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Untold combinations of properties for engineering resins.

Untold Combinations Of Properties For Engineering Resins

Copolymerization and alloying will drive advances in new engineering thermoplastics of the 1990s. Breakthroughs in polymerization and compatibilization technologies promise to deliver resins with improved processing characteristics as well as "built-in" higher performance capabilities. A glimpse of this potential was unveiled earlier this year at Compalloy '90 in New Orleans (see PT, May '90, p. 25).

Polymer researchers believe they will be able to engineer more thermal stability, greater impact resistance, higher stiffness, flame retardance and better processing characteristics into the molecular structure of a single polymer. Thus, the secondary incorporation of additive packages, which add cost and extra compounding steps, and may disrupt processability or compromise other properties, will be avoided.

Nylons and polyesters look to be the most active areas of new development among engineering thermoplastics in the 1990s, while TP elastomers also hold promise for major advances.

R&D on entirely new polymer groups will continue through the 1990s, despite the far greater emphasis placed on technologies of alloying and copolymerizing of existing resins. Research executives consider the latter two as the most attainable, desirable, cost-effective means of achieving the polymer advances that will be required this decade.

Most resin producers declined to comment on totally new material developments, simply stating that there are "several" new developments underway in their labs, which are too formative to discuss. One totally new polymer system, now being researched at GE Plastics, Pittsfield, Mass., involves a crystalline thermoplastic that draws from elements of silicone and polyphenylene oxide (PPO) technologies, while not necessarily making use of those materials, according to Joseph G. Wirth, v.p. and general manager of GE's Technology Div. The new polymer has an HDT in the range of 480 F, along with good flame resistance, being an even better char former than GE's Ultem polyetherimide.

Citing a "gut feeling" about the future importance of thermoplastic composites in the 1990s, Wirth points to advances GE Plastics has announced in the field of "cyclics" chemistry. These new low-molecular-weight, low-viscosity cyclic oligomers, or precursors of engineering thermoplastics, can be used to impregnating reinforcing fibers in the melt phase, and then polymerize in the mold to form a high-molecular-weight polymer (PT, Oct. '89, p. 131). The technology is said to be applicable to polycarbonate, polyetherimide, polyesters and several other resins.

The new cyclics, in their present stage of development, are "a piece of science rather than a technology," according to Wirth, with applications as yet undefined. He suggests that thermoplastic RIM or pultrusion of large composite structures as possible applications for the 1990s.

The GE Plastics cyclics approach appears to have some advantages in common with the Isoplast "live" engineering thermoplastic development now underway at Dow Chemical Co., Midland, Mich. Fred P. Corson, v.p. of R&D, explains that Isoplast is an amorphous, rigid thermoplastic urethane, which "unzips" to a low-viscosity oligomer when melted and then quickly repolymerizes when cooled in a mold. Like GE's cyclics, Isoplast could offer good wet-out of composite fibers in its low-viscosity state.

Corson cites Isoplast as an example of thermoplastic and thermoset technologies "coming together" as a unified technology for the 1990s. He also points out that flexible monomer selection in the Isoplast technology can help tailor properties. It's expected that initial grades of Isoplast composites will have a heat-deflection range up to 220 F, with future high-heat grades capable of reaching 300 F and beyond.

BIOPOLYMERS ARE COMING

Mindful of environmental awareness and niche markets for biodegradability in certain plastic products, several resin producers have ongoing research programs to develop biologically made polymers, or materials that make use of organic feedstocks. One program that seeks to harvest biologically produced resins is at ICI Biological Products in London, England, and its Marlborough Biopolymers Ltd. affiliate. ICI's "Biopol," which the firm seeks to introduce commercially during the first half of this decade, is produced from genetically enhanced bacteria that convert glucose into a melt-processable thermoplastic fatty-acid ester.

The Biopol material is a linear polyester of hydroxybutyric and hydroxyvaleric acids made from the fermentation of sugar by a bacterium (PT, Sept. '87, p. 111). These organisms produce polymer micro-granules. Biopol can be produced in high-crystalline PHB homopolymer and semicrystalline PHBV copolymer versions. The material has a narrow melt-temperature range of 343-356 F. It rapidly degrades above 400 F. Scrap can be used as regrind at levels of up to 20% only if melt residence time and temperature are carefully monitored.

