Study On Toughening PP By Modified Nano-CaCO₃

Polypropylene?PP?is one of the five universal plastics.It has low density,low cost,good transparency and comprehensive performance,and is widely used in daily life,industry,transportation and other fields.However,its poor toughness at low temperature also limits its application in some fields.Therefore,the modification of PP material has been an extensive research topic.In practice,PP is often toughened by blending with other polymers or adding inorganic fillers.Nano calcium carbonate,as a widely sourced filler,is not only cheap but also effective.It is an inorganic filler which is widely used in polymer modification.In this paper,nano calcium carbonate was physically or chemically modified,and it was filled into the resin matrix by melt blending method,so as to toughen PP.The changes of properties and states before and after modification of nano calcium carbonate and their transformations in resin matrix were discussed.The microstructure,thermal and mechanical properties of the composite system were studied.The main research contents are as follows:1.Nano calcium carbonate powder was added into PP/PA6 system to play the role of"emulsifying"nanoparticles so as to refine the second phase.The effect of filling quantity on mechanical properties was investigated and it was found that the system achieved better comprehensive performance when the filling quantity was 10%.After that,nano-CaCO₃ was surface modified with 10%ionic liquid?IL?to solve the agglomeration problem of nano-filler,and a more uniform resin system was obtained by mixing the modified filler with PP.Transmission electron microscopy?TEM?was used to demonstrate that the dispersion of the modified CaCO₃ was improved.The Contact Angle test showed that IL had the characteristics of amphiphilic.Fourier infrared spectroscopy?FTIR?proved that IL was successfully loaded onto the surface of calcium carbonate.Finally,the impact strength of the system was increased by 23%when the nanometer calcium carbonate was filled with 10%modified by ionic liquid.2.Synthesis of nano CaCO₃ and heptanoic acid?HA?as nucleating agents.Two synthesis methods were used:the loading method and the preheating reaction method.Firstly,the nucleating agent was characterized by infrared spectroscopy,and the results showed that special coordination bonds were formed in the nucleating agent after thermal reaction,and the preparation process of the nucleating agent by thermal reaction was optimized by thermogravimetric?TG?and infrared spectroscopy.The microstructure of the two nucleating agents was observed by transmission electron microscopy.Finally,two nucleating agents were mixed with PP to explore the effects of nucleating agent content and load on the crystallization,microstructure and mechanical properties of PP.The results showed that76.8%crystallization was induced when 0.2%nucleating agent was added.Among the loaded nucleating agents,the induction efficiency of nucleating agent was the highest when the load was 3%,reaching 78.3%.We also observed the material section by scanning electron microscopy?SEM?,and found that due to the high initiation efficiency of the two nucleating agents,the content of?-PP in the resin was large,and the material had changed from brittle fracture to ductile fracture.At the same time,the impact toughness of materials has been improved in different degrees.