'Infrastructure' is theme of SPI Composites conference.

Beckoning opportunities for composites in the civil-engineering or "infrastructure" field and in other construction areas are the focus of the 50th Annual SPI Composites Institute Conference and Expo, to be held Jan. 30-Feb. 1 in Cincinnati.

At least eight out of 18 conference sessions are devoted to such topics as FRP beams, polymer concrete, composite rods for reinforcing concrete, use of composites for "rehabilitation" of wood and concrete structures, and FRP in bridges, docks, and pilings.

Several presentations will suggest ways to tap into these markets and offer early results on current "showcase" demonstration programs. One session will report on the National Science Foundation's research on advanced composites for construction. Another session will focus on how standards development will foster market penetration of FRP in civil engineering. Two more sessions will cover the Council of Great Lakes Governors Polymer Concrete Initiative and the American Concrete Institute's development activities in FRP-reinforced concrete systems.

Although market and design topics will occupy more of the conference than usual, there will be no shortage of papers on innovations in resins, additives, and processing technology.

A conference session devoted to RTM and two sessions on pultrusion testify to continued interest in these fast-growing technologies. (One pultrusion session is specifically concerned with construction applications.) In sheer volume of papers (three conference sessions), SMC/BMC manufacturing will again dominate other process technologies. The latest steps in computer process modeling and simulation of SMC will be one area of focus.

RTM: TRY 'SOFT' TOOLING

One of several intriguing developments to be presented for RTM is new soft tooling that's really soft. Use of one rigid tool haft and one tool half with flexible walls will be presented as a new solution for hard-to-mold RTM parts by Dow Plastics, Midland, Mich., and the Center for Composite Materials at the University of Delaware, Newark. The flexible walls can be inflated or deflated. During filling, the tool would be deflated, allowing it to deform. At or near completion of filling, the tool can be inflated to apply consolidation pressure.

This approach reportedly prevents either too-dense preforms from inhibiting flow or insufficient fiber fraction from inducing resin "racetracking." The authors will present a computer simulation of the process in a soft tool.

Equipment developments aimed at achieving higher automation in RTM will be presented by the British firm of Plastech Thermoset Tectonics (represented here by RTM Systems, Inc., Indianapolis) along with the School of Manufacturing, Materials and Mechanical Engineering at the University of Plymouth, England. Plastech TT recently developed a fully automated injection unit that's close-coupled to automatic injection sprues and a 150-psi pneumatic press. Novel approaches to monitoring feedback signals (catalyst flow sensing, mold-cavity deflection, and backpressure control) will be described, as will use of computer simulation for process optimization.

Samsung Heavy Industries Co., Ltd. of South Korea will share results of a new technique for molding high-fiber-volume parts (greater than 55%) that combines RTM and compression molding. Company officials will discuss how void formation is determined by initial fiber volume and speeds of resin injection and mold closing.

For shorter tooling lead times, Reichhold Chemicals Inc., Research Triangle Park, N.C. will recommend mass casting of RTM molds using a low-shrink, modified polyester filled with aluminum powder and pellets.

NEW PULTRUSION TECHNOLOGIES

Injection dies for pultrusion, which provide a closed impregnation system with low VOC emissions, will be the topic of two papers at the conference. Refinements of injection dies will be presented by The Werner Co., Franklin Park, Ill., and Owens-Corning Fiberglas Corp., Toledo. Their newly developed method for producing ladder rail (ANSI 14.5 Type-I) uses a modified injection die to control the permeation rate of resin through the reinforcement pack. The special impregnation-chamber design is said to create a pressure gradient of sufficient magnitude to fully wet the reinforcement and ensure adequate volume flow of resin.

Pultrusion machinery supplier Composite Process Equipment Inc. of Haslet, Texas, will also discuss recent developments in injection dies and identify areas of needed research.

PPG Industries Inc. and Advanced Textiles Inc., both based in Pittsburgh, will jointly describe results of research on reinforcements for phenolic pultrusion. A new triaxially stitched fabric made from PPG's phenolic-compatible yarn reportedly produces stronger, stiffer, thinner, and lighter-weight profiles.

Flame-resistant phenolic pultrusions will also be discussed by two resin suppliers, Georgia-Pacific Resins, Inc., Decatur, Ga., and Indspec Chemical Corp., Pittsburgh. G-P plans to unveil new solvent-free phenolic resin technology designed specifically for pultrusion.

Meanwhile, Indspec will discuss hybrid composites of wood and pultruded phenolic FRP. Development work involving Indspec, Creative Pultrusions Inc. of Alum Bank, Pa., and the American Plywood Association shows that resorcinol-modified phenolic wood adhesives can achieve improved adhesion between wood and pultruded sheets made with resorcinol-modified phenolic resin.

Two other papers will discuss wooden beams and transportation structures reinforced with pultruded or other FRP.

