Poly(Propylene Carbonate)/Graphene Nacre-like Nanocomposites

Polypropylene carbonate(PPC)as a substitute for petroleum-based plastics is a promising biodegradable polymer.Due to its own shortcomings in thermal and mechanichal properties,PPC is still less competitive campare to traditional petroleum-based plastics.Rigid filler compositing is an effective method to improve the properties as well as realize multifunctionality of PPC.However,the thermal stability,electrical and thermal conductivities of conventional PPC composites are still unsatisfactory.Nacre has an unique "bricks-and-mortar" layered structure.Such structured designability often is ulitized to endow composite materials with multifunctionality,which is expected to make up for the existed shortcomings of PPC composites.In this paper,combing the solvent evaporation and hot-pressing forming technologies,the PPC nanocomposites with controllable size and morphology and ordered structure were successfully prepared.To ensure the layered structure of the reduced graphene oxide(RGO)can be built in the PPC matrix during the solvent evaporation process,the controllable synthesis of polytetrahydrofuran(PTHF)grafted RGO was systematically studied.PTHFfunctionalized RGO(PTHF-fRGO)with good dispersibility in a variety of organic solvents as well as PPC matrix was obtained.In this paper,the co-precipitation method was emploied to prepare the disordered PPC / RGO nanocomposites as a comparison.At low filler loadings,the thermal,mechanical,shape memory and gas barrier properties of the resultant composites were studied.The reasons for the differences in the above properties were discussed.On this basis,the properties of thermal conduction,electrical conduction and electromagnetic shielding of composites with different structures under high filler contents were also evaluated.The PPC / PTHF-fRGO nanocomposites with high performance and ordered stcuture were prepared.The main results are as follows:1.By adjusting the density and chain length of grafted PTHF on the surface of RGO,PTHF-fRGO hybrids with complete surface structure and good dispersion in various solvents and PPC matrix were synthesized,which laid the foundation for the preparation of PPC / PTHF-fRGO nanocomposite.2.A method with strong feasibility,wide applicability,simple and high efficiency was designed by combining the solvent evaporation and hot pressing forming technology.Such approach was carried out the efficient,large-size and large-scale preparation of PPC / PTHFfRGO nanocomposites,which made it possible to evaluate the effect of the orientation of nanofillers on the performance of the matrix.3.On the basis of the above,the effects of oriented and randomLy dispersed of fillers on the thermal,mechanical,shape memory and oxygen barrier properties of PPC matrix were invested under low loading(<5 wt%).It was found that the above properties of PPC were effectively enhanced by surface modification of RGO,which were further improved by constructing the ordered structure in the resultant materials.4.The differences of the thermal and electrical conductions,electromagnetic shielding effectiveness in the nancomposites with order and disorder structures in under high filler loadings(>20 wt%)were studied.Increasing filler loading significantly improved the above properties of PPC,indicating that the surface modification of RGO gived the nanocomposites multi-functionality.In addition,the orientation of fillers in the matrix constructed a continuous network structure,which resulted in great prominence in terms on in-plane thermal and electrical conductions and electromagnetic shielding effectiveness,and successfully realized the PPC / PTHF-fRGO composite materials with high performance.