New resins, new applications highlight composites conference.

New Resins, New Applications Highlight Composites Conference

PLASTICS TECHNOLOGY turned up lots more resin news at SPI's Composites Institute conference in Dallas this February than first reported in our pre-show coverage (see PT, Dec. '88, p. 15). Highlights of the show include new applications for still relatively new IPN and hybrid resin systems; an assortment of new polyester resins, including several for SMC; an update on thermoplastic powder technology, said to be the only solvent-free process available for the manufacture of thermoplastic preforms; wear-resistant thermoplastics based on aramid fiber reinforcement systems; and a new non-RIM polyurea spray technology.

IPN/HYBRID RESIN DEVELOPMENTS

Several years ago, Amoco Chemicals Corp., Chicago, made freely available to resin producers research that it was then conducting into hybrid isopolyester/urethane materials, in hopes of expanding the market for its isophthalic acid products. Later, the information flow was cut off when Amoco decided to develop and sell its own hybrid material. That product was introduced at last year's show in Cincinnati as Amoco's Xycon hybrid resin (see PT, Mar. '88, p. 44).

At this year's show in Dallas, Amoco showed off a new sailboard, made by Shark Technology of Denver, that was recently converted from vinyl esters to Xycon hybrid resin in order to enhance stiffness in critical parts. The entire sailboard, including fins and centerboards, is now made from a translucent composite consisting of a semi-rigid Xycon formulation, a polyurethane foam core, E-glass, and an aerospace-grade carbon fiber that includes scrim. In describing the materials used, an Amoco spokesman emphasizes that Xycon is not really sold in "grades" as such, but is specially formulated for each and every application. (CIRCLE 17)

Several companies that started out working with Amoco in hybrid resins (Mar. '87, p. 58) now continue to develop the technology independently. These include Freeman Chemical Corp., Port Washington, Wis.; Reichhold Chemicals, Inc., Sewickley, Pa.; and Silmar of Hawthorne, Calif., formerly a div. of Standard Oil and now a div. of BP Chemicals International, Cleveland.

Freeman markets its version of this hybrid technology under the same "Interpol" trade name with which it markets its related interpenetrating polymer network (IPN) technology. One brand-new IPN application that Freemen announced at the show is a helmet made by the Bell Pro Police Div. of Montpelier, Idaho, that's reportedly able to stop a .357 Magnum bullet at a range of 6 ft. It was developed jointly by Freeman and by Allied Signal Inc.'s New York City-based Fibers Div. The helmet (see photo) combines multiple layers of Allied's Spectra 900 fibers, Freeman's new Interpol 47-1050 IPN resin and its Stypol 40-7236 polyester resin (combined in a 30:70 ratio), as well as thermoset fibers, and metallic woven fabrics. (CIRCLE 18)

EVOLUTION IN SMC

New angles continue to emerge in sheet molding compound technologies, as well. GenCorp Automotive, Farmington Hills, Mich., for example, introduced a low-density SMC compound that's based on hollow glass sphere technology, providing a 30% weight reduction vis-a-vis standard SMC.

For the past five years, GenCorp had been molding front underbodies for GM's Corvette using Derakane 790 vinyl ester resin by Dow Chemical Co., Midland, Mich. But GM requested a lower density product specifically to reduce vehicle weight, so GenCorp went to work with Dow to develop a new formulation. For the past six months, the new low-density product has been used for all Corvette structural panels (see photo).

According to a GenCorp spokesman, alternative low-density SMC materials do exist, but only yield density reductions on the order of 17%. GenCorp is eager to sell the proprietary compound to interested molders, he says, but he won't divulge the price, saying only that it does cost more than standard SMC. As consumption increases, though, economies of scale should bring the price closer to that of standard SMC. (CIRCLE 19)

For the automotive/transportation market, a new fast-cure, class "A" SMC resin system was announced by Freeman Chemical. Cure times for Acpol XXCEL resin can be as low as 30 sec, says a spokeman, compared to the existing standard of approx. 2 min. He reports excellent processing and moldability characteristics, along with good paint adhesion and bondability with all conventional adhesives. The material has reportedly passed extended molding trials, including those for the GM 80, in which it reportedly ranked among the top four materials. Price was not available. (CIRCLE 20)

