Study On Chain-Extending Modification Of Biobased Polyester Polymer

Because of high consumption, heavy pollution problems of non-renewable resources such as oil, the preparation of bio-materials has become the focus among the scientific research workers. In this context, biobased elastomer (BEE) was prepared and its properties (resistance to oil, blending compatibility, thermodynamics, etc) were studied. But due to the polycondensation reaction, which requires high vacuum degree, this causes the difficulty in synthesis of high molecular weight BEE. Therefore, this paper in view of the low molecular weight of BEE, the method of chemical chain extension modification was studied for the BEE, and focused on the type of chain extenders, process conditions and so on.This paper first studied chain extension reaction between pyromellitic dianhydride (PMDA) and BEE, which we found PMDA cannot effectively improve the molecular weight of BEE. Then we selected triphenyl phosphite (TPP) as chain extender. In the experiments, we selected factors such as temperature, amount of TPP and molecular weight of BEE prepolymer to study. After exploration of experimental conditions, we found out that with increasing dosage of TPP, the molecular weight of chain-extended product increases. And when adding15%wt TPP, we obtained product with highest molecular weight. At180℃, when the molecular weight of BEE prepolymer was about10000, the molecular weight of chain-extended BEE was up to48198.The effect of TPP as chain extender is limited, and4,4-diphenyl methane diisocyanate (MDI) is a common highly active chain extender, therefore, MDI as a chain extender was studied for the BEE. We explored factors such as temperature, time and amount of MDI respectively. We can find through the experiments:with the increasing molar ratio of-NCO/OH, the torque and gel content increased, and the molecular weight of BEE rised firstly then decreased. When the mole ratio of-NCO/OH=2/1, and the chain extension conducted for4min at80℃, the molecular weight of BEE was up to86716. Enhanced by adding SiO2, we obtained improved mechanical properties compared with original BEE.