Preparation And Properties Of Natural Rubber Latex Films Modified With Silica Sol

Natural rubber latex is a kind of biosynthetic and renewable resource. It is widely used as medical elastic films by virtue of its excellent elastic and film-forming properties. However, natural rubber latex films have some defects such as poor solvent resistance, incompactness and low tensile strength, which restrict the development of nature rubber latex. In this paper, silica sol, modified sol and a kind of soy protein/silicon dioxide composite were used to modify nature rubber latex, respectively, which improved the mechanical property, compactness and solvent resistance of natural rubber latex films.Tetraethoxysilane (TEOS) was used as the precursor of silica sol through a hydrolytic process in ammonia. During different stages of condensation, the prepared silica sol was blended with natural rubber latex, and an organic-inorganic hybrid film was then prepared. The research showed that SiO2partilces could reinforce the film in stiu, but SiO2particles easily migrated to the surface of the film, which would have negative effects on the reinforcement. The hydrophilia and anti-ultraviolet of natural rubber latex were also improved for the presence of SiO2partilces.With the blending of silica sol and cationic polyelectrolyte, a polyelectrolyte-coated SiO2partilces with positive charge was generated.Through the electrostatic attraction between the positive SiO2particles and negative rubber particles, a new core-shell structure was successfully formed by the mixture of the modified SiO2partilces and natural rubber latex partiles. The compact core-shell structure could enhance the mechanical property and solvent resistance of films through increasing the degree of cross linking between organic-inorganic phases, and the migratory problem of the SiO2particles was also solved.The soy protein possesses good film-forming property, interface bonding ability and compatibility with non-rubber components in the surface of latex. The polar groups of soy protein are apt to constitute the physical and chemical junction with other materials. The sol-gel reaction of TEOS was happened in the soy protein solution to generate composite, and this composite was used to modify natural rubber latex. Studies in this part showed that the composite could fill the interspace between the nature rubber latex particles, which could further enhance the surface density and solvent resistance of the nature rubber latex films with the reservation of its good mechanical property.