Synthesis Of PBAT Possessing Excellent Environmentally Degradability With Biogenic Guanidine Catalysts

In recent years,with the expand production and the indiscriminate application of non-degradable petroleum-based plastics "plastic pollution" has become a global problem.Exploring and developing biodegradable polyester has become an urgent task for the mankind.Poly(butylene adipate-co-butylene terephthalate)(PBAT)is a copolyester of aliphatic and aromatic acids which combines the excellent degradability of aliphatic polyester and the excellent mechanical properties of aromatic polyester,thus it becomes a hot field in green environmentally materials.However,there are four problems in the process of synthesis of PBAT:the traditional catalyst has a certain physiological toxicity and it was used excessive amount,and the catalytic effect was poor;The synthesized PBAT product had poor environmental degradation performance;In the process of synthesis of PBAT,the consumption of raw materials was too much,the reaction time was long,and the reaction yield was low;the THF generation rate was high.This study effectively solved these four issues.The main experimental results of this thesis are as follows:(1)A PBAT copolymer(Mw 1.27×105Da,PDI 1.50～2.00,Tm131.54℃,white color)of BA/BT 50:50 possessing excellent environmentally degradability was synthesized via direct melt polycondensation using biogenic guanidine for the first time.In addition,P(BA55-BT45)、P(BA60-BT40)were synthesized using the same kind of catalyst and synthesis method.The characterization of the polymer structure by 1H-NMR indicated that the molar ratios of BA/BT in P(BA55-BT45)molecule was 2.23:1.79,close to the theoretical value,proving that the experimental results conform to the designed copolymer composition.The thermodynamic property by DSC indicated that the Tm value and thermal stability increase while BT mole fraction in the PBAT molecules increases.The analysis of TGA showed that with the increase of BA mole fraction,the degradation temperature is reduced,which proves that BA has the effect to improve environmentally degradability of the PBAT.(2)The effects of ratio of alcohol and acid on the emergence of clear point(The polymerization system reaches a homogeneous state),reaction time,copolyester molecular weight and reaction yield were investigated,The experimental results prove:(1)while BA/BT=50/50,the best ratio of alcohol and acid is n(BDO):n(AA+TA)=1.45:1.00,Mw 1.27×105Da,PDI 1.79;(2)while BA/BT=55/45,the best ratio alcohol and acid is n(BDO):n(AA+TA)=1.42:1.00,Mw 1.00×105Da,PDI 1.81;(3)While BA/BT=60/40,the best ratio of alcohol and acid is n(BDO):n(AA+TA)=1.38:1.00,Mw 9.75×104Da,PDI 1.84.(3)The effects of TA,AA,ratio of alcohol and acid,stirring speed,esterification temperature and the catalyst on the generation rate of tetrahydrofuran(THF)were explored.The results showed that TA and AA play a catalytic role in the secondary reaction of BDO cyclization to TH.While the ratio of alcohol and acid was increasing,the THF generation rate became much higher.As the temperature was between 190 to 228℃,the THF generation rate reduced while the temperature was increasing.While the stirring speed was much faster,the THF generation rate became much lower;As the PBAT copolyester was synthesized by biogenic guanidine,the generation rate of THF was only 4.25%.Under the optimum conditions,the generation rate of THF was 4.10～4.30%,which was lower than the lowest value reported in the current literature.