Recycling will be a new theme at SPI composites expo.

Recycling Will Be a New Theme At SPI Composites Expo

For the first time, SPI's annual Composites Institute conference and exhibit, to be held the 18th to 21st of this month in Washington, D.C., will include a session on Recycling. A sign of the growing perception that environmental issues will have an impact on thermoset producers and processors, the session will include three papers on SMC/BMC recycling and one on reclaiming glass fiber from epoxy circuit boards.

Among 100 other technical papers, the greatest area of news will be in SMC and BMC, especially for automotive, followed by the latest developments in RTM and SRIM preforming and process analysis, thermoplastic composites, and a crop of new resins for open-mold laminating and cultured marble.

SMC/BMC RECYCLING

EMERGES

Thermoset recycling is grabbing fresh attention, but it's not totally new. According to knowledgeable sources, Harrison Radiator Div. of General Motors Corp. in Lockport, N.Y., used around 10% regrind in BMC underhood automotive parts for several years prior to 1981, when Harrison ceased injection molding BMC in-house.

At the SPI conference, Premix Inc., North Kingsville, Ohio, will give a progress report on its commercial recycling of SMC and BMC molding scrap, first announced last spring (see PT, July '90, p. 13). Premix developed the technology mainly to permit its molding-compound customers to return their scrap for recycling into fresh compound, according to v.p. and compounding division general manager David Clavadetscher. He adds that Premix is willing to share its know-how with others. "We did it for the good of the industry," he says. Premix forecasts around 38 million lb/yr of in-plant scrap accumulating by the end of this decade (Fig. 1), representing about 5% of U.S. production.

Premix developed its own in-house regrinding system from available standard components: a granulator, a hammermill pulverizer, and a classifier (Fig. 2). This two-stage grinding system is said to give good particle-size control, since oversized particles are fed back from the classifier to the hammermill for a second pass. Material is ground so it will pass through a 200-mesh screen, yielding an average particle size of 30.1 microns (1.2 mils).

Premix has used up to 88 phr of regrind - replacing an equal amount of calcium carbonate - in SMC and BMC, constituting up to 30% of the paste formulation and 20% of total weight, with "only slight" effect on physical properties. Premix found that use of regrind increases paste viscosity and reduces overall density. And though high levels of regrind degrade surface quality, a low level (30 phr, or around 10%) actually produces a smoother surface than standard SMC, Premix says. Material sold so far has contained such a low regrind level, which reportedly causes no statistically significant change in properties.

While sales volume is still relatively small, a developing application is shower-stall bases, where mixed-color or black-and-white regrind gives a decorative terrazzo-style appearance. A sample part will be displayed in Washington. There is a small cost premium for SMC containing regrind, which is partly offset by the reduced density.

Premix is also using a process it calls "fuel blending" to consume waste liquid resin and compound paste from its manufacturing operations and reduce disposal costs. A chemical solvent and inhibitors are added to the waste to keep it in a pumpable state, and it is then used to fire cement kilns, with the resulting ash going into the cement itself. (CIRCLE 29)

Owens-Corning Fiberglas Corp., Toledo, Ohio, will discuss its own approach to "controlled mechanical granulation" of cured SMC to yield a blend of free glass fiber, ground polyester powder, and calcium carbonate filler. (Premix says its process does not cause such a separation of components.) OCF used a shredder from Saturn Shredders, div. of MAC Corp., Grand Prairie, Texas, to reduce parts from a max. of 18 x 14 in. to 2 x 8 in. chunks. These were then fed into a granulator from AEC/Nelmor Div. of AEC, Inc., North Uxbridge, Mass., for grinding as fine as 3/16 in. OCF cited equipment and installation costs of about $95,000 for this 1000-lb/hr system. Total processing costs were estimated as 2.8[cents]/lb of regrind.

