| Silicone rubbers have taken an important role in a variety of applications for almost 40 years. Among them the moisture-curable room-temperature vulcanizable (RTV) silicone rubber represents one of the largest volume and commercially most successful silicone technologies. The networks have excellent primerless adhesion to substrates, such as, glass, metal, wood, masonry and plastics. Additional benefits include excellent weatherability, durability, electrical insulation, chemical resistance, stability at high temperature. It is well known that fumed silica is the well-reinforcing filler for RTV silicone rubber, for silica filled rubbers show an increase in modulus, hardness, tensile strength, abrasion as well as resistance to fatigue and cracking. Calcium carbonate has been long time considered as mineral fillers that extended and cheapened the rubbers. Nowadays, nano-calcium carbonate has attracted considerable interest because of its raw materials abundance in nature, low cost compared with fumed silica and the presence of activity by treatment of the surface. The nano-size, larger specific surface area and active points of nano-calcium carbonate make it possible to be used as reinforcing agent just like carbon black or silica. Although a number of investigations have been devoted to the analysis of silica-filled rubber networks, little work has been done on the reinforcement of calcium carbonate filled rubber network. Therefore, it is our purpose in this work to study the relationship of reinforcement RTV silicone rubber by using nano-calcium carbonate and filler characteristics such as filler size, structure, surface activity, and to carry out a systematically investigation on interaction between RTV silicone rubber and nano-calcium carbonate compared with silica filled RTV silicone rubber.It have been found that there is a simultaneously increase of tensile strength, modulus and elongation of nano-CaCO3 filled RTV silicone rubbers no matter what the kinds of nano-CaCO3 compared with unfilled silicone rubber. The mechanical properties can be improved slightly with increasing the filler content which is lower than 80 phr while these properties of 80 phr nano-CaCO3 filled RTV silicone rubbers greatly increase whereafter little decline with adding more fillers. The same trendence has been observed in the stress-softening effect of different filler content of RTV silicone rubbers. It is concluded that the trend of effect on the reinforcement of the nano-CaCO3 appears two-step.The dispersion of nano-CaCO3 particles in rubber was studied via SEM after the samples were fractured in liquid nitrogen. It is revealed that the three kinds of nano-CaCO3 can disperse evenly in rubber matrix. The indistinct interface of filler and rubber shows that there has been interaction between filler and rubber. At the same time, the more the content of filler is, the smaller the size of the agglomerate, For viscosity of 80 phr nano-CaCO3 filled rubber is much higher than that of pure rubber, which conduces to the even dispersion of filler in the matrix.The interaction between nano-CaCO3 and RTV silicone rubber has been characterized by DSC, stress relaxation, DMA, balance swelling and TG. DMA and DSC results showed that the interaction can decrease the melting temperature for filler might hold the rubber molecular chain crystallization for the interaction between filler and rubber. The results of IR and Dynamic Laser Light exhibit that the interactions between filler and rubber are chemical adsorptions, which is consistent with TG results that are revealed that this chemical interaction between nano-CaCO3 and RTV silicone rubber could improve the thermal stability of filled rubbers. Stress relaxation results showed that both the stress relaxation rate and relaxation degree augment, which indicated that the interaction between filler and rubber concludes physical adsorption. The crosslinking degree obtained by balance swelling illustrated that interaction can increase the crosslinking degree and the int...
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