Study On Preparation,Properties And Application Of PBS Copolyester Modified By MPO

In recent years,synthetic plastics have been widely used in all walks of life.And the accompanying environmental pollution problem has become increasingly serious.As a result,biodegradable materials have begun to attract worldwide attention.Poly（butylene succinate）（PBS）is a semi-crystalline thermoplastic with good biodegradability,excellent processability and good mechanical properties.And it has good industrial development prospects.However,PBS has a regular molecular chain,high crystallinity,high brittleness and low degradation rate,which limits its application.In this thesis,2-methyl-1,3-propanediol（MPO）was used to chemically modify PBS,in order to destroy the regularity of PBS molecular chain structure,reduce its crystallization ability,and improve its brittleness and slow degradation.PBS copolyester（PBMS）modified by MPO of different contents（0-15mol%）were synthesized by direct esterification-melt polycondensation method.Fourier Transform Infrared Spectroscopy（FTIR）,Nuclear Magnetic Resonance Spectroscopy（¹H-NMR）and Gel Permeation Chromatography（GPC）studies show that PBMS samples contained two repeating structural units of butylene succinate（BS）and 2-methyl-1,3-propanediol succinate（MS）in the molecular backbone.The content of MS is basically consistent with the content of MPO added,it is the designed polymer.And its M_w reaches more than 7.5×10⁴g·mol^-1,to the polymer level.Simultaneous Thermal Analyzer（STA）,Differential Scanning Calorimeter（DSC）and Melt Flow Rate Analyzer（MFR）studies show that the thermal degradation temperature of PBMS samples is above 400℃.With the increase of MPO content,its glass transition temperature increase slightly,and the melting transition temperature decreases gradually from 118℃to102℃.The crystallization ability of the PBMS sample gradually declines,and the crystallinity decreases from 74.57%to 49.42%.The melt index（MI）gradually increases.X-Ray Diffractometer（XRD）and Polarizing Microscopy（POM）studies show that the spherulite size of the samples decreases with the addition of MPO without changing the crystal structure of PBS.The test results of mechanical properties show that with the addition of MPO,the elongation at break of the samples increase from 10.5%to 71.2%and the impact resistance increase from 3.9KJ/m² to 24.6KJ/m².The toughness was improved.PBS and PBMS sample films were prepared using the hot pressing method.The dynamic contact angle and water absorption test studies show that the addition of MPO makes the dynamic water contact angle of the PBMS film smaller,the water absorption rate increases,and the hydrophilicity is significantly improved.Gas permeability studies show that the addition of MPO can increase the water vapor transmission rate of the membrane by 68%.The enzymatic degradation study shows that the enzymatic degradation rate of PBMS copolyester film increased greatly with the increase of MPO content,and the copolyester film with 15%MPO content could be completely degraded within 25 days,while the PBS film degraded and lost weight at this time.The rate can only reach 38.18%.The SEM pictures show that the degradation of polyester starts from the amorphous region,proceeds from the periphery to the middle,and from the surface to the interior.The mechanical properties study shows that the addition of MPO can increase the elongation at break of the PBMS film by a maximum of 24times,and the ductility of the PBMS film is well improved.PLA blends with different contents of PBMS-15%plasticized were prepared by melt blending in an internal mixer.TGA test shows that the thermal degradation temperature of the blend is above 300℃,and its thermal stability is improved compared with PLA.The MFR test shows that with the increase of PBMS content,the MI of the blend increases and its flowability become better.The mechanical properties study shows that the impact strength is10.3KJ/m²,which is 415%higher than that of PLA,when the addition amount of PBMS is20%.PBMS has a certain toughening effect on PLA.