Unsaturated polyester resin glass fibre-reinforced

DIN 16869 Centrifugally cast filled glass fibre reinforced unsaturated polyester resin (UP-GF) pipes, 1989- 1990... 

Results are presented of experiments undertaken by Gaiker in the manufacture of sandwich panels containing foam cores based on PETP recycled by a solid state polyaddition process developed by M G Ricerche. Panels were produced with glass fibre-reinforced unsaturated polyester and epoxy resin skins, and allthermoplastic panels with PE, PP, PS and glass fibre-reinforced PETP skins were also produced. EVA hot melt adhesives and thermoset adhesives were evaluated in bonding glass fibre-reinforced PETP skins to the foam cores. Data are presented for the mechanical properties of the structures studied. 

This is also known as Bulk Moulding Compound (BMC). It is blended through a mix of unsaturated polyester resin, crosslinking monomer, catalyst, mineral fillers and short-length fibrous reinforcement materials such as chopped glass fibre, usually in lengths of 6-25 mm. They are all mixed in different proportions to obtain the required electromechanical properties. The mix is processed and cured for a specific time, under a prescribed pressure and temperature, to obtain the DMC. 

Nowadays the major thermosetting resins used in conjunction with glass fibre reinforcement are unsaturated polyester resins and to a lesser extent epoxy resins. The most important advantages which these materials can offer are that they do not liberate volatiles during cross-linking and they can be moulded using low pressures at room temperature. Table 3.1 shows typical properties of fibre reinforced epoxy. 

Finally, glass-reinforced unsaturated polyesters are well known as building materials for boats, yachts and cars and generally termed fibre-glass resin . The preparation, properties and applications of these unsaturated polyesters are summarized in Chapter 21, while the chemistry and properties of a new unsaturated polyester resin for fibre-reinforced composite materials are discussed in Chapter 22. 

Maleic anhydride is used as a chemical intermediate in the synthesis of fumaric and tartaric acids, certain agricultural chemicals, resins in numerous products, dye intermediates and pharmaceuticals [2]. It is primarily used as a co-monomer for unsaturated polyester resins, which are used in the production of bonding agents for plywood manufacture and when mixed with glass fibres for reinforced plastics. Annual production of maleic anhydride is estimated to be over one million tormes [3]. 

Figure 2.9 Left Good adhesion between fibres and resin is demonstrated by the residual resin on the fibre surfaces after fracture. The specimen was a carbon fibre reinforced PEEK (polyester ether ketone) material. Right Exposure to hot water has caused some loss of adhesion between the glass fibres and the unsaturated polyester resin, as shown by the smooth regions of the fibre where little resin adheres after fracture...

Fibre reinforced plastics. The most wide-spread reinforcement is glass fibre as roving, chopped strand mat, fabric, etc. The most usual matrix materials are unsaturated polyesters and epoxy resins as thermosets. In glass fibre reinforced thermoplastics (e. g. ABS, PA, PPO), the length of the glass fibres is 1 to 3 mm. Other reinforcing fibres are aramide, asbestos, boron, carbon, etc. 

Polyesters. Main chain of their macromolecules is characterized by repeated — CO—O— groups. Unsaturated polyester resins are thermosets used mainly for manufacturing glass fibre-reinforced plastics products. The most wide-spread type of thermoplastic polyesters are polymers of an aromatic dicarboxylic acid (mainly terephthalic acid) and an aliphatic diol (e. g. ethyleneglycol or butanediol). The most important representatives of this group are poly(ethylene terephthalate) and poly-(butylene terephthalate). Polyarylate aromatic polyester is a high-temperature thermoplastic of an aromatic dicarboxylic acid (terephthalic acid) and an aromatic diol (bisphenol-A). In the chemical sense, polycarbonate is also a polyester. 

By incorporating unsaturated dicarboxylic acids (e.g. maleic acid), besides phthalic acid, into the polycondensation reaction, unsaturated polyesters are formed. These are then cross-linked with a low-molecular unsaturated monomer, usually styrene, in the presence of a peroxide catalyst and a cobalt compound as accelerator. Unsaturated polyesters are applied as cast resins or glass fibre-reinforced composites. The latter product was the first large-scale plastic material in the self-extinguishing category for the building industry... 

Krigbaum [12] has reported on the use of glass fibre reinforced composites, both from Cytec Industries, based on Cyglas 685 unsaturated polyester [bulk moulding compound (BMC)] and Cyglas 695 vinyl ester resin (BMC) in automotive valve covers and other engine cover applications. The recycling of these valve covers is also discussed. 

Vinyl ester resins (epoxy diacrylates) are used by the glass-fibre-reinforcement industry for products that are resistant to chemicals and corrosion. They are epoxy di(meth)acrylates (P-hydroxyester acrylates) that are usually obtained by reacting epoxy resins of glycidyl derivatives with (meth)acrylic acid. They can also be manufactured from bisphenol A and glycidyl (meth) acrylates (Kanerva et al. 1986 Kanerva et al. 1989 Jolanki 1991). Acrylates based on bisphenol A or epoxy resin can be polymerised by electron beams, ultraviolet light, and also by the addition of various peroxides (Jolanki et al. 1995). The same cross-linker (styrene), hardeners (organic peroxides) and accelerators (cobalt) as for unsaturated polyester resin are used in composite epoxy acrylates (Rolston 1980). 

Reinforced plastics a wide range of products produced from reinforcing fibre (notably glass, but others such as asbestos and carbon fibres, etc, are used) and synthetic resin (called a matrix ). Both thermosetting and thermoplastic polymers are used as a matrix. Unsaturated polyester resins are still usually looked upon as the major matrix material, but many other plastics can be and are used extremely successfully (the best known being nylon). 

The use of accelerated ageing tests and spectrophotometric techniques in studying the photooxidative degradation of unsaturated polyester resins and glass fibre-reinforced composites is examined. Results of accelerated and natural ageing tests are compared, and criteria to be taken into account in achieving accelerated test results representative of reality are discussed. 5 refs. 

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