Nano-calcium Carbonate Filled Powdered Rubber Composite Particle Used As Impact Modifier For PVC

Nano-CaCO3 filled powdered styrene-butadiene rubber (P(CaCO3/SBR)) composite particle was prepared using nano-CaCO3 slurry and styrene-butadiene latex as raw materials. It was showed that the P(CaCO3/SBR) was tended to coacervate during drying process and the content of nano-CaCO3 has a great influence on the drying properties of P(CaCO3/SBR). When the proportion of nano-CaCO3 was less than 80%, it needed to be dried in a dynamic drying way, such as the spray drying method. When the proportion of nano-CaCO3 was larger than 80%, the coacervation phenomenon of P(CaCO3/SBR) could be ignored and a more efficient drying method could be used. The formation of P(CaCO3/SBR) was due to the attractive interaction of dissolved Ca2+and COO" originating from the surface of CaCO3 and the anionic surfactant absorbed on the latex surface respectively, the particles were formed when latex aggregated on the surface of nano-CaCO3. When the weight ratio of nano-CaCO3 to SBR was larger than 1, the P(CaCO3/SBR) without any additives could be prepared. It was found that P(CaCO3/SBR) had a synergistic toughening effect on PVC. The maximum notched impact strength reached 20.9kJ/m2 when the ratio of P(CaCO3/SBR) to PVC was 15/100 and the content of nano-CaCO3 in P(CaCO3/SBR) was 70%. Another two composite particles (nano-CaCO3 filled powdered carboxylated styrene-butadiene rubber (P(CaCO3/X-SBR) and acrylonitrile-butadiene rubber (P(CaCO3/NBR)) with good compatibility with PVC were prepared when the ratio of nano-CaCO3 to rubber was 7/3. These two particles could realize synergistic reinforcing and toughening PVC compared with P(CaCO3/SBR) and P(CaCO3/NBR) having the best compatibility with PVC showed the best modifying effect. When the content of P(CaCO3/NBR) was 15%, the notched impact strength of PVC/P(NBR/CaCO3) reached its maximum (43.4 kJ/m2), meanwhile, tensile strength & flexural modulus increased by 17.4% and 25.2% respectively in comparison with pure PVC.TEM observation demonstrated that composite particles dispersed uniformly in the PVC matrix and two forms of particle morphology were existed, one was naked nano-CaCO3 structure, the other was "Wrapping" structure, in which nano-CaCO3 particles were embedded in rubber particles at nano-size. The solubility between PVC and composite particle is the crucial factor for toughening effect according to the study of fracture surface of the blends by SEM.