Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HIGH-SPEED PULTRUSION POLYESTER RESINS AND PROCESS
Background of the InYention
This invention relates generall~ to a process for producing rein-
forced polyester products employing a pultrusion process and to polyester
resin compositions used therein. More particularly, it is directed to a
pultrusion process that is run at significantly greater pulling or running
speeds, and to particular new polyester resin compositions that make possible
the use of such higher speeds.
Pultrusion is a newer process of producing reinforced plastic prod-
ucts than are molding or hand-lay-up methods having its origin in the fifties.
lo Generally, the term "pultrusion" is used to describe any process of producing
reinforced plastics in which continuous reinforcing material is impregnated
with resin and pulled through a die of desired cross section to shape and cure
the resin and produce continuous lengths of cured product having a uniform
cross section and the shape of the die. Thermosetting-type resins are used
almost exclusively at the present time with polyester resins comprising 85 to
90 percent of the total and expoxies the rest.
In pultrusion, the reinforcing material may be any filamentary mate-
rial having strength, such as glass fiber, Aramid fibers, boron fibers or
graphite fibers. Bustomarily, E-glass fibers constltute the majority of
20 reinforcing material used. Most commonly, filamentary reinforcing materials
are used in the forms of: rovings, tows, mats, or cloth, or combinations of
these forms.
Because pultrusion incorporates continuous strands of reinforcing
material, it produces a product much stronger and flexible than those produced
by older extrusion processes, which can only utilize discontinuous lengths of
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~reinforcing f lement material, Beceuse of these characteristlcs, whenever
high~strength products having the customary properties of polyester resins are
desired, such as Corrosion resistanCe, electrical resistance or lightweight,
then pultrusion will be used. The sizes and shapes of products, either solid
or hollow, produced by pultrusion is virtually unlimited, as for example, I-
beams, channel "Yide-flange beams, solid bars and rods, round and square
tubing, rectangular beams, an91es, and eVen flat sheets. Customarily, the
thickness of these parts can range from as little as 1/8 inch up to a practi-
l cal maximunl of about three inches.
10 ¦ Ini-tially, pultrusion did not grow rapidly because it WdS costly and
was limited to products With small cross-sectional areas. During the 1950's,
however, radio frequency (RF) preheating was developed, which permitted faster
line speeds and larger cross-sectional products to be made. However, even
with RF-augmented heating, there is a prac-tical limit to pultrusion speed
beyond which puliruded parts exhibit either internal -thermocracking due to
excessive exotherm or external or internal cracking due to undercuring and
monomer gaSsing. Typically, products having a thickness of about 0.25-0.375
inch made with relatively fast-curing polyester resins can be pultruded at a
l maximum speed of about 8 to 9 feet per minute With fairly smooth surfaces;
¦ products having a -thickness of about 0.375 to 0.675 inch made With an inter-
¦ mediate reactivity resin can be pultruded at speeds up to 6 feet per minute
¦ with only mildly abraded surfacesi while thick products over 0.67 inches in
¦ thickness and made with mediuM reactivity resins are limited to speeds of
about 0.5-5 feet maximum depending on thickness and have pronounced surface
abrasion and roughness. Additionally, because of the thermal cracking that
occurs when the curing exotherm is excessive, thick parts generally can only
be made With medium reaCtiVity resins having a maximum degree of unsaturation
of about 50 to 55 mole percent of the total diacids (100 mole percent) em-
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ployed in producing the resin. Because of their limited reactivity, these
resins tend to sive softer cured surfaces that are more prone to be abraded in
~the die and to give products having rough, uneven surfaces.
Summary of the Invent~on
Accordingly, it is an objec-t of the present invention to provide new
polyester resin composition for pultrusion which either do not have or have to
a lesser degree the deficiencies of presently-used polyester resins. More
particularly, it is an object of this invention to provide polyester resin
compositions that can be pultruded more rapidly, thus Making possible higher-
o productivity pultrusion processes.
¦ A further object is the provision of pultrusion polyester resins that ;-
not only pultrude faster but also give pultruded products having smoother
surfaces and diminished occurence of internal and/or external cracks.
