Study On Polymer/Nano-CaCO₃ Composites

The paper was aimed at the modification of traditional polymer filled withnano-CaCO₃ powder, and investigated the application of nano-CaCO₃ in NBR and PVCmatrixes separately. The results followed that:1. The properties of NBR composites filled with untreated nano-CaCO₃ and boricacid ester coupling agent modified nano-CaCO₃ were characterized by SEM, RPA2000,cross-link density measurement apparatus, mechanical test, oil resistance test and agingtest. The results showed that The mechanical properties of NBR vulcanizates wereimproved apparently by filling of the modified nano-CaCO₃. When the amount of boricacid ester was 4% and modified nano-CaCO₃ was 75 phr, the composite had optimummechanical properties. The oil resistance and anti-aging properties of NBR vulcanizatewere also improved by filling modified nano-CaCO₃. According to results of RPA2000,the G' and payne effect of NBR compound filled with modified nano-CaCO₃ decreasedapparently but tanδincreased, comparing with those filled non-modified nano-CaCO₃.These indicated that the surface hydrophobic of nano-CaCO₃ particles and thecompatibility between filler and matrix were improved; at the same time the processibilityof the NBR compound was improved too. The G' of NBR vulcanizate filled withmodified nano-CaCO₃ decreased apparently and tanδincreased, comparing with thatfilled with non-modified nano-CaCO₃. The cross-link density measurement proved thatthe addition of the modified nano-CaCO₃ increased the chemical cross-link contents ofNBR vulcanizates.2. The PVC/NBR/nano-CaCO₃ ternary composite was also studied, in which NBRwas used for the interface modifier. The mechanical properties, rheological behavior,dynamic mechanical properties, glass transition temperatures, thermal properties andmorphology were characterized by mechanical test, capillary rheometer, DMA, DSC,TGA, and SEM. The results indicated that NBR had good toughening effect onPVC/nano-CaCO₃ composites, impact strength increased to 30.10 KJ/m² forPVC/NBR/nano-CaCO₃ at a weight ratio of 100/12/8, and improved 27% comparing withcorresponding PVC/nano-CaCO₃ composite. The addition of NBR decreased the viscosityof composites and improved the processibility. The Tg of the PVC/NBR blends turnedlower with the addition of nanoparticles, which showed that nano-CaCO₃ might havesome effect on the compatibility of the PVC/NBR blends. At the same time T_g of composites decreased and thermal stability turned to be bad. The scanning electronmicroscope (SEM) photograph indicated that when PVC/NBR/nano-CaCO₃ was at aweight ratio of 100/12/8, the NBR could enhance the nanometer dispersive degree ofnano-CaCO3 to some extent and the plastically deformed fibrils of the PVC matrix werepulled up on the fracture surface, which were associated with the improvement of impactstrength.