Degradability Regulation Of Poly(Butylene Succinate)

In recent years,environmental pollution which is caused by non-degradable polymer materials is getting more serious.Biodegradable polymer materials,a kind of friendly materials to environment,are gradually appearing in front of the researchers and attracting people's attention.In these biodegradable polymer materials,poly(butylene succinate)(PBS)has relatively high melting point,good thermal stability and comprehensive mechanical properties,so the value of its theoretical research and practical application is worthy of further study.In order to broaden the application range,prolong the service life and storage time,and can not affect its biodegradability after using PBS products.in this paper,PBS was modified by changing the end group structure to achieve the goal of controlling the degradation rate.In this thesis,hydroxyl-terminated PBS with different molecular weights were synthesized by direct melt polycondensation,and succinic acid and 1,4-butanediol were used as raw materials.Viscosity measurement,FT-IR and 1H-NMR were used to verify the molecular weight and structure of products.The thermal and biodegradability of products were analyzed by DSC and biodegradation experiments.Then,we used maleic anhydride(MA)and epichlorohydrin(ECH)as blocking agents respectively to change the end group structure of PBS.The end-group modification of PBS were carried out by adding different amounts of blocking agents during the polymerization process and extruding in the twin-screw extruder.The biodegradability and thermal degradation process and mechanism of the products influced by modification were studied.The main research contents are as follows:(1)Four kinds of PBS with different molecular weights were synthesized by melt polycondensation.The effect on crystallinity of the molecular weight was investigated.The biodegradability of PBS with different molecular weights was studied in enzyme buffer.The results indicate that PBS have good biodegradability in enzyme buffer.With increasing the molecular weight,crystallinity of the PBS decreased and the degradation improved on the contrary,indicating that the end group content had great effects on its biodegradability.(2)Different amounts of maleic anhydride and epichlorohydrin were added to PBS during the polymerization process to obtain capped products PBS-MAa and PBS-ECHa,and the biodegradability was investigated.It is found that the weight loss are as follows: PBS-OH> PBS-MAa> PBS-ECHa.The effects on biodegradability of blocking modification are obvious,and different capping agents have different effects on its biodegradability.(3)A series of PBS-MAb and PBS-ECHb were obtained by adding different proportions of MA and ECH in the twin-screw extruder,and we compared their effects of the degradation property.By measuring the FT-IR,water absorption and degradation performance and morphology during the degradation,It is found that: water absorption of the modified PBS is lower than that before modification.When the addition of MA is 3%,the weight loss is the slowest and about 5wt% at 50d;and when the amount of ECH is 4%,the weight loss is the lowest and only about 3wt% at 50 d.The effect of extruding modification is better than that of modificating during the polymerization process.(4)The thermal degradation process and mechanism of PBS-OH,PBS-MA and PBS-ECH have been studied by TG.The results show that the thermal degradation temperature of PBS-OH,PBS-MA and PBS-ECH are 378.4?,381.5? and 384.2?,respectively;the thermal degradation processes of them are one-step reaction,and the reaction orders are close to 1,which indicates that changing end group structure of PBS can not change its thermal degradation mechanism.