162476-2
THERMOPLASTIC WEAR RESISTANT COMPOSITIONS, METHODS OF
MANUFACTURE THEREOF AND ARTICLES CONTAINING THE SAME
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application Serial Number
60/629439, filed November 19, 2004.
BACKGROUND
This disclosure relates to thermoplastic wear resistant compositions, methods of
manufacture thereof and articles containing the same.
Machine components that are subjected to frictional forces generally use external
lubricants, such as oil or grease, to increase the wear resistance and reduce frictional
losses. However, such external lubricants often must be replaced periodically and
may be unevenly distributed over the wear surface, resulting in increased cost and
inefficiency of the machine components. In addition, external lubricants are often not
desirable, for example, in the areas of food processing or photocopying where product
contamination is a concern.
The need for external lubricants may be reduced or eliminated by the use of polymeric
machine components that contact each other. Polymeric components may be easily
and inexpensively manufactured by such processes as injection molding to form
intricately shaped components such as gears, cams, bearings, slides, ratchets, pumps,
electrical contacts and prostheses.
Polymeric contacting components provide an economical and essentially maintenance
free alternative to metallic or ceramic contacting components. Components formed
from polymeric compounds have reduced weight, enhanced corrosion protection,
decreased running noise, decreased maintenance and power use, and allow increased
freedom of component design over non-polymeric components. Internal lubricants,
such as polytetrafluoroeth, lene, graphite, molybdenum disulfide, and various oils and
reinforcing fibers may be included in polymeric components to enhance wear
resistance and decrease frictional losses. However, such internal lubricants are costly
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and increase the complexity and number of processing steps. In addition, polymeric
contacting components often undergo physical ageing with time and fracture because
of an inability to withstand impact forces encountered during operation. It is therefore
desirable to have polymeric contacting components which are wear resistant, impact
resistant and which are easy to manufacture using existing equipment.
SUMMARY
Disclosed herein is a composition comprising a polycarbonate resin; a polycarbonate-
polysiloxane copolymer; and an anhydride modified polyolefin.
Disclosed herein too is a composition comprising a blend of a polycarbonate resin
with a polycarbonate-polysiloxane copolymer; and an anhydride modified
polyethylene, wherein the composition has a wear factor of less than or equal to about
350 in5min/ftlb-hr and an impact strength of greater than or equal to about 500 joules
per meter and wherein the wear factor is measured according to the formula:
Wear Factor - [(6.1 x 108)(W)]/[(Px V) x (D) x (T)]
where P is the applied pressure in pounds per square inch and V is the velocity in feet
per minute, W is the weight loss in grams, D is the density in grams per cubic
centimeter and T represents 100 hours.
Disclosed herein too is a method comprising blending a polycarbonate resin, a
polycarbonate-polysiloxane copolymer, and an anhydride modified polyolefin to form
a thermoplastic composition, wherein a blend of the polycarbonate resin and the
polycarbonate-polysiloxane copolymer is either optically transparent or opaque.
DETAILED DESCRIPTION OF EMBODIMENTS
It is to be noted that as used herein, the terms "first," "second," and the like do not
denote any order or importance, but rather are used to distinguish one element from
another, and the terms "the", "a" and "an" do not denote a limitation of quantity, but
rather denote the presence of at least one of the referenced item. Furthermore, all
ranges disclosed herein arc inclusive of the endpoints and independently combinable.
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Disclosed herein is a wear resistant thermoplastic composition that comprises a
mixture of a polycarbonate, a polycarbonate-polysiloxane copolymer and an
anhydride-modified polyolcfin. The thermoplastic compositions display a high
impact strength and have higher crack propagation resistance over existing wear
resistant compositions. Articles manufactured from the thermoplastic composition
advantageously display impact strengths of greater than or equal to about 500
joules/meter at a temperature of-30°C and a wear resistance factor K of less than or
equal to about 350 in5min/ftlb-hr at room temperature. The thermoplastic
compositions can be advantageously used in a variety of high temperature
applications where large loads are applied.
The term "mixture" as described herein refers to the combination of polycarbonate,
polycarbonate-polysiloxane copolymers and modified polyolefins. The term blend as
described herein refers to the combination of polycarbonate with polycarbonate-
polysiloxane copolymers.
As used herein, the terms "polycarbonate", includes compositions having structural
units of the formula (I):

in which greater than or equal to about 60 percent of the total number of Ri groups are
aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic
radicals. In one embodiment, R1 is an aromatic organic radical of the formula (II):

wherein each of A1 and A2 is a monocyclic divalent aryl radical and Y| is a bridging
radical having zero, one, or two atoms which separate A1 from A2. In an exemplary
embodiment, one atom separates Ai from A2. Illustrative examples of the Y1 radicals
are -O-, -S-, -S(O)-, -S(O)2, -C(O)-, methylene, cyclohexyl-methylene,
2-[2,2,l]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene,
cyclohexylidene, cyclopentadecylidene, cyclododecylidene, adamantylidene, or the
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like. In another embodiment, zero atoms separate A1 from A2, with an illustrative
example being biphenyl. The bridging radical Y1 can be a saturated hydrocarbon
group such as methylene, cyclohexylidene or isopropylidene.
Polycarbonates may be produced by the Schotten-Bauman interfacial reaction of a
carbonate precursor with dihydroxy compounds. Typically, an aqueous base such as
sodium hydroxide, potassium hydroxide, calcium hydroxide, or the like, is mixed with
an organic, water immiscible solvent such as benzene, toluene, carbon disulfide,
chloro-benzene, chloroform or dichloromethane, which contains the dihydroxy
compound. A phase transfer agent is generally used to facilitate the reaction. As
carbonate precursor carbonyl hahdes are employed. An exemplary carbonyl halide is
carbonyl chloride (phosgene). Molecular weight regulators may be added either singly
or in admixture to the reactant mixture. Branching agents, described forthwith may
also be added singly or in admixture.
Polycarbonates can be produced by the interfacial reaction of dihydroxy compounds
in which only one atom separates A1 and A2. As used herein, the term "dihydroxy
compound" includes, for example, bisphenol compounds having general formula (III)
as follows:

4
wherein R and R each independently represent hydrogen, a halogen atom, or a
monovalent hydrocarbon group, p and q are each independently integers from 0 to 4,
and Xa represents one of the groups of formula (IV):


