strengthening or reinforcing component may be of mild steel. The surface
oxyfluorination method; for activating the surface of the polyolefin substrate
component before it is adhesively encapsulated or clad by the metal
reinforcing
component, may be similar to that described above for protection of the
substrate
25 component by the polyolefin component; and adhesively securing the
reinforcing
component to the polyolefin component may be effected using a similar adhesive
composition as described above for protection of the substrate component by
the
polyolefin component. A suitable adhesive composition is an epoxy resin-based
adhesive such
as that available in South Africa as PRO-STRUCT 7907 A and B from Pro-Struct,
a
AMENDE~ SHEET
IPEA/EP
CA 02192946 2002-06-11
7
division of KayMac Limited. Typically, the resin may be cured by using a
suitable curing agent
or catalyst, eg a commercial curing system or package supplied by, and used in
the
appropriate amount as recommended by, the manufacturer of the particular resin
used. This
version of the method may also include the further step, prior to the adhesive
securing, of
subjecting the fluorinated surface of the polyolefin suk>strate component to
hydrolysis, as
described above, to enhance the adhesion of the oxyfluorinated surface to the
adhesive
composition. Plastics pipes are widely used for the transport of fluids and
the pressure in
such pipes may vary from below atmospheric (vacuum) up to tens of atmospheres.
Polyolefin
pipes and tanks can be lined or encapsulated by metal reinforcing components
in accordance
with the method of the invention to increase their pressure rating, and/or to
increase their
rigidity. Such composite pipes and tanks combine the advantages of the
strength (for
pressure) and
rigidity of eg steel and the relative chemical and abrasion resistance of
polyolefin plastics.
The invention extends to a method of producing a composite material, the
method comprising:
subjecting a surface of a polyolefin component comprising a polyolefin
material to
surface activation thereof;
and adhesively securing together the polyolefin component and a substrate
component selected from cementitious components and metal components, at the
activated
surface of the polyolefin component,
the activation being by surface oxyfluorination activation by exposing the
polyolefin
component to an oxyfluorinating gas mixture comprising at least 5% by volume
of a
fluorine-containing gas and at least 5% by volume of oxygen, at a pressure of
1-500 kPa and
at a temperature above 0°C and below the melting paint of the
polyolefin material of the
polyolefin component, the activation acting to incorporate fluorine and oxygen
into the
surface of the polyolefin component and the adhesively securing together of
the polyolefin
component and the substrate component being effected by means of an adhesive
composition, the method including the step, prior to said adhesively securing,
of subjecting
the activated surface of the polyolefin component to hydrolysis and the step,
after the
hydrolysis and prior to said adhesively securing, of subjecting the activated
surface to
degreasing, to form carboxylic acid groups on the surface, which groups
contribute to the
activation of the surface, and to said adhesion thereof to the substrate.
CA 02192946 2002-06-11
7a
The invention extends further to a method of producing a composite material,
the method comprising:
subjecting a surface of a polyolefin component comprising a polyolefin
material
to surface activation thereof, and
adhesively securing together the polyolefin component and a substrate
component selected from cementitious components and metal components, at the
activated surface of the polyolefin component,
the activation being by surface oxyfluorination activation by exposing the
polyolefin
component to an oxyfluorinating gas mixture at a pressure of 1-500 kPa and at
a
temperature above 0°C and below the melting point of the polyolefin
material of the
polyolefin component, the activation acting to incorporate fluorine and oxygen
into the
surface of the polyolefin component and the adhesively securing together of
the polyolefin
component and the substrate component being effected by means of an adhesive
composition, the method further including the step, prior to said adhesively
securing, of
subjecting the activated surface of the polyolefin component to hydrolysis by
contacting the
activated surface of the polyolefin component with liquid water for a period
of 2-6 hours, to
form carboxylic acid groups on the surface, which groups contribute to the
activation of the
surface, and to said adhesion thereof to the substrate. 'The invention will
now be described,
by way of non-limiting illustrative, example, with reference to the following
Examples and
with reference to the accompanying diagrammatic drawings.
Examples 1-3 illustrate the method of the invention applied to the protection
of
cementitious substrates by a polyolefin surface cladding. Example 4
illustrates the method of
the invention applied to the strengthening of a polyolefin
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s
component by a metal reinforcing surface cladding. Example 5 Illustrates the
method of the invention employing various resins. Example 6 illustrates the
method
of the invention employing various degreasing agents. Example 7 illustrates
the
method of the invention employing various drying times prior to
oxyfluorination.
