Abstract:
Thermoplastic compositions comprising, in intimate admixture, polyethylene terephthalate and a rubber-modified graft copolymer of a vinyl aromatic compound and an α,β-unsaturated cyclic anhydride. These compositions display desirable thermal properties, particularly elevated heat deflection temperatures.

Description:
REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of prior copending application Ser. No. 162,138 filed June 23, 1980. 
    
    
     BACKGROUND 
     Polyethylene terephthalate (PET) has become an important raw material for production of moldings, film and fibers. Preparation of PET is described inter alia in Whinfield et al., U.S. Pat. No. 2,465,319 and in Pengilly, U.S. Pat. No. 3,047,539, and in Kirk-Othmer, Encyclopedia of Chemical Technology, Second Edition, Vol. 16, pp. 159 et seq. (1968), all disclosures being incorporated herein by reference. 
     Many applications for injection and extrusion molded parts require heat resistance, and it is in such applications that PET manifests certain undesirable properties. Unreinforced PET has been of limited interest for making such parts due to its low HDT (Heat Deflection Temperature)--about 75° C. at 264 psi. HDT is a measure of an important thermal property of a thermoplastic material wherein a bar of the material, held in flexure under constant load (usually at 264 or 66 psi), deforms a specified amount and the temperature at which this specified deformation occurs is the HDT--see Billmeyer, Textbook of Polymer Science, p. 112, John Wiley and Sons, Inc. (1962). 
     U.S. Pat. No. 3,644,574 discloses blends of 1,4-butanediol polyesters with from about 1 to about 40 weight percent of a vinyl aromatic polymer (e.g., a styrenic polymer) which polymer may be, inter alia, a copolymer with maleic anhydride. The blends of this patent exhibit increased HDT over the unblended polyester. However, that patent discloses at Column 1, lines 42-47 that the improvements observed with polybutylene terephthalate are not obtained when the polyester is poly(ethylene terephthalate). 
     SUMMARY OF THE INVENTION 
     The present invention provides a thermoplastic composition which comprises an intimate admixture of: (a) a polyethylene terephthalate and (b) a rubber-modified graft copolymer of a vinyl aromatic compound and an α,β-unsaturated cyclic anhydride. 
     The blends of this invention have a heat deflection temperature of at least about 80° C., preferably above about 90° C., at 264 psi as measured by the ASTM procedure D 648-72. In a preferred embodiment, the copolymer is a rubber-modified copolymer of a styrene, preferably styrene, and maleic anhydride. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The polyethylene terephthalate used herein is preferably homopolymeric PET. Halogenated PET can also be used and is normally formed by condensation of a mixture of a halogenated, preferably brominated, terephthalic acid (e.g., 2,5-dibromoterephthalic acid and 2,3,5,6-tetrabromoterephthalic acid) and terephthalic acid with ethylene glycol. Additionally, the polyethylene terephthalate used herein can also contain up to 10 mol percent, relative to the acid component, of radicals of other aromatic dicarboxylic acids such as, for example, phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, diphenyl-4,4&#39;-dicarboxylic acid and the like as well as their halogenated counterparts. The copolymers can also contain up to 10 mol percent, relative to the glycol component, of radicals of other glycols such as, for example, propylene glycol, butylene glycol, dibromoneopentyl glycol, bis(2-hydroxyethyl) ether of tetrabromobisphenol A and tetrabromo-p-xylylene glycol. See for example Kirk-Othmer, Encyclopedia of Chemical Technology, Second Edition, Vol. 16, pp. 161-173 (1968). 
     The polyethylene terephthalates used herein should be moldable (i.e., injection moldable or moldable by extrusion), and thus generally will have an intrinsic viscosity (I. V.) falling between about 0.25 and 1.5, and more usually between about 0.5 and 1.2, as measured at 25° C. using a solvent consisting of 60 percent by weight phenol and 40 percent by weight of tetrachloroethane. For best results the polyethylene terephthalate should have an I. V. (measured in the foregoing manner) in the range of 0.4 to 1.2, more preferably between 0.5 and 1.1, and for most injection molding applications polyethylene terephthalates in which the I. V. is in the range of 0.5 to 0.9 are deemed most desirable. 
     The amount of polyethylene terephthalate resin used in the blends of this invention preferably falls within the range of from about 10 to about 90 weight percent based on the total weight of resin in the blend and the amount of the unsaturated cyclic anhydride copolymer falls within the range of from about 90 to about 10 weight percent also based on the total weight of resin in the blend. In a particularly preferred embodiment the relative amounts of the PET and the copolymer fall within the range of from about 20 to about 80 and from about 80 to about 20 weight percent, respectively, the total being equal to 100. Most preferably the amounts used fall within the range of 30 to 70 and from about 70 to 30 weight percent, respectively. 
     Copolymers of a vinyl aromatic compound and an α,β-unsaturated cyclic anhydride are well known in the art and are described in the literature. In general, they are prepared by conventional bulk or solution techniques using free-radical initiation. For example, styrene-maleic anhydride copolymers can be obtained by simply reacting the two monomers, i.e., styrene and maleic anhydride, at 50° C. in the presence of benzoyl peroxide. The rate of polymerization may be better controlled if a solvent such as acetone, benzene or xylene is used. 
     Vinyl aromatic compounds of component (b) can be derived from compounds of the formula: ##STR1## where R 1  and R 2  are selected from the group consisting of (lower) alkyl groups of from 1 to 6 carbon atoms and hydrogen. R 3  and R 4  are selected from the group consisting of chloro, bromo, hydrogen and (lower) alkyl of from 1 to 6 carbon atoms; R 5  and R 6  are selected from the group consisting of hydrogen and (lower) alkyl groups of from 1 to 6 carbon atoms or R 5  and R 6  may be concatenated together with hydrocarbyl groups to form a naphthyl group. These compounds are free of any substituent that has a tertiary carbon atom. Styrene is the preferred vinyl aromatic compound. 
     The cyclic anhydride compounds of component (b) are preferably α,β-unsaturated dicarboxylic anhydrides. For example, the term cyclic anhydride identifies anhydrides having the formula: ##STR2## wherein the dotted lines represent a single or a double carbon-to-carbon bond, R 7  is selected from the group consisting of hydrogen, alkyl or aryl radicals containing up to 8 carbon atoms, R 8  is selected from the group consisting of hydrogen, vinyl, alkyl, alkenyl, alkylcarboxylic or alkenyl carboxylic of from 1 to 12 carbon atoms and n is an integer of from 0 to about 10. Examples include maleic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, citraconic anhydride, itaconic anhydride, phenylmaleic anhydride, aconitic anhydride, and mixtures thereof. Maleic anhydride is the preferred anhydride of component (b). 
     Copolymers of vinyl aromatic compounds and α,β-unsaturated cyclic anhydrides which can be used are described in U.S. Pat. Nos. 2,769,804; 2,971,939 and 3,336,267. 