Once discarded, ICI says the Biopol material will break down into carbon dioxide and water. The homopolymer version of Biopol is a relatively stiff, brittle material, which can be modified through the use of impact modifiers and plasticizers. The company says the material would be suitable for fibers, blown film and injection molding. A blow molded cosmetic bottle is expected to be among the first consumer items produced from Biopol. Material purity rates up to 99.5% also may lead to medical applications.

An ICI spokesman says the company has made great strides in R&D on Biopol, but government regulations, commercial approvals, and economic considerations have thus far hindered its introduction. He admitted initial projections on the applications and introduction of Biopol going back to 1983 were "too optimistic."

It recently was reported Wella "Sanara" shampoo bottles, made from the Biopol were test marketed in West Germany in May. ICI produces the material at a pilot plant in Billingham, England. The British firm is considering whether to build a 20-million-lb/yr production facility, which reportedly would allow ICI to sell the resin in the $2-$3/lb range.

Another "fully biodegradable" polymer now under development is the cornstarch-based Novon material introduced by Warner-Lambert Co., Morris Plains, N.J. First announced earlier this year, few details are available on Novon, except to say the starch was polymerized under heat and pressure with water as a plasticizer, and that it could be blended with up to 15% petrochemical materials (PT, March '90, p. 14).

An expanded line of resorbable glycolide and lactide Medisorb polymers and copolymers, designed for medical applications, was launched last year by Du Pont Co., Wilmington, Del. (PT, March '89, p. 14). The materials biodegrade to form lactic and glycolic acids, and can be used for medical sutures, surgical staples and implantable prosthetic devices.

NEW NYLONS GALORE

There appears to be no limit in sight for the continued prolific technical advances in nylon materials. This ongoing flurry of activity was best illustrated at last year's K'89 show in Dusseldorf, when a host of new nylons were unveiled, including Gelon A100, the first grade in a new family of amorphous nylons from GE Plastics, Stanyl, a high-crystalline nylon 46 being developed by DSM of the Netherlands; MCX-A high-heat (610 F melting point) crystalline resin from Mitsui Petrochemical Industries of Japan; and a transparent amorphous and opaque crystalline pair from Rhone-Poulenc of France (see PT, Jan. '90, p. 89).

Nylon has far to go before approaching its thermal property limitations, say almost all suppliers interviewed. A realistic assessment of heat-deflection-temperature increases to be achieved by nylons during the next 10 years is at least 50[degrees] F, they contend. However, the major challenge for nylon development will be to improve its dimensional stability and barrier properties, and to reduce its inherent sensitivity to hydrolysis.

All of these aims, including improvements in thermal properties, are expected to be achieved through new copolymerization and comonomer technology. Many researchers also cited the "polymer-friendly" aspects of polyamide technology, making it a material of choice for new alloys.

One new semicrystalline nylon now in development at Dow Chemical, and expected to be commercially introduced by mid-decade, will provide heat-deflection temperatures in excess of 450 F. Corson says the program represents an extension of novel polyamide chemistry based on methylene diisocyanate (MDI) that Dow acquired from Upjohn in 1986 (see PT, Feb. '90, p. 14). While the material offers enhanced processing and flow characteristics, Corson says, the challenge will be to control its crystallinity in order to maintain dimensional stability of molded parts and reduce molded-in stresses.

An early research program at Monsanto Chemical Co.'s Springfield, Mass., facility is studying the commercial feasibility of a new high-clarity amorphous nylon. Victoria M. Franchetti, director of technology, says the focus of the Monsanto program will be to stress the clarity, barrier properties and heat resistance of the material. She expects a decision will be forthcoming next year on whether to proceed with commercial development of the material.

The amorphous nylon effort is just one of several research areas at Monsanto dedicated to polyamide materials. "New copolymer technology represents possibilities to expand our base of nylon materials," Franchetti says. "For the 1990s, we will design performance characteristics into the polymer molecule to achieve various properties, rather than use additives." Nylon block copolymers tailored for better toughness, and advances in polyamide composites and filled or reinforced systems, will be development trends for the 1990s, she adds.

New combinations of monomers will also be a path for upgrading nylon performance at Du Pont, according to William D. Foglesong Jr., technical director of engineering polymers. Foglesong says a new engineering grade of nylon in the 1990s will have better dimensional stability and be capable of performing at temperatures 50[degrees]F or more above existing grades.

