Compatibilizing Effect Of Nano-CaCO₃ On Immiscible PVC/LDPE Blends

Blending of two polymers has become an increasingly importance method not only for the development of new materials but also for practical recycling. However, as we know, most polymer blends are immiscible, that is, simply mixing these polymer pairs can not get practically useful materials. Therefore improving the compatibility and controlling the phase separation and morphologies of polymer blends turn out to be one of the most key factors in polymer blending. Introducing the third part as compatibilizer is considered to be the most effective way to improving the compatibilization of polymer blends. The use of nano-particles in polymer has been gathering considerable attention in recent years for their potential applications such as colorants, fillers, pigments, sensors, adsorbents as well as catalytic supports'1"4'. The high surface area property of these nano-particles is highly desirable for polymer filler because high surface area provides more active sites for polymer/filler interactions.The blends of poly(vinyl chloride) (PVC) with low density polyethylene(LDPE) and nano-CaCO₃ were prepared by melt blending and characterized by DMA, DSC and phase diagram. And adding nano-CaCO₃ can increase tensile strength. The influence of nano-CaCO₃ on the compatibility of PVC and LDPE was discussed. It was found that the blend system of PVC with LDPE and nano-CaCO₃ was a partial compatible system and the compatibility of PVC and LDPE was increased by addition of nano-CaCO₃. When the sample shows the smallest domain size and gives a very good distribution. But when nano-CaCO₃ content was added further, we discover that the PVC particle aggregated again . The function of the compatibilizer is to increase the interfacial adhesion between the two phases .The dispersed phase morphology as a function of mixing time and nano-CaCO₃ content was investigated for PVC/LDPE, PVC/LDPE/ nano-CaCO₃ blends. As a phase dispersant, nano-CaCO₃ can accelerate the phase dispersion process, but it cannot stabilize the phase structure. The nano-CaCO₃ content and mixing time also has profound effects on the compatibility of PVC/LDPE blends. Thecompatibilization of nano-CaCO₃ particles in PVC/LDPE blends is a kinetic controlled process. After sufficient experimental time the phase morphology will reach to the equilibrium state.Nano-CaCO₃ can act as compatibilizer of LDPE/PVC blends.