     In preparing the rubber-modified copolymers use of such rubbers as polybutadiene, an isobutylene-isoprene copolymer, a styrene-butadiene copolymer, a butadiene-acrylonitrile copolymer, an ethylene-propylene copolymer, a polyisoprene, ethylene-propylene-diene monomer terpolymers (EPDM) and the like can be employed. For a description of a typical method of preparing the rubber-modified graft copolymers see U.S. Pat. No. 3,919,354 which is incorporated herein by reference. 
     Component (b) copolymers can comprise from about 40 to about 5 parts by weight of the α,β-unsaturated cyclic anhydride, from about 60 to about 95 parts by weight of a vinyl aromatic compound, and up to 50 parts by weight of the rubber. Preferred polymers include those wherein the relative proportions of the styrene and the anhydride fall within the range of from about 90 to about 70 weight percent and from about 10 to about 30 weight percent, respectively. Preferred rubber-modified polymers used herein contain about 5-25 parts by weight of the α,β-unsaturated cyclic anhydride, 40-85 parts by weight of the vinyl aromatic compound, and from about 5 parts to about 30 parts by weight of rubber. 
     A preferred unmodified vinyl aromatic α,β-unsaturated cyclic anhydride copolymer useful in the compositions of this invention is Dylark®332, supplied by ARCO/Polymers, Inc. Dylark®332 is a styrene-maleic anhydride copolymer containing about 14 percent maleic anhydride, the balance being styrene. Still another preferred unmodified vinyl aromatic α,β-unsaturated cyclic anhydride copolymer is Dylark®DKB 134, also made by ARCO/Polymers. This SMA copolymer contains about 17 percent maleic anhydride, the balance being styrene. A preferred rubber-modified vinyl aromatic α,β-unsaturated cyclic anhydride copolymer is Dow Experimental Resin XP-5272.07 made by Dow Chemical Company. This is a high impact styrene-maleic anhydride copolymer believed to contain about 21.5 weight percent butadiene, about 21 weight percent maleic anhydride and about 57.5 weight percent styrene. Still another preferred rubber-modified copolymer is Dylark®350 (ARCO/Polymers) containing 15 percent by weight rubber, 11 percent maleic anhydride, with the balance being styrene. Still other preferred rubber-modified copolymers are identified in the Examples hereinafter. Typically such preferred graft copolymers will contain from 4 to 25 weight percent rubber, from 10 to 25 weight percent cyclic anhydride, and from 50 to 85 weight percent vinyl aromatic compound. 
     Compositions of this invention can also include other ingredients, such as flame retardants, extenders, processing aids, pigments, stabilizers and the like, for their conventionally employed purposes. Reinforcing fillers, in amounts sufficient to impart reinforcement, can be used, such as carbon filaments; silicates, e.g., acicular calcium silicate; asbestos; titanium dioxide; potassium titanate; titanate whiskers; and glass flakes and fibers. 
     Particularly preferred compositions of this invention include those containing impact modifiers. Examples include ethylene/vinyl acetate copolymers, ethylene/acrylic acid copolymers (having some of the acid functions neutralized), ethylene/methacrylic acid copolymers (having some of the methacrylic acid functions neutralized), ethylene/alkyl acrylate/methacrylic acid terpolymer (also having some of the methacrylic acid functions neutralized), ABS, oxidized polyethylene, styrene-butadiene-styrene (S-B-S) block copolymers, styrene/butadiene multiblock copolymers, styrene/butadiene radial block copolymers, hydrogenated S-B-S block copolymers, styrene/butadiene rubber, acrylic rubbers, EPDM, ethylene/acrylic acid copolymers, ethylene/methyl acrylate copolymers, ethylene/ethyl acrylate copolymers, polyester-ether multiblock copolymers, and the like. These materials are available in a wide range of molecular weights and it is generally desirable that the impact modifier, when used, have a melt viscosity close to that of the substrate. Amounts of impact modifiers generally fall within the range of from about 5 to about 40 percent by weight. The results obtained in any given situation will, of course, depend upon a variety of factors such as the impact modifier selected, the manner by which it is compounded into the blends, the concentration in which it is employed, and indeed upon the criteria used in measuring or judging the toughness of the resultant blend. On the basis of the work performed thus far, the most preferred impact modifiers are the polyether-ester segmented block copolymers, a number of which are available commercially from du Pont under the trademark Hytrel®. The composition and synthesis of these copolyetherester block copolymers have been described in the literature--see for example U.S. Pat. Nos. 3,784,520; 3,766,146 and 3,763,109, the disclosures of which are incorporated herein by reference. Note also the text of U.S. Pat. No. 4,259,458 from Column 13, line 15 through Column  17, line 23 which likewise is incorporated herein by reference. 
     For protection against thermo-oxidative degradation, the customary amounts of stabilizers, preferably 0.001 to 0.5 percent by weight, relative to the unfilled and unreinforced compositions of this invention, can be added to the compositions according to the invention. Examples of suitable stabilizers are phenols and phenol derivatives, preferably sterically hindered phenols which contain alkyl substituents with 1-6 carbon atoms in the two positions ortho to the phenolic hydroxyl groups, amines, preferably secondary arylamines and their derivatives, phosphates and phosphites, preferably the aryl derivatives thereof and quinones. Non-limiting examples include 4,4&#39;-bis-(2,6-di-tert-butylphenol); 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; 4,4&#39;-butylidene-bis-(6-tert-butyl-m-cresol); 3,5-di-tert-butyl-4-hydroxybenzyl-phosphonic acid diethyl ester; N,N&#39;-bis(β-naphthyl)-p-phenylenediamine; N,N&#39;-bis-(1-methyl-heptyl)-p-phenylenediamine; phenyl-β-naphthylamine; 4,4&#39;-bis(α,α-dimethylbenzyl)diphenylamine; hydroquinone; p-benzoquinone; toluhydroquinone; p-tert-butylpyrocatechol; chloranil; and naphthoquinone. 
     Flame-retarding additives which can be used for the compositions according to the invention comprise a large number of chemical compounds which are well known to those skilled in the art. In general, they contain chemical elements which are used because of their flame-retarding capacity, for example bromine, chlorine, antimony, phosphorus and nitrogen. Preferably, the flame-retarding additives are halogenated organic compounds (brominated or chlorinated), optionally used together with auxiliary compounds sometimes referred to as synergists, such as antimony trioxide, zinc borate, or the like. Elementary phosphorus or phosphorus compounds such as ammonium polyphosphate are also preferred flame retardants. Other examples include bromine or chlorine containing organic phosphate esters, hexaphenoxyphosphazene, and the like. 
     Preferred reinforcing fillers are fiberglass, mineral fillers, particulate fillers such as mica and the like. In general, optimum physical properties can be obtained if glass filaments are employed in amounts of from about 5 to about 40 percent by weight, based on the combined weight of glass and resin. However, higher amounts can be used. 
     Compositions of the invention may be prepared by blending the components in a mixer (e.g., a Henschel mixer) and compounding the mixture on an extruder (e.g., a twin-screw compounding extruder such as a 28 mm Werner-Pfleiderer extruder or the like). Thereafter, the extrudate is chopped into pellets and molded on an injection molding machine. 
    