Example 8 illutrates the method of the invention employing various
oxyfluorination
methods. Examples 9A, 9B and 9C illustrate the method of the invention
employing varying activation times. Examples 1 OA and 1 OB illustrate the
method
of the invention in the light of various adhesion tests and kinetics tests.
Examples
1 1 A and 1 1 B illustrate the method of the invention employing various
hydrolysis
media. Example 12 illustrates the method of the invention employing varying
drying
times after hydrolysis. Example 13 illustrates the method of the invention
with
regard to degreasing of substrates after activation and prior to adhesion.
In the drawings:
Figure 1 shows a plot of shear strength (MPa) against sample number for
polypropylene pipe samples provided with an exterior lining of mild steel,
with
reference to the required shear strength according to British Standard
B.S.6464;
Figure 2 shows a plot of peel strength against time for Pro-Struct 30/71 with
hydrolysis in water; and
Figure 3 shows a plot of mass change against time for activation of H DPE with
a F2/02 mixture comprising 10% by volume F2.
EXAMPLE 1 LResin Choice)
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Gas Mixture . l OkPa air, 20kPa F2/N2 mixture comprising 20% by
volume F2.
Oxy-fluorination Time
and Temperature . 30min at 50°C
AMENDED SHEET
(P~r~IFp
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9
Surface Dimensions : length:
200mm, width: 200mm, thickness:
2mm
Resins , a) Pro-Struct 121,
b) Pro-Struct 30/71,
c) Free Fix 40/6345,
d) Gelcoat 65,
e) Polylite 8130.
The HDPE tiles (untreated and activated) were stuck to a concrete wall using
the
above resins by means of hand pressure. After one week a force was applied to
the
tiles to endeavour to peel the tiles from the wall.
The results of these adhesion tests are set out in Table 1 below.
Table 1: Results of adhesion tests between PE 300 and concrete usine various
adhesives
Resin Manufacturer Type of Resin Observation
Pro-Struct 121 Pro-Struct Multi-purpose Breakline within
Epoxy the Concrete
Pro-Struct 30/71Pro-Struct Abrasion ResistantBreakline within
Epoxy the Concrete
FreeFix 40/6345 NCS Resins Filled PolyesterAdhesive Failure
Adhesive Paste between Adhesive
and Concrete
Gelcoat 65 NCS Resins Resilient Adhesive Failure
Isophthalic between Adhesive
Polyester Resin and Concrete
Polylite 8130 NCS Resins Isophthalic, Adhesive Failure
Non-
accelerated, between Adhesive
Resilient and Concrete
Polyester resin
None of the untreated HDPE tiles remained stuck to the concrete wall.
~:~vILi~D~~ SHED
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CA 02192946 1996-12-13
2192~4G
to
The results in Table 1 indicate that epoxy resins appear to be the most
suitable. Pro-Struct 30/71 (polyamido-amine curing agent) appeared to be the
most
suitable resin due to its cost, ease of mixing, ease of application and it
removed less
concrete from the wall compared to the other resins when the peel tests were
conducted.
EXAMPLE 2
From the results of Example 1 it was clear that further work should be focused
on
the use of epoxy adhesives. The aim of the further 'work was to optimise the
fluorination conditions for maximum adhesion between the epoxy adhesives
listed in
Table 1 and fluorinated polyolefin sheet.
Black pigmented HDPE strips (26 x 300 mm) were cut from a PE 300 sheet. The
strips were placed in a stainless steel vacuum reaction vessel which was
evacuated and
then charged with a 10/90 F2/02 mixture. The vessel was kept at 50 °C
and the
strips were fluorinated for different periods of time to provide a surface
fluorine
concentration of 55,4 NgF/cm2. After the selected period of time, the
fluorinating
atmosphere was evacuated from the vessel and the strips removed.
The adhesive strength of PRO-STRUCT 30/71 on these strips was evaluated by T-
peel tests, according to ASTM D 1876-92. The only changes to the prescribed
ASTM procedure were that the crosshead speed used was 200 mm/min and that the
signal integration interval was 10 cm.
From the T-peel tests, it was clear that the optimum treatment time for
maximum
adhesion was reached within 30 minutes, using the above treatment conditions.
It
was also observed that a post-treatment of the fluorinated surface by
hydrolysis had
a material influence on the adhesion strength. It was found that the maximum
adhesion strength (typically 8 N/mm) was obtained when the strips were
submerged
in water overnight at 50 °C. Strips which were glued immediately after
fluorination
~~l~h~I7;~1~ ~H~~-_
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CA 02192946 1996-12-13
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11
without post treatment by hydrolysis, or which were treated with a basic
solution,
eg a NaOH solution, showed relatively weak bonding to the epoxy adhesive.
