Reinforced thermosets

ERCOM runs a mobile shredder unit that will visit plants or collection points of member companies to size-reduce scrap parts on site and so reduce transport costs. It then ships the compacted material to a central fractioning plant at Rastatt, Germany where, with a 30 t/day facility, it produces a range of active fillers and fibrous reinforcement material for sale back to SMC producers and other users. Primary SMC products have been developed containing up to 25% recyclate without loss in properties. Several have already been approved by the automotive industry for commercial use and product testing continues as a high priority to demonstrate consistent quafity for recyclate material, SMC product, and finished molding. 

To meet automotive demand for parts with high gloss Class A finish, ERCOM has to resort to heavy grinding of the recovered material, which is expensive and degrades the length of fiber to a point where mechanical properties are so poor as to be indistinguishable from cheap fillers. The cascade effect is therefore in play, rather than the closed loop. ERCOM notes that the most valuable component of recovered SMC is, in fact, the glass, at a value of DM 1.98-2.10/kg. 

The project has demonstrated that up to 25% hammer mill regrind can be reused in SMC/BMC formulations without significandy affecting properties the cost is 5% higher by weight but about 7% lower by volume due to the lower density of the recyclate. Up to 8% of virgin fiber can also be replaced, and the fines and milled fiber from the process could also be used as an additive in TPs, or as a medium for blast-removal of paint. 

By mid-1996, ERCOM Composite Recycling GmbH had mechanically recycled over 1 million SMC parts. Production scrap accounted for 750,000 parts and post consumer scraps 250,000 (from the Mercedes Recycling System MeRSy, BMW repair shops and Deutsche Telekom dismantling plants). As a result, over 2 million parts containing recyclate were put back into service in automobiles, including spare wheel well (Audi 320,000), noise barrier shield (VW 250,000), truck bumpers and front end panels (Mercedes Benz 600,000), sunroof frames (350,000), and other components (450,000). 

Studies carried out so far indicate that the particle size is critical in determining the new compounds in which the recyclate can be used, and the most effective percentage of recyclate. For commonly-used SMC/BMC compounds, it is possible to use up to 25% regrind, if the fraction coded RC are used (Tables 3.30 and 3.31). 

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Reinforced thermo.setting resin.s. Table 10-17 lists the normally accepted maximum temperature limits for reinforced-thermosetting-... 

TABLE 10-17 Temperature Limits for Reinforced Thermosetting Resins t... 

In joining reinforced thermosetting pipe it is particularly important that the pipe be cut without chipping or cracking it. It is also important to sand, file, or grind any mold-release agent from the surfaces to be cemented. Joints are built up layer by layer of adhesive-saturated reinforcement by following the manufacturer s recommended procedure. Application of adhesive to the surfaces to be joined and assembly of these surfaces shall produce a continuous bond and provide an adhesive seal to protect the reinforcement from attack by the contents of the pipe. Unfilled or unbonded areas of the joint are considered defects and must be repaired. 

The methods used for manufacturing articles using fibre reinforced thermosets are almost as varied as the number of material variations that exist. They can, however, be divided into three main categories. These are manual, semiautomatic and automatic. 

PPFA Plastics Pipe Fittings Assoc. RTS reinforced thermoset... 

Laurence J Craigie, B S>Chem. Composite Resources, LLC industry consultant in regulatory, manufacturing, and business needs for the composite industry Member, American Society of Mechanical Engineers (Chairman RTP Corrosion Resistant Equipment Committee) Member, American Society of Testing and Materials Member, National Association of Corrosion Engineers International Member, Composite Fabricators of America (received President s Award) (Reinforced Thermosetting Plastie)... 

Ohsawa, T., Nakayama, A., Miwa, M. and Hasegawa, A. (1978). Temperature dependence of critical fiber length for glass fiber-reinforced thermosetting resins. J. Appl. Polym. Sci. 22, 3203-3212. 

Crasto. A.S. and Kim, R.Y. (1993). On the determination of residual stresses in fiber-reinforced thermoset composites. J. Reinforced Plast. Composites. 12, 545-558. 

TABLE 10-21 Recommended Temperature Limits for Reinforced Thermosetting Resin Pipe ... 

Reinforced Thermosetting Resins and Reinforced Plastic Mortars ... 

Unlike ductile metals, composite laminates containing fiber-reinforced thermosetting polymers do not exhibit gross ductile yielding. However, they do not behave as classic brittle materials, either. Under a static tensile load, many of these laminates show nonlinear characteristics attributed to sequential ply failures. One of the difficulties, then, in designing with laminar composites is to determine whether the failure of the first ply constitutes material failure, termed first-ply failure (FPF), or if ultimate failure of the composite constitutes failure. In many laminar composites, ultimate failure occurs soon after first ply failure, so that an FPF design approach is justified, as illustrated for two common laminar composites in Table 8.9 (see Section 5.4.3 for information on the notations used for laminar composites). In fact, the FPF approach is used for many aerospace and aircraft applications. 

Reactive surface treatment assumes chemical reaction of the coupling agent with both of the components. The considerable success of silanes in glass reinforced thermosets have led to their application in other fields they are used, or at least experimented with, in all kinds of composites irrespective of the type, chemical composition or other characteristics of the components. Reactive treatment, however, is even more complicated than non-reactive polymerization of the coupling agent, development of chemically bonded and physisorbed layers render the identification of surface chemistry, characterization of the interlayer... 

ALLYL ESTER RESINS. The allyl radical (CH2CH=CH2) is the basis of the allyl family of resins. Allyl esters arc based on monobasic and dibasic acids and are available as low-viscosity monomers and thermoplastic prepolymers. They are used as crosslinking agents for unsaluraied polyester resins and in the preparation of reinforced thermoset molding compounds and high-performance transparent articles. All modem thermoset techniques may be used for processing allyl resins. 

Thermosets. The potential of thermosets is not solely a function of mechanical performance. These materials have established themselves as suitable for many demanding environments. The potential must be measured in terms of their ease of fabrication into parts. This is where limitations have existed for reinforced thermosets, specifically polyesters this, in combination with the limitation related to the necessity of postmolding operations to obtain high appearance surfaces. 

The precursors of thermosetting polymers are usually one of the ingredients of complex formulations. They may be present in very small amounts, as in the manufacture of abrasive disks where the thermoset acts as an aggluti-nant in medium amounts, as in the case of filler-reinforced thermosets or as the only components, in formulations used for encapsulation purposes. Apart from fillers, fibers, pigments, etc., some formulations contain rubber or thermoplastic modifiers that phase-separate upon the polymerization reaction (cure). 

TABLE 10.3 Effect of Various Silanes on Glass Reinforced Thermoset Resins7... 

Bonding Adhesives for Design of Structural Joints D 5677 Specification for Fiberglass (Glass Fiber Reinforced Thermosetting Resin)... 

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