Study On Structure Design And Properties Of Biodegradable Composites

While traditional petroleum based plastics bring convenience to mankind,the environmental harm is becoming more and more obvious.The development and use of biodegradable materials as an effective way to solve environmental problems has attracted extensive attention of scientific researchers.As two new biodegradable materials,poly(butylene adipate-co-terephthalate)(PBAT)and poly(propylene carbonate)(PPC)have excellent biodegradability and biocompatibility.They have a wide application prospect in the fields of packaging,medical treatment and so on.However,the problems of high production cost,poor thermal stability and mechanical properties of PBAT and PPC restrict their practical application.Therefore,in order to solve the problem of high cost of PBAT and PPC,PBAT/starch and PPC/starch composites were prepared by melt blending with PBAT and PPC as matrix resin and low-cost,green and environmental friendly starch(CS)as filler.In order to solve the problem of poor thermal stability and mechanical properties of PPC,PPC/layered double hydroxdes composites were prepared by melt blending with PPC as matrix resin and layered double hydroxdes(LDH)with excellent thermal stability and dimensional stability as filler.By modifying the filler and adding reactive compatibilizer to improve the compatibility between matrix resin and filler,the composites have excellent comprehensive properties.The details are as follows:1.Starch was modified by sodium hexametaphosphate(SHMP)and polyethylene glycol(PEG),and PBAT/MS composites were prepared by melt blending of modified starch(MS)and PBAT.The effects of different addition of SHMP and PEG on the structure and thermal stability of MS,as well as the effects of different MS on the compatibility,mechanical properties and water absorption of the composites were studied.The results showed that the more addition of SHMP and PEG in MS,the higher thermal stability of MS,the mechanical properties of the composites increased first and then decreased,and the water absorption decreased gradually.When the addition of SHMP and PEG in MS are 10 phr,MS has excellent thermal stability,and the composite has the best mechanical properties and excellent water resistance.2.PBAT/CS/PBO composites were prepared by using oxazole,2-2’-(1,3-phenylene)bis[4,5-dihydro](PBO)as reaction compatibilizer.The effects of different PBO addition on the thermal properties,mechanical properties,thermal stability and compatibility of the composites were studied.The results showed that with the increase of PBO addition,the compatibility of starch and PBAT in the composites was improved,the mechanical properties of the composites first increased and then decreased,and the thermal stability gradually increased.When the addition of PBO is1 phr,the composite has the best mechanical properties and thermal stability.3.PPC/CS/PD composites were prepared by using composite compatibilizer PD,which is compound PBO and diglycidyl terephthalate(DGT).The effects of different PD addition on the compatibility,mechanical properties,thermal stability and melt flow properties of the composites were studied.The results showed that with the increase of PD addition,the compatibility of PPC and starch in the composites was improved,the mechanical properties of the composites first increased and then decreased,the thermal stability gradually increased,and the melt flow rate gradually decreased.When the addition of PD is 0.9 phr,the composite has the best mechanical properties,thermal stability and small melt flow rate.4.KH550-LDH was obtained by surface modification of LDH withγ-aminopropyl triethoxysilane(KH550);Melt blended with PPC,LDH,KH550-LDH and TGIC to prepare composites.The effects of LDH surface modification and the addition of KH550-LDH and TGIC on the compatibility,mechanical properties,thermal conductivity,thermal stability and melt flow rate properties of the composites were studied.The results show that KH550-LDH has better compatibility with PPC,and the comprehensive properties of PPC/KH550-LDH/TGIC composites are better than PPC/LDH/TGIC composites.In PPC/KH550-LDH/TGIC composites,with the increase of the addition of KH550-LDH,the tensile strength of the composites first increased and then decreased,the thermal conductivity gradually increased,the thermal stability of the materials gradually increased,and the melt flow rate gradually decreased.With the increase of TGIC addition,the tensile strength,elongation at break,thermal conductivity and thermal stability of the composites gradually increased and then tended to be stable.When the addition of KH550-LDH and TGIC are 10 phr and 2 phr respectively,the composite has the best mechanical properties,thermal stability,high thermal conductivity and small melt flow rate.