As for Du Pont's current line of nylons, Foglesong sees a "huge amount of potential" for developing improved toughened grades. "We'll be looking to develop supertough nylons with higher modulus. We want to shift the balance for toughening technology, delivering nylons that have greater impact strength while maintaining their stiffness." Improvements in filler technology and coupling agents also will be part of the equation for toughened, filled nylons, he said.

Du Pont this year will be commercializing six grades of its long-awaited nylon 1212 technology (PT March '90, p. 55). Foglesong says nylon 1212 represents a major thrust for Du Pont in the 1990s. The company says the material offers improved solvent resistance and reduced moisture absorption, which enhances its dimensional stability, and it includes a new proprietary mold-release agent to improve cycle times. The new nylon grade will be produced by Du Pont Canada Inc. in Mississauga, Ontario (see PT July '89, p. 90).

Upgrading melt strength of crystalline nylon 66 for large-part blow molding is another research thrust for Du Pont (PT, May '89, p. 62 and Feb. '89, p. 14). The technology reportedly is an offshoot of reactively alloying polyolefins with nylon to produce "supertough" nylons. The alloying is said to overcome nylon 66's inability to produce molecular weights high enough to support long parisons for large-part blow molding. The Du Pont technology permits extrusion of a nylon 66 parison in excess of 4 feet. The technology is said to have applications in blow molding of acetal, PET and polyarylate as well.

TP POLYESTERS PROLIFERATE

Improved product stability and consistency, better processability, increased thermal properties and new advances in copolymers and alloys will characterize the growth of amorphous and crystalline thermoplastic polyesters during the next 10 years. Suppliers have begun test marketing several new product lines in the last eight months, with optimistic prospects of reaping full commercial benefits by 1995.

The groundswell of technical advances and new products seems to be most prevalent on the amorphous side. Higher temperature properties and optical clarity have been identified as two key areas of development. Robert W. Seymour, research associate at Eastman Chemical Products, Inc., Kingsport, Tenn., said efforts to improve the company's PETG and PCTG amorphous polyesters include pushing their glass-transition temperatures beyond 212 F, compared with the current range of 176-194 F.

Methods of improving thermal properties of these materials could include new monomers, novel polymerization chemistry, or alloying and compatibilizing them with another resin, perhaps polycarbonate. Seymour envisions [T.sub.g]'s as high as 390 F, perhaps by the year 2000. Improved polymerization technology for more consistent resin quality is another key developmental area for Eastman's amorphous polyesters.

On the crystalline polyester side, Eastman has only begun to exploit a new family of PCT polyesters, and also has new PCTA versions (PT, April '88, p. 105; Sept. '89, p. 14). Seymour believes improved processing capability, greater oxidative and thermal stability and better toughness will be the main thrusts for evolution during the next 10 years. Heat-deflection resistance will see only incremental gains, he says--although he specifically excludes consideration of liquid-crystal polymers, which are aromatic TP polyesters.

A long-range development for GE Plastics this decade will be compounding new high-temperature injection and blow molding grades of Eastman's PCT polyester. GE's Wirth says along with elevated thermal properties, developmental grades will possess improved moisture and uv resistance and color retention. "We've identified the polymer structures to give us the performance we require," he said, noting the material would have an HDT of 527 F, and a processing temperature of 572 F.

A major focus in the 1990s will be broadening the chemical resistance of polyesters, according to Seymour. Once again, these improvements will be accomplished through novel copolymerization and/or alloying technologies. One method currently receiving attention at various resin producers, including Eastman, involves developing compatibilizers to alloy crystalline and amorphous polyesters with immiscible polymers, such as polyolefins. Seymour explains that addition of a polyolefin could provide improved resistance to aromatic hydrocarbons and fuels, currently a weakness for some crystalline polyesters. The same compatibilization strategy would be employed to improve the toughness of crystalline polyesters by alloying them with elastomers or rubbers.

HIGH HOPES FOR PEN

At least four resin producers have expressed interest in developing a new amorphous TP polyester known as PEN (polyethylene naphthalate), which is said to offer better thermal and gas-barrier properties than PET (PT, Sept. '89, p. 33; Dec. '89, p. 25). Goodyear Tire & Rubber Co., Akron, Ohio, ICI Americas, Wilmington, Del., Hoechst Celanese Corp., Chatham, N.J., and Eastman all see PEN as a polyester for the 1990s. Amoco Chemicals Co., Chicago, and Mitsubishi Gas Chemical Co. of Japan have announced that they would produce special feedstocks for the material. PEN is the basis of Goodyear's new Cleartuf HP family, slated for full commercialization in 1993. PEN offers a 57% higher [T.sub.g] (248 F) than PET, plus up to five times greater oxygen barrier.