Since 1987, Koppers Co., Inc., Pittsburgh, has been producing the urethane-thickened "ITP" (Interstitial Thickening Process) materials that it acquired early that year from ICI Americas (see PT, Dec. '88, p. 19). In Dallas, a spokesman for Premix Inc., North Kingsville, Ohio, announced that Premix is now compounding and selling Kopers' ITP's in its Premi-Glas 1200 VE line. Among the many claimed advantages over standard SMC is elevated temperature performance. At 284 F, 50% glass-reinforced High Performance ITP 1094, for example, has a tensile strenght of 16,530, flexural modulus of 1,015,266 psi. Values for conventional vinyl ester, on the other hand, are reported to be 12,905, 20,155, and 1,160,304 psi, respectively. (CIRCLE 21)

Finally, Aristech Chemical Corp., Pittsburgh, presented background on experiments it conducted to develop its MR 13006 unsaturated polyester resin into a one-component, low profile system for the automotive industry, now commercially available as MR 13200. (CIRCLE 22)

NEW LAMINATING/RTM RESINS

Two new vinyl ester resins were presented at the show by Dow - one reportedly the industry's first premium-grade resin shipped in a promoted and accelerated state. Dow's Derakane 411-350PA needs only to be catalyzed to be made workable, thus reducing the number of steps performed by fabricators. Typical properties for a 1/4-in. hand lay-up laminate, for example, are flexural strength of 29,600 psi, flexural modulus of 1030 kpsi, and tensile strength of 20,700 psi. The resin reportedly complies with the U.S. Food, Drug and Cosmetic Act as amended under FDA regulation 21 CFR 177.2120. (CIRCLE 23)

Dow's other new vinyl ester is a brominated version with an epoxy backbone, a structure that reportedly gives it both a high degree of mechanical strength and good chemical resistance. With Derakane 510B-700PAT, fire retardance is achieved without use of additives (the absence of which is said to facilitate visual inspection of laminates). In addition, resistance to hydrolytic attack is maintained despite the absence of additives. Typical physical properties for a hand lay-up laminate include flexural strength of 22,400 psi, flexural modulus of 1020 kpsi, and tensile strength of 17,900 psi. The primary market for this product is in lightweight laminates for shipboard transportation and/or armoring systems. (CIRCLE 24)

Dow also reported that a new experimental cyanate ester resin system has recently replaced bismaleimide (BMI) in an experimental program for development of a missile body section. Experimental system XU 71787.02L reportedly meets the same mechanical requirements as BMI, yet is easier to process. The 18-in.-long part is made by U.S. Composites Corp. of Troy, N.Y., under subcontract to Boeing, and is produced by means of tri-axial braiding and resin transfer molding (RTM). (CIRCLE 25)

Southern California's rule 1162 affecting styrene vapor emissions has now gone into effect, and use of low styrene content unsaturated polyester resins has emerged as one means of staying in compliance (July '88, p. 38). At the show, Reichhold Chemicals presented its Polylite 33-231, a low-styrene-content, low-profile laminating resin said to retain performance characteristics typical of high-quality polyester materials. Properties for a 42-45% glass mat laminate include flexural strenght of 35,000 psi, flexural modulus of 1120 kpsi, and tensile strength of 22,000 psi. (CIRCLE 26)

Finally, a new trade name was announced at the show. ICI Americas Inc., Wilmington, Del., has been marketing its methacrylate-based resins in North America under the "MDR" name. Now, these materials - used in processes such as RTM, cold press molding and pultrusion - will be marketed here under the "Modar" name, a name already in use throughout the rest of the world. (CIRCLE 27)

THERMOPLASTICS NEWS

Ongoing work to extend the number and quality of thermoplastic matrix materials that can be used in high-performance thermoplastic composites was presented at the conference by the Thermoplastic Composites (TPC) group of BASF Structural Materials, Inc., Charlotte, N.C. TPC has developed a powder impregnation technology (see PT, Aug '88, p. 37 and May '88, p. 16) for production of drapable, tacky prepregs. Previous announcements have cited work with a variety of resins, including PPS, PEK, PEEK, PEI, and various polyimides. In Dallas, that list was extended to include promising work with an improved version of LARC-TPI polyimide recently developed by Rogers Corp., Rogers, Conn. Mechanical properties have not yet been generated. (CIRCLE 28)

One thermoplastics presentation that surprised some conference attendees was given by Du Pont Co., Wilmington, Del., on the use of short aramid fiber-reinforced thermoplastics for wear-resistant applications. Resin systems developed so far include nylon 66, acetal, PPS, PET, PBT, PP, copolyester TPE and TPU, though only the first three were discussed in detail.

