Study On Degradation And Chain Extender Of PBS And PBS-based Polyester

Aliphatic polyesters, because of outstanding biodegradability, hadbecome the hotspot in the R&D all over the world. Poly(butylenesuccinate)(PBS) had high melting point and good processing properties,while introducing methyl(group) into the main chain could mademodification and became molecular asymmetry in the main chain, thusP(BS-co-BA) and P(BS-co-BE) got a better tensile properties andbiodegradability than PBS did. However, though conventional syntheticmethods were difficult to obtain a higher molecular, either meltpolycondensation, solution polycondensation or melt and solution phasepolycondensation, which largely limited the processing and applicationperformance of PBS、 P(BS-co-BA) and P(BS-co-BE). In this thesis,succinic chloride (SUC) were used as chain extender to synthesis thehigh molecular of PBS、 P(BS-co-BA) and P(BS-co-BE).(1) SUC was used as chain extender to synthesis PBS instead ofthe conventional synthetic method. The optimal reaction conditions ofthe extended chain reaction were studied,and molecular weight, meltingpoint and mechanical properties and so on were tested at the same time.The results were showed as following.①The optimum reactionconditions of the extended chain reaction was that the addition of HDIwas3%, reaction temperature was140℃, reaction time was60minutes.②Molecular weight of PBS expanded from6.17×10~4to12.35×10~4.③Melting point of PBS reached to127℃, which increasing10℃.④Theelongation of PBS was changed from132%before to253%.⑤Thermal decomposition temperature of PBS was increased to335℃.(2) Based on the best reaction conditions, with the SUC as chainextender to synthesis P(BS-co-BA) and its series of copolymers. Themolecular weight, melting point and other properties of P(BS-co-BA)and copolymers were detected before and after chain extension. The results showed that:①The best ratio between SUC and P(BS-co-BA)and its copolymers was20%.②The molecular weight of P(BS-co-BA)and its copolymers increased from6.02×10~4to11.07×10~4.③Meltingpoint of P(BS-co-BA) and its copolymers was up to119℃.(3)Based on the optimum conditions of our laboratory to synthesisP(BS-co-BE) and its copolymers with SUC used as chain extender.Molecular weight, melting point and thermal decompositiontemperature of polymers were tested. The results were showed asfollowing.①Under the optimum conditions, The best ratio betweenSUC and P(BS-co-BE) and its copolymers was15%.②Melting pointof P(BS-co-1,2-PS) and its copolymers was reached to103℃.③Themolecular weight of P(BS-co-BE) and its copolymers increased from5.96×10~4to11.71×10~4.④Thermal decomposition temperature ofP(BS-co-BE) and its copolymers reached up to309℃.(4)Biodegradability of PBS, P(BS-co-BA) and P(BS-co-BE) andits copolymers were tested in the degradation nutrient solution,conclusion were obtained through the weight loss:①Without chainextender, the degradation rate of copolymers of PBS, P(BS-co-BA) andP(BS-co-BE) which were greater than PBS was, and PBSE-20had themaximum weight loss rate.②With SUC chain extender, thedegradation rate of copolymers of PBS、P(BS-co-BA) and P(BS-co-BE)which were greater than PBS was. The degradation rate ordered:SUC-PBSE-20﹥SUC-PBSA﹥PBS， PBSE-20﹥PBSA﹥PBS.