TOUGHENING OF UNSATURATED POLYESTERS BY REACTIVE LIQUID POLYMERS .1. SYNTHESIS AND CHARACTERIZATION OF THE MODIFIERS

Two series of unsaturated polyesters were prepared by reacting 1 mol o f maleic anhydride (MAN) with 2 mol of poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPG) of differing molecular weights. The polye sters were characterized using various techiques such as acid value, h ydroxyl value, vapor pressure osmometry (VPO), IR spectroscopy, and NM R spectroscopy. It was shown that the polyesters based on MAN and PEG had a structure similar to the idealized structure based on the stoich iometry of the reactants, except in the case of the polyester based on PEG 200. It was shown that an idealized structure could not be obtain ed in the case of the polyester based on PEG 200 due to the presence o f ''Ordelt reaction''. In the case of polyesters based on MAN and PPG idealized structures could be obtained. It was shown that, longer poly esterification times were needed for the PPG reactions due to the pres ence of a secondary hydroxyl group at chain ends. The PEG-based reacti ve liquid polymers were found to be miscible with the unsaturated poly ester resin, whereas the PPG-based reactive liquid polymers were immis cible. However, both these adducts were found to improve the toughness of the base unsaturated polyester resin significantly, without any ma jor adverse effect on its modulus.