Although PPS offers excellent chemical resistance and good service temperature, it is not usually specified for wear-resistance because it has always required glass reinforcement to improve its mechanical properties, especially impact resistance. But in wear applications, use of glass in unsatifactory as it can cause counter-surface abrasion. On the other hand, Du Pont says the wear characteristics of the new aramid-reinforced PPS can exceed those of unreinforced nylon 66.

Du Pont produces these aramid fiber-reinforced materials by melt-impregnating continuous filament yarns, rather than by extrusion compounding. That permits use of longer fibers and helps to avoid fiber damage. What observers find surprising is that Du Pont, both a producer of PTFE-based lubricated resins and a manufacturer of PTFE itself, should market a product which, though offering the potential for higher performance capability, could still compete so directly with these products. (CIRCLE 29)

Though perhaps not truly RP/C materials, three new UL-listed, flame retardant, halogen- and phosphorous-free nylon alloys were presented in Dallas by Comalloy International Corp., Nashville, Tenn. Voloy 684, 685, and 686 are said to be based on polymeric FR technology, reportedly eliminating the need for special waste disposal and reducing associated health hazards.

While other materials in the Voloy 680 series are VO rated at 1/8 in., the new ones are rated down to 1/50 in. Voloy 685, for example, has a tensile strength of 17,200 psi, flexural strength of 25,800 psi, flexural modulus of 1420 kpsi, and an HDT of 500 F @ 264 psi. Price is $2.45 to $2.65 tl. (CIRCLE 30)

POLYUREA SPRAYING EMERGES

When polyurea materials were first introduced, they were presented as candidates for spray foam applications. Though that application never panned out, things have nonetheless come almost full circle. In Dallas, Texaco Chemical Co. of Bellaire, Texas, presented a new polyurea spray coating and elastomer (though not foam) technology said to present significant opportunities in areas outside of molded RIM parts.

Texaco has developed a two-component, 1:1 mix-ratio spray system that can be formulated into products ranging from soft rubbers to hard elastomers. As with RIM polyurea systems, gel times are typically 3 sec or less, so impingement mixing is required. Working with a high-pressure proportioner (Model H-V) and high-pressure spray gun (Model GX7) or pour gun (Model AR-C) provided by Gusmer Corp., Lakewood, N.J., the company reports excellent results in lab trials. Chopped glass rovings can also be used; these have been incorporated into hard elastomeric formulations and applied with Gusmer's Venus R-84 glass chopper.

According to a Texaco spokesman, the new spray technology has several unique advantages. Due to the fast cure, for example, sloped or even vertical surfaces can be sprayed without forming drips or runs. And thanks to polyurea's water insensitivity, the material is affected very little by humidity and temperature variations. Excellent physical properties are also reported, including tensile strength, abrasion resistance, and thermal stability as high as 350 F. Finally, the material can be pigmented to improve light stability or to enhance appearance.

As with its RIM polyurea systems, Texaco does not sell directly to processors and fabricators, but is making the new spray system available to systems formulators for evaluation and testing. (CIRCLE 31)

PHOTO : This ballistic helmet, which incorporates Freeman's Interpol 47-1050 IPN resin, absorbs impact so well that a wearer who takes a direct hit from a .357 Magnum is not incapacitated.

PHOTO : This sailboard is now made from Amoco's Xycon hybrid resin because it requires no gel coat, isn't brittle in resin-rich areas, and reportedly has 60% less shrinkage than vinyl esters.

PHOTO : This Corvette structural underbody panel is made from a new low-density SMC material developed by Dow and GenCorp that's 30% lighter than standard SMC.