    
     The present invention is further illustrated in the following examples, which are not to be construed as limiting. All parts are by weight. 
     EXAMPLES I AND II 
     Compositions of the following examples were prepared by mixing the components to form a premix, compounding the premix on a single screw extruder at temperatures about 525° to 550° F. (274°-288° C.), and molding the pellets into test bars on a New Britain injection molding machine. 
     The particular materials used in these compositions were as follows: 
     a. Polyethylene terephthalate; from Goodyear Tire and Rubber Company; VFR 2977A-crystalline PET having an intrinsic viscosity of 0.68±0.025 as measured at 25° C. using a solvent consisting of 60 percent by weight phenol and 40 percent by weight of tetrachloroethane. 
     b. Styrene/maleic anhydride copolymer; from ARCO/Polymers; Dylark®DKB 134. 
     The PET/SMA copolymer weight:weight ratio in the blend of Example I was 70:30 and that of Example II was 60:40. Test bars of the above compositions were tested according to ASTM procedures to evaluate physical properties. The ASTM designation numbers for the properties measured were as follows: Specific Gravity--D792-66 (1975); Tensile-Yield, Elongation and Tensile Elastic Modulus--D 638-77a; Flexural Strength and Flexural Elastic Modulus--D 790-71 (1978); Izod Impact for 1/4&#34; bar, 1/8&#34; bar and 1/8&#34; bar at -40° C.--D 256-78; Heat Deflection Temperature--D 648-72 (1978); Vicat Softening Point--D 1525-76; and Rockwell Hardness--D 785-65 (1976). The results are shown in Table I. 
     