PET & PBT DEVELOPMENTS

There also will be new developments in PET itself, as compounders come up with higher performance additive packages. Polysar Inc.'s Engineering Plastics group in Leominster, Mass., has shown PET's processability "window" can be broadened considerably with additives, to increase flow, permit lower mold temperatures (comparable to those for PBT), and reduce its notorious moisture sensitivity (see p. 37 of this issue).

A new developmental amorphous PET alloy from Allied-Signal Engineered Plastics, Morristown, N.J., is currently undergoing test evaluations with select customers (PT Feb. '90, p. 80). Scheduled for commercial introduction next year, the material will be part of Allied-Signal's Synergy series, making use of the firm's proprietary compatibilization techniques. A company executive would not elaborate on the alloy, other than to say it will exceed the temperature and impact capabilities of standard PET, while maintaining good processing characteristics for both injection molding and extrusion.

Much of the recent PET development efforts at Du Pont have gone towards its Bexloy K-550 program, the glass-filled crystalline polyester engineered for injection molded automotive body panels. Du Pont formally unveiled the technology at this year's SAE show in Detroit, although the material has been under development for nearly two years (PT April '90, p. 20).

The main new technical thrust that has become apparent in PBT is its use in blends with styrenics and PPO, where it can contribute heat and chemical resistance, while the blend retains amorphous-like overall processing characteristics. Examples include GE's Gemax PBT/PPO (PT, April '87, p. 39) and new Cycolin ABS/PBT (PT, Oct. '89, p. 14); PBT/ASA alloys from BASF Corp., Parsippany, N.J. (PT, April '89, p. 127); and SMA/PBT alloys from ARCO Chemical Co., Newtown Square, Pa. (PT, May '89, p. 45).

POLYARYLATES AND PECs

Both polyarylates and polyestercarbonates belong within the amorphous polyester family (they're also related to polycarbonate), and are in the early stages of their life cycles.

Anticipating a commercial payoff later this decade, the Engineering Plastics Div. of Hoechst Celanese has begun test marketing its Durel polyarylate (PT, Oct. '89, p. 33; Feb. '90, p. 85). James J. Conway, v.p. and general manager, says Durel will be one of the firm's key new material platforms for this decade.

Though considered to be a new product for the 1990s, Hoechst Celanese has had the material under development since 1983, when it acquired the technology from Occidental Chemical Corp. Conway says the major R&D hurdle during those ensuing years was unacceptable resin clarity. During the developmental period, the firm opened and closed two start-up plants (in Corpus Christi, Texas, and Summit, N.J.) only to return to Corpus Christi, where the current development effort is now based.

Du Pont has markedly reduced its own polyarylate effort after disappointing results as an auto body-panel candidate, concedes Foglesong. "It's on the back burner. We have a low level of effort in polyarylate at this point. We're not yet sure enough of the market interest or potential applications," he says.

Mobay Corp., Pittsburgh, recently introduced its tranparent Apec aromatic polyestercarbonates to the U.S. (PT, May '88, p. 93; Aug. '88, p. 101). In one effort to explore its potential, Mobay's parent, Bayer AG in W. Germany, plans to begin test-market trials of an automotive alloy of Apec and PBT in the second half of this year (PT, Jan. '90, p. 93). The material has a processing window of 500-554 F and offers low-temperature ductile impact performance down to -40 F. Bayer also launched a new generation of Apec at K'89. Along with better optical properties and uv stability, the new versions offer 26% higher HDT (464 F vs. 367 F) than the previous Apec generation (PT, Jan. '90, p. 95).

LCPs IN THE STARTING GATE

Liquid-crystal polymers (LCPs), comprising random copolymers of aromatic polyesters, have been identified as a strong contender for sharp growth as engineering materials in the '90s. While the mechanical and thermal properties of these resins is impressive, much work remains to develop more effective process technologies to better utilize these novel materials.

Hoechst Celanese and Amoco Performance Products, Inc., Ridgefield, Conn., are the dominant LCP material suppliers today, while Eastman, Du Pont and the French parent of Rhone-Poulenc Inc., Monmouth Junction, N.J., also are developing product lines. Several Japanese LCPs are also said to exist, though none has appeared commercially in the U.S. (A full report on LCPs appears in PT, April '90, p. 92).