Because the regrind has higher resin demand than standard calcium carbonate filler, OCF recommends replacing only 5-10% of the calcium carbonate in standard BMC with regrind. BMC made with regrind retained about 70% of the mechanical properties of all-virgin compound, and surface quality also deteriorated, giving a porcelain granite-ware appearance. (CIRCLE 30)

An update on SMC recycling will also be made in Washington by the SMC Automotive Alliance, a consortium of 11 molders and 15 suppliers, which has been investigating regrinding and pyrolysis methods (see PT, April '90, p. 7). New information includes a laboratory study by Ashland Chemical Co., Columbus, Ohio, which determined that up to 20% of ground SMC could be substituted for calcium carbonate in its Phase Alpha automotive Class A formulation, with no detrimental effect on initial viscosity, ultimate thickening, gel or cure times, or surface profile.

CLEAN GLASS FROM REGRIND

Recycled glass fiber from scrap circuit boards is a new venture of Peninsula Copper Industries, Inc. (PCI), Hubbell, Mich. In the last six years the company has accumulated over 45 million lb of scrap epoxy/glass circuit boards, from which it has stripped and recycled the copper plating. In the last two years, PCI has recovered heat-cleaned glass fiber from a continuous calcining process, which vaporizes the resin, combusts the gases to generate electricity, and yields patches of woven roving of 1/4 to 3/4 in. diam. Broader applicability of the glass-recovery process has been demonstrated with limited amounts of automotive SMC, overspray from FRP spray-up, and reject tub/shower enclosures.

Independent testing reportedly shows that the recovered glass - either in original or milled form - performs comparably to virgin glass in thermoset and thermoplastic compounds. PCI is exploring use of the recovered glass patches in directed-fiber preforming, as well. (CIRCLE 32)

NEW MATERIALS FOR SMC, BMC

A host of new resins, systems, and additives will be introduced this month for achieving new performance levels in SMC and BMC:

* Class A finish - Reichhold Chemicals, Inc., Research Triangle Park, N.C., is test marketing a new automotive Class A SMC resin system that's said to give consistently lower porosity than competing formulations. This "X-1" system, developed in Japan and also discussed in a paper at last year's conference, contains a novel low-profile system, which reportedly gives 3-10 times fewer pinholes than other SMC, and gives no pinholes at all when molded under vacuum (see PT, Jan. '90, p. 17). Reichhold is working closely with target accounts to provide guidance in formulating and processing.

* Low-modulus, Class A - SMC has not generally been used for vertical auto body panels such as fenders, because it has been difficult to combine adequate flexibility with sufficient flexural strength and surface smoothness. Interplastic Corp.'s Molding Products Div., South Bend, Ind., claims to have developed an SMC formulation that meets these requirements, using a proprietary reactive flexibilizing agent.

And Union Carbide Chemicals and Plastics Co. Inc., Danbury, Conn., will introduce Neulon-H, a newly commercial low-profile agent that reportedly gives flexible but tough and strong Class A vertical panels when used with a flexible polyester resin. (CIRCLE 35)

* Injection molded BMC - Union Carbide also claims to have injection molded BMC auto body panels with "truly super Class A surface at impact strengths 80% above those of the best standard injection materials," thus solving the major limitation inhibiting progress of BMC injection molding in this application. The work was accomplished with a Billion ZMC machine, a new developmental fiberglass reinforcement from Vetrotex of France (partner of Certain Teed Corp., Valley Forge, Pa.), and a developmental UCC low-profile agent, XLP-40V22, described as a modified polyvinyl acetate.

Owens-Corning has introduced a new generation of chopped strands in 1/4-in. and 1/2-in. lengths, which are said to give 30-55% impact and other property improvements in injection molded BMC over the company's 832 and 405 glass products. Good dispersability reportedly also cuts mixing time in half. The company also has developed a choppable continuous-strand version, which gives 80% higher impact than OCF's SMC rovings. OCF also worked with Battenfeld GmbH in Germany to modify its screw injection unit so as to reduce shear as much as possible.