Thes~ and other objects and advantages, which will become apparent
from the following description and claims, are obtained with polyester resin
compositions containing ~-10 parts of particular cellulose acetate butyrate
resins per 100 parts of particular polyester resins, as hereinafter more fully
described. Such compositions can be pultruded at greater speeds to give
products having diminished sur~ace roughness and internal and/or external
20 cracking. Additionally, certain of these compositions have been found to glve
bulk or sheet molding compositions capable of producing thick moldings that
are crack-free.
Description of the Preferred Embodiments
In the following description and claims:
(a) All parts, phr (parts per hundred of resin), and percentages are
calculated and expressed on a weight basis;
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(b) The term "polyester" refers to d polymerizable unsaturated alkyd
resin formed by the condensation of diacid(s) and glycol(s)
hereinafter described;
(c) The term "polyester resin" refers to a stable homogeneous solu-
tion of the polyester and monomer(s), ~ereinafter described,
copo1ymerizable with the polyester; and
(d) The term "pultrusion (or invention) polyester resin" refers to a
stable homogeneous solution formed by dissolving into the poly-
ester resin a cellulose acetate butyrate resin useful in the
lO ¦ invention process, as hereinafter described.
Polyesters employed in the invention polyester resins are the conden-
sa-tion products of one or more dicarboxylic acids and/or anhydrides (100 moles
%) with a slight excess of one or more glycols (about 105-110 mole %), chosen
¦ to provide a polyester, ~ich, when combined with the vinyl monomers, herein- ~-
after described, and cured, give a Barcol hardness of about 45 or greater, as
determined by ASTM test method, D 2583-75 employing a 0.125 inch-thick cured
clear casting. For the polyester to provide this hardness and the reactivity ;
necessary for the invention process, at least about 60 mole percent of the
total dicarboxylic acids (and/or anhydrides) used to make the resin should be
20 of the alpha, beta-unsaturated type, copolymerizable with the vinyl monomers.In some instances when high reactivity is desired, as for example when the
polyester resin is to be u-tilized with a large quantity of the CAB resin, 90-
100 mole percent of the dicarboxylic acids employed will be alpha, beta-
unsaturated. More typical, however, are polyesters made with about 65 to 85 ...
- mole percent unsaturation, with about 75-~0 mole percent being optimum.
Examples of alpha, beta-unsaturated acids that can be employed to
provide this unsaturation are: maleic, fumaric, chloromaleic, itaconic, and
like acids and/or anhydrides. The balance of any diacids or anhydrides em-
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ployed to modify the reactivity and properties of the polyester may be eithersaturated or of the non-alpha, beta-unsaturated type, and may be, for example,
phthalic, isophthalic, tetrahydrophthalic or tetrachlorophthalic acid, hexa-
chloroendomethylenetetrahydrophthalic acid or low-molecular-weight aliphatic
dicarboxylic acids, such as succinic, adiptic or diglycolic acid9 or their
anhydrides. As previously described, the degree of alpha, beta-unsaturation
and, hence, reactivity of the polyester and the modifying diacids should be
chosen so as to give a polyester resin having the desired Barcol hardness. In
this connection, it is known that the aliphatic diacids tend to impart soft-
ness and, therefore, must be used in minor amounts. Conversely, it is knownthat the aromatic diacids, such as the phthalic or the halophthalic acids,
impart hardness and can be used in larger quantities. When fire retardancy is
desired, a halogenated diacid, such as tetrachlorophthalic acid or anhydride
is used, or a non-alpha, beta-unsaturated acid, such as tetrahydrophthalic
acid is used and then halogenated after condensation.
Examples of suitable glycols that may be used are ethylene glycol,
propylene glycol, 1,4-butane diol, neopentyl glycol, 2,2-bis-(4-hydroxycyclo-
hexyl)-propanë and the adduc-t of two moles of propylene oxide with bisphenol
A. Polyether glycols, such as diethylene glycol and dipropylene glycol also
may be utilized but only in small quantities, because of their softening
effect on the polyester after cure. Similarly, it may be necessary to limit
the quantity of ethylene glycol in the polyester when the resin is to be
dissolved in large quantities of monomer, as for example 55 to 60 percent
i monomer, since ethylene glycol lowers the monomer solubility of the polyester.The molecular weight of the invention polyester is not narrowly
critical and varies typically between a~out 1500 and 3500 with an acid number
in the range of about 20 to 35.
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Lastly, in the invention polyester resin, either a single polyester
may be employed or a mixture of two or more polyesters may be employed such
that, after mixing, the combined total of the diacids and glycols present in
each will give a final polyester resin system having the desired Barcol hard-
ness and reactivity. An example of such a mixture is shown in Example 1.
