Synthesis And Biodegrad Ability Studies Of Aliphatic Copolyesters

As environment-friendly biodegradable polymer materials,aliphatic polyesters not only can replace traditional plastic products tomeet the needs of the community, but also to a certain extent eased thepressure on the environment. Adding monomers to the aliphaticpolyesters, aliphatic copolymers have been synthesized bycopolymerization method, with excellent performance, reaching thematerial requirements in more applications of biodegradable polymermaterials.Ring caprolactone(CL), Diglycollicacid(DGA) and1,4-cyclohexanedimethylene(1,4-CHDM) were used to modify thepoly(butylenes-succinate)(PBS)or poly(ethylene-succinate)(PES), theproducts were different types and proportion copolymers andterpolymers.The structures of the copolymers were identified by1H-NMR and FTIR. The properties of the copolymers were investigatedby TG, GPC and WXRD.The copolymers were degraded by soilburial， and degradation of the copolymers of performance were testedand analysised.The conclusions of this study are as follows:(1) Different types of PBS-based and PES-based copolymers hasbeen successfully synthesized, and80%of the copolymers molecularweight distribution in the range1.6～1.9. The molecular weight ofPES-based copolymers is relatively lower than PBS-based copolymers.(2)Td5%of PBS and PES respectively for330℃、285℃. With theincreasing of monomers, the thermal stability of PBS-based copolymersdecreased, but in the terpolymers, when CL exists, the thermal stabilityof terpolymers increased by adding a small amount of1,4-CHDM. Inthe PES-based copolymers, when the molar ratio of greater than90:10, the thermal stability of copolymers decreased, with the increasing of1,4-CHDM and CL.(3)By WXRD analysis showed that, after different monomermodified, crystal structure of copolymers and crystal structure of purematrix are similar. However, the spherulite size and crystallinity ofcopolymers decreased. Crystallinity of1,4-CHDM copolymerscompared to CL copolymers or DAG copolymers low.(4)After degradation of four months, the mass loss rate ofPBS-based and PES-based copolymers from fast to slow orderrespectively for: P(BS-co-CL)> P(BS-co-CHDM)>P(BS-co-CL-co-CHDM)>P(BS-co-CL-co-DGA)> P(BS-co-DGA)>PBS； P(ES-co-CL)>P(ES-co-CHDM)> P(ES-co-DGA)> PES>P(ES-co-CL-co-DGA)> P(ES-co-CL-co-CHDM)。(5)After degradation, the molecular weight of all copolymersreduced, the molecular weight distribution broadens. After differentmonomer modified, it is effective to improve the biodegradability of thecopolymer. Compared to pure PBS, the relative molecular weight ofPBS-based copolymers reduced more,but molecular weight distributionvalues increased more. The relative molecular weight of pure PESdropped from6.67×104to4.92×104, the distribution coefficientincreased from1.67to1.96, pure PES than pure PBS changes more.(6) Compared to the degradation before, the overall trend ofthermal stability of pure PBS and their PBS-based copolymers reduced,and the Td5%of the first two months reduced more. Compared to thedegradation of the first two months, the Td5%has increased with theextension of the degradation time. PES-based copolymers of the Td5%the first three months of the degradation gradually increased, but in thefirst four months of the degradation process, the thermal decompositiontemperature has a certain degree of reduction.(7) After degradation, crystallinity of pure PBS reduced to39.4%.In the overall trend of the degradation and degradation process,the crystallinity of PBS-based copolymers and pure PBS are basicallythe same, but after degradation, crystallinity of the modified copolymers decreased more. Crystallinity of the PES-based copolymersslightly improved.