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wherein Rc and Rd each independently represent a hydrogen atom or a monovalent
linear or cyclic hydrocarbon group, and Re is a divalent hydrocarbon group, oxygen,
or sulfur.
Examples of the types of bisphenol compounds that may be represented by formula
(III) include the bis(hydroxyaryl)alkane series such as, l,l-bis(4-
hydroxyphenyl)methane, 1,1 -bis(4-hydroxyphenyl)ethane, 2,2-bis(4-
hydroxyphenyl)propane (or bisphenol-A), 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-
hydroxyphenyl)octane, l,l-bis(4-hydroxyphenyl)propane, l,l-bis(4-
hydroxyphenyl)n-butane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxy-l -
methylphenyl)propane, 1,1 -bis(4-h> Jroxy-t-butylphenyl)propane, 2,2-bis(4-hydroxy-
3-bromophenyl)propane, or the like; bis(hydroxyaryl)cycloalkane series such as, 1,1-
bis(4-hydroxyphenyl)cyclopcntane, l,l-bis(4-hydroxyphenyl)cyclohexane, or the like,
or combinations comprising at least one of the foregoing bisphenol compounds.
Other bisphenol compounds that may be represented by formula (III) include those
where X is -O-, -S-, -SO- or -S(O)2-. Some examples of such bisphenol compounds
are bis(hydroxyary])cthcrs such as 4,4'-dihydroxy diphenylether, 4,4'-dihydroxy-3,3'-
dimethylphenyl ether, or the like; bis(hydroxy diaryl)sulfides, such as 4,4'-dihydroxy
diphenyl sulfide, 4,4'-dihydroxy-3,3'-dimethyl diphenyl sulfide, or the like;
bis(hydroxy diaryl) sulfoxides, such as, 4,4'-dihydroxy diphenyl sulfoxides, 4,4'-
dihydroxy-3,3'-dimcthyl diphenyl sulfoxides, or the like; bis(hydroxy diaryl)sulfones,
such as 4,4'-dihydroxy diphenyl sulfone, 4,4'-dihydroxy-3,3'-dimethyl diphenyl
sulfone, or the like; or combinations comprising at least one of the foregoing
bisphenol compounds
5
Other bisphenol compounds that may be utilized in the polycondensation of
polycarbonate are represented by the formula (V)


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wherein, Rr, is a halogen atom or a hydrocarbon group having 1 to 10 carbon atoms or
a halogen substituted hydrocarbon group; n is a value from 0 to 4. When n is at least
2, Rf may be the same or different. Examples of bisphenol compounds that may be
represented by the formula (V), are resorcinol, substituted resorcinol compounds such
as 5-methyl resorcin, 5-ethyl resorcin, 5-propyl resorcin, 5-butyl resorcin, 5-t-butyl
resorcin, 5-phenyl resorcin, 5-cumyl resorcin, or the like; catechol, hydroquinone,
substituted hydroquinones, such as 3-methyl hydroquinone, 3-ethyl hydroquinone, 3-
propyl hydroquinone, 3-butyl hydroquinone, 3-t-butyl hydroquinone, 3-phenyl
hydroquinone, 3-cumyl hydroquinone, or the like; or combinations comprising at least
one of the foregoing bisphenol compounds.
Bisphenol compounds such as 2,2, 2', 2'- tetrahydro-3, 3, 3', 3'- tetramethyl-1, 1'-
spirobi-[IH-indene]-6, 6'- diol represented by the following formula (VI) may also be
used.

6
Suitable polycarbonates further include those derived from bisphenols containing
alkyl cyclohexane units. Such polycarbonates have structural units corresponding to
the formula (VII)


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wherein Ra-Rd in the formula (VII) are each independently hydrogen, C1-C12
hydrocarbyl, or halogen: and Re-R' in the formula (VII) are each independently
hydrogen, C1-C12 hydrocarbyl As used herein, "hydrocarbyl" refers to a residue that
contains only carbon and hydrogen. The residue may be aliphatic or aromatic,
straight-chain, cyclic, bicyclic, branched, saturated, or unsaturated. The hydrocarbyl
residue may contain heteroatoms over and above the carbon and hydrogen members
of the substituent residue. Thus, when specifically noted as containing such
heteroatoms, the hydrocarbyl residue may also contain carbonyl groups, amino
groups, hydroxyl groups, or the like, or it may contain heteroatoms within the
backbone of the hydrocarbyl residue. Alkyl cyclohexane containing bisphenols, for
example the reaction product of two moles of a phenol with one mole of a
hydrogenated isophorone, are useful for making polycarbonate polymer s with high
glass transition temperatures and high heat distortion temperatures. Such isophorone
bisphenol-containing polycarbonates have structural units corresponding to the
formula (VIII)