Generally, such mixtures have the same physical properties as a single poly-
ester made with the same to-tal quantity and types of condensation reactants
used to make the two separate polyesters. The expression "polyester" used in
the claims is intended to cover such mixtures.
Polyesters giving especially high pultrusion speeds and pultruded
products with minimal or nO surface abrading or internal or external cracks,
and hence constituting one of the preferred embodiments of the pultrusion
polyester resins of this invention, are those having a styrene compatibility
of about 25% or less and an alpha, beta-unsaturation (-C=C-) equivalent weight
of about 200 to 275. Such polyesters are typically made by the condensation
of about 65 to 85 mole percent of a suitahle alpha, beta-unsaturated diacid
(usually maleic) and 15-35 mole percent of a suitable modifying diacid with a
slight excess (e.g. 105-llO mole percent) of suitable glycol(s) - the conden-
sation reactants being chosen to provide the polyester with this degree of
20 styrene compatibility. The definition and method of determining "styrene
compatibility" is given in U.S. 3,940j350, column 4, lines 3-50.
In addition, pultrusion polyester resins made with polyesters having
~ this degree of styrene compatibility and (-C=C-) equivalent weight have been
- discovered to give bulk and sheet molding compounds capable of being molded in
thick sections (0.67 inch and greater) without cracking.
The monomers used in the invention polyester resin are, most prefer-
ably, styrene or vinyl toluene or mixtures of the two employed in a quantlty
2 ~S ~30
of about 45 to 55 weight percent of the total weigh~ of the polyester resin.
In certain instances, as little as 40 percent or as much as 60 percent monomer
may be employed. Ho~YeYer, when less than about 45 percent mon~ner is used,
low-molecular-weight cellulose acetate butyrates, such as EAB 551-0.01, may be
required to give acceptably low resin viscosity. Alternatively, such low-
monon~er resins may be heated in the impregnation tank to reduce viscosity to
an acceptable level. This, of course, may require using catalysts having
higher activation temperatures to prevent premature gellation. Conversely,
more than about 55 percent monomer is usually only employed when physical
properties are not especially critical and lower cost is paramount. Typical-
ly, physical properties are maintained at high levels up to about 55 percent,
at which point they start to drop.
Generally, the quantity of mon~ner is determined by the viscosity
requirement of the intended pultrusion process, taking into consideration the
type and molecular weight of the polyester and cellulose acetate butyrate
being employed in the system--viscosity decreasing with increasing rnonomer.
In this connection, when the pultrusion composition is to be used for impreg-
nating roving or tows, viscosities in the range of 800 to 1500 centiposes
(cps) may be employed, with viscosities of 900 to 1000 cps generally being
20 1 preferred. With mat or fabric reinforcement, typical viscosities are of the
order of about 1500 to 2000 cps. Bearing in mind that the impregnating poly-
ester resin formulation can be compounded with varying amounts of filler, it
can be appreciated that the raw or neat polyester resin may typically bè made
to have a viscosity ranging ~rom about 500 to 2000 cps depending upon the type
- I and quantity of filler subsequently added.
~ hen other monomers are used to partially replace styrene and/or
vinyl toluene in the inventicin polyester resin, the type and quantity chosen
should be such that they give a polyester resin having a length to peak exo-
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thenn tLPE) not in excess of about 90 seconds when the resin is catalyzed ~lith
2 percent Percadox 16 (98 percent active bis-4-t butyl cyclohexyl peroxydicar-
bonate) and tested for reactivity in accordance with the Society of the
P~astic Industry (SPI) gel-time test. When very high reactivity resins are
desired, the LPE should not exceed about 70 seconds. Illustrative of other
monomers that may be employed are: divinyl benzene, for increased cured resin
hardness; vinyl acetate, for lower resin viscosity, and acrylate esters, for
improved light stability. Other monomers that might be considered for inclu-
sion in the polyester resin are, for example, alpha-methylstyrene, chlorosty-
rene, diallphthalate, and triallyphosphate. In addition to providing a poly-
ester resin having the aforedescribed reactivity (LPE), any replacement
monomers chosen should have in combination with the styrene and/or vinyl
toluene an acceptable degree of solvating properties for the polyester.