                       TABLE I______________________________________Property             Example I Example II______________________________________Specific Gravity     1.260     1.247Tensile-Yield, psi   7310      7590Elongation, %        1.6       2.0Tensile Elastic Modulus, 10.sup.3 psi                470       447Flexural Strength, psi                12,700    13,500Flexural Elastic Modulus, 10.sup.3 psi                441       465Izod Impact, 1/4&#34; bar, ft.-lb./in.                0.4       0.3Izod Impact, 1/8&#34; bar, ft.-lb./in.                0.4       0.3Izod Impact, 1/8&#34; bar, ft.-lb./in.(at -40° C.)  0.4       0.3Heat Deflection Temp. at 264 psi, °C.                95        94Heat Deflection Temp. at 66 psi, °C.                120       117Vicat Softening Point, °C.                207       195Rockwell Hardness, R Scale                120       119______________________________________ 
    
     EXAMPLES III-XII 
     The following components were blended and molded as described in Examples I and II. 
     a. Polyethylene terephthalate--Cleartuf®8502A; from the Goodyear Tire and Rubber Company having an intrinsic viscosity of 0.85 as measured at 25° C. using a solvent consisting of 60 percent by weight phenol and 40 percent by weight of tetrachloroethane. 
     b. Styrene/maleic anhydride copolymer; Dylark®332 from ARCO/Polymers. 
     The proportions (weight percentages) used were as follows: 
     
         ______________________________________       ExampleComponents    III      IV    V     VI  VII______________________________________a.    PET         70       55  40    25  10b.    Styrene/Maleic Anhydride   30       45  60    75  90______________________________________ 
    
     Physical property testing as in Examples I and II gave the results shown in Table II. 
     