NEW POLYETHERIMIDE 'COUSINS'

An amorphous "cousin" of GE Plastics' Ultem polyetherimide (PEI) is under development, with plans for commercial introduction next year, according to Wirth. A crystalline relative also is being researched, but is in more formative stages with no timetable for introduction. Market sampling of the amorphous material is under way.

The new-generation PEIs will boost the material's continuous-use temperature above 440 F, up from the current level of 356 F, Wirth says. Glass-transition temperature is 509 F. He adds that the new Ultem generation "will push the state of the art for today's injection molding machines. Processed at higher temperatures, we'll see comparable flow characteristics to the current Ultem; but it will be a material with better thermal and physical properties and slightly better impact capabilities." Processing temperatures for the new Ultem will be over 572 F.

Wirth emphasizes PEI technology offers considerable flexibility in choice of monomers and consequent latitude in tailoring the materials' temperature performance. He adds that a new copolymerization technology will allow researchers to tinker further with the molecular structure of the material.

Another offshoot of GE Plastics' polyetherimide R&D, now being test marketed, is a copolymer with silicone rubber for impact strength (PT, May '87, p. 11; July '87, p. 102). Known as Siltem STM-1500, there will be block-and random-copolymer versions in the future, according to R. Bruce Frye, R&D manager for GE Silicones, Waterford, N.Y. The new grade offers an alternative to Ultem's inherent stiffness.

Described as an amorphous copolymer, Siltem will have a continuous-use temperature range of up to 302 F. Frye says it will process easier than Ultem, due to the lubricity of the silicone, with better mold-release characteristics. The material has a tensile strength of 3600 psi, flex modulus of 60,000 psi, and elongation of 105%. Siltem reportedly is a true thermoplastic, with the ability to reuse scrap.

PPS GETS TOUGH

Tougher grades and improvements in processability will be among the trends steering development of polyphenylene sulfide (PPS) in the 1990s. The challenge for material suppliers will be to achieve these improvements while maintaining the material's high thermal properties (HDTs in the mid- to high-400[degrees]F range).

Phillips 66 Co., Bartlesville, Okla., the only U.S. producer of the resin at present, will be devoting considerable effort toward toughened grades in coming years. Phillips' newest Ryton compound, introduced earlier this year, is a toughened grade known as R4XT. He would not elaborate on the technology used to toughen the new compound, saying only that Phillips makes use of a new polymerization method and monomers. Like other Ryton compounds, R4XT can reach crystallinity rates of up to 60%.

Phillips also says it has increased fracture toughness of its PPS composites by 500% through improved glass sizings and prepregging techniques (PT, May '90, p. 13). The new Avtel L composites are also said to have better flow and faster crystallization, but with no change in normal Ryton thermal properties.

Blow molding could be a new area of potential for PPS; Phillips introduced a blow molding grade, Ryton BR95 with 30% glass, for automotive underhood parts at this year's SAE show (PT, April '90, p. 15).

Phillips also has started to broaden its line with a new amorphous version of crystalline PPS, called polyphenylene sulfide sulfone (PPSS), or Ryton S (PT, April '89, p. 125). Developmentally designated PAS-2, this newly commercial product has a lower HDT than PPS (347 to 374 F at 264 psi), but boasts "outstanding" chemical and solvent resistance for an amorphous resin. It can be injection and blow molded and extruded.

A strategic thrust in new thermoplastic technology for Hoechst Celanese in the 1990s will be the development of its Fortron PPS, according to Conway. Hoechst presently imports it from Kareha Chemical Industry Co. of Japan, and compounds it here, but a U.S. plant is planned for start-up in early 1993. New developments will include grades for extrusion and blow molding and a new low-molecular-weight injection grade for improved flow in thin-walled parts.

PPS also will be a major thrust for Bayer and Mobay in the 1990s, with the start-up of production of Bayer's semi-crystalline Tedur line this year in Antwerp, Belgium. Bayer executives say Tedur PPS will have an HDT range up to 464 F, with flow characteristics similar to nylon 66. The Antwerp facility will produce linear, high-purity PPS, with a wide range of molecular weights. Processing applications will include injection molding, extrusion of fibers, film and sheet, and thermoplastic composites.

