Preparation And Properties Of Cross-linked Poly(Propylene Carbonate)

Poly?propylene carbonate??PPC? prepared from carbon dioxide?CO₂? and propylene oxide ?PO?is a hot product among biodegradable polymers.This kind of material is transparent,tough,non-toxic,tasteless,and of biocompatibility.It can be used as both packaging materials and biomedical materials.However,defects such as low thermal decomposition temperature,weak mechanical strength and poor dimensional stability limit the application scale and scope of PPC.In order to comprehensively improve the properties of PPC,different cyclic anhydrides oligomers were prepared by a simple method.As the third monomer,they were copolymerized with CO₂and PO to obtain cross-linked PPC.The structure of the copolymer was characterized,the thermal,mechanical and dimensional stability properties were tested,and the influence of the third monomer on the properties of cross-linked PPC was studied.The contents and conclusions are as follows:?1?A series of cross-linked copolymers PPC-MAOx were prepared by copolymerization of maleic anhydride oligomer?MAO?with CO₂and PO under Zn GA catalyst and gradient feed?0.625-5 wt%of PO?.With increasing MAO,the yields and gel contents of the copolymers also increased,and the 5%weight loss decomposition temperature(T_d,-5%)exceeded 280?.The maximum decomposition temperature(T_d,max)was close to 300?,and the glass transition temperature increased first and then decreased.The tensile strength of PPC-MAO5was up to 38.4 MPa,nearly twice as much as that of PPC,and its permanent deformation rate was reduced to 0 with excellent dimensional stability,while that of PPC was more than 100%.?2?The MA/1,2,3,6-tetrahydrophthalic phthalic anhydride?THPA?oligomer was synthesized by copolymerization of MA and THPA,and using it as a third monomer to copolymerize with CO₂and PO,a series of cross-linked copolymers ppcx were prepared by adjusting the MA/THPA oligomer feeds?0.5-4wt%of PO?.With the increase of MA/THPA,the yields and gel contents of the copolymers increased,while the molecular weight increased first and then decreased.T_d,-5%and T_d,maxreached 290?and 300?,respectively,and the highest glass transition temperature of 38.4?was obtained.The tensile strength of PPC4was 44.3 MPa and the elongation at break was 11%.The permanent deformation rate of the copolymer has been reduced to 0 when the MA/THPA feed was increased up to 3 wt%of PO,which has stronger deformation resistance.?3?MA oligomer or copolyoligomer with other monomers can be copolymerized with CO₂and PO to prepare cross-linked PPC,which can comprehensively improve the thermal stability,mechanical properties and dimensional stability to varying degrees.?4?The cross-linked PPC with MA and the rigid monomer THPA as the third monomer has better mechanical properties and dimensional stability when compared with the MAO third monomer.