Unsaturated Polyester Resins Reinforced with Fibres

3 Unsaturated Polyester Resins Reinforced with Fibres 

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Used as fibres, particularly in textiles and film. Many other polyester polymers are of importance, e.g. unsaturated polyester resins from phthalic anhydride, propylene glycol and maleic anhydride used with reinforcement in boats, cars, etc. (alkyd resins). U.S. production 1983 1-7 megatonnes. 

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. 

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]. 

The unsaturated polyester resin with trade mark Mitsubhisi Yukalac type BQTN and its catalis is used as a matrix. The palm fibre or palmyra(from arenga pinnata reinforcement in this experiments were obtain from Sibolangit around 50 Km from Medan with diameter 0.2 - 0.3 mm, and the coir(from cocos nucifera lynn) were obtain from Lubuk Pakam around 30 Km from Medan and around 3 Km from sea-side with 0.2 - 0.3 mm diameter. As chemical solvent was used sodium hydroxid for treated of the fibres from E. Merck. 

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). 

The surface energy of fibres is closely related to the hydrophility of the fibre. Some investigations are concerned with methods to decrease hydrophility. The modification of wood-cellulose fibres with stearic acid [49] causes those fibres to become hydrophobic and improves their dispersion in PR As can be observed in jute reinforced unsaturated polyester resin composites, treatment with polyvinylacetate increases the mechanical properties [50] and moisture repellence. Silane coupling agents may contribute hydrophilic properties to the interface, especially when amino-functional silanes, such as epoxies and urethane silane are used as primers for reactive polymers. The primer may supply much more amine functionality than can possibly react with the resin at the interphase. Those amines, which could not react, are hydrophilic and therefore responsible for the poor water resistance of the bonds. An effective way to use hydrophilic silanes is to blend them with hydrophobic silanes such as phenyltrimethoxysilane. Mixed siloxane primers also have an improved thermal stability, which is typical for aromatic silicones [48]. 

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. 

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... 

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