POLYCARBONATE AND ACETAL

Improved processability, surface quality, and uv stability, and ultra-high-purity grades will mark the development of polycarbonate in the next 10 years. New PC alloys will continue to multiply, with companion resins bolstering its thermal, mechanical and barrier properties.

A new polycarbonate copolymer that reportedly provides improved processing characteristics yet maintains high molecular weight and desirable physical properties is now in development at GE Plastics. It's slated for commercial introduction next year. GE's Wirth explains that an entirely new molecular structure, with new monomer sources, provides a major improvement in flow characteristics with no sacrifice in properties, except for a slight decline in HDT. "We'll give up a little bit of thermal properties and gain a lot of flow, and mechanical properties will remain the same," he said.

Exemplifying what is expected to be an active area of development in the '90s, Mobay, GE and Dow Chemical recently introduced ultra-high-purity PC grades for demanding optical requirements--eyewear and optical disks. Both companies said their respective resins were processed and packaged under clean-room conditions. Special isolation techniques are used to eliminate airborne and organic particle impurities that can cause yellowing and/or deterioration of properties. For eyewear, GE introduced Lexan OQ3120, OQ3420 and OQ3820, while Dow brought out Calibre LG 2020 and 2010 grades. Dow also recently released early details of a developmental high-purity Calibre 1001 PC for optical disks (PT Jan. '90, p. 28).

Mobay has a new high-flow CD grade of PC, Makrolon CD-2005 (65-70 MFR). Mobay also is seeking to raise the temperature capability of PC through its new Apec polyestercarbonates, which it plans to make domestically during this decade, although timetables are uncertain. One example of this family is Apec DP-9-9350, launched earlier this year, which has a Vicat softening temperature of 363 F, a 26% improvement over conventional PC.

ACETALS: FEWER DISTINCTIONS

There have been substantial material property and processing improvements in acetal resin technology during the last two years, leading to a softening of the once-sharp distinctions between homopolymer and copolymer acetals. (A full report on developments in acetals appears in PT, Nov. '89, p. 56).

The field of acetal suppliers will become more crowded in the 1990s, with at least two Japanese firms--Mitsubishi Gas Chemical and Asahi Chemical Industry Co.--challenging the "big three" acetal producers (Du Pont, Hoechst Celanese and BASF).

STYRENICS: UPGRADING PROCESSABILITY

Enhanced mechanical properties, better processability, and an increased heat-resistance range will be targets for styrenic material development in the 1990s.

Monsanto will be seeking to broaden its range of ABS products, says Franchetti. New alloying technology to compatibilize thermoset rubbers and other unnamed polymers into ABS, as well as new monomers and random copolymers will be the keys, she says. For example, Monsanto will expand upon its already successful use of alphamethyl styrene to raise the heat resistance of its Lustran Elite HH products.

However, Franchetti anticipates no major upgrades in the thermal properties of ABS, saying the material's Vicat temperature of 284 F is "about as high as we can go without sacrificing other critical performance properties." ABS areas that should see considerable improvement during the next 10 years, she says, will be weatherability (retention of color and gloss), impact resistance and processing characteristics.

Alloying will be another key focus for ABS. Monsanto has just begun a new family of styrenic/PVC alloys with Triax CBE/1, based on Lustran Elite HH, in a joint effort with Vista Chemical Co., Houston (PT, April '90, p. 63). Monsanto has further plans to expand its Triax line with ABS/TP polyester alloys (Triax 4000). GE Plastics, Dow, and Mobay have all recently expanded their ABS/PC lines (PT, Jan. '90, p. 26; Feb. '90, p. 88; March '90, p. 14; April '90, pp. 15, 145). GE also has new ABS/PBTs (see above), and Dow is launching ABS/TPUs for auto bumper fascias (PT, Feb. '90, p. 88; March '90, p. 13). See below under TP elastomers for more details.

Alloying is also a new focus of interest in styrene maleic anhydride (SMA) copolymers, owing to its utility as a compatibilizer to alloy other polymers.

Advances in compounding and molding technology for glass-reinforced SMA materials will be a key effort for ARCO Chemical. Al Wambach, manager of engineering resin R&D, said his company is not alone in working on new processing techniques to advance productivity in compression and injection molding of styrenic structural composites. The goals of this effort will be to develop processes requiring lower clamp tonnages and injection pressures, enabling processing of larger, more complex structural parts on smaller machines.