The Applicant has found the improved adhesion arising from the hydrolysis to
be
surprising and cannot account therefor. However, without being bound by
theory,
the Applicant believes that the fluorination treatment may form aryl fluoride-
and
carboxylic acid groups on the surface of the polyolefln component. On
hydrolysis,
the aryl fluoride groups may either be removed or they may be transformed into
additional carboxylic acid groups. These carboxylic acid groups possibly act
as curing
agents for the epoxy resin. A chemical bond may thus actually be formed
between
the adhesive and the fluorinated surface, which can lead to the high bond
strength
between the polyolefin component and the epoxy adhesive. This mechanism would
explain why basic hydrolysis of the fluorinated surface does not enhance
adhesion to
the epoxy adhesive, since basic hydrolysis leads to the formation of salts on
the
polyolefin surface, and not to additional carboxylic acid groups.
EXAMPLE 3
Tests similar to Example 1 were carried using tiles of EPDM instead of HDPE.
in
control tests, tiles which were not fluorinated showed no adhesion to the
concrete
wall using PRO-STRUCT 30/71 as adhesive. When the tiles were fluorinated as In
Example 1, adhesion was so strong that breakllne within the elastomer was
observed.
EXAMPLE 4
Push out tests were done on a PP pipe which was provided with an external
lining/cladding of a mild steel pipe by the method according to the invention.
The
PP pipe was 90 mm OD class 4 pipe having a wall thickness of 5 mm. The PP was
available from Megapipe, a division of Mega Plastics, which is in turn a
division of
Sentrachem limited. The outer surface of the PP was fluorinated in a manner to
that described in Example 1, using the same fluorination conditions. After
CA 02192946 1996-12-13
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WO 95!35341
12
fluorination, the PP pipe was inserted into a pipe of mild steel. The outside
diameter
of the PP pipe was 1 mm smatter than the inside diameter of the steel pipe. At
each
end of the steel pipe, a cup flange was bolted, each cup flange incorporating
a spacer
to keep the steel pipe and the PP pipe apart and also nozzles to allow both
adhesive
to be injected and air to escape. This technique is known as crack injection.
The
PP pipe and the steel pipe were then suspended at about ~ 60 ° and an
epoxy-
containing adhesive composition, available as PRO-STRUCT 7907 A and B from
Pro-Struct, was then injected into the botxom cup flange under pressure, from
a
pressure pot where the adhesive composition was also premixed. Curing of 'the
epoxy adhesive was by means of a curing agent package supplied by, and used in
an
amount as recommended by, the manufacturer of PRO-STRUCT 7907 A and B.
The epoxy adhesive was allowed to partially cure after which the cups were
removed
and the composite pipe allowed to stand unfit full cure was achieved.
The composite pipe was cut into 60 mm lengths to form samples numbered as
follows:
I I 2 I 3 I 4 I 5 I 6
A I 5 mm length of the PP was machined out of each end of each 60 mm Length
for
the purposes of push out tests conducted in accordance with B.S. 6464. The
push
out tests involved the remaining length of the PP pipe of the test pieces
being pushed
out of the metal cladding and measuring the force required to do so. The shear
strength or "push-out" strength was then calculated as follows:
Shear strength (MPa) - F
d.rr.h
where F - maximum force required to shear the PP pipe from the steel pipe
cladding [N]
d - PP pipe outer diameter (mm)
h - remaining encapsulated inner plastics liner length (mm)
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WO 95135341 219 2 9 4 6
13
The push out test results are summarised tn Table 2 below. The supporting
strength
profile of the steel clad PP pipe samples is shown in the accompanying figure.
The
figure shows for comparison the required shear strength according to the
British
Standard B.S. 6464. Table 3 shows the average shear forces, taking ail the
test
results, as well as the average when disregarding the highest and lowest
values. The
standard deviation and variance is also shown, and then finally, whether or
not the
shear strength of the pipe samples matches or exceeds that specified by B.S.
6464.
From Table 3, it can be seen that the pipe samples, thougfi not complying to
B.S.
6464, fared well.
Table 2 Steel/PP
SAMPLE HIGHEST PIPE MAXIMUM SHEAR
NO. VALVE OF OUTER SHEAR STRENGTH
PIPE DIAMETER FORCE [MPa]
LENGTH [mm] [N]
is [mm]
1 30 111 10.98 1.05
2 30 110 14.56 1.4
3 30 110 14.21 1.3
4 30 110 12.93 1.2
24 5 30 110 12.22 1.17
6 30 110 13.07 1.26
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~~9~~46
WO 95135341 PCT/IJS95/07635
14
Table 3
SHEAR STRENGTH
(MPa)
Average 1.23
Average 1 1.23
Std devn 0.1 1
Variance 0.0I
Acceptable NO
Average 1 Highest and lowest not included.