                       TABLE II______________________________________           ExamplesProperty          III    IV     V    VI   VII______________________________________Tensile Yield, 10.sup.3 psi             8.89   8.26   7.90 6.57 6.27Elongation, %     2.8    2.1    1.8  2.8  1.4Tensile Modulus, 10.sup.3 psi             434    456    482  497  424Flexural Strength, 10.sup.3 psi             15.2   13.3   13.1 11.6 10.4Flexural Modulus, 10.sup.3 psi             441    455    473  480  485Notched Izod, 1/8&#34; bar,ft.-lb./in.       0.3    0.3    0.2  0.2  0.2Unnotched Izod, 1/8&#34; bar,ft.-lb./in.       6.8    5.4    3.8  2.8  2.0Heat Deflection Temp.at 264 psi, °C.             84     105    105  109  110Heat Deflection Temp.at 66 psi, °C.             110    122    121  120  121______________________________________ 
    
     EXAMPLES VIII-XII 
     Rubber-modified styrene/maleic anhydride copolymers were blended and molded in the same manner outlined in Examples I and II. The following components were used: 
     a. Polyethylene terephthalate-Vituf®5900; from Goodyear Chemical Company, having an intrinsic viscosity of 0.59 as measured at 25° C. using a solvent consisting of 60 percent by weight phenol and 40 percent by weight of tetrachloroethane. 
     b. Styrene/maleic anhydride copolymer; Dylark®332 from ARCO/Polymers. 
     c. Rubber-modified SMA containing 15 percent rubber, 11 percent maleic anhydride, with the balance being styrene; Dylark®350 from ARCO/Polymers. 
     d. Rubber-modified SMA believed to contain 21.5 weight percent butadiene, 21 weight percent maleic anhydride and 57.5 weight percent styrene; Dow XP 5272.07 from Dow Chemical Company. 
     The proportions (weight percentages) used were as follows: 
     
         ______________________________________      ExamplesComponents   VIII    IX      X     XI    XII______________________________________a.  PET          70      55    66.7  50    60b.  Styrene/Maleic    Anhydride    30      45    None  None  Nonec.  Rubber-Modified    Styrene/Maleic    Anhydride    None    None  33.3  50    Noned.  Rubber-Modified    Styrene/Maleic    Anhydride    None    None  None  None  40______________________________________ 
    
     Physical property testing as in Examples I and II gave the results shown in Table III. 
     
         ______________________________________           ExamplesProperty          VIII   IX     X    XI   XII______________________________________Notched Izod, 1/8&#34; bar,ft.-lb./in.       0.3    0.3    0.5  0.6  0.6Unnotched Izod, 1/8&#34; bar,ft.-lb./in.       6.9    4.8    16.0 11.5 20.8Heat Deflection Temp. at264 psi, °C.             87     95     87   96   85Heat Deflection Temp. at66 psi, °C.             124    117    119  117  137______________________________________ 
    
     COMPARATIVE EXAMPLE 
     The PET used in Examples XIII-XII was molded in the manner outlined in Examples I and II. Physical property testing in accordance with the ASTM procedures of Examples I and II showed the neat PET to have a HDT of 76° C. at 264 psi, a HDT of 104° C. at 66 psi, a 1/8 inch notched Izod impact of 0.6 ft.-lb./in., a flexural strength of 15,200 psi and a flexural modulus of 400,000 psi. 
     EXAMPLES XIII-XV 
     Additional blends were made from the PET referred to in Examples VIII-XII using either Dylark®350 rubber-modified SMA or Dylark®338S, a rubber-modified SMA containing about 4 weight percent rubber and 13.4 weight percent maleic anhydride with the balance being styrene. The makeup of the blends and their heat deflection temperatures at 264 psi (°C.) are shown in Table IV. 
     
                       TABLE IV______________________________________Ex-               Wt. Percentage                         Heat Deflectionample Components  in Blend    Temperature of Blend______________________________________XIII  PET         50 Dylark® 350             50           87XIV   PET         55 Dylark® 338S             45          104XV    PET         50 Dylark® 338S             50          100______________________________________ 
    
     EXAMPLES XVI-XIX 
     Four blends were made using an SMA graft copolymer composed of about 16 weight percent maleic anhydride, 59 weight percent styrene and 25 weight percent rubber. The same PET as in Examples VIII-XII was used. Table V gives the heat deflection temperatures at 264 psi (°C.) of the blends. 
     