* Low profile with colorability - Two firms will present papers on novel low-profile additives that function by means other than the conventional phase-separation mechanism, thus avoiding the light-scattering or whitening effect that inhibits uniform coloration or transparent effects. ECC America, Atlanta, is now sampling a product developed in England called Polarite 420. It's a 3-micron calcium carbonate filler with a proprietary thermoplastic coating (available in natural white and black), which is designed to replace all of the usual filler and low-profile agent. Polarite 420 is said to produce zero-shrink compounds that are easily colorable with standard pigment pastes; with the black version, no additional pigmentation is needed. Pricing is in the range of 50-65[cents]/lb. It's currently recommended only for BMC, not SMC.

Ferro Enamels (Japan) Ltd., sub. of Ferro Corp., Cleveland, has an equally novel but quite different approach, aimed at making BMC simulated onyx or granite tabletops, kitchen counters and sanitary ware with a smooth surface and high degree of transparency - something that's impossible with conventional low-profile agents. The secret is a low-profile agent consisting of particles of lightly crosslinked "microgel" of a styrene-acrylic copolymer. The agent is a dry powder composed of particles with surface unsaturation that reacts with the polyester matrix resin and helps form an interpenetrating polymer network (IPN).

* High-heat SMC - Interplastic Corp.'s Commercial Resins Div., Minneapolis, has two new high-heat polymers for SMC. One is CoRezyn VE8935-1, a one-component vinyl ester said to have higher temperature capabilities and significantly better surface profile than current SMC vinyl esters. Retention of strengths and moduli at 300 F are reported to be significantly better than the current industry standard. Retention of flexural properties are termed "excellent" at 350 F and "good" at 400 F. It reportedly approaches Class A. (CIRCLE 40)

The second new resin is a proprietary polyester that's said to be similar in cost to a PG-MA polyester, while superior in performance to PG-MA and even to higher-cost NPG-IPA polyesters and vinyl esters. The new resin has higher tensile strength than PG-MA at temperatures up to 300 F, and is stiffer than the two premium resins even above 300 F. It has higher notched Izod impact, abrasion resistance, and accelerated weathering performance than all three. Water-immersion property retention is comparable to PG-MA, and stain resistance is better than PG-MA or vinyl ester and comparable to NPG-IPA. Surface quality is equal to PG-MA and better than NPG-IPA or vinyl ester (Class A reportedly can be achieved). Interplastic is sampling several versions with different gel times and viscosities, including a BMC resin. (CIRCLE 41)

SMC/BMC PROCESS

INNOVATION

Premix will give the first detailed public presentation of its work over the last four years to computerize its SMC sheet-making lines with the aid of gamma-backscatter gauges (see PT, March '85, p. 76; May '88, p. 21; March '90, p. 70). Premix has now put as many as five transverse-scanning gamma gauges on one machine to measure paste thickness at both ends of both doctor blades, as well as on the final sheet. Not only does this provide on-line statistical process control (SPC) of mat weight and glass/resin ratio, with no need to cut and measure samples by hand, but Premix has just now installed closed-loop control of the doctor blades. Mat-weight consistency has already improved 72% and is expected to reach 85% with the new PC-based control system. Start-up scrap has been cut by 70%.

An innovative process for combining the high-strength properties of SMC compression molding with the productivity and automation benefits of BMC injection will be presented by Takeda Chemical Industries Ltd. and Kobe Steel Co. of Japan, which built the machinery. (Kobe Steel America Inc. is in N.Y.C.) The system uses a standard SMC press, but automatically deposits TMC material onto the mold in a continuous log by means of a reciprocating extruder on a sled that allows it to move in and out of the mold area. The extruder has a stuffer hopper and plunger rather than a screw to minimize glass breakage. Izod impact strength of parts is said to be twice that of injection molded BMC, though not quite equal to SMC. Flexural strength and modulus are reportedly higher than SMC, however.

