Thermoplastic natural rubbers based on blending of ethylene-vinyl acetate copolymer with different types of natural rubber

Abstract

Thermoplastic natural rubbers based on reactive blending of maleated natural rubber/ethylene-vinyl acetate copolymer and epoxidized natural rubber/ethylene-vinyl acetate copolymer blends were prepared via a simple blend technique. Phenolic-modified ethylene-vinyl acetate copolymer was used as a blend compatibilizer for the unmodified natural rubber, air dried sheet/ethylene-vinyl acetate copolymer blend. Dynamic, rheological, morphological, thermal, and mechanical properties of the blends were investigated. It was found that the epoxidized natural rubber/ethylene-vinyl acetate copolymer blend showed higher tensile modulus, tension set properties as well as smallest dispersion of the co-continuous phase than those of the maleated natural rubber/ethylene-vinyl acetate copolymer and air dried sheet/ethylene-vinyl acetate copolymer blends, respectively. Furthermore, the air dried sheet/ethylene-vinyl acetate copolymer and epoxidized natural rubber/ethylene-vinyl acetate copolymer blends exhibited similar values of tensile strength, while the maleated natural rubber/ethylene-vinyl acetate copolymer blend gave the lowest value. The air dried sheet/ethylene-vinyl acetate copolymer blend gave higher extensibility than that of the epoxidized natural rubber/ethylene-vinyl acetate copolymer and maleated natural rubber/ethylene-vinyl acetate copolymer blends. This is attributed to the molecular characteristics in terms of molecular mass and level of interaction between the chains. Furthermore, the blends showed higher thermal stability than pure rubber because of high heat resistance of the ethylene-vinyl acetate copolymer component. The epoxidized natural rubber/ethylene-vinyl acetate copolymer blend exhibited the highest heat stability because of higher chemical interaction between molecules and between phases. Also, the degree of crystallinity in the ethylene-vinyl acetate copolymer phase in the blends was lower than that of the pure ethylene-vinyl acetate copolymer. Among the various types of blends, the epoxidized natural rubber/ethylene-vinyl acetate copolymer blend showed the highest degree of crystallinity.

Keywords

thermoplastic natural rubber epoxidized natural rubber maleated natural rubber ethylene-vinyl acetate copolymer

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