The invention pultrùsion polyester resin contains, per 100 parts of
the resin, 4 to 10 parts of a cellulose acetate butyrate resin (CAB) that is
soluble in the polyester resin to give a stable one-phase solution, which,
when cured in the neat form at a thickness of 0.125 inches, has a heteroge-
neous opaque appearance. CAB resins having these properties typically have an
average butyrate content of about 0.9 to 2.0 percent. Best results have been
obtained with CAB resins having a butyrate content of about 49 to 55 percent
by weight. Further, to obtain pultrusion polyester resins that are not exces-
sively VlSCOUS, it is preferred to employ CAB's having a viscosity not exceed-
ing about 5 seconds, as determined by ASTM test method, D 817-65 (Formula A),
and D 1343-56. Most preferred are CAB resins having a viscosity of one second
or less. Cellulose acetate butyrate resins having these characteristics are
available from Eastman Kodak under the following designations: CAB-551-0.01,
-0.1, -0.1, -0.2 and -1; CAB-500-5; and CAB-451-1. If desired, mixtures of
suitable CAB reins may be used. Also, there could be used, if available,
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cellulose acetate pentoate or cellulose acetate or cellulose acetate hexoate
resins having the aforedescribed solubility and cured~compatibility character- ¦istics in the polyester resin.
t~hen less than abou-t four parts of CAB resin are employed, pultruded
products exhibit internal cracking and/or surface abrasion, ~hile more than
ten parts of CAB can ~ive viscosities too high for satisfactory pultrusion.
Too-high viscosities require the use oF monomers in quantities greater than
about 60 percent ~ere, as previously described, physical properties are
diminished. Most preferred are pultrusion polyester resins containing 5-~ phr
lo I of the CA resin.
¦ lypically, the amount of CAB resin added is adjusted to the reactiv-
ity of the polyester resin being employed in the pultrusion invention composi-
tions. For example, a polyester having high reactivity (i.e., one made with
95 to 100 mole percent of unsaturated acid) usually requires about 7 to 10
parts of CAB; a fairly high-reactivity resin (i.e., one made ~ith about 75
mole percent of unsaturated acid), about 5 to 8 parts of CAB; a polyester of
intermediate reactivity (i.e., one made with about 67 mo1e percent of unsatu-
rated acid), about 5 to 6 parts of CAB, while a low-reactivity polyester
(i.e., one made with about 60 mole percent of unsaturated acid), about 4 to 5
20 ¦ parts of CAB. Generally, the higher the unsaturated content of the polyester,
the grea-ter the cross-linking density and the peak exotherm temperature, and,
hence, the shrinkage of the polyester upon cure. Both factors contribute to
gross internal stresses, which result in internal cracking, and~ hence, pro-
portionally increasing amounts of CAB are required as the resin reactivity
increases to alleviate these effects.
^ The inven-tion polyes-ter resins utilized in the pultrusion invention
process are easily prepared by dissolving the cellulose acetate butyrate resin
in the polyester resin, by means known to those skilled in the art and then
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adding additional monomer, if required, to give the specification viscosity
desired. Alternatively, some of the monomer may be withheld from the poly-
ester resin to predissolve the CAB resin, with the resulting CAB solution then ¦being admixed with the polyester resin and the viscosity adjusted with addi-
tional monaner. If desired, solvation of the CAB resin can be accelerated by
heating the polyester resin or monolner to moderately elevated temperdtures,
such as 50 to 60C.
The invention pultrusion polyester resins are compounded into the
final pultrusion compositions used to impregnate the reinforcing material by
usual means and utilize the kinds and quantities of ingredients and adjuvants
typically used for polyester resins in this process.