New compounding technologies also are being explored as a complementary effort, seeking ways of pelletizing ARCO's Dylark SMA with long-fiber reinforcements for injection molding. A trend will be to significantly increase the glass-fiber loadings in SMA compounds up to 45%, compared with current 20% levels, Wambach says. ARCO is involved in strategic partnerships aimed at new chemistry to improve the wettability of glass fibers by SMA resins. Molding techniques to achieve substantially longer fiber lengths in molded parts will be another thrust. The goal of all these developments will be to produce styrenic compounds with higher strength and greater structural capabilities.

Improved fabrication techniques for reinforced styrenics also was identified as a major trend for the 1990s by Monsanto, which also produces SMA (Cadon). Franchetti says Monsanto has several "early-stage development programs now underway dealing with improved processing of styrenic composites.

Besides ARCO and Monsanto, the list of SMA suppliers in the U.S. will soon include DSM Engineering Plastics North America Inc., Reading, Pa., which plans to introduce Stapron S from Holland (PT, April '90, p. 163). Unique technology reportedly allows higher-than-usual rubber loadings, for higher impact at the same level of heat resistance, or vice versa.

ACRYLIC ALLOYS, COPOLYMERS

Increased toughness, new alloys, and better heat resistance will be the targets for acrylic development in the 1990s, based largely on new alloys and copolymers.

Rohm & Haas Co., Philadelphia, will expand its new Kamax acrylic-imide copolymer family during the next 10 years, improving the thermal properties and blending with elastomeric materials for toughness. The current HDT range of Kamax is 284 to 304 F, which is capable of moderate improvement, depending on the overall balance of properties desired, says a company spokesman (PT, May '88, p. 91).

CYRO Industries, Mt. Arlington, N.J., appears to share similar development goals for its Acrylite acrylic compounds. A company spokesman said Cyro's initial emphasis for new material development during the next 10 years will be research into acrylic/polycarbonate alloys. Developmental opaque grades reportedly have notched Izod ratings up to 24 ft-lb/in.

Also in development at CYRO are impact-modified "engineering" acrylic resins, including an RDT series of clear and opaque acrylics with notched Izod impact strengths up to 2 ft-lb/in. These and the new alloys can be extruded, thermoformed, blow molded and injection molded (PT, Oct. '89, p. 131).

A new family of high-impact acrylic/polycarbonate alloys will continue to expand at Polysar Engineering Plastics. These employ a proprietary modified acrylic developed by Polysar. The company just added a higher-heat SD-9104 grade to the initial SD-9101 version (see New Products section). A flame-retardant version is in development.

Polysar's Clear Plastics group is developing an improved clarity and flow version of its NAS 20 styrene methyl methacrylate copolymer. Known as NAS 21, the material is expected to have a melt-flow rate of 4.3 g/10 min.; nearly double the rate for NAS 20.

NEW FLUORO-COPOLYMERS

Advances in random and block copolymerization technology, utilizing various monomers to lower crystallinity levels and control flexibility, as well as improve low-temperature mechanical properties, will be among the key developmental trends for fluoropolymers in the 1990s, according to a spokesman at Philadelphia-based Atochem North America (formerly Pennwalt Corp.), which produces Kynar PVDF. He cited the use of a more highly fluorinated comonomer (hexafluoropropylene) in the polymer backbone, which can lower the crystallinity of the material by 20%.

Two new fluoropolymer materials, representing leading-edge technologies, were introduced at last year's K'89 show in Dusseldorf, West Germany (PT, Jan. '90, p. 109). Teflon AF, a high-clarity amorphous resin designed for coatings and molded parts, was unveiled by Du Pont, while a new family of modified PTFE compression molding powders known as Hostaflon TFM was displayed by Hoechst AG.

The Du Pont material represents an expansion of its existing semi-crystalline Teflon line, and offers an upper use HDT of 545 F. Compared with PTFE, these amorphous resins offer unusually high [T.sub.g]'s (320-464 F) and low dielectric constants (1.89-1.93), as well as good mechanical properties.

Hostaflon TFM, an upgraded version of Hoechst's existing Hostaflon TF line, features higher mechanical properties and better weldability.

FAST TRACK FOR TP ELASTOMERS

An abundance of new material technology continues to push thermoplastic elastomers into the spotlight as a key engineering-resin group for this decade. Rapid proliferation of TPE families began to gather momentum in the late 1980s, and is expected to continue during the 1990s. (For an in-depth report, see PT, Aug. '88, p. 44).