Two methods were employed to evaluate adhesion strength, namely a T-peel test
10. and a Lap shear test (ASTM test method)
T-Peel Test ~'ASTM D 1876-92):
Polymer strips {300mm width x 26mm length and 2mm thickness) were glued
along - 22cm of the length thereof. After curing the joints were evaluated
using
an lnstron 4465 tensometer with a 5000N load cell and a crosshead speed of
200mm/min. The peel strength was obtained from the average peel force over the
central 20cm of pees.
Lao Shear Test~ASTM D 1002-72):
Polymer strips (26mmwith x 50mm length) were mounted onto roughened mild
steel platforms with Pro-Struct 30/71. The strips were masked with masking
tape
leaving l Omm available for testing. The physical overlap dimensions were 26mm
width x l Omm length. This procedure was used to eliminate any peel forces.
The
adhesion strength was evaluated using an Instron 4465 tensometer with a 5000N
Toad cell and a crosshead speed of 5mm/min.
CA 02192946 1996-12-13
WO 95!35341 219 2 9 4 6 PCT~S95/07635
MATERIALS USED
The material used was PE 300 HDPE in the form of tiles. PE300 is a GM 5010
based High Density Polyethylene (HDPE) which was obtained from Maizey
Plastics,
Pretoria, South Africa.
5 Example 5
OXYFLUOR,1_NATION COMPARED WITH FLUOR~IAT10N
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agenu
!d Prior to Activation TCE
.
Surface Area Activated 0.0312m2
:
Gas Mixture : a) lOkPa air, 40kPa F2/N2 mixture comprising
11.6% by volume F2
b) 40kPa FZ/N2 mixture comprising 11.6%
by
15 volume F2
Oxyfluorination Time
and Temperature . a) 30min at 50C
b) 3hrs at 50C
Hydrolysis technique . Exposure to moisture in air for 1 week
2o Test Method . L.ap Shear
Dimensions . length: 26mm, width: l0mm, glue-line thickness:
0.16mm
Resin . Pro-Swct 30/71
The resulu of the lap shear tesu conducted are set out in Table 4 below
CA 02192946 1996-12-13
1 ~2~4~~
16
Table 4: Results of the tests conducted Qn black PE 300 with oxvfluorination
and fluorination
Sample Number Lap Shear Strength
(MPa)
Oxyfluorination Fluorination
1 1 1.00 1.786
2 15.120 1.392.
3 9.788 1.464
4 Poor Glue-line Poor Giue-line
5 _ _
Average 1 1.97 1.547
As can be seen in Table 4, oxyfluorination has better adhesive properties than
fluorination on PE 300 with Pro-struct 30/71.
DEGREASING PRIOR TO ACTIVATION
Various contaminants that can influence activation as well as the
adhesion process may be present on the surface. It is desirable to clean the
surface
thoroughly prior to activation. Sample surfaces were degreased by wiping each
surface with a tissue properly wetted with a degreasing agent.
Examnie 6: CHOICE OF DEGREASING AGENT
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . a) Trichloro-ethylene {TCE),
AMENDED SHtET
IPEAfEP
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b) Methyl Ethyl Ketone (MEK),
c) Ethanol (EtOH),
d) Handy Andy (N/A) available from Lever
Industrial (Proprietary) Limited.
Drying Time Prior
to Activation . 24hrs
Surface Area Activated . 0.1248m2
Gas Mixwre . l OkPa air, 40kPa F2/N2 mixture comprising
15% by
volume F2
1Q Oxyfluorination Time
and Temperature . 30min at 50C
Hydrolysis technique . Immersion in water at room temperature
for 18hrs
Drying Time Prior to
Adhesion . 1 week
Test Method . T-Peel
Dimensions . length: 300mm, width: 2bmm, thickness:
2mm
Resin . Pro-Struct 30/71
The results of the peel tests conducted are set out in Table 5 below.
Table 5: Peel test results obtained for PE 300 with Pro-Struct 30/71 with
various
2o deereasin~ aeents prior to oxv-fluorination
Sample Peel Strength
(N/mm)
Number -
TCE MEK Ethanol Handy Andy
1 5.109 4.310 3.24b 3.750
2 4.704 3.210 3.738 4.0bb
Average 4.906 3.760 3.492 3.908
Degreasing with TCE prior to oxy-fluorination gave the best results. The four
particular degreasing agents were chosen as they cover a broad spectrum of
chemical
groups i.e. an alcohol, a ketone and a soap.
