| Polypropylene carbonate)(PPC)is a non-toxic,fully biodegradable and excellent toughness aliphatic carbonate.Compared with other biodegradable materials,PPC has good gas barrier properties.However poor thermal stability and tensile strength constrain the practical application of PPC.In this work,PPC composites are prepared by melting blending and multilayer compounding.The thermal stability,mechanical,shape memory and water vapor barrier properties of PPC composites are improved by adding reinforcement fillers and designing multi-layer structures,which can provide a new method to expand the application of PPC in the field of shape memory and packaging materials.Tartaric acid(TA)and anhydrous zinc acetate(ZA)were used to modify thermoplastic starch(TPS)to obtain TA-TPS and ZA-TPS composites,then PPC composites with different contents of modified TPS were prepared by melt blending.The effect of modification methods and modified TPS content on the structure and properties of composite materials were investigated.FTIR results showed that there was an interaction between TPS and PPC,and the introduction of TA promoted the further interaction between PPC and TPS.SEM microphotographs showed that the dispersion size of TA with TPS became smaller,which improved the compatibility of PPC and modified TPS.Due to the plasticizing effect of tartaric acid on PPC,the flow performance became better.When the content of TA-TPS is 10wt%,the storage modulus(G’)loss modulus(G")and complex viscosity(η*)of the composites were the lowest.The compatibility between PPC and ZA-TPS was lower than that of PPC and TATPS.Zn2+released by ZA-TPS at high temperature could accelerate thermal decomposition of the composites.Therefore,PPC/TA-TPS composites had better thermal stability and mechanical properties than PPC/ZA-TPS composites.When the content of TA-TPS was lower than 10 wt%,water vapor barrier performance and tensile strength of PPC composites were improved.With the increase of TA-TPS content,the agglomeration of TA-TPS became more obvious,and the performance of PPC composites began to decrease.Oxidized microcrystalline cellulose(OMCC)and oxidized nano-microcrystalline cellulose(OCNC)were introduced into PPC.By changing the mixing sequence,effect of TA-TPS and cellulose in the PPC matrix on performance was studied.The G’G" and η*of the PPC/OMCC composites were higher than those of the PPC/OCNC composites.Combined with the analysis of SEM photomicrographs,the dispersion size of OMCC in the composite was larger than that of OCNC.When the OMCC content was increased,the compatibility between OMCC and PPC became weaker,which made the modulus and viscosity increased.For PPC/OCNC composites,with the content of OCNC increase,the tensile strength of PPC composites was increased.Rigid OCNC at low content could inhibit the plastic deformation of the system,thus its cycle recovery Rr remained above 90%.With the content of OCNC increased,the water barrier performance of the PPC/OCNC composites increased.The PPC/modified TPS/OCNC composites prepared by blending PPC,TA-TPS and OCNC had better mechanical properties,water vapor barrier and thermal stability,and its G’,G" and η*were higher,which related to the formation of part network structure in the composites.After stacking two composites of PPC/OCNC and PPC/TA-TPS through multilayer compounding,multilayer composites were prepared.The dispersed phase of the composites formed a three-dimensional multilayer network structure,which improved the tensile strength,hydrophilicity,glass transition temperature and water vapor barrier properties of the PPC composited.In addition,the PPC composites had undergone multiple thermal processing history,thus its thermal stability of high temperature was weaker.The increase of the layer number in the multi-layer composites was beneficial to increase the shape recovery rate of the multilayer PPC composites,and its cyclic shape recovery performance was improved. |
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