wherein Ra-Rd are as defined above in the formula (VII). These isophorone bisphenol
based polymers, including polycarbonate copolymers containing nonalkylcyclohexane
bisphenols and blends of alkyl cyclohexyl bisphenol containing polycarbonates with
nonalkyl-cyclohexyl bisphenol polycarbonates, are supplied by Bayer Co. under the
APEC trade name. An exemplary bisphenol compound is bisphenol A.
Examples of suitable carbonate precursors include the carbonyl halides, for example
carbonyl chloride (phosgene), and carbonyl bromide; the bis-haloformates, for
example the bis-haloformates of dihydroxy compounds such as bisphenol A,
hydroquinone, or the like, and the bis-haloformates of glycols such as ethylene glycol
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and neopentyl glycol; and the diary] carbonates, such as diphenyl carbonate, di(tolyl)
carbonate, and di(naphthyl) carbonate. An exemplary carbonate precursor for the
interfacial reaction is carbonyl chloride.
It is also possible to employ polycarbonates resulting from the polymerization of two
or more different dihydnc phenols or a copolymer of a dihydric phenol with a glycol
or with a hydroxy- or acid-terminated polyester or with a dibasic acid or with a
hydroxy acid or with an aliphatic diacid in the event a carbonate copolymer rather
than a homopolymer is desired for use. Generally, useful aliphatic diacids have about
2 to about 40 carbons An exemplary aliphatic diacid is dodecanedioic acid.
Branched polycarbonates, as well as blends of linear polycarbonate and a branched
polycarbonate may also be used in the composition. The branched polycarbonates
may be prepared by adding a branching agent during polymerization. These
branching agents may comprise polyfunctional organic compounds containing at least
three functional groups, which may be hydroxyl, carboxyl, carboxylic anhydride,
haloformyl, and combinations comprising at least one of the foregoing branching
agents. Specific examples include tnmellitic acid, trimellitic anhydride, trimellitic
trichloride, tris-p-hydroxy phenyl ethane, isatin-bis-phenol, tris-phenol TC (1,3,5-
tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA (4(4(1, l-bis(p-
hydroxyphenyl)-ethyl) a,a-dimethyl benzyl)phenol), 4-chloroformyl phthalic
anhydride, trimesic acid, benzophenone tetracarboxylic acid, or the like, or
combinations comprising at least one of the foregoing branching agents. The
branching agents may be added at a level of about 0.05 to about 4.0 weight percent
(wt%), based upon the total weight of the polycarbonate in a given layer.
In one embodiment, the polycarbonate may be produced by a melt polycondensation
reaction between a dihydroxy compound and a carbonic acid diester. Examples of the
carbonic acid diesters that may be utilized to produce the polycarbonates are diphenyl
carbonate, bis(2,4-dichlorophenyl)carbonate, bis(2,4,6-trichlorophenyl) carbonate,
bis(2-cyanophenyl) carbonate, bis(o-nitrophenyl) carbonate, ditolyl carbonate, m-
cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, diethyl carbonate,
dimethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, bis(o-
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methoxycarbonylpheny])carbonale, bis(o-ethoxycarbonylphenyl)carbonate, bis(o-
propoxycarbonylphenyl)carbonate, bis-ortho methoxy phenyl carbonate, bis(o-
butoxycarbonylphenyl)carbonate, bis(isobutoxycarbonylpheny))carbonate, o-
methoxycarbonylpheny]-o-ethoxycarbonylphenylcarbonate, bis o-(tert-
butoxycarbonylpheny])carbonatc, o-ethylphenyl-o-methoxycarbonylphenyl carbonate,
p-(tertbutylpheny])-o-(tcrt-butoxycarbonylphenyl)carbonate, bis-(ethyl salicyl)
carbonate (this is bis(o-ethoxycarbonylphenyl)carbonate etc), bis(-propyl salicyl)
carbonate, bis-butyl salicyl carbonate, bis- benzyl salicyl carbonate, bis-methyl 4-
chlorosalicyl carbonate or the like, or combinations comprising at least one of the
foregoing carbonic acid diesters. An exemplary carbonic acid diester is diphenyl
carbonate or bis(methyl salicyl) carbonate (BMSC).
The weight average molecular weight of the polycarbonate is about 3,000 to about
1,000,000 grams/mole (g/mole). In one embodiment, the polycarbonate has a
molecular weight of about 10,000 to about 100,000 g/mole. In another embodiment,
the polycarbonate has a molecular weight of about 15,000 to about 50,000 g/mole. In
yet another embodiment, the polycarbonate has a molecular weight of about 18,000 to
about 40,000 g/mole.
The polycarbonate polysiloxanc copolymers can be block copolymers, random
copolymers, star block copolymers or alternating copolymers. Exemplary
polycarbonate polysiloxane copolymers are block copolymers. The polycarbonate-
polysiloxane block copolymers comprise polycarbonate blocks having recurring units
represented by the formula (IX):

where R3 and R4 are each independently selected from hydrogen, hydrocarbyl or
halogen-substituted hydrocarbyl and polysiloxane blocks represented by the formula
(X):
9

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where R5 and R6 are each independently hydrogen, hydrocarbyl or halogen-
substituted hydrocarbyl, D is an integer of from about 10 to about 120, and Y is
hydrogen, hydrocarbyl, hydrocarboloxy or halogen. In one embodiment, the weight
percent of blocks of formula (IX) is from about 10 to about 96% of the copolymer and
the weight percentage of polysiloxane from the blocks of formula (X) is about 4 to
about 90%.
In one exemplary embodiment, R3 and R4 in the formula (IX) are methyl groups,
while R5 and R6 in formula (X) are methyl groups, D is an integer of about 40 to
about 60, while Y is mcthoxy.
The block copolymers are prepared by the reaction of a carbonate forming precursor
with a mixture of an aromatic dihydroxy compound of the formula (XI):

where R3 and R4 are as defined above; and a polysiloxane diol of the structure
depicted by the formula (XII):

where R5, R6, Y and D are as defined above.
The polysiloxane diols depicted in formula (IV) above as precursors of the siloxane
block may be characterized as bisphenolsiloxanes. The preparation of these
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bisphenolsiloxanes is accomplished by the addition of a polydiorganosiloxane (V) to a
phenol (VI) containing an alkenyl substituent, according to the reaction:

