Study On The Synthesis Of P(MMA-MA)/OMMT Nanocomposites And Their Blending Modification With PVC

Poly(vinyl chloride)(PVC)is one of the most important general plastics and has been widely used in many areas because of its excellent physical properties,solvent resistance and flame retardancy.However,PVC has bad thermal stability and impact strength,therefore extensive studies have been carried out on the modification of PVC in order to meet requirements for new appliations.Polymer/organo-montmorillonite (OMMT)nancomposites have been studied extensively for their excellent physical properties and thermal stability compared with virgin polymers,and have been widely used as thermal-stable materials to modify the polymer matrix.In this study, poly(methylmethacrylate/methylacrylate)/organo-montmorillonite(P(MMA-MA)/ OMMT)nanocomposites were synthesized by in situ emulsion polymerization,then the nanocomposites were blended with PVC for the purpose of improving its thermal stability and impact strength.P(MMA-MA)/OMMT nanocomposites were prepared by in situ emulsion co-polmerization initiated by oxidation reduction initiating system.The optimum parameters were determined by analyzing the latex size and stability of resultant emulsion,including optimum emulsifier concentration,initiator concentration and reaction temperature.The results showed that when the emulsifier concentration was 7%,the initiator concentration was 0.3%and the reaction temperature was 60℃,the resultant latex was smaller and the emulsion had good stability.After P(MMA-MA)/OMMT)nanocomposites had been successfully synthesized, X-ray diffraction(XRD)and transmission electron microscopy(TEM)were used to characterize the dispersion of OMMT in nanocomposites.The thermal stability was measured by thermogravimetric analysis(TGA).The mechanism of thermal degradation of the resultant co-polymer was investigated by pyrolysis gas chromatography-mass spectrum(PGC-MS).The results showed that both intercalated and exfoliated OMMT structures had been formed in the nanocomposites.Thermal stability of the nanocomposites increased with increasing of OMMT content and reached maximum value when the OMMT content was 5%.However,much more OMMT affected the stability of resultant emulsion,therefore the theremal stability of the nanocomposites decreased.The adding of the comonomer methacrylate(MA)also enhanced the thermal stability of the nanocomposites.When the ratio of MMA to MA was 2:1 and the OMMT content was 5%,the resultant nanocomposites had an increase of 48.3℃in the thermal stability at 10%weight loss compared with virgin PMMA matrix.(P(MMA-MA)/OMMT)/PVC polymer blends were prepared by plasticator.The compatibility was characterized by scanning electron microscope(SEM).The thermal stability of the blends were measured by TGA.The mechnical property of the blends were characterized by tensile test,impact test and dynamical mechanical thermal analysis(DMA).The result showed that the compatibility between P(MMA-MA)/OMMT nanocomposite and PVC was good and the cracking of the blends was tough.Thermal stability of the blends increased with increasing of nanocomposites content and gradually reached the optimum.When the blending ratio of PVC and nanocomposites was up to 100:20,the blends had an increase of 17.4℃in the thermal stability at 10%weight loss.The mechanical properties of the blends increased with increasing of nanocomposites content.When the blending ratio of PVC and nanocomposites was up to 100:30,the mechanical property of the blend reached the maximum value.Compared with virgin PVC,the tensile strength,flexural modulus and impact strength of the blend increased about 34.6%,75.4%and 21.1%, respectively.However,adding much more nanocomposite affected the mechanical properties of the blends.The results of DMA showed that glass-transition temperature and the storage modulus of the blends were all higher than that of virgin PVC.For the blends of nanocomposites and PVC,adding more nanocomposites had less effect on the Tg and loss modulus of the blends,while the storage modulus of the blends were increased significantly. New ideas mainly brought forward in this study are:①P(MMA-MA)/OMMT nanocomposites were synthesized by in situ emulsion co-polmerization initiated by oxidation reduction initiating system.Both intercalated and exfoliated OMMT structures were formed in the nanocomposites.②P(MMA-MA)/OMMT nanocomposites were blended with PVC and successfully improved the thermal stability and impact strength of PVC.