Thus, the level of catalyst chosen is such that the pultrusion poly-
ester resin will be substantially fully cured during its residence time in the
pultrusion die, and typically will be about 0.75 to 1.25 phr3 with about 1 phr
most commonly being employed. Preferred are catalysts having a critical
temperature (or activation temperature) of about 120-145F, such as Percadox
16 (98 percent active bis-~-t~butylcyclohexyl peroxydicarbonate having a
critical tempèrature of about 120 to 122F) or Catalyst USP-245 (5-dimethyl-
hexane-2,5-diper 2-ethylhexoate having a critical temperature of about
145F). Catalysts having this range of activation temperatures allow the
pultrusion compound to be cured at lower temperatures which permits higher
pultrusion speeds and minimizes internal thermal cracking. Catalysts having
higher critical temperatures, however, mqy at times ~e used to advantage with
RF-augmented heating to give high pultrusion speeds, but generally are less
pre~erred because of the necessity of heating the resin-impregnated rein~orce-
ment to d temperdture within 40 to 50F of the critical temperature of the
catalyst. For example, temperatures of 100 to 120F may be needed when
benzoyl peroxide having a critical temperature of 160F is used. At these
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higher temperatures, monomer vapori~ation increases, changing the desired
ratio of polyester to monomer-in the resin system. Additionally, increased
monomer vapor in the air constitutes possible health and fire hazards to
people working in the vicinity of the pu1trusion machine. Particularly, fire
caused by sparking of the radio frequency heating equipment can be a threat
that must be guarded against.
Besides benzoyl peroxide, other catalysts having high critical tem
peratures, such as t-butyl perbenzoate having a critical temperdture of about
~ 200F, may be utilized, particularly in combination with catalysts having low
activation temperatures. Such combinations may be advantageous when higher
running speeds are to be utilized. Generally, undercuring due to insufficient
catalyst results in monomer gassing causing internal voids and/or surface
hairline cracks running for various lengths through the length of the pultru-
sion. '~hen observed, increasing the level of catalyst will increase the
degree of cure and eliminate these defects.
The kinds and quantities of other ingredients used in the pultrusion
compositions of the invention are conventional and like those used in standard
pultrusion colnpounds. Thus, fillers, such as calcium carbonate, clay and
hydrated alumina, may be utilized in quantities varying from 0 to 100 phr of
the pultrusion polyester resin, with the quantity being dictated primarily by
the viscosity of the initial pultrusion polyester resin and the final viscos-
ity required of the pultrusion composition for the intended use. Bearing this
in mind, typically about 0 to 25 phr filler will be employed for tows and
roving to give the desired 800-lS00 cps impregnation viscosity while about 10
_ to 100 phr filler will be required for mat and fabric pultrusion compositions
to give the desired 1500-2000 cps final viscosity. In addition to adjusting
viscosity, the use of fillers also reduces cost and further lowers cure
shrinkage of the pultrusion composition.
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¦ Similarly, inhibiters also are present in the invention resin compo-
sitions to prevent premature gelation of the resin during mdnufactue and
storage and subsequently during utilization in the pultrusion process. Illus-
trative of useful inhibiters utilized in quantities giving the desired gel
time according to standard industry practices are: hydroquinone, t-butyl
catechol, and di-t-butyl-p-creosol. Other inhibiters, either individually or
in combination, may alternatively be eMployed so long as the kinds and quanti-
ties are judiciously chosen to provide the desired SPI gel time, previously
described in connection with the mon~ners.
Lastly, the pultrusion compositions typically utilize standard mold
release agents in quantities (1-5 phr) promoting smooth extrusion and rninimal
die sticking. Exemplary of materials that may be used are: calcium or zinc
stearate, phosphate esters or very fine (1 micron) polyethylene powder.
In the invention process, any type of reinforcement may be utilized
that is customarily employed in standard pultrusion processes and includes
filamentary reinforcelnents in the Form of rovings, tows, mats, woven cloth and
the like, either singly or in various combinations. Glass fiber constitutes
the majority of reinforcement material used today and will be normally em-
ployed in the invention process. When special properties, such as higher
20 I strengths or lower weights, are desired, rnore esoteric reinforcements, such as
¦ Aramid, boron or graphite fibers may be used in any of the forms previouslydescribed. Conventionally, flat sheets are pultruded with mats or woven
cloths--often reinforced with longitudinal lengths of fiber or rovi-ng--in
quantities representing about 25 to 60 percent of the pultruded product, with
about 50 percent being most typical. When maximuM adhesion between fiber
reinforcement and pultrusion polyester resin is desired, che~ical coupling
agents are applied to the reinforcing material.