wherein R5, R6, Y and D are as defined above
In one embodiment, the polysiloxane diols of formula IV can be prepared by reacting
a hydrogen-terminated polydimethylsiloxane with an allylphenol in the presence of a
catalytic amount of chloroplatinic acid-alcohol complex at about 90° to about 115°C.
Exemplary polysiloxane blocks can also be prepared by addition of a hydrogen-
terminated polysiloxane to two molar equivalents of eugenol (4-allyl-2-
methoxyphenol) in a reaction catalyzed by platinum or its compounds. The
conversion of the bisphenolpolysiloxane (IV) and the bisphenol (III) to the block
copolymer may be conducted by interfacial polymerization processes for making
polycarbonates.
Although processes for manufacturing the copolymer may vary, an exemplary process
involves dissolving or dispersing the reactants in a suitable water immiscible solvent
medium and contacting the reactants with the carbonate precursor in the presence of a
phase transfer catalyst, such as a tertiary amine co-catalyst and an aqueous caustic
solution under controlled pH conditions. An exemplary process comprises a
phosgenation reaction where the carbonate precursor is phosgene. The temperature at
which the phosgenation reaction proceeds may vary from about 0°C to about 100°C.
Since the reaction is exothermic, the rate of phosgene addition may be used to control
the reaction temperature. Sufficient alkali metal hydroxide base can be utilized to
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raise and maintain the pH of the mixture. The base is added in an amount effective to
maintain the pH of the aqueous part of the reaction mixture in an amount of about 10
to about 12. The pH of the aqueous phase of the reaction mixture may also be
controlled by the gradual addition of caustic such as sodium hydroxide, using an
automatic pH controller.
A molecular weight regulator, i.e., a "chain stopper", may be added to the reactants
prior to or during the contacting of them with the carbonate precursor. Examples of
suitable molecular weight regulators are monohydric phenols such as phenol,
chroman-I, paratertiarybutylphenol, or the like, or a combination comprising at least
one of the foregoing molecular weight regulators. Exemplary water immiscible
solvents include methylene chloride, 1,2-dichloroethane, chlorobenzene, toluene or
the like, or a combination comprising at least one of the foregoing water immiscible
solvents.
The phosgenation reactions are generally completed within a period of from about ten
minutes to several hours. The reaction mixture should be agitated to enhance contact
between phases and thereby promote the rate of reaction. Prior to product resin
recovery, which can be achieved by techniques such as filtration, decantation and
centrifugation, chloroformate end groups are normally substantially eliminated.
When a phase transfer catalyst is used without a co-catalyst, the reaction mixture can
be agitated for a long period of time until the presence of chloroformates can no
longer be detected. Alternatively, the addition of an equivalent level of a phenolic
compound, based on the level of chloroformate, can be added at the end of the
reaction. The polycarbonate-polysiloxane copolymer can be a block copolymer that is
optically transparent or opaque.
The polycarbonate in the blend of polycarbonate and polycarbonate-polysiloxane
copolymer may be present in an amount of about 15 to about 85 weight percent
(wt%), based upon the weight of the blend. In one embodiment, the polycarbonate is
present in the blend in an amount of greater than or equal to about 30 wt%, based
upon the weight of the blend. In another embodiment, the polycarbonate is present in
the blend in an amount of greater than or equal to about 45 wt%, based upon the
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weight of the blend. In yet another embodiment, the polycarbonate is present in the
blend in an amount of greater than or equal to about 75 wt%, based upon the weight
of the blend.
The blend can be optically transparent or opaque. Exemplary blends of polycarbonate
with polycarbonate-polysiloxanc copolymer are commercially available from General
Electric Company as EXL1414® (an opaque blend) and EXRL0049® (a transparent
blend).
The polycarbonatc-polysiloxane copolymer is present in the thermoplastic
composition in an amount of about 15 to about 85 wt%, based upon the total weight
of the thermoplastic composition. In one embodiment, the polycarbonate-
polysiloxane copolymer is present in the thermoplastic composition in an amount of
about 20 to about 80 wt%, based upon the total weight of the thermoplastic
composition. In another embodiment, the polycarbonate-polysiloxane copolymer is
present in the thermoplastic composition in an amount of about 30 to about 70 wt%,
based upon the total weight of the thermoplastic composition.
The modified polyolefin resin can be any polyolefin to which an epoxy, a carboxyl,
or an acid anhydride group is reacted. Examples of suitable polyolefins are crystalline
polypropylene, crystalline propylcne-ethylene block or random copolymers, low
density polyethylene, high density polyethylene, linear low density polyethylene,
ultra-high molecular weight polyethylene, ethylene-propylene random copolymer,
ethylene-propylene-diene copolymer, or the like, or a combination comprising at least
one of the foregoing polyolefins. Exemplary polyolefin resins are low density
polyethylene, high density polyethylene, linear low density polyethylene, and the
ultra-high molecular weight polyethylene.
The modified polyolefin resin may be any polyolefin resin described in the above to
which an unsaturated monomer containing epoxy, carboxyl, or an acid anhydride
group is copolymerized. Examples of suitable epoxy-containing unsaturated
monomers include glycidyl methacrylate, butylglycidyl malate, butylglycidyl
fumarate, propylglycidyl malate, glycidyl acrylate, N-[4-(2,3-epoxypropoxy)-3,5-
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dimethylbenzyl]-acrylamide, or the like, or a combination comprising at least one of
the foregoing monomers. An exemplary epoxy-containing unsaturated monomer is
glycidyl methacrylate and N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylarnide
in view of its price and availability.
Exemplary carboxyl-containing unsaturated monomers include acrylic acid,
methacrylic acid, maleic acid, and the like. Exemplary unsaturated monomers
containing an acid anhydride group are maleic anhydride, itaconic anhydride,
citraconic anhydride, and the like. Among these, acrylic acid and maleic anhydride
are desirable in view of their reactivity and availability.
The unsaturated monomer containing epoxy, carboxyl, or an acid anhydride group
may be copolymcrizcd with the polyolefin resin by any desired means. Exemplary
means include melt kneading of the polyolefin resin and the unsaturated monomer in
a twin screw extruder, a Banbury mixer, a kneader or the like in the presence or
absence of a radical initiator, and copolymerization by the copresence of the monomer
constituting the polyolefin with the unsaturated monomer containing epoxy, carboxyl,
or acid anhydride. The content of the unsaturated monomer is about 0.01 to about 10
wt%, of the modified polyolefin resin. In one embodiment, the content of the
unsaturated monomer is about 0.1 to about 5 wt%, by weight of the modified
polyolefin resin. In one embodiment, the modified polyolefin resin is pre-
compounded with an cpsilon-amino-N-caproic acid prior to mixing with the blend of
the polycarbonate resin and the polycarbonate-polysiloxane copolymer.
The content of the modified polyolefin resin is about 0.5 to 60 wt%, of the
thermoplastic composition. In one embodiment, the content of the modified