PROGRESS IN RTM, SRIM

Though not quite as hot a topic as at the last two SPI conferences, preforming will again receive attention in the RTM session. Cannon U.S.A., Mars, Pa., will introduce its improved Compotec preformer (Fig. 3), which is said to reduce mat waste and cycle time by using two moving platens instead of one.

And further evidence of numerous efforts to mathematically model the mold-filling process in liquid composite molding (LCM) will be presented by the Center for Composite Materials at the Univ. of Delaware, Newark; the Engineering Research Center of Ohio State Univ., Columbus; and GenCorp Automotive's Reinforced Plastics Div., Marion, Ind. The latter two papers show that proper flow simulation must take into account how porosity of the reinforcements is locally affected by stretching during mat performing, and by deformation from the pressure of resin injection.

Other LCM news will include a new low-profile polyester resin system from Reichhold for faster RTM cycles, while maintaining good mechanical properties and Class A surface quality. Polylite 31-515 is a one-pack low-profile system that reportedly doesn't separate during long-term storage. It gels in 5 min and cures in 14 min at 80 F. At 140 F it gels in 1 min and cures in 3.7 min, while still providing room-temperature pot life of 14 min.

Degussa Corp., Ridgefield Park, N.J., will describe how RTM tools can be produced quickly and easily by mass casting the company's Atlas M130 system of thermosetting methacrylate resin filled with 85% aluminum powder and granules, a system that has already proven successful in RIM tools. Masses up to 4000 lb can be poured at one time, with no limitation on thickness. After gel coating, the tool can be poured, cured and demolded in about half a day.

Also, Micromet Instruments, Inc., Cambridge, Mass., will illustrate the possibilities of real-time SPC in RTM, RIM and SMC molding by means of tool-mounted sensors for temperature, pressure and dielectric properties, together with the company's ICAM-1000 high-speed monitor. Dielectric monitoring can show the time to viscosity minimum, gelation, and cure on each shot.

TP COMPOSITE R&D

The University of Delaware's Center for Composite Materials will present its latest work on robotic placement of PP/glass filaments. A computer-controlled Puma 762 electric-driven, six-axis, jointed-arm robot from Westinghouse Automation Div., Pittsburgh, was outfitted with a pair of torches that electrically heat nitrogen gas to melt the filaments without oxidizing the resin (Fig. 4). An air cylinder and linear bearings provide continuous control of consolidation pressure to [plus or minus]1.1 lb. No active cooling is required. Preheated mandrels are turned by an electric servo motor, which is controlled directly by the robot's computer. Using CAD/CAM techniques, winding patterns are first simulated on a computer, then the resulting laminate design is subjected to computerized stress analysis. Only after the latter is found to meet design requirements does the computer generate winding pattern control files for downloading to the robot controller. Actual winding speeds with PP are currently up to 4-5 in./sec.

New approaches to thermoplastic pultrusion have been investigated by Alcoa Laboratories in Alcoa Center, Pa. One approach is to use a stack of alternating plies of resin film and reinforcing fabric as the infeed material, which is much lower in cost than either preimpregnated fibers or costitched plies of commingled-fiber fabric.

Alcoa's pultrusion setup (Fig. 5) includes a preheater and a segmented die with zoned temperature control, including cooling in the final zone, achieved by means of a combination of cartridge heaters and compressed-air jets. To keep the outer layers of resin film from being stripped off by friction in the die, Alcoa installed endless belts that traveled with the plystack through the die. Polyimide film was used, but aluminum belts would be preferable for higher-temperature resins and would better resist stretching. In order to consolidate high fiber loadings, Alcoa developed proprietary die designs, including a large chamfer at the die entrance, which gradually decreased throughout the total die length.

