In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO_2 hybrids based on terephthalic acid(TPA),poly(L-lactic acid) oligomer(OLLA),1,4-butanediol(BDO) and nano-SiO_2.TEM and FT-IR characterizations confirmed that TPA,OLLA and BDO copolymerized to obtain biodegradable copolyesters,poly(burylene terephthalate-co-lactate)(PBTL),and the abundant hydroxyl groups on the surface of nano-SiO_2 provided potential sites for in situ grafting with the simultaneous resulted PBTL.The nano-SiO_2 particles were chemically wrapped with PBTL to form PBTL/nano-SiO_2 hybrids.Due to the good dispersion and interfacial adhesion of nano-SiO_2 particles with the copolyester matrix,the tensile strength and the Young's modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO_2 hybrids with 5 wt.%nano-SiO_2,respectively.The mechanical properties of PBTL/nano-SiO_2 hybrids were substantially improved.
Yan ZhangBing Tao WangZheng Hong GuoJie ChenZheng Ping Fang
Biodegradable aliphatic/aromatic copolyesters,poly(butylene terephthalate-co-lactate)(PBTL) were prepared via direct melt polycondensation of terephthalic acid(TPA),1,4-butanediol(BDO) and poly(L-lactic acid) oligomer(OLLA). The effects of polymerization time and temperature,as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated.The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃for 6 h.DSC,XRD,DMA and TGA analysis clearly indicated that the degree of crystallinity,glass-transition temperature,melting point,decomposition temperature, tensile strength,elongation and Young's modulus were influenced by the ratio between TPA and OLLA in the final copolyesters.Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.
