The Properties Of In Situ Formed Nano-Silica/Natural Rubber Composites

Natural rubber is collected from the natural plant,after a series of processing to become an indispensable highly elastic material.Its excellent comprehensive performance and low price make it difficult to be replaced by other materials.Rubber vulcanizates need to add reinforcing agent to expand its use value.As an important reinforcing agent of rubber,silica can reduce rolling resistance,improve the tire tread wet resistance.Since the birth of the rubber industry,usually added SiO₂ use mechanical refining method,or dry refining method to disperse in rubber.Dry refining method energy consumption is very big,account for the whole more than 50%of the energy consumption of rubber industry.Ordinary dry refining method just rely on mechanical shear force is difficult to evenly disperse powder filler and make small particle size of particles dispersed in rubber matrix.The difference between various batches rubber is so big,which is not conducive to the follow-up working procedure quality control and at the same time will cause dust pollution.The wet refining method could easily overcome the shortcomings which are difficult to be overcome by dry refining method,improve the dispersion of inorganic filler in rubber,reduce the dust pollution and to achieve continuous mixing process.The wet refining method is usually divided into two cases,one is in the condition of latex mixed with filler,even down after the preparation of mixing rubber,but filler is hard to down completely;Second,add the precursor of inorganic filler in the rubber latex,through the chemical reaction in latex in situ generated inorganic filler,then mixing rubber latex coagulation and preparation.In this paper,the natural rubber latex?NRL?was mixed with Sodium silicate solution and then the pressurized carbon dioxide gas was bubbled into NRL,in situ generated nano-SiO₂/NR composites were obtained by means of coagulation.The effects of the variety of latex concentration,curing agent and the surface treatment agent type reinforcing effect of composite materials.Confirm the most suitable conditions for the experiment of in situ-wet refining method is:the latex concentration was 25%,the surface modification agent chooses Levelling Agent O and using acetic acid latex solidification.The distribution of SiO₂ in the rubber was observed through the scanning electron microscopy?SEM?,and using single factor variable method,discuss the effect of dosage of surfactant or different SiO₂ contents on the vulcanization properties,mechanical properties and the glass temperature?Tg?of the composites were investigated.The results indicate that add the right amount of surfactant is good for control the SiO₂ particle size and promote its dispersion in NR,when the content of SiO₂ is 30 phr,the surfactant dosage shoulds not be more than 7 phr.When dosage of surfactant in 3.5 phr,vulcanizates have minimal swelling index,largest crosslinking degree and the best mechanical properties.The size of in-situ formed SiO₂ has reached nanometer scale,and SiO₂ is dispersed homogeneously in NR when the content of SiO₂ is no more than 60 phr.The physical and mechanical properties of the composites increase after filled with SiO₂,and reach the highest when the content of SiO₂ is 60 phr.Tg of the composites and its vulcanizates do not change significantly with the SiO₂ contents increasing.The Payne effect and the SiO₂ network architectures of the vulcanizates do not increase significantly even if the content of SiO₂ is up to 75 phr.