The diacid and most probably the dialcohol contribute to the major portion of --C[H.
These byproducts represent the diacid and dialcohol, which were proposed based upon of the hydrolysis of ester bond as a mechanism of the PUR degradation.
Although it is most often used, unpolar styrene is not a thermodynamically good solvent for relatively polar polyester (10), (12), (13), and so various saturated diacids or higher dialcohols
are added in the preparation of polyesters to improve compatibility.
It contains mainly fatty esters (80 percent-85 percent), free alcohols, (10 percent-15 percent), acids (3 percent-6 percent), hydrocarbons (1 percent-3 percent), esterified fatty dialcohols
(up to 20 percent), hydroxylated fatty acids (up to 6 percent) and cinamic acid (up to 6 percent).