polyolefin resin is about 1 to 30 wt%, of the thermoplastic composition. In another
embodiment, the content of the modified polyolefin resin is about 2 to 20 wt%, of the
thermoplastic composition.
When the modified polyolefin is mixed with the blend comprising polycarbonate and
polycarbonate-polysiloxane copolymer, the functionalized group covalently bonds to
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the polycarbonate. An exemplary modified polyethylene is commercially available
from DuPont is FUSABOND®.
The thermoplastic composition can also contain optional additives such as fibrous
fillers, mineral fillers, antioxidants, lubricants, surfactants, antistatic agents, flow
control agents, flow promoters, impact modifiers, nucleating agents, coupling agents,
flame retardants, and the like. Similarly, addition of pigments and dyes (inorganic
and organic) may also be used.
As used herein, "fibrous" fillers may therefore exist in the form of whiskers, needles,
rods, tubes, strands, elongated platelets, lamellar platelets, ellipsoids, micro fibers,
nanofibers and nanotubes, elongated fullerenes, and the like. Where such fillers exist
in aggregate form, an aggregate having an aspect ratio greater than 1 will also suffice
for the purpose of this invention. • Non-limiting examples of suitable fibrous fillers
include short inorganic fibers, including processed mineral fibers such as those
derived from blends comprising at least one of aluminum silicates, aluminum oxides,
magnesium oxides, and calcium sulfatc hemihydrate, boron fibers, ceramic fibers
such as silicon carbide, and fibers from mixed oxides of aluminum, boron and silicon
sold under the trade name NEXTEL® by 3M Co., St. Paul, MN, USA. Also included
among fibrous fillers are single crystal fibers or "whiskers" including silicon carbide,
alumina, boron carbide, iron, nickel, copper. Fibrous fillers such as glass fibers,
basalt fibers, including textile glass fibers and quartz may also be included.
Also included are natuial organic fibers including wood flour obtained by pulverizing
wood, and fibrous products such as cellulose, cotton, sisal, jute, cloth, hemp cloth,
felt, and natural cellulosic fabrics such as Kraft paper, cotton paper and glass fiber
containing paper, starch, cork flour, lignin, ground nut shells, com, rice grain husks,
or the like, or a combination comprising at least one of the foregoing.
In addition, organic reinforcing fibrous fillers and synthetic reinforcing fibers may be
used. This includes organic polymers capable of forming fibers such as polyethylene
terephthalate, polybutylene tercphthalate and other polyesters, polyarylates,
polyethylene, polyvin\lalcohol, polytetrafluoroethylene, acrylic resins, high tenacity
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fibers with high thermal stability including aromatic polyamides, polyaramid fibers
such as those commercially available from DuPont under the trade name KEVLAR®,
polybenzimidazole, polyimide fibers such as those available from Dow Chemical Co.
under the trade names POLYIMIDE 2080® and PBZ® fiber, polyphenylene sulfide,
polyether ether ketone, polyimide, polybenzoxazole, aromatic polyimides or
polyetherimides, and the like. Combinations of any of the foregoing fibers may also
be used.
Such reinforcing fillers may be provided in the form of monofilament or
multifilament fibers and can be used either alone or in combination with other types
of fiber, through, for example, co-weaving or core/sheath, side-by-side, orange-type
or matrix and fibril constructions, or by other methods of fiber manufacture.
Cowoven structures generally include glass fiber-carbon fiber, carbon fiber-aromatic
polyimide (aramid) fiber, and aromatic polyimide fiber-glass fiber. Fibrous fillers
may be supplied in the form of, for example, rovings, woven fibrous reinforcements,
such as 0-90 degree fabrics, non-woven fibrous reinforcements such as continuous
strand mat, chopped strand mat, tissues, papers and felts and 3-dimensionally woven
reinforcements, performs and braids.
Useful glass fibers can generally be formed from a fiberizable glass including those
fiberizable glasses referred to as "E-glass," "A-glass," "C-glass," "D-glass," "R-
glass," and "S-glass". Glass fibers obtained from E-glass derivatives may also be
used. Most reinforcement mats comprise glass fibers formed from E-glass and are
included in the thermoplastic compositions. Commercially produced glass fibers
generally having nominal filament diameters of greater than or equal to about 8
micrometers can be used in the thermoplastic compositions. It is desirable to use
glass fibers having filament diameters of less than or equal to about 35 micrometers.
In one embodiment, it is desirable to use glass fibers having filament diameters
having diameters of less than or equal to about 15 micrometers.
The filaments may be produced by steam or air blowing, flame blowing, and
mechanical pulling processes Exemplary filaments are made by mechanical pulling.
Fibers having an asymmetrical cross section may also be used in the thermoplastic
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composition. The glass fibers may also be sized or unsized. Sized glass fibers are
coated on at least a portion of their surfaces with a sizing composition selected for
compatibility with the thermoplastic polymers. The sizing composition facilitates
wet-out and wet-through of the matrix material upon the fiber strands and assists in
attaining desired physical properties in the thermoplastic composition.
In one embodiment, the glass fibers comprise glass strands that have been sized. In
preparing the sized glass fibers, a number of filaments can be formed simultaneously,
sized with a coating agent and then bundled into what is called a strand. Alternatively
the strand itself may be first formed of filaments and then sized. The amount of
sizing employed is generally an amount effective to bind the glass filaments into a
continuous strand and is generally greater than or equal to about 0.1 wt% based on the
total weight of the glass fibers in the strand. In one embodiment, the amount of sizing
is less than or equal to about 5 wt%, based upon the weight of the glass fibers. In
another embodiment, the amount of sizing is less than or equal to about 2 wt%, based
upon the weight of glass fibers. In yet another embodiment the amount of sizing is
about 1 wt%, based on the weight of the glass fibers.
In general, the amount of fibrous filler present in the thermoplastic composition can
be up to about 50 wt%. In one embodiment, the amount of fibrous filler present in the
thermoplastic composition can be up to about 20 wt%. .
Carbon nanotubes that can be used in the composition are single wall carbon
nanotubes (SWNTs), multiwall carbon nanotubes (MWNTs), or vapor grown carbon
fibers (VGCF). Single wall carbon nanotubes (SWNTs) used in the composition may
be produced by laser-evaporation of graphite, carbon arc synthesis or a high-pressure
carbon monoxide conversion process (H1PCO) process. These SWNTs generally
have a single wall comprising a graphene sheet with outer diameters of about 0.7 to
about 2.4 nanometers (nm). The SWNTs may comprise a mixture of metallic SWNTs
and semi-conducting SWNTs. Metallic SWNTs are those that display electrical
characteristics similar to metals, while the semi-conducting SWNTs are those that are
electrically semi-conducting. In order to minimize the quantity of SWNTs utilized in
the composition, it is generally desirable to have the composition comprise as large a
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fraction of metallic SWNTs as possible. SWNTs having aspect ratios of greater than
or equal to about 5 arc generally utilized in the compositions. While the SWNTs are
