A Research Of Using Soybean Protein To Modify Natural Rubber Latex

Nowadays, natural rubber latex (NRL) based on biosynthetic and renewable natural resources have attracted much attention because of its good elasticity, resilience and film-forming ability. The NRL has been widely used in the production of medical catheter, latex gloves, condoms and so on. But the NRL has poor oil resistance and compactness due to the unsaturated double bond. It is noted that even if a little of water soluble protein (WSP) in NRL might cause allergic reaction. In this paper, soy protein (SPI) combined with propylene glycol alginate (PGA), chitosan (CHI) to form conjugations and modify the NRL. The modified rubber membranes with low allergy, high mechanical properties and compactness was made to satisfy the applications.Soy protein has strong intra-and inter-molecular interactions, such as hydrogen bonding, dipole-dipole, charge-charge, and hydrophobic interactions. The strong charge and polar interactions between side chains of soy protein molecules restricts segment rotation and molecular mobility to increase the film forming ability and strong interface bonding strength. The SPI could combine with non-rubber substances of latex and change the chemical microenvironment of the natural rubber particles. The SPI was wrapped in the surface of the rubber particle to increases the particle size, the film-forming ability and the density after the NRL blend with SPI. The modified membranes were endowed with smoother surface, more hydrophilic and oil resistance. The SPI loading0.83%is the optimum mechanical properties of the modified membranes. With the further addition of PGA, the NRL membranes modified by SPI-PGA conjugates owe better surface smoothness, dense resistance, oil resistance, the hydrophilic and mechanical properties than that were modified by the pure SPI. When the loading of PGA and SPI were0.25%and0.83%, the mechanical properties achieved maximum.Chitosan owing active hydroxy and amino grouSPI-PGA has strong chemical reaction ability and easily capture the proteins. But it is hard to mix with the NRL in the alkaline environment which the NRL has. SPI and CHI were used as the main materials to prepare soybean protein-chitosan conjugations by the dry-heat reaction. The blend films were successfully prepared by heterocoagulation blending the conjugations in the natural rubber latex (NRL). The covalent attachment of SPI and CHI was confirmed by the changes of the particle size distribution. The mechanical property and water soluble protein (WSP) of films were studied. The results showed that the compound film was endowed with smoother surface morphology, higher mechanical property and fewer WSP. And this kind of compound rubber film has a broaden prospect of application in medical film materials...