Synthesis,Preparation And Properties Of Bio-based Copolyesters Containing Furan Ring

Non-renewable resources such as oil and coal are facing depletion,while the large use of them has also brought increasing pollution to the environment.Therefore,how to get rid of the dependence on oil and coal,and gradually replace non-renewable resources with new energy sources to achieve "green" in the polymer industry has become a common goal of researchers.In recent years,bio-based polymeric materials will bring a "green" revolution in energy,environment,economy and other aspects because of its characteristics of small pollution,degradability,renewable and abundant raw materials.In this thesis,a series of sustainable and reprocessible fully biobased thermoplastic polyester elastomers P(BF-EF)s were synthesized using dimethyl-2,5-furandicarboxylate(DMFD),1,4-butanediol(1,4-BDO),and synthetic low-molecular-weight bio-based polyester(PE).The hard segment of P(BF-EF)s is poly(butylene 2,5-furandicarboxylate)(PBF),while the soft segment is copolyester(PEF)which was polymerized by four alkyd monomers.The effects of the mass ratio of soft and hard segments on the molecular weight and distribution,molecular chain structure,thermal properties and mechanical properties of the synthesized P(BF-EF)s were studied.The results show that there is a two-phase structure in P(BF-EF)s:one is crystalline PBF and the other is a mixture of amorphous PBF and PEF.At the same time,the micro-phase separation of P(BF-EF)s is mainly caused by the crystallization of PBF segment.The thermal properties,crystallization properties and mechanical properties can be regulated by adjusting the content of PEF.The results showed that P(BF-EF)containing 20wt% PE exhibits high elongation at break(? 1100%),low modulus(9Mpa)and relatively high tensile strength(34mpa).In addition,P(BF-EF)s showed low or no cytotoxicity to L929 cells.P(BF-EF)s is expected to be used in biomedical materials due to its advantages of renewability,good thermal stability,non toxicity and good tensile properties.Then,a series of heat-induced shape memory materials containing furan ring(copolyester PDBSB)were successfully prepared by transesterification and melt polycondensation with DMFD,1,4-BDO,sebacic acid(Se A)and 1,4-butenediol(1,4-BEO).The effects of the molar ratio of DMFD/Se A on the molecular weight and distribution,molecular chain structure,thermal properties and mechanical properties of copolyester PDBSB were studied.The results of differential scanning calorimetry,X-ray diffraction and thermal weight loss showed that with the increase of furan ring content,the melting point andcrystallization ability of the polymer first decreased and then increased,while the thermal stability gradually decreased;From the tensile stress-strain curve of polyester,it can be seen that with the increase of furan ring content,the bio-based polyester showed the change from ductile plastic to elastomer to rigid plastic.For crosslinkable semi-crystalline copolyester PDBSB,it can be used as shape memory material.Therefore,by changing the molar ratio of DMFD/Se A and the degree of sample crosslinking,changing the melting temperature of copolyester,and then changing the transition temperature(Ttrans),the shape fixing rate of PDBSB is more than 90%,and the shape recovery rate is about 100%.