Natural rubber latex blended polystyrene emulsion for dipping products: preparation and properties

Deproteinized natural rubber latex (DPNR) was prepared using KAO protease enzyme to digest proteins from natural rubber low ammonia concentrated latex (NR-LA). Polystyrene latex (PS) was synthesized by emulsion polymerization technique for blending with natural rubber. The maximum fraction of PS blended NR-LA or DPNR used to obtain a homogenous film was 20% w/w. The 300% modulus of PS blended NR film was increased before and after aging at 100oC for 22 hrs. The tensile strength and elongation at break were increased at NR/PS = 95/5 w/w and tended to decrease as PS blended fraction increased. DPNR films had a lower friction coefficient than NR-LA films. PS blended NR-LA or DPNR would decrease the friction coefficient of films. The rubber-surfaced friction is reduced. The extractable protein of NR-LA film was higher than 200 μg/g whereas that of DPNR film was lower than 50 μg/g. PS blended NR-LA and DPNR could reduce the extractable protein to less than 60 μg/g and 30μg/g, respectively. The physical properties of PS blended NR-LA met ASTM D3577 and ASTM D3578 standards for dipping products of surgical gloves and examination gloves at the maximum fraction of PS 15% w/w and 20% w/w, respectively, whereas PS blended DPNR only met ASTM D3577 standard at the maximum fraction of PS < 5% w/w.