Study On Preparation Of Nano-CaCO₃/P(BA-co-MMA) Core-Shell Composite Particles And Its Application In Toughening PVC

Study on polymer toughened by inorganic nano-calcium carbonate particles, is one of the promising research fields. Focusing on optimizing the interfacial design to get the well dispersion of inorganic nanoparticles in the matrix and the reasonable compatibility between nanoparticles and the resin to improve the interface adhesion strength, the present thesis explores two proper methods to modify the surface of nano-CaCO₃ by preparing the core-shell composite particles, which have CaCO₃ as the core, PBA as the inner shell and PMMA as the outer shell. Besides, the thesis researches the application of modified nano-CaCO₃ in toughening poly(vinyl chloride).Pretreated nano-CaCO₃ were encapsulated .with P(BA-co-MMA) by emulsion polymerization and precipitation polymerization in Chapter 2 and Chapter 3 respectively, and the surface properties of modified nano-CaCO₃ by the two polymerization methods were studied by contact angle measurement. The influences of reaction conditions on the polymerization process and the structure of composite particles were analyzed. The applications of modified CaCO3 in toughening PVC were studied by orthogonal experiments for choosing the appropriate polymerization conditions.The mechanical properties, thermal properties and rheological properties of PVC/CaCO₃ and PVC/CPE/CaCO₃ composites were researched in chapter 4. Because of the weak interfacial adhesion with the PVC matrix, untreated nano-CaCO₃ tends to aggregate and has the poor dispersion in PVC and can't toughen PVC with satisfaction. On the contrary, the charpy impact strength of the PVC filled with 10 phr CaCO₃ encapsulated with P (BA-co-MMA) is 2.53 times than that of pure PVC, and the tensile strength maintains essentially the same. Besides, as the blend ratio of PVC/ CPE/CaCO₃ is 100/8/10, modified CaCO₃ and CPE perform remarkable synergistic toughening effect, and the charpy impact strength of composite comes to 15.24 kJ/m², 3.98 times of pure PVC matrix. Furthermore, the addition of modified CaCO₃ can improve heat resistance of PVC and vicat softening temperature with 1.9～2.4℃. Low addition of modified CaCO₃ can also shorten the plasticizing time and improve the rheological properties.In addition, ESEM pictures show that the morphology of the fracture surfaces is rough with slippages and drapes, which indicate that PVC/CaCO₃ composites have made great change from brittleness to toughness. And the markable network structure is observed in PVC/CPE/CaCO₃.