NEW PHENOLIC FAMILY ARRIVES

British technology for making heat-resistant, flame-retardant, low-smoke and low-toxic-emission phenolic composites was commercialized this past summer by BP Chemicals Inc. (formerly Silmar) from a new office in Keasbey, N.J. BP's Cellobond phenolic resins have been used for critical mass-transit, mining/tunneling, and automotive applications in Europe for over five years, and are now being toll-produced in the U.S. for BP. They are said to be easier to work with than other phenolics and to have very low odor. Since they don't require filler for fire resistance, laminate density can be lower than with FR polyesters. Price range is $1.55-2.00/lb.

They include five resins spanning a viscosity range of 300 to 4800 cp, for processing by virtually all methods - hand lay-up, spray-up, filament winding, pultrusion, RTM, and press molding (wet mat, SMC, BMC). One resin is thixotropic. Two acid catalysts (one faster, one slower) are also offered, as is a sprayable phenolic surfacing paste or gel coat. The highest viscosity resin, for SMC/BMC and pultrusion, uses no catalyst, relying on heat cure instead (5 min at 265 F).

Phenolic business manager Aram Mekjian notes that Cellobond phenolics require storage at or below 40 F to provide three-month shelf life. Also, since acid catalysts are used with all but one resin, users must be aware of the potential for tool and equipment corrosion. Acid-cured systems gel at room temperature (5-8 min with the slower catalyst), and thereafter require post-curing for 3-4 hr at 140 F. Cellobond phenolics are not pigmentable, but BP offers its own compatible low-smoke paints; others are said to be available from Akzo Coatings Co., Troy, Mich.

Spray-up requires modifying equipment with stainless-steel tubing and ability to handle higher catalyst ratios (5-10 phr). Venus-Gusmer Corp., Kent, Wash., and Poly-Craft Systems, div. of Binks Mfg. Co., Burbank, Calif., reportedly offer phenolic conversion kits for spray equipment.

RESINS FOR OPEN MOLDING

Interplastic's Commercial Resins Div. will introduce three of the first corrosion-resistant, flame-retardant polyesters to meet California's new Rule 1162 for reduced styrene emissions. Although the Rule went into effect in July 1989, corrosion-resistant resins were granted an exemption, owing to the lack of suitable low-emissions technology to modify these resins at the time. Now, with the aid of organic additives, Interplastic has come up with three styrene-suppressed versions of its CoRezyn 16-AA-060 series halogenated polyesters, which are reportedly said to meet the Rule 1162 volatility requirements with no sacrifice in corrosion, fire, mechanical or processing performance.

Another "first," or close to it, is claimed for a light-stable vinyl ester that overcomes these resins' traditionally poor uv stability while retaining their toughness and corrosion resistance. CoPlas, Inc., Fort Smith, Ark., developed these resins, and has them custom manufactured on a toll basis, for the purpose of formulating tough, corrosion-resistant gel coats for outdoor uses, such as building panels or high-quality boats. Gel coats formulated with its new VE5000 light-stable vinyl ester have demonstrated, both in Florida sunlight and QUV accelerated testing, much greater yellowing and chalking resistance than either conventional orthophthalic or IPA/NPG gel coats.

What's said to be a "new class" of polyesters for superior thermal shock resistance in cultured-marble and onyx sinks will debut from Reichhold Chemicals. Designated Polylite 32-201, they have high HDTs but low enough exotherms to prevent mold damage. These resins produce castings that reportedly will not crack under the severe conditions of a proposed new Cultured Marble Institute test.

NEW COUPLING AGENTS

Petrarch Systems, part of Huls America, Inc., Bristol, Pa., will introduce the Hydrosil 2600 and 2700 series of hydrolytically stable, water-borne silanes that don't generate volatile alcohol byproducts when they react with fillers or reinforcements, thus minimizing health and fire hazards. Nine grades with various functionalities are said to be stable in water for over six months, and to give performance comparable to standard silanes - perhaps even better in moist environments.