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EXAMPLE 7: DRYING TIME PRIOR TO OXY-FLUORINATION
The following experimental
conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . TCE
Drying Time Prior
to Activation . a) ~ 3 months
b) 24hrs
Surface Area Activated . 0.156m2
to Gas Mixture . l OkPa air, 40kPa F2/N2 mixture comprising
15.8%
by volume F2
Oxyfluorination Time
and Temperature . 30min at 50C
Hydrolysis technique . immersion in water at room temperature
for 18hrs
Drying Time Prior to
Adhesion . 72hrs
Test Method . T-Peel
Dimensions . length: 300mm; width: 26mm, thickness:
2mrr~
Resin . Pro-Struct 30/71
2o The results of the peel tests conducted are set out in Table 6 below.
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Tab a P I r 3 P S /71 a n
drvine time urior to oxv-fluorination
Sampfe Number Peel Strength
(N/mm)
3 Manths 24hrs
g 1 0.8335 5.109
2 1.608 4.704
3 1.007 -
4 2.887 -
5 1.229
Average 1.513 4.906
Table b shows that a long drying time prior to activation (after degreasing)
caused
reduced peel strengths. It is believed that adverse effects arising from
additive
migration from the bulk of the polymer to the surface are reduced by the
degreasing
step, the degreasing step thus resulting in more effective oxyfluorination.
Without
the degreasing, additive on the surface can be fluorinated or oxyfluorinated,
instead
of the bulk polymer, and this is undesirable.
EXAMPLE 8: CHOICE OF OXYFLUORINAT10N METHOD
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . MEK
Drying Time Prior
to Activation . 24hrs
Surface Area Activated . O.Ob24m2
Gas Mixture . a) F2/02:- 57kPa of a F2/02 mixture comprising
10% by volume F2
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b) F2/N2 + Air : 50kPa air, 7kPa F2/N2
mixture comprising 15.8% by volume F2, the
total mixture of air, F2 and N2 comprising
10% by volume F2
5 c) 10-40 :- lOkPa air, 40kPa F2/N2 rnix~xture
comprising 15.8% by volume F2
Oxyfluorination Time
and Temperature . 30min at 50°C
Hydrolysis technique . Immersion in 0.48N solution of Hydrochloric Acid
l0 (HC!) for l8hrs
Drying Time Prior
to Adhesion . 24hrs after rinsing with distilled water
Test Method . T-Pee!
Dimensions , length: 300mm, width: 26mm, thickness: 2mm
15 Resin . Pro-Struct 30/71
The results of the peel tests conducted are set out in Table 7 below.
Table 7: Peel test results obtained for PE 300 with Pro-Struct 30/71 with
various
oxyfluorination methods
OxyfluorinationPeel strength
(N/mm)
2o Method ~""'
1 2 Average
a) F2/02 2.192 1.665 1.929
b) F2/N2 + Air 1.543 0.9083 1.226
c) 10-40 4.303 2.954 3.658
The 10-40 condition yielded the best peel strengths when combined with the
degreasing, hydrolysis and drying steps described in Example 8.
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EXAMPLE 9: ACTtV~TION TIME
The following experimental conditions were employed:
Example 9A: Activation
Time Studv usine F2/02
Material . Black HDPE (PE 300)
Degreasing Agenu
Prior to Activation . TCE
Surface Area Activated . 0.156m2
Gas Mixture . 50.9kPa F2/02 mixwre comprising 10%
by volume
F2
to Oxyfluorination Time
and Temperature . 2min, l Omin, 20min and 30min at 50C
Hydrolysis technique . Immersion in water at 50C for 18hrs
Drying Time Prior
to Adhesion . 1 hr at 50C followed by 24hrs at room
temperature
Test Method . T-Peel
Dimensions . length: 300mm, width: 2bmm, thickness:
2mm
Resin . Pro-Struct 30/71
The resulu of the peel tesu conducted are set out in Table 8 below:
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Table 8: Peel stren s obtained for PE 300 with Pro-Struct 30/71 with various
oxvfluorination times
Sample Peel Strength
(N/mm)
Number
2 min 10 min 20 min 30 min
1 3.7909 6.904 8.7309 6.268
2 1.553 6.123 7.311 7.5597
3 5.413 5.393 7.2613 8.235
4 2.951 8.461 7.3083 9.2347
- 6.8838
5
Average 3.4063 6.75296 7.6526 7.8248
The data in Table 8 are illustrated in Figure 2.