generally closed structures having hemispherical caps at each end of the respective
tubes, it is envisioned that SWNTs having a single open end or both open ends may
also be used. The SWNTs generally comprise a central portion, which is hollow, but
may be filled with amorphous carbon.
MWNTs derived from processes such as laser ablation and carbon arc synthesis, may
also be used in the compositions. MWNTs have at least two graphene layers bound
around an inner hollow core. Hemispherical caps generally close both ends of the
MWNTs, but it may desirable to use MWNTs having only one hemispherical cap or
MWNTs, which arc devoid of both caps. MWNTs generally have diameters of about
2 to about 50 nm. When MWNTs are used, it is desirable to have an average aspect
ratio greater than or equal to about 5. In one embodiment, the aspect ratio of the
MWNTs is greater than or equal to about 100, while in another embodiment, the
aspect ratio of the MWNTs is greater than or equal to about 1000.
Vapor grown carbon fibers (VGCF) may also be used in the composition. These are
generally manufactured in a chemical vapor deposition process. VGCF having "tree-
ring" or "fishbone" structures may be grown from hydrocarbons in the vapor phase, in
the presence of particulate metal catalysts at moderate temperatures, i.e., about 800 to
about 1500°C. In the "tree-ring" structure a multiplicity of substantially graphitic
sheets are coaxially arranged about the core. In the "fishbone" structure the fibers are
characterized by graphite layers extending from the axis of the hollow core.
VGCF having diameters of about 3.5 to about 2000 nanometers (nm) and aspect ratios
greater than or equal to about 5 may be used. When VGCF are used, diameters of
about 3.5 to about 500 nm arc desirable, with diameters of about 3.5 to about 100 nm
being more desirable, and diameters of about 3.5 to about 50 nm being most desirable.
It is also desirable for the VGCF to have average aspect ratios greater than or equal to
about 100. In one embodiment, the VGCF can have aspect ratios greater than or
equal to about 1000.
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Carbon nanotubes are generally used in amounts of about 0.001 to about 80 wt% of
the total weight of the thermoplastic composition when desirable. In one
embodiment, carbon nanotubes arc generally used in amounts of about 0.25 wt% to
about 30 wt%, based on the weight of the thermoplastic composition. In another
embodiment, carbon nanotubes are generally used in amounts of about 0.5 wt% to
about 10 wt%, based on the weight of the thermoplastic composition. In yet another
embodiment, carbon nunotubes are generally used in amounts of about 1 wt% to about
5 wt%, based on the weight of the thermoplastic composition.
Various types of conductive arbon fibers may also be used in the composition.
Carbon fibers are generally classified according to their diameter, morphology, and
degree of graphitization (morphology and degree of graphitization being interrelated).
These characteristics are presently determined by the method used to synthesize the
carbon fiber. For example, carbon fibers having diameters down to about 5
micrometers, and graphene ribbons parallel to the fiber axis (in radial, planar, or
circumferential arrangements) are produced commercially by pyrolysis of organic
precursors in fibrous form, including phenohes, polyacrylonitrile (PAN), or pitch.
The carbon fibers generally have a diameter of greater than or equal to about 1,000
nanometers (1 micrometer) to ;bout 30 micrometers. In one embodiment, the fibers
can have a diameter of about 2 to about 10 micrometers. In another embodiment, the
fibers can have a diameter of about 3 to about 8 micrometers.
In one embodiment, in one method of manufacturing the wear resistant composition,
an anhydride-modified polyolefin is mixed with a blend comprising polycarbonate
and polycarbonate-polysiloxane copolymer. The blending can be conducted in
solution or in the melt. An exemplary form of blending is melt blending.
Melt blending of the composition involves the use of shear force, extensional force,
compressive force, ultrasonic energy, electromagnetic energy, thermal energy or
combinations comprising at least one of the foregoing forces or forms of energy and is
conducted in processing equipment wherein the aforementioned forces are exerted by
a single screw, multiple screws, intermeshing co-rotating or counter rotating screws,
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non-intenneshing co-rotating or counter rotating screws, reciprocating screws, screws
with pins, barrels with pins, rolls, rams, helical rotors, or combinations comprising at
least one of the foregoing.
Melt blending involving the aforementioned forces may be conducted in machines
such as, single or multiple screw extruders. Buss kneader, Henschel, helicones, Ross
mixer, Banbury, roll mills, molding machines such as injection molding machines,
vacuum forming machines, blow molding machine, or then like, or combinations
comprising at least one of the foregoing machines. It is generally desirable during
melt or solution blending of the composition to impart a specific energy of about 0.01
to about 10 kilowatt-hour/kilogram (kwhr/kg) of the composition.
The thermoplastic compositions can be manufactured by a number of methods. In
one exemplary process, the thermoplastic polymers, the glass fibers, and additional
ingredients are compounded in an extruder and extruded to produce pellets. During
the extrusion, the anhydride-modified polyolefin, the blend of polycarbonate with
polycarbonate-polysiloxane copolymer and other optional ingredients are mixed with
each other under shear. The extrudate is pelletized and then injection molded to form
a wear resistant article. In another exemplary process, the thermoplastic composition
can also be mixed in a dry blending process (e.g., in a Henschel mixer) and directly
molded, e.g., by injection molding or any other suitable transfer molding technique. It
is desirable to have all of the components of the thermoplastic composition free from
water prior to extrusion and/oi molding.
In another exemplary method of manufacturing the thermoplastic composition, the
optional fibrous fillers can be masterbatched into the blend of the polycarbonate with
the polycarbonate-polysiloxane copolymer. The masterbatch may then be let down
with additional polymer that comprises the modified polyolefin during the extrusion
process or during a molding process to form the wear resistant thermoplastic
composition.
Exemplary extrusion temperatures are about 260 to about 310°C. The compounded
thermoplastic composition can be extruded into granules or pellets, cut into sheets or
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shaped into briquettes for further downstream processing. The composition can then
be molded in equipment generally employed for processing thermoplastic
compositions, e.g., an injection molding machine with cylinder temperatures of about
250 to about 300°C, and mold temperatures of about 50 to about 90°C.
Wear resistant thermoplastic compositions thus obtained display a number of
advantageous properties over other available wear resistant compositions. The wear
resistant thermoplastic compositions of the present disclosure display a useful
combination of high impact strength as well as a low wear factor. The wear resistant
thermoplastic composition displays a notched Izod impact strength of greater than or
equal to about 500 joules/meter at -30°C. In another embodiment, the wear resistant
thermoplastic composition displays a notched Izod impact strength of greater than or
equal to about 650 joules/meter at -30°C. In yet another embodiment, the wear
