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New engineering materials revealed at ANTEC.

New copolymers, alloys, and modified compounds of engineering thermoplastics were discussed at the recent SPE ANTEC in Detroit. Among the more novel materials talked about were a PPS/PPSS copolymer and a nylon/polysulfone alloy--representing two different ways of combining crystalline and amorphous properties in the same material. Also new are unusual hydrophilic TPEs, a lower-cost alternative to PTFE for polymer lubrication, and use of novel "bilobe" glass fibers for reducing warpage in crystalline resins.

NOVEL PPS/PPSS COPOLYMER

A new engineering thermoplastic copolymer that combines the crystalline properties of polyphenylene sulfide (PPS) and the amorphous characteristics of polyphenylene sulfide sulfone (PPSS) is slated for U.S. market introduction later this year by Dainippon Ink & Chemicals Inc. of Japan, represented here by DIC Trading (USA) Inc., Fort Lee, N.J. "Amorvon" is described as a polythioethersulfone (PTES) block copolymer, composed of 53% PPS and 47% PPSS. Juheiji Kawabata, manager of the Materials Div. technical department, says the company produces both resins with functional end groups so that they react together. (In the U.S., Phillips 66 Co., Bartlesville, Okla., produces PPS and is the only maker of PPSS.) Kawabata says negotiations are now under way to license a domestic compounder to produce the alloy. He says the alloy will be priced at about $10/lb tl.

The alloy is expected to be attractive for automotive applications, as it reportedly combines high heat and chemical resistance, good mechanical properties, high dimensional stability, and flow suitable for filling thin-wall, complex parts.

Unfilled Amorvon has a density of 1.38 and glass-transition temperature of 401 F, higher than polysulfone or PEEK. With 40% glass, Amorvon has a specific gravity of 1.66, HDT of 464 F at 264 psi, tensile strength of 26,100 psi, elongation of 1.6%, flex strength of 34,800 psi, flex modulus of 1.9 million psi, compressive strength of 26,100 psi, and notched Izod impact of 2 ft-lb/in. It also attains a UL 94V-0 flame-resistance rating without additives.

Amorvon will be offered in four grades: unfilled, with 30% and 40% glass, and with both glass fiber and PTFE. There also is a proprietary developmental grade (AV-130) that employs an unnamed filler system. Current development efforts also include boosting the alloy's impact strength. Amorvon has processing characteristics similar to PPS, Kawabata says.

POLYSULFONE/NYLON ALLOY

An experimental alloy that combines amorphous polysulfone with crystalline nylon 66 or 6 has been developed at Amoco Chemical Co., Naperville, Ill.

Charles L. Myers, associate research scientist, says that inclusion of about 10% of a special anhydride-terminated form of Amoco's Udel polysulfone acts as the compatibilizing agent between the nylon and Udel P-1700 grade during twin-screw reactive extrusion. Myers said the functionalized polysulfone forms an in situ block copolymer between the two resins, with the polysulfone's anhydride end groups reacting with the nylon. The nylon, which accounts for about 50% of the alloy volume, becomes the continuous matrix phase while the polysulfone is the dispersed phase.

The result, according to Myers, is a chemically coupled morphology in which the polysulfone reinforces the nylon matrix, improving its heat-distortion properties and impact resistance while reducing its moisture absorption. However, the alloy retains the crystalline profile of the nylon, thereby maintaining properties such as good processability and chemical resistance.

Though the alloy is still in the experimental research stage, Amoco is conducting tests of injection molding, extrusion and fiber spinning. Tests of a 50% nylon 6, 40% Udel, 10% reactive polysulfone alloy show an ultimate tensile strength of 9710 psi, yield elongation of 11%, ultimate elongation of 124%, and tensile impact of 91 ft-lb/in. Substituting nylon 66 in the same overall recipe raises the ultimate tensile strength to 11,100 psi and tensile impact to 131 ft-lb/in. with no change in elongation. HDT at 264 psi for both alloy versions is 233 F.