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Similarly the invention pultrusion polyester resin is pultruded in a
manner like the polyester of the prior art except for the pulling speed which
can be two to four times more rapid than the speeds used for polyesters of the
prior art. Ideally, pultrusion compounds employing the invention polyester
resins are pultruded through a heated die, usually 3-5 feet long, arbitrarily
divided for temperature sensing and control purposes into 4 zones. A typical
die temperature profile for pultruding a compound like that used in Example 1
is sho~ln in Table A, which shows the temperatures used as the pultruding speed
is increased.
o As can be seen fran Table A, the initial set point For the control
probe in Zone I should be 325F. Zone II can go up to 340F and Zone III to
400F. Zone IV should be greater than 250F before processing begins. As
line speed increases and the heat from the exotherm raises the die heat, the
control temperature in Zone I is incrementally lowered so as to keep Zone IV
greater than 300F, preferably 325F. An indication of too low die heat will
be the presence of internal voids. This is easily remedied by increasing the
control temperature 10-20F or lowering the radio frequency plate current so
as to reduce the resin temperature 5-10F. The speed and heat profiles shown
in Table A are for R.F.-augmented-cure pultrusion equipment, but are equally
applicable to thermal-only equipment, but at somewhat lower speeds.
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Example 1
A polyester resin ~Jas made by admixing together:
Polyester A 20.9%
Polyester B 23.8%
Styrene 55.3%
Total 100.0% -
¦Polyester A and polyester B and the mixture of the two c~nprised:
Polyester A Pollyester B Mixture
maleic anhydride (moles) 0.5 1.0 0.765
isophthalic acid (moles) 0.5 ' 0.235
propylene glycol (moles) 1.05 1.11 1.085
Properties
Styrene Compatibility 10% 40~ 25%
LPE (2% Percadox 16) 57 sec.
¦ (-c = c-) equivalent weight37.0 160 225
¦ Cured Barcol hardness 45 60 55
~ viscosity 500 cps
¦ A pultrusion polyester resin was then prepared by admixing and dis-
¦ solving into 100 parts of the polyester resin, 5.7 parts of Eastman Kodak's
j CAB-551-0.1 resin (cellulose acetate butyrate resin having about 55% b~tyl, 2%¦ acetyl and 1.6% hydroxyl average content). Finally, a pultrusion composition
having a viscosity of 1000 cps was prepared by homogeneously admixing: :~
Parts
.- pultrusion polyester resin 105.7
mold release agent (,phosphate ester) 1.06
catalyst USP-245 1.06
calcium carbonate fil`ler 10.6
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This compound was used to impregnate 66-end-count glass roving that
was subsequently pulled through a die producing a -flat bar, 1-1/2 inch x 1/4
¦ inch having bbed e~ges, utilizing the processing conditicn- shown in Table
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Example 2
A pultrusion polyester resin having.a viscosity of lO00 cps was
prepared by admixing and dissolving together first: I
Parts
Polyester of Example 1 47.6
Styrene 52.4
CAB-551-0.1 7.85
and then admixing into the resulting solution:
Parts
¦ mold release agent 1.08
. I catalyst USP-245 1.08
The resulting pultrusion composition was used to impregnate a 68-end-
count glass roving that was pulled through the same die as used in Example 1
¦ utilizing he processing cond~tions llown in 'able 2.
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The physical properties of the bars produced in Examples 1 and 2 are
given in Table 3, which also gives the properties of a one-inch diameter
pultruded bar made ~ith 69 percent glass roving and a polyester -typically used
for thick-pultruded products. All property values are in pounds per square
inch (psi).
TABLE 3
Typical
! Example 1 Example ? Prior Art
Flexural Strength 134,600 136,700 128,000
Flexural Modulus 5.6 x 106 6.1 x 106 5.3 x 106
Tensile Stren~th 131,200 125,700 154,000
Tensile Modulus 6.1 x 106 6.7 x 106 4.8 x 106
Compressive Strength 78,000 55,000 58,000
Compressive Modulus 5.9 x 106 6.8 x 106 3,5 x 105
From the data in Tables 1, 2 and 3, it is apparent that the invention
pultrusion resins can be pultruded at high speeds to give products having
smooth surfaces and no internal or external cracking. Additionally, the data
shows that the invention pol~ester resins give pultruded products having
superior physical properties as compared to products made with polyester
resins typically employed at the present time.
In production runs at two different pultrudersj a pultrusion poly-
ester resin like that of Example 1 was used to: a) increase the pultrusion
speed of a one-inch-diameter rod from 3 feet/minute to 6 feet/rninute, and b)
increase the pultrusion speed of a ~ammer handle frorn 8 inches/minutes to 36
inches/minute.
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