Pvc-nanometer Of Caco <sub> 3 </ Sub> Preparation And Properties Of Composite Materials Research

The research on the PVC modified with nano-sized CaCO3 has been attended extensively. But the dispersion of the nano-sized CaCO; in PVC is not good enough by the surface treatment and the extruding technology used now.In this thesis, the PVC/nano-sized CaCO3 composites with remarkable performances have been manufactured by dispersing the nano-sized CaCO3 particles which were modified with wet method in PVC. The mechanical properties and processing property of the composites were then tested. The dispersion of the modified nano-sized CaCO3 in the PVC matrix was observed in TEM (transmission electron microscope). The influences of surface treatment and the contents of nano-sized CaCO3, extrusion technology and other additives on the properties of the composites were investigated.The results show that the surface treatment of the nano-sized CaCO3 particleswith wet method enlarged the specific surface area and reduced the surface energy ofthe particles, and made the particles dispersed at the nanometer level in the PVCmatrix, which improved the mechanical properties of the composite. The dispersion ofthe nano-sized CaCO3 in the composites fabricated by the twin-screw extrudingtechnology is better than that by the single-screw extruding technology, accordingly,the properties of the composites improved. The optimum contents of the nano-sizedCaCO3 particles in the soft and hard PVC/nano-sized CaCO3 composites have beenfound respectively. The contents of other additives also have influence on thedispersion of the particles and the properties of the composites.In the PVC/nano-sized CaCO3 composites, the rolling state between the additional nano-sized CaCO3 and the particles of other additives will exist, and the processing property will be improved correspondingly.The nano-sized CaCO3 particles were well dispersed in the PVC matrix, the sharp angles that formed when the PVC molecular chains stressed have an tendency to be changed to the obtuse angles. Therefore, the stress concentration could be$? Vl A 'T: C$ -h 'T: I"/, vfe ;? A bstrac tavoided and the defects be made up, which toughen and strengthen the PVC.