Optimization study of polyurethanes based on unsaturated polyester blends

In this paper, an optimization study of some polyurethane samples based on unsaturated polyester blends is presented. This work aims to establish a se ries of products with increased mechanical properties. A number of unsatura ted polyesters based on maleic anhydride and various glycols were used: pol y(ethylene-maleate-fumarate)diol; poly(diethylene-maleate-fumarate)diol; po ly(neopentyl-maleate-fumarate)diol, and 4,4'-dibenzyldiisocyanate. Mechanic al tests were performed on a TIRA-test 2161 apparatus (Germany). The influe nce of the amount of polyesters, used as reagents, versus mechanical proper ties of the ensued polyurethanes was studied. Therefore, we conducted an op timization study using an experimental matrix which gives the following reg ression equation: [GRAPHICS] where X-i, X-j are the polyester amount (independent variable); Y-i, the me asured mechanical property value (dependent variable) and b(i), the regress ion coefficients. To show the good influence of the polyester amounts, poly urethanes with a low concentration of urethane groups (maximum 2%) were syn thesized. The macromolecular chain growth of the unsaturated esteric struct ures lead to an increase of the elasticity modulus and tensile strength. Th e tensile strength had its better value on polyurethanes based on fumarate polyesteric structure, through increase of the induced crystallinity. Compa ring experimental and theoretical data on the basis of these equations, a g ood agreement resulted. This creates the possibility to select the samples with predetermined and useful properties. (C) 2000 Elsevier Science Ltd. Al l rights reserved.