Synthesis And Modification Of Poly(Butylene Terephthalate-Cosebacate)Copolymer With Excellent Water Vapor Barrier

With the rapid development of traditional plastics,a large number of discarded plastics and their subsequent disposal have become an urgent problem to be solved.In the world,the concept of environmental protection is constantly upgraded and optimized,and the concept of sustainable development has been put forward,making biobased and biodegradable materials stand out among many traditional plastics.Some aliphatic co-polyesters can decompose into carbon dioxide and water under the action of microorganisms,and have good biodegradability,so they are widely used.With the enhancement of human environmental awareness and the deepening of the concept of green chemistry,biodegradable plastics have gradually become the focus of daily life and scientific research.Aliphatic-aromatic co-polyester is a kind of biodegradable plastics,among which Poly(butylene terephthalate-co-sebacate)(PBSeT)is a new kind of biodegradable material.As a derivative of PBAT,it has the advantages of aliphatic polyester and aromatic polyester,which not only has good mechanical properties and thermal stability,but also has excellent ductility and biodegradability.This paper focuses on the synthesis and modification of high barrier Poly(butylene terephthalate-co-sebacate)(PBSeT)with the introduction of bio-based monomers.It is divided into two parts.Specific research contents and achievements are as follows:In order to improve the performance of biodegradable materials,aliphatic–aromatic co-polyesters were synthesized from sebacic acid,terephthalic acid,1,4 butanediol and 2,5-furandicarboxylic acid via two-step esterification and polycondensation.Co-polyesters were characterized by intrinsic viscosity,gel permeation chromatography,X-ray diffraction,Fourier infrared spectroscopy,nuclear magnetic resonance,differential scanning calorimetry,thermogravimetric analysis,lipase biodegradation,tensile and cup method testing.All the co-polyesters had a weight-averaged molecular weight over 61,000 g/mol or intrinsic viscosity over 1.1 dL/g when the 2,5-furandicarboxylic acid content was in the range from 2 to 10%of terephthalic acid content.Particularly,the tensile strength,yield strength,elongation at break,molecular weight and water vapor barrier of co-polyesters were improved to different extents.Obviously,the addition of 2,5-furandicarboxylic acid did not significantly affect the glass transition temperature and thermal stability of polyesters.When the addition amount of 2,5-furandicarboxylic acid was 10%,the water vapor barrier of co-polyester reached the highest,which was increased by 89%compared with PBAT.On the whole,the co-polyesters with the addition of 6%of 2,5-furandicarboxylic acid had the best comprehensive performance.On the basis of the previous chapter,the introduction of biobased monomer sebacediamine,the polar amide unit into the molecular chain,at the same time through the amide group and the hydrogen atom on the chain formed hydrogen bond,the synthesis of PBSeT containing amide.Two-step esterification and one-step condensation melt polymerization were used.ATR-FTIR and ~1HNMR confirmed the successful introduction of the amide unit.The effects of adding different content of amide units on various properties were discussed.Due to the introduction of amide unit,the interchain force was increased,and the crystallinity was increased by 5.91%.The mechanical test results showed that the yield and tear strength increased by 40.7%and 74.8%,respectively.The addition of 1,10-sebacediamine has no significant effect on the glass transition temperature and thermal stability of co-polyesters.The introduction of amide unit reduces the free volume and obtains higher crystallinity,which also improves the water vapor barrier.At the same time,the biodegradability of PBSeT co-polyester under different PH values and lipase was investigated,and the changes of surface morphology after degradation were observed by atomic force microscope(AFM).The amide-enhanced PBSeT co-polyesters have higher crystallinity,better mechanical properties,and better water vapor barrier while maintaining certain biodegradation ability.