                       TABLE V______________________________________      Wt. Percentage                  Heat DeflectionExample    PET/SMA     Temperature of Blend______________________________________XVI        85/15       78XVII       70/30       80XVII       55/45       87XIX        40/60       80______________________________________ 
    
     EXAMPLES XX-XXVII 
     Eight blends were prepared using a PET from American Hoechst Company identified as Hoechst 018 and having an intrinsic viscosity (measured as above) of 0.60. In each case a mixture of two different SMA copolymers was used, one SMA being the rubber-modified graft copolymer referred to in Examples XVI-XIX, the other being either an unmodified copolymer containing 18 weight percent maleic anhydride (DKB-290) from ARCO/Polymers, Inc.) or Dylark®338S rubber-modified SMA (note Examples XIV and XV above). Four of these blends were prepared by a double pass extrusion-compounding procedure in which the two SMA copolymers were blended together in the first-pass and the PET was added in the second-pass. Izod impact and heat deflection temperature (264 psi) data are given in Table VI. 
     
                                           TABLE VI__________________________________________________________________________         Example         XX XXI               XXII                   XXIII                       XXIV                           XXV                              XXVI                                  XXVII__________________________________________________________________________Blend Composition, wt %PET           70 70 55  55  55  55 40  40SMA (Ex. XVI-XIX)         20 20 30  30  30  30 40  40DKB-290       10 -- 15  15  --  -- 20  --Dylark® 338S         -- 10 --  --  15  15 --  20Melt Compounding MethodNumber of Passes         2  2  1   2   1   2  1   1Properties1/8&#34; Notched Izod,ft.-lb./in.   0.6            0.8               0.7 0.8 0.7 1.1                              0.6 0.71/8&#34; Unnotched Izod,ft.-lb./in.   15.3            18.3               12.0                   18.7                       9.5 18.9                              9.9 10.9HDT at 264 psi, °C.         81 79 90  85  90  84 91  91__________________________________________________________________________ 
    
     EXAMPLES XXVIII-XXIX 
     A pair of blends of this invention were formed from the Hoechst 018 PET and Dylark®338S rubber-modified SMA. One such blend additionally contained as an impact modifier a polyether ester segmented block copolymer containing approximately 50 percent soft (polyether) segments available commercially from du Pont under the trademark Hytrel®4056. Izod impact and heat deflection temperature (264 psi) data are given in Table VII. 
     
                       TABLE VII______________________________________           Example           XXVIII XXIX______________________________________Blend Composition,wt %PET               50       44Dylark® 338S  50       44Hytrel® 4056  --       12Properties1/4&#34; Notched Izod,ft.-lb./in.       0.5      1.11/8&#34; Notched Izod,ft.-lb./in.       0.5      1.11/8&#34; Unnotched Izod,ft.-lb./in.       11.4     26.0HDT at 264 psi, °C.             99       89______________________________________ 
    
     EXAMPLES XXX-XXXIII 
     Four PET/SMA blends were formed, each containing Hytrel®4056 as an impact modifier. The PET&#39;s used were Goodyear Vituf®5900, Goodyear Cleartuf®7202A and Rohm &amp; Haas X 5028-0.82 having intrinsic viscosities of 0.59, 0.72 and 0.82, respectively. The rubber-modified SMA&#39;s were Dylark®338S and Dylark®350. The makeup of the blends and their properties are summarized in Table VIII. 
     
                       TABLE VIII______________________________________     Example     XXX     XXXI    XXXII     XXXIII______________________________________Blend Composition,wt %PET (0.50 I.V.)       40        --      --      --PET (0.72 I.V.)       --        40      --      --PET (0.82 I.V.)       --        --      40      45Dylark® 338S       40        40      40      --Dylark® 350       --        --      --      45Hytrel® 4056       20        20      20      10PropertiesSpecific Gravity       1.206     1.200   1.201   1.191Flexural Strength,10.sup.3 psi       10.1      10.1    10.6    9.8Flexural Modulus,10.sup.3 psi       277       295     303     2991/8&#34; Notched Izod,ft.-lb./in. 1.2       1.1     1.2     1.31/8&#34; Unnotched Izod,ft.-lb./in. 20.6      25.7    N.B.*   N.B.*HDT, 264 psi, °C.       90        88      88      82______________________________________ *Did not break. 
    
     Various modifications of the invention are possible without departing from the scope of the invention as set forth in the claims.