Effect of montmorillonite on abrasion resistance of SiO2-filled polybutadiene

The effect of organically modified montmorillonite (OMMT) and silane coupling agent on the abrasion resistance of SiO₂-filled butadiene rubber (BR) vulcanizates has been investigated. Various amounts of OMMT are added into SiO₂-filled BR vulcanizates. A silane coupling agent, bis-(3-triethoxysilyl propyl) tetrasulfide (Si69), is used to modify OMMT during the masterbatch preparation for evaluating the influence of surface treatment on the abrasion resistance. Incorporation of OMMT into BR results in deterioration of the abrasion resistance as compared to unfilled BR vulcanizate due to poor dispersion of OMMT and insufficient interfacial adhesion between OMMT and BR matrix. The use of Si69 improves dispersion of OMMT particles and rubber/OMMT adhesion, resulting in abrasion resistance enhancement of BR/OMMT vulcanizates. By using similar compounding conditions as those for BR/OMMT vulcanizate, nanodispersion of OMMT in BR/SiO₂/OMMT vulcanizate has been achieved as judged by the high viscosity of the SiO₂-filled BR compound. This improved dispersion leads to better abrasion resistance of the BR/SiO₂/OMMT than that of the BR/SiO₂ composite. Utilization of Si69 slightly affects the DIN volume loss of BR/SiO₂/OMMT vulcanizates and the abrasion pattern.     

Protein-free natural rubber

Some properties of protein-free natural rubber were investigated by measurements of both water uptake and stress versus strain. The protein-free natural rubber was prepared in latex stage by the novel procedure to remove all proteins from natural rubber with urea and a polar organic solvent in the presence of surfactant, which had been developed in our recent work. First, the condition for the removal of the proteins was investigated in terms of affinity of the polar organic solvents, concentration of the solvents, type of surfactant, and repeating times for washing latex with a centrifuge. Acetone and anionic surfactant were found to be effective for the removal of the proteins. Under an optimum condition, total nitrogen content and amount of extractable proteins of deproteinized natural rubber were 0.000 w/w% and 0.00 μg/ml, respectively. The removal of the proteins from natural rubber was confirmed through Fourier transform infrared (FT-IR) spectroscopy. Water uptake, hydration, and tensile strength of the rubbers were measured by water swelling method, FT-IR spectroscopy, and measurement of stress versus strain, respectively. The water uptake and the hydration were dependent upon the content of the proteins. The tensile strength of the rubbers, which were prepared to be as-cast films without crosslinking, decreased after removal of the all proteins.     

Preparation and characterization of protein‐free natural rubber

Protein‐free natural rubber was prepared by incubation of natural rubber latex with urea and polar organic solvent in the presence of surfactant. Effect of the polar organic solvent on the removal of the proteins was investigated with respect to chemical affinity and concentration of the solvents. Under a suitable condition, nitrogen content of the deproteinized natural rubber (DPNR) was 0.000 wt%, which was less than that of natural rubber deproteinized with proteolytic enzyme or urea in the presence of surfactant. The removal of all proteins from natural rubber was proved through FT‐IR spectroscopy. Changes in morphology of the DPNR were also investigated by transmission electron microscopy. Copyright © 2011 John Wiley & Sons, Ltd.