UNSATURATED POLYESTER FOR LARGE CASTINGS

A series of unsaturated polyesters based on phthalic anhydride (PHA), maleic anhydride (MA), ethylene glycol (EG), diethylene glycol (DG), t riethylene glycol (TG), propylene glycol (PG), and styrene (Sty) were prepared. The molecular weights of the prepared polyesters were determ ined by the end group analysis. The crosslinking of unsaturated polyes ters by copolymerization reaction between the double bonds from maleic anhydride and styrene has been studied. The effect of the structure o f the resin on its curing behavior has been investigated. A marked del ay in cure has been observed when EG was replaced or combined with oth er glycols. The maximum curing temperature, Young's modulus and compre ssive strength were found to be related to the molecular weight of the glycol incorporated in these castings.