As can be seen in Figure 2, the peel strength reaches a plateau after about
15min
of oxyfluorination. It appears that 20 - 30 min is the preferred
oxyfluorination time
for PE 300 with Pro-Struct 30/71 under these hydrolysis conditions.
Examale 9B: Reaction Time Study usine the 10-40 Oxyfluorination Method
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . TCE
Drying Time Prior
to Activation . 24hrs
Surface Area Activated . 0.0624m2
Gas Mixture . l OkPa air, 40kPa F2/N2 mixture comprising 15.8%
by volume F2
Oxyfluorination Time
and Temperature . 1 min, 15min and 30min at 50°C
Hydrolysis technique . Immersion in water at room temperature for 18hrs
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Drying Time Prior
to Adhesion . 1 week
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness: 2mm
Resin . Pro-Swct 30/71
The results of the peel tests conducted are set out In Table 9 below.
Table 9: Peel test results of PE 300 with Pro-Stnlct 30/71 with varvin~
oxyfluorination times
Sample Number Peel Strength
(N/mm)
1Q 1 min 15 min 30min
1 1.457 4.385 5.109
2 0.9284 4.847 4.704
Average 1.1920 4.61 b 4.90b
Table 9 shows that the longer the oxyfluorination time, the better the
adhesion
with Pro-Struct 30/71. There is however a cut off time where adhesion
decreases
due to the formation of a weak boundary layer within the polymer. In such
cases,
a thin layer of the polymer breaks from the bulk. it appears that it is not
the
adhesive-polymer interface that fails. This phenomenon is illustrated in
Example ~9C
below.
EXAMPLE 9C: Excessive Reaction Time Investigation
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . TCE
Drying Time Prior
to Activation . 1 month
Surface Area Activated . 0.156m2
Gas Mixture . 50.9k1'a (;2/02 mixture comprising 10% by volume
F2
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Oxyfluorination Time
and Temperature . 25hrs at 50°C
Hydrolysis technique . Immersion in water at 50°C for 18hrs
Drying Time Prior
to Adhesion . 24hrs
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness 2mm
Resin . Pro-Struct 30/71
The results of the peel tests conducted are set out in Table 10 below:
Table 10: Peel strengths obtained on over activated PE 300
Sample Number Peel Strength (N/mm)
1 0.5715
2 1.3860
3 -
4 -
5 _
Average 0.9788
As can be seen in Table 10, peel strength decreased when the surface was
over- activated. The resin within the joints was black after peeling,
indicating a weak
boundary layer. Only two values are shown since the other three samples gave
no
peel measurements.
EXAMPLE 10: SUBSTRATE AND SURI'AC~ AREA ACTIVATED
The following experimental conditions were employed:
Example 10A: Adhesion Tests
Material . Black and Natural HDPE (PE 300)
AMENDED SHEET
IPEAfEP
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Degreasing Agenu
Prior to Activation . TCE
Surface Area Activated . 0.0936m2 and 0.156m2
Gas Mixture . 1 OkPa air, 40kPa F21N2 mixture comprising 1 1.6%
by volume F2
Oxyfluorination Time
and Temperature . 30min at 50°C
Hydrolysis technique . Exposure to moisture in air for 1 week
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness: 2mm
1o Resin . Pro-Struct 30/71
The resulu of the peel tests conducted on natural and black PE 300 are set out
in Table 11 below.
Table 11: Results of the peel tesu on black and natural PE 300 for different
activated surface areas
15 Sample 0.0936m2 0.156m2
Number Peel Peel
Strength(N/mm) Suength(N/mm)
Black Natural Black Natural
1 3.74 2.808 2.224 1.941
2 4.422 4.104 2.837 1.828
20 3 2.541 3.665 2.519 2.195
4 - - 2.604 Poor Glue-line
5 - - - 2.195
Average 3.568 3.525 2.546 2.039
From Table 11 it can be seen that black PE 300 gives slightly higher peel
strengths
25 than natural PE 300. Higher peel strengths were obtained as the activated
surface
area decreased. This was expected for fluorination reactions since the same
amount
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of fluorine was used inrespective of the area treated which reduced activation
on
larger treated surface areas. With oxyfluorination this was not expected since
the
reaction did not proceed to completion within 30min as oxyfluorination
reactions
are usually very slow (and appear to be inhibited by the presence of oxygen)
Example 108: Kinetics Studv
Material . Black and Natural HDPE (PE 300)
Gas Mixture . F2/02 comprising 10% by volume F2
Dimensions . length: Smm, width: 5mm, thidmess: 2mm (0.9cm2)
Change of mass was monitored using a Perkin Elmer TG2 for a period of 1 hr
1Q l0min (70min). The sampling frequency was 0.2Hz under isothermal conditions
at 50°C.
