Study On The Degradation Of Biodegradable Aliphatic Aromatic Copolyesters In Compost

As the problem of plastic pollution becomes more and more serious,biodegradable plastics have drawn great public attention.The biodegradable aliphatic-aromatic co-polyester represented by Poly(butylene adipate-co-terephthalate)(PBAT)have the advantages of extensive raw materials,good biodegradability and easy large-scale production,thus have great development prospects.Composting treatment is one of the important harmless treatment methods for such biodegradable materials after being used.Therefore,it is of great significance to study the degradation rate and degree of the copolyesters under the condition of controlled composting and evaluate their biodegradation characteristics.However,due to many influencing factors and long period in the composting process,the research on the degradation of aliphaticaromatic copolyesters in composting is insufficient,which seriously restricts the development and utilization of biodegradable polyesters.To this end,this thesis constructed a laboratory controlled compost degradation evaluation system,and carried out an in-depth study on the degradation process of biodegradable aliphatic-aromatic copolyesters such as PBAT and poly(ethylene succinate-co-ethylene terephthalate)(PEST)under composting conditions.The main contents include:(1)According to GB/T 19277.2-2013 standard,the laboratory controlled compost degradation evaluation system was constructed,and the validity of the evaluation system was verified by the degradation test of microcrystal cellulose and PBAT powder,the test conditions were optimized,too.The study on water content showed that 20%water content was the most suitable for degradation in compost.It was also found that the degradation process of PBAT could affect the population types of microorganisms in compost,and the degradation of PBAT was beneficial to the growth of microorganisms such as heterogenous rhizobia and Fusarium xylosum.(2)The effects of copolymerization composition and sample geometry on the degradation process of aliphatic-aromatic copolyesters were studied,and the changes of copolymerization composition,relative molecular weight,thermal properties and surface morphology of samples during the degradation process were also studied.The results showed that the log value of the number average molecular weight of the polyester material decreased linearly during the degradation process,and the slope of the log value could be used as an indicator of biodegradability.The increase of the molar content of aromatic compounds was not conducive to biodegradation.Compost degradation was characterized as surface reaction,and the increase of specific surface area was beneficial to the degradation.Degradation process shows the "amorphous region quickly,crystalline region slow" characteristics.(3)Based on cellular automata method,a two-dimensional mathematical model of polyester composting degradation process was constructed.By comparing simulation result with experimental data and literature data,it was proved that the model could effectively simulate the degradation process of polyester materials in the composting environment,and the biodegradability of polyester materials could be rapidly evaluated by using this model.