resistant thermoplastic composition displays a notched Izod impact strength of greater
than or equal to about 700 joules/meter at -30°C.
The wear resistant thermoplastic composition also displays a wear factor K of less
than or equal to about 350 in5min/ftlb-hr. The wear factor is based upon the weight
lost during the test. In one embodiment, the wear factor K is less than or equal to
about 200 in5min/ftlb-hr. In another embodiment, the wear factor K is less than or
equal to about 100 in5min/ftlb-hr. In another embodiment, the wear factor K is less
than or equal to about 80 in5min/ftlb-hr. In yet another embodiment, the wear factor
K is less than or equal to about 60 in^min/ftlb-hr.
The wear resistant thermoplastic compositions can be molded to have a smooth
surface finish. In one embodiment, the thermoplastic compositions can have a Class
A surface finish. When the thermoplastic composition comprises electrically
conductive fibrous fillers (e g., carbon fibers, carbon nanotubes, carbon black, or
combinations thereof) articles molded from the composition can have an electrical
volume resistivity of less than of equal to about 1012 ohm-cm. In one embodiment,
the thermoplastic composition can have an electrical volume resistivity of less than of
equal to about 108 ohm-cm. In another embodiment, the composition can have an
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electrical volume resistivity of less than of equal to about 105 ohm-cm. The
thermoplastic composition can also have a surface resistivity of less than or equal to
about 1012 ohm per square centimeter. In one embodiment, the thermoplastic
composition can also have a surface resistivity of less than or equal to about 108 ohm
per square centimeter. In another embodiment, the thermoplastic composition can
also have a surface resistivity of less than or equal to about 104 ohm per square
centimeter.
The composition is also flame retardant. In one embodiment, the composition can
have a UL-94 (Underwriters Laboratories) flame retardancy rating of V-0. In another
embodiment, the composition can have a UL-94 flame retardancy rating of V-l. In
another embodiment, the composition can have a UL-94 flame retardancy rating of V-
2. The composition displays a heat distortion temperature (HDT) of greater than or
equal to about 100°C. In one embodiment, the composition displays a heat distortion
temperature (HDT) of greater than or equal to about 120°C.
The wear resistant thermoplastic compositions can be manufactured into articles that
are subjected to high temperature applications where large dynamic loads are applied.
They can be advantageously used in automotive applications or in machines as gears,
cams, bearings, or as components where increased impact strength, wear resistance
and high crack propagation resistance are desirable.
The following examples, which are meant to be exemplary, not limiting, illustrate
compositions and methods for manufacturing the wear resistant thermoplastic
compositions described herein.
EXAMPLES
This example demonstrates the advantageous wear resistance and the impact
properties of a thermoplastic composition comprising polycarbonate, polycarbonate-
polysiloxane copolymer and anhydride-modified polyethylene. Two blends of
polycarbonate with polycarbonate-polysiloxane copolymer were used. They were
EXRL0049®, a transparent blend containing 17 wt% polycarbonate with 83 wt%
polycarbonate-polysiloxane copolymer and EXL1414® an opaque blend of 82.5 wt%
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polycarbonate with 17.5 wt% polycarbonate-polysiloxane copolymer. The respective
blends were mixed with a LUBR1LOY D EP® intermediate manufactured by LNP as
detailed below.
71.600 parts per hundred (phr) of FUSABOND MB226D®, a maleic anhydride
modified polyethylene commercially available from DuPont was pre-compounded
with 3.4 phr of A2504, an epsilon-amino-N-caproic acid commercially available from
Sigma Chemicals. The precompounding was conducted in a twin screw extruder. To
the precompound was added 25 phr of additional FUSABOND MB226D®. The
additional FUSABOND MB226D® was mixed with the precompound in a twin screw
extruder, to form the LUBRILOY D EP® intermediate. The extrusion is carried out at
a temperature of 240°C. The respective wear resistant thermoplastic compositions are
shown in the Table 1.
The respective components for the samples in Table 1 were extruded in a 37 mm
twin-screw extruder (ZSK-40®) manufactured by Krupp, Werner and Pfleiderer. The
twin screw extruder had a length to diameter ratio of 41. Table 1 shows the wear
resistant compositions obtained when the LUBRILOY D EP® intermediate was
extruded with either EXL1414® or with EXRL0049® Samples #1 and #2 in Table 1
are comparative compositions comprising only the blend of polycarbonate with the
polycarbonate-polysiloxane copolymer.
The compositions in Table 1 were extruded under the following conditions. The
extruder had 11 barrels or healing zones set at temperatures of 50°C, 100°C, 250°C,
290°C, 290°C, 290°C, 290°C, 290°C, 290°C, 290°C and 290°C. The die temperature
was set at 270°C. The extruder was run at 300 rpm. The extruder can be run at
speeds of 30 to 300 rpm. The extrusion rate was 30 kilograms per hour but greater
extrusion rates can also be used. The strand emanating from the extruder was
pelletized, dried and subjected to injection molding to manufacture the test parts. The
molding machine was a Cincinnati 220T. The amounts of each component employed
in the various compositions are shown in Tables 1. All components were added
directly in the extruder during extrusion.
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Following extrusion and injection molding, the samples were subjected to testing.
Tensile testing was conducted as per ASTM D 638. Impact testing was conducted as
per ASTM D 256. Flcxural testing was conducted as per ASTM D 790. The heat
distortion temperature (I IDT) test was conducted using a distortion force of 1.84 MPa
on samples having a thickness of 3.2 millimeters. Melt flow rate (MFR) was
conducted at 300°C using a shearing force of 1.2 kilograms.
The wear factor K was measured as per WI-0687 (which is a modified wear testing
method and is similar to ASTM D 3702-78). The standard test is conducted by
rotating a plastic thrust washer, at a specified speed and under a constant pressure,
against a steel wear ring counterface, which is held stationary. Variations of the
standard test include using alternate counterface materials, alternate counterface
surface finishes and testing at elevated temperatures. The applied pressure (psi) and
speed (feet per minute (fpm)) condition, when multiplied together, is known as the PV
(pressure-velocity) value for the test. The test is conducted by running the thrust
washer test specimen approximately 24 hours under the specified PV conditions, then
removing the specimen and measuring weight loss. From this weight loss value a
wear factor (K) can be calculated using following formula:
Wear Factor = [(6.1x108)(W)]/-(P x V) x (D) x (T)]
where W is the weight loss in grams. D is the density in grams per cubic centimeter, T
is the time in hours. The applied pressure P is 40 psi while the velocity is 50 fpm.
This procedure is repeated for approximately 100 hours and the wear factors for each
interval are averaged to yield an average wear factor (K) for the material.
Additionally, static and dynamic coefficients of friction (COF) are measured for each
interval. These COF \alucs are averaged over the length of the test to yield an
average static and dynamic coefficient of friction for the material. All test results are
shown in Table 1.
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Table 1

