Effects of phthalic anhydride polyester polyol on mechanical properties of polyurethane resin system based on polymethylene polyphenyl isocyanate-polypropylene glycol

In this paper, a series of two-component polyurethane resins were prepared by using polymethylene polyphenyl isocyanate (PMDI) and polypropylene glycol (PPG400) respectively as hard and soft segment. In order to further increase strength, stiffness and heat resistance of resin system, phthalic anhydride polyester polyol (PAPP) was used as second soft segment. The effects of content, functionality and molecular weight of PAPP on mechanical properties of PMDI-PPG resins were mainly studied. The results indicated comprehensive performance of polyurethane resin was best in the case of employing tri-functionality PAPP with a molecular weight of 400 and 40% content in soft segment. The resulting tensile, flexural and impact strength of polyurethane respectively reached 66.4, 92.0 MPa and 66.1kJ/m². The tensile and flexural strength of glass fibre-reinforced polyurethane composite respectively reached 465 and 552 MPa. PMDI-PPG/PAPP system thus is expected as a new type of resin matrix used for high-performance polymer composites.