COMPUTER SIMULATION OF SMC

Several presentations will update work on computer modeling and simulation of SMC compression molding. Researchers from the Polymer Processing Research Group in the Dept. of Mechanical Engineering at the University of Wisconsin-Madison will report on their finite-element simulation program, which accounts for the effects of cure-induced stress buildup and thermal history during molding.

The simulation program considers thick SMC parts with complex geometries that include fibs and bosses. It demonstrates that non-uniform curing and thermal gradients occur during the molding process. These effects are strongly dependent on part geometry, cure kinetics, and processing conditions. Wisconsin researchers say that these thick SMC regions require a 3-D simulation program to fully calculate and predict the build-up of residual stress.

Premix Inc., North Kingsville, Ohio, will describe work on a different phase of SMC manufacturing--numerical computer modeling and design of the resin-paste coating process in sheet impregnation. Premix researchers say this coating process has "the most profound effect" on the uniformity of mat weight of SMC sheets. Typical SMC machines use a slot-coating device in which a PE fill is continuously drawn beneath a paste reservoir. Here, the film picks up a layer of resin metered through a small gap controlled by a blade dam.

Variables considered in this computer model include fluid viscosity, density, and surface tension; conveyor speed and paste-head pressure; and paste-reservoir and blade geometries. First, Premix modeled the velocity profile and pressure distribution of flow inside the paste reservoir using standard computational fluid-dynamics software. The results were then applied as the boundary condition in step two, where the blade exit and the moving PE film were modeled. Simulation results were verified in tests on actual SMC equipment, and those results were used to improve the design of the paste-metering equipment for a controlled and uniform coating.

A joint presentation by Dainippon Ink & Chemicals Inc. of Japan and Reichhold Chemicals will evaluate available SMC molding simulation methods. These programs, many of which are theoretical in character, may help processors and designers select optimal charge location, ensure fill, and maximize part performance for warpage and strength before steel is cut for tooling.

NEW RESINS FOR SMC

Continuing the focus on low-pressure SMC (LPMC) materials evident at last year's conference, Takeda Chemical Industries Ltd. of Japan will introduce new resins for low-pressure/low-temperature SMC molding. Takeda has a technology alliance with Owens-Corning, a firm already involved in joint LPMC market development with National Composites Inc., South Bend, Ind. (see PT, April '94, p. 15; Jan. '94, p. 30).

Takeda's new LPMC resin can be compression molded at 290 psi in a temperature range of 176 to 212 F. The company says inexpensive clamping mechanisms and epoxy or nickel-shell molds can be utilized to substantially reduce the capital investment required.

Takeda will also present a novel approach to making cultured-marble sanitary ware using a TMC process (a hybrid of SMC and BMC) and a novel low-profile additive. This technology is said to yield translucent parts that formerly could be produced only by casting.

A new angle on SMC and recycling and will be presented at the conference by Ashland Chemical Co., Columbus, Ohio. The company is developing a new family of unsaturated polyesters based on chemical raw materials reclaimed from post-consumer PET by glycolysis. Such "recycled" resins have previously been used for open-mold laminating in marine and other applications. Ashland may be the first to use this approach for an SMC resin. The new resins, together with thermoplastic low-profile additives, have been used to produce zero-shrink SMC with "near-Class A" finish, according to the company. Such a material, Ashland says, would be suited to non-premium and structural applications. Incorporating recycled feedstocks reportedly does not affect the resin's processing, handling, or mechanical properties.

DIOL FOR WEATHERABLE GEL COATS

A new way to make weatherable gel-coat resins will be introduced by Arco Chemical Co., Newtown Square, Pa. Arco says polyester gel coats based on its MPDiol Glycol demonstrate excellent uv resistance and humid aging in accelerated-weathering tests.

NEW FILLERS AND REINFORCEMENTS

Alcan Chemicals Div. of Alcan Aluminum Corp., Cleveland, will roll out what it describes as a new generation of alumina trihydrate (ATH) fillers and flame retardants. A new manufacturing process reportedly yields ATH with "fundamentally different particle characteristics" as compared to the usual ground product. The new Alcan ATH particles are smoother, more rounded, and more uniform, and have lower surface area and surface moisture.

In resin systems, the new ATH reportedly provides lower viscosity, faster cures, and better control of SMC thickening than does ground ATH. Lower viscosity can permit higher loadings, Alcan says, providing enhanced flame retardance, lower smoke and toxic gas emission, and lower cost. Alcan will discuss advantages in SMC, pultrusion, and hand lay-up.

Isorca Inc., Granville, Ohio, will also provide details on a cooperative program undertaken with material suppliers and an unnamed automotive company to develop a novel reinforcement known as LO-D Mat for liquid molding processes. This new reinforcement holds promise for reducing the density of composites with minimum effect on mechanical properties. LO-D Mat contains hollow microspheres that are bonded uniformly to reinforcing fibers in a manner that allows resin penetration without displacing the microspheres or increasing the resin viscosity.