From the Table 1 it may be seen that the wear resistant thermoplastic compositions
are far superior to the blend of polycarbonate resin with polycarbonate-polysiloxane
copolymer. Similarly, it may be seen that when the transparent blend is combined
with the modified polyethylene, the wear properties are superior to the corresponding
properties for a combination of the opaque blend with the modified polyethylene.
Without being limited by theory, it is believed that the smaller and uniform
distribution of polysiloxane domain sizes and the uniform distribution of interdomain
spacings in the transparent blend facilitate a controlled interaction between the
polycarbonate and the modified polyethylene. This controlled interaction produces
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superior wear properties. Despite, the improved results for the thermoplastic
composition comprising the transparent blend, it can be seen that the thermoplastic
composition comprising the opaque blend also has a unique combination of wear
resistance and impact resistance
The wear resistant compositions can be advantageously used in gears, cams, bearings,
sliding surfaces, and the like, where a combination or wear resistance, impact
resistance and optional features such as electrical conductivity and flame retardancy
are desired.
While the imention has been descubed with reference to exemplary embodiments, it
will be understood by those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without departing from the
essential scope thereof. Therefore, it is intended that the invention not be limited to
the particular embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments falling within the
scope of the appended claims.
What is claimed is:
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CLAIMS:
1. A composition comprising
a polycarbonate resin;
a polycarbonate-polysiloxane copolymer. and
a modified polyolefin.
2. The composition of Claim 1, wheiein the composition has a weight loss wear
factor of less than or equal to about 350 m5min/ftlb-hr and a notched Izod impact
strength of greater than or equal to about 500 joules per meter at -30°C and wherein
the wear factor is measured according to the formula:
Wear Factor = [(6.1x108)(\V)]/[(PxV) x (D) x (T)]
where P is the applied pressure in pounds per square inch and V is the velocity in feet
per minute, W is the weight loss in grams, D is the density in grams per cubic
centimeter and T represents 100 hours.
3. The composition of Claim 2, wherein the composition has a weight loss wear
factor of less than or equal to about 100 in5min/ftlb-hr and a notched Izod impact
strength of greater than or equal to about 500 joules per meter at-30°C.
4. The composition of Claim 1, wherein the composition has a Class A surface
finish when molded.
5. The composition of Claim 1. wherein the composition has a tensile strength of
greater than oi equal to about 50 MPa and ~ heat distortion temperature of greater
than or equal to about l00cC
6. The composition of Claim 1, wherein the composition has a bulk volume
resistivity of less than o: equal to about 1012 ohm-cm.
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162476-2
7. The composition of Claim 1, wherein the composition has a flammability
rating of V-2, V-l or V-0 in UL-94 tlame letardancy test.
8. The composition of Claim 1, comprising about 15 to about 85 weight percent
polycarbonate resin, based upon the weight of the blend.
9. The composition of Claim 1, wherein the blend of polycarbonate resin with
the polycarbonatc-polysiloxane copolymer is optically transparent.
10. The composition of Claim 1. wherein the modified polyolefin comprises about
0.01 to about 10 wt% of epoxy, carboxyl or acid anhydride functionalities, based on
the total weight of the modified polyolefin and wherein the modified polyolefin
further comprises an epslon-amino-N-cjproic acid.
11. The composition of Claim 1, comprising about 0.5 to about 60 weight percent
of the modified polyolefin, based upon the total weight of the thermoplastic
composition.
12. The composition of Claim 1. wherein the polyolefins are crystalline
polypropylene, crystallire propylene-ethylene block or random copolymers, low
density polyethylene, high density polyethylene, linear low density polyethylene,
ultra-high molecular weight polyethylene, ethylene-propylene random copolymer,
ethylene-propylene-diene copolymer, or a combination comprising at least one of the
foregoing polyolefins.
13. The composition of Claim 1, rurthei comprising fibrous fillers.
14. The composition of Claim 13. wherein the fibrous fillers are glass fibers,
polymeric fibers, carbon nanotubes, carbon fibers, or a combination comprising at
least one of the foregoing fibers.
15. A composition co.uprising.
a blend of a polycarbonate resin with a polycarbonate-polysiloxane copolymer; and
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162476-2
a modified polyethylene, wherein the composition has a wear factor of less than or
equal to about 350 in5min/filb-hr and an impact strength of greater than or equal to
about 500 joules per metel. and wherein the wear factor is measured according to the
formula:
Wear Factor = [(6. lxl08j(\v )]/[(IJ\V) x (D) x (T)]
where P is the applied pre sure in pounds per square inch and V is the velocity in feet
per minute, W is the weight loss in grains, D is the density in grams per cubic
centimeter and T represents 100 hours.
16. The composition of Claim 15, wherein the composition has a wear factor of
less than or equal to about 100 in5min/ftb-hr and a notched Izod impact strength of
greater than oi equal to about 500 joules per meter at -30°C.
17. The composition of Claim 15, wherein the composition has a Class A surface
finish when molded.
18. The composition of Claim 15, wherein the composition has a tensile strength
of greater than or equal to about 50 MPa and a heat distortion temperature of greater
than or equal to about 10C C.
19. The composition of Claim 15, wherein the modified polyolefin comprises
about 0.01 to about 10 XXX of eproxy, cari-oxyl, or acid anhydride functional groups,
based on the total weight of the modified polyolefin.
20. The composition of Claim 19, wherein the modified polyolefin further
comprises an eXXXilon-amn -N-caproic acid
21. The composition of Claim 15, comprising about 0.5 to about 60 weight
percent of the modified XXX yolefin, based upon the total weight of the thermoplastic
composition.
22. The composition of Claim 15, wherein the polyolefin is a crystalline
polypropylene a crystal XXX propylene-ethylene block or random copolymer, a low
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density polyethylene, a high density polyethylene, a linear low density polyethylene,
an ultra-high molecular weight polyethylene, an ethylene-propylene random
copolymer, an ethylene-propylene-diene copolymer, or a combination comprising at
least one of the foregoing polyoltfins.
23. A method comprising
blending a polycarbonate resin, a polycarbonate-polysiloxane copolymer, and a
modified polyolefin to form a thermoplastic composition, wherein a blend of the
polycarbonate resin and the polycarbonate-polysiloxane copolymer is either optically
transparent or opaque.
24. The method of Claim 23. wherein the blending is melt blending or solution
blending.
25. The method of Claim 23, wherein the blending involves the use of shear force,
extensional force, compressive foice, ultrasonic energy, electromagnetic energy,
thermal energy or combinXXXons comprising at least one of the foregoing forces or
forms of eproxy and s conducted in processing equipment wherein the
aforementioned forces are exerted by a single screw, multiple screws, intermeshing
co-rotating of counter is XXXng screws, non-intermeshing co-rotating or counter
rotating screws, reciprocXXX screws, screws with pins, barrels with pins, rolls, rams,
helical rotors, or combiXXX is comprising at least one of the foregoing.
26. The method of claim 23 wherein the blending is conducted in a single or
multiple screw extruder. XXX as Kiuader, Menschel, helicones, Ross mixer, Banbury,
roll mills, moXXX XXX injection molding machines, vacuum forming machines,
blow molding machine, XXXons comprising at least one of the foregoing
machines.
27. The method of Claim 23, further comprising molding the composition.
28. The method of Claim 27 w herein the molding comprises injection molding. '
29. An article comprising the composition of Claim 1.
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31
30. An article comprising the composition of Claim 15.
31. An article manufactured by the method of Claim 23.

Disclosed herein is a composition comprising a polycarbonate resin; a polycarbonate-
polysiloxane copolymer; and an anhydride modified polyolefin. Disclosed herein too
is a composition comprising a blend of a polycarbonate resin with a polycarbonate-
polysiloxane copolymer; and an anhydride modified polyethylene, wherein the
composition has a wear factor of less than or equal to about 350 in5min/ftlb-hr and an
impact strength of greater than or equal to about 500 joules per meter, and wherein the
wear factor is measured according to the formula:
Wear Factor = [(6.1 x108)(W)]/[(PxV) x (D) x (T)]
where P is the applied pressure in pounds per square inch and V is the velocity in feet
per minute, W is the weight loss in grams, D is the density in grams per cubic
centimeter and T represents 100 hours.