NYLON/POLYOLEFIN ALLOY

A new family of reactively extruded alloys that combine nylon 6 with an unnamed functionalized polyolefin has been commercially introduced by DSM Engineering Plastics, Evansville, Ind. Akuloy RM (reduced moisture) is being unveiled in three grades: unfilled, 30% glass-filled, and high-impact/high-heat, 30% glass-filled, according to Steve Gerteisen, manager of new product development. Aimed at under-the-hood auto parts, Akuloy was initially revealed as an unnamed test development grade last year at the NPE '91 show in Chicago, just prior to the merger of Akzo Engineering Plastics with DSM (see PT, Aug. '91, p. 67).

A key feature of the alloys is the significant reduction in moisture pick-up for the nylon 6 while enhancing processability. Gerteisen says the alloy absorbs only one-third as much moisture as standard nylon 6. Reduced moisture absorption is a synergistic effect of the functionalized polyolefin, rather than simply of replacing nylon 6 with a polyolefin dispersed phase.

Akuloy RM J-75/30/HI, the 30%-glass, high-impact/high-heat grade, offers an HDT at 264 psi of 390 F, tensile strength of 18,000 psi, elongation of 5%, flexural strength of 25,000 psi, flex modulus of 1 million psi, notched Izod of 3.2 ft-lb/in., specific gravity of 1.25, and 24-hr water-absorption rate of 0.38%.

The unfilled grade has an HDT at 264 psi of 150 F, while the 30%-glass grade is 330 F. Price of the 30% glass-filled grade is $1.63/lb tl.

LOWER-COST LUBRICATION

DSM Engineering Plastics also presented a paper on a series of engineering resins that achieve low friction and wear at lower cost than standard PTFE-filled compounds. The key is replacing part of the PTFE with another proprietary polymeric lubricant (PL). Acceptable wear resistance can be retained with no significant change in coefficient of friction or limiting PV, says Akzo's Jeffrey A. Harding. In fact, the presence of the alternate polymer lubricant reportedly reduces frictional heating at high PV levels; as a result, the limiting PV of unreinforced polycarbonate is improved substantially. Some slight reductions in mechanical properties may be experienced, however.

Cost of lubricated compounds can be about 20% less than all-PTFE systems because the alternate lubricant is both lower in specific gravity than PTFE and also 75-85% lower in cost (PTFE costs $6-7/lb). Lubricated compounds end up 5-8% lower in density. DSM offers its PL modification in polycarbonate, nylon and acetal.

HYDROPHILIC TPEs

A number of unusual applications beckon for a series of hydrophilic TP elastomers recently commercialized by Elf Atochem North America's Polymers Div., Philadelphia. By altering the polyether type, Pebax polyether-block-amide (PEBA) TPEs can be produced with high affinities for moisture and high moisture-transmission rates. Such Pebax versions have been developed in 40-60 Shore D hardness (hydrophilic properties correlate negatively with hardness and crystallinity). The company sees commercial potential in films for hospital garments that could be highly breathable yet nonporous, providing protection against blood-borne viral diseases. Water-absorbing films could form part of a multilayer packaging structure, serving as an integral polymer desiccant.

BILOBE GLASS BEATS WARPAGE

Robert Gallucci of GE Plastics, Pittsfield, Mass., told an ANTEC audience about significant reductions in warpage of reinforced crystalline resins obtained through the use of unusual "bilobe" glass fibers that have a figure-eight cross-section. This R&D was conducted jointly by GE and Owens-Corning Fiberglas Corp., Toledo, Ohio, which has been developing the bilobe glass.

According to Gallucci, the bilobe glass appears to reduce warpage in virtually any reinforced crystalline thermoplastic with no significant difference in mechanical properties or surface appearance compared with standard glass fibers. Data were shown for Valox PBT, GE's Lomod and Du Pont's Hytrel copolyester TPEs, GE's Xenoy polycarbonate/PBT alloy, GE's Gemax PBT/PPO blend, and a Valox PBT/PET blend reinforced with mica and glass. In the latter case, bilobe glass proved even more warp-resistant than a glass-fiber/mica combination developed for an automotive cowl vent grille. (GE also experimented with trilobe glass fibers.)

Owens-Corning's bilobe glass is available today only in pilot-plant quantities. Says Gallucci, it will take customer "pull-through" demand to justify scale-up to commercial production.
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Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:Aug 1, 1992
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