Joseph H. Muhs, marketing director of the Elastomers Business Group of Monsanto, speculates that key development areas for TPEs will include improvements in flame retardance, colorability, uv stability, surface quality, stability in contact with fluids, and ability to be sterilized for medical and food-contact applications. Much as in other thermoplastic segments, compatibilization technology --in this case between plastics and rubbers--will be an essential area for the 1990s, he observes.

The recent TPE '90 technical conference in Dearborn, Mich., sponsored by Schotland Business Research Inc., Princeton, N.J., reconfirmed this ongoing vitality in elastomeric technologies. Many of the new materials discussed at this forum represented strategic thrusts for the coming years.

One of them is the first-ever fluorinated TP elastomer, being test marketed by 3M Industrial Chemical Products Div., St. Paul, Minn., with the first of three planned grades scheduled for commercialization in early 1991 (PT, May '90, p. 11). Kenneth D. Goebel, research specialist, says the unique aspect of this new alloy was the reversed roles of elastomer and plastic; fluoroelastomer accounts for the continuous phase and preponderance of the alloy, while a thermoplastic (an unidentified nylon) makes up the dispersed phase.

Goebel says the as-yet-unnamed material can be processed as a true thermoplastic, with the ability to reprocess scrap. However, finished parts can be crosslinked by gamma irradiation, if desired. The material will have a continuous-use temperature range of -60 to +356 F. The initial grade, known as FTPE 76A, has a Shore A hardness value of 76, ultimate elongation of 260%, tensile strength of 1770 psi, and 35% compression set at 350 F.

The fluoroelastomer component of the alloy is an existing 3M material known as FKM, while the nylon is supplied by an unnamed source, he said, adding that 3M also performed the compatibilization research to alloy the materials.

Two new grades of "third-generation" Kraton styrenic TPEs have been developed by Shell Chemical Co., Houston. Known as Kraton GSK, they are designed to improve upon the traditional poor mechanical performance of SEBS triblock copolymer elastomers at elevated temperatures. G7702X (36 Shore A) and G7722X (59A) are two new SEBS grades, with the latter representing the higher-end performance material of the two. G7722X has a tensile strength of 220 psi at 212 F, compared with 100 psi for conventional Kraton G7720, as well as 350% elongation, vs. 140% for G7720. Compression set at 253 F for 30 min is 18% for G7722X, vs. 34% for conventional Kraton G. At room temperature, G7722X has tensile strength of 1050 psi and elongation of 520%, vs. 750 psi and 700% for conventional Kraton G.

A new family of TP urethane (TPU) alloyed with ABS through a proprietary compatibilization chemistry, will be launched later this year by Dow Chemical for auto bumper fascias. Augustin T. Chen, a TPU researcher at Dow, described properties of two blends of this unnamed material at TPE '90: a 50/50 mix and a 70% TPU/30% ABS mix. The first grade has a tensile strength of 4300 psi, flex modulus of 105,000 psi, enlongation of 240%, and density of 1.11 g/cc. The second grade has a tensile strength of 5650 psi, flex modulus of 33,940 psi, elongation of 650%, and density of 1.17. It's expected the material will include glass- and mineral-filled commercial grades.

A new TP elastomer of ethylenepropylene thermoset rubber crosslinked into an unidentified thermoplastic matrix through a dynamic vulcanization process is expected to be commercialized by Monsanto next year. Joseph Muhs says the material will have a continuous-use temperature up to 347 F.

VINYL TPEs COMING ON

Vinyl-based TPEs are an emerging family that's expected grow in the next 10 years, offering an answer to the problem of PVC plasticizer migration during long-term heat aging and weather exposure.

Two new-generation vinyl-based TPEs were unveiled earlier this year by BFGoodrich Co., Cleveland, and The Sunprene Co., a Bellevue, Ohio, joint venture of A. Schulman Inc. and Mitsubishi Kasei Vinyl Co. of Japan (PT, Feb. '90, p. 19). The Supreme material is based on special, proprietary PVC resins, while the Goodrich Flexel material is described as an alloy of low-crystalline copolymers "based on vinyl technology," which does not contain PVC or nitrile rubber.
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Title Annotation:Thermoplastics in the '90s
Publication:Plastics Technology
Date:Jun 1, 1990
Words:6079
Previous Article:Processability meets performance.
Next Article:Volume thermoplastics to challenge higher-cost 'engineering' resins.
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