Phthalic acid reinforced

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... 

Aromatic amorphous or semicrystalline polyamides, PARA, such as copolyamide from caprolactam, hexamethylenediamine and iso- and tere-phthalic acids, PA-6IT6, or copolyphthalamide, PPA, are frequent components of polymer blends. Their advantage is low permeability to liquids and gases, stiffness and high HDT. Several blends of PP with PARA have been described, e.g. with either PP-MA, PE-MA, or PP grafted either with acrylic acid or GMA. Usually, these blends must be heat stabilized with phosphite ester or hydrazine. The alloys are often reinforced by addition of glass fibers and talc. 

MAJOR USES Manufacture of diphthalic anhydride, phthalic anhydride, phthalonitrile, benzoic acid, ethyl benzene, high performance polymers, plasitcizers, alkyd resins, glass reinforced polyesters, dyes, insecticides and motor fuels. 

Intrinsically non-flammable polymers are few, but phenolic resins have a good reputation both in Are and smoke performance, which has resulted in their becoming increasingly favoured for reinforced plastics structures, for example, underground transport, where such concerns are greatest. Polyether ether ketone (PEEK) is also a low fire and smoke polymer. Unsaturated polyesters, vinyl esters and epoxy resins bum readily, but modified versions are available with improved behaviour. For example, both bromine and chlorine are used extensively in the form of chlorendic (HET) acid, tetrachlorophthalic anhydride (TCPA) and tetrabromo-phthalic anhydride (TBPA) which can be reacted into the polyester in small quantities and can act as permanent (non-migrating) flame retardants. 

Cblorendic resins are prepared by reacting propylene glycol with a combination of endomethylenehexachloropthalic anhydride (cblorendic anhydride) and phthalic anhy-dride. This resin shows excellent corrosion resistance and fire retardancy (due to the presence of chlorine) when used as a matrix for fibre-reinforced composites. Cblorendic resins are used in applications that require exceptional resistance to acidic and oxidising environments. In recent years, BPA fumarate resins have been extensively replaced by cblorendic resins for various industrial applications. 

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