The results of the kinetic studies on black and natural PE 300 are set out in
Figure
3.
As can be seen in Figure 3, black PE 300 oxyfluorinates faster than natural PE
300 for times under 60min. At 60min, both substrate surfaces reacted at the
same
rate. Natural PE 300 reacted faster at times longer than 60min than black PE
300
did. The mass changes were 0.02mg/cm2 and 0.013mg/cm2 for black and natural
PE 300 respectively at typical oxy-fluorination times used in adhesion
studies, eg
30min. It is believed that the reason why natural PE 300 has lower adhesion
2Q properties than black PE 300 (Table 8 ) is that natural PE 300
oxyfluorinates far
slower at times of 30min and therefore has a lower degree of activation.
HYDROLYSIS OF ACTIVATED POLYMER SURFACE
On oxyfluorination of HDPE carboxylic acid, aryl fluoride and fluorocarbon
groups
are formed on the surface. During hydrolysis the acyl fluoride groups are
converted
into carboxylic acid groups which it is believed act as a curing agent for
epoxy resins,
ie a chemical bond is actually formed between the HDPE and the epoxy resin.
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EXAMPLE 11: CHOICE OF HYDRO~MEDIUM
Example 11 A: Hvdrolvsis Medium Studv on HDPE acthrated using F2/02-
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . TCE
Surface Area Activated . 0.156m2
Gas Mixture . 50.9kPa F2/O2 mixture comprising 10% by volume
F2
Oxyfluorination Time
1o and Temperature . 30min at 50°C
Hydrolysis technique . a) No hydrolysis
b) Immersion in 0.1 M Sodium Hydroxide (NaOH)
at 50°C for Smin
c) Immersion in water at 50°C for 18hrs
Drying Time after
Hydrolysis . 1 hrs at 50°C followed by 24hrs at room temperature
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness: 2mm
Resin . Pro-Swct 30/71
2o The results of the pees tests conducted are set out in Table 12 below:
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Table 12: Peel stren hs obtained on PE 300 with Pro-Struct 30/71 usine
different hydrolysis mediums
Sample Peel Strength
(N/mm)
Number
No HydrolysisNaOH Hot Water
1 0.6959 ~ ~ 6.268
2 0.7800 - 7.5599
3 1.34b W 8.235
4 1.704 - 9.2347
l0 5 ~ ~ ~ '
Average 1.131 ~ ~ 7.848
a
From the results in Table 12, it appears that a hydrolysis step is necessary
and that
the correct choice of hydrolysis medium is very important. It can be concluded
from the above results that aryl fluoride groups on the polymer surface do not
enhance the adhesion but actually decrease the adhesion properties with Pro-
Struct
30/71.
No values for the samples hydrolysed in NaOH could be measured thus indir~ting
that the NaOH treatment weakened the bond dramatically. With the NaOH
treatment, hydrolysis did initlatly occur but due to a large excess of base in
the
2o system, deprotonation of the carboxylic acid group followed yielding an
ionic salt on
the surface.
Example 1 1 B: Hydrolvsis Medium Studv on HDPE Activated usine~ the 10-40
Oxyfluorination Method
Material . Black HDPE (PE 300)
Degreasing Agents
Prior to Activation . TCE
Drying Time Prior
to Activation . 24hrs
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Surface Area Activated : 0. l 5bm2
Gas Mixture . lOkPa air, 40kPa F2/N2 mixture comprising 11.6%
by volume F2
Oxyfluorination Time
and Temperature : 30min at 50°C
Hydrolysis technique : a) Exposure to moisture in air for 1 week
b) Immersion in 0.48N HCI for l8hrs
Drying Time after
Hydrolysis . 24hrs
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness: 2mm
Resin . Pro-Struct 30/71
The results of the peel tests conducted are set out in Table 13 below.
Table 13: Peel strengths obt~~~)ned on PE 300 with Pro-Struct 30/71 using
different hvdrolvsis media
Sample Number Peel Strength
(N/mm)
Air HCI
1 2.224 4.67
2 2.837 2.674
2d 3 2.519 2.5420
4 2.b04 3.584
5 - 3.047
Average 2.546 3.299
Similar increases in peel strength as for the HCI hydrolysis had been
previously
witnessed with water. !t appeared to be better to hydrolyse the surface with a
wet
process than with air for adhesion with Pro-Struct 30/71. Water gave the best
results.
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Examule 12: DRYING TIME AFTER HYDROLYSIS
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agents
5 Prior to Activation . TCE
Drying Time Prior
to Activation . 24hrs
Surface Area Activated . 0.156m2
Gas Mixture , 50.9kPa F2/02 mixture comprising 10%
by volume
to fit
Oxylluorination Time
and Temperature . 30min at 50C
Hydrolysis technique . Immersion in water at 50C for 18hrs
Drying Time after
15 Hydrolysis . 1 hr
Test Method . T-Peel
Dimensions . length: 300mm, width: 26mm, thickness
2mm
Resin . Pro-Sttuct 30/71
The results of the peel tests conducted are set out in Table 14 below.
2o Table 14: Peel streneths obtained on PE 300 with Pro-Struct 30/71 after a
dOrin~ time of 1 hr
Sample Number Peel Strength (N/mm)
1 0.8950
2 1.340
25 3 2.057
4 1.224
5 ~
Average ~ 1.379
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On comparison between the results in Example 1 1 A (peel strengths of 7.8
N/mm were obtained on dry samples) it can be seen that it is undesirable to
use Pro-
Struct 30/71 on a wet substrate. It is important that the polymer is properly
dried
prior to adhesion.
DEGREASING AFTER ACTIVATION PR10R TO ADHESION
Once the surface of a polyolefin component has been activated, subsequent
handling can contaminate the surface rendering it relatively inactive towards
adhesion. A further cleaning step can therefore be an important step to
promote
the adhesion properties of the activated surface.
During transportation of activated HDPE sheets to a user, the sheets may
become contaminated. The contamination may be due to dust as well as fats and
oils as a result of handling of the sheets. Since dirt on the surface of the
HDPE sheet
will interfere with the adhesion it is important to elean the sheet prior to
gluing.
EXAMPLE 13:
The following experimental conditions were employed:
Material . Black HDPE (PE 300)
Degreasing Agents Prior
to Activation . TCE
Drying Time Prior to
Activation . 24hrs
Gas Mixture . l OkPa air, 40kPa F2/N2 mixture
comprisingl 1.6% by volume F2
Oxyfluorination Time
and Temperature . 30min at 50°C
Hydrolysis technique . Exposure to moisture in air for 1
week
Degreasing Agents
Prior to Adhesion . a) TCE
b) Acetone
AMENDED SHEET
IPEAfFP
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c) Ethanol
d) MEK
e) Xylene
Drying Time Prior
to Adhesion . 3hrs
Test Method : Lap Shear
Dimensions : length: 26mm, width: l0mm, glue-line thickness:
0.16mm
Resin : Pro-Struct 30/71
l0. The results of the lap shear tests ace set out in Table 15 below.
Table 15: h r v ob l d fo P ea ed ith vari s
deereasina aeents prior to adhesion
Sample Lap Shear
Strength
(MPa)
Number
~n~"ol
TCE
Acetone
Ethanol
MEK
Xylene
1 11.21 b.331 10.42 4.b73 4.950 5.346
2 10.14 10.71 10.62 6:481 6.054 8.796
3 10.9 8.438 Platform5.585 6.0b8 4.262
Failure
4 Poor 8.188 Platform8.bb9 5.012 9.385
Glue- Failure
line
5 Poor Poor Platform4.946 7.792 Platform
Glue- Glue- Failure Failure
line line
Average 10.75 8.41 10.52 b.071 6.083 6.947
b
As can be seen from Table 15, degreasing of the surface prior to gluing made a
difference to adhesion strength. Acetone appeared to be the best degreasing
agent
for this particular system, i.e. black PE 300 and Pro-Snvct 30/71, as the
shear
3o strength was practically the same as the control samples.
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It must be stressed that these results showed only an interaction with the
surtace
and the resin and do not necessarily give similar results when used together
with peel
tests. However, it can be seen that degreasing prior to adhesion with Pro-
Struct
30/71 is not recommended.
It is an advantage of the invention that it provides a method of protecting a
cemendtious or metal substrate component, eg against corrosion, corrosive. or
aggressive chemicals or the like, using a pofyofefin cladding, which does not
involve
mechanical securing methods. It is a further advantage that the invention
provides
a method of strengthening a polyolefin substrate component, using a metal
cladding,
to which similarly does not involve mechanical securing methods.
