Thermal Ageing of Thermoplastic Elastomeric Natural Rubber-Low Density Polyethylene Blends

Abstract

The effect of amount and type of antioxidants on the mechanical properties in the 65/35 NR/LDPE blend was investigated using thermal aging both unstressed and under tensile elongation. The ageing of a family of thermoplastic elastomers from blends of natural rubber and low density polyethylene was studied using thermal treatments at 60°C for 3 days, and 70°C for 5 days. Thermal ageing of the blends of two polymers caused the tensile properties to deteriorate, especially at longer times or higher temperatures of ageing. When an antioxidant for rubber or heat or light stabilizer for polyethylene was added, thermo-oxidative stability was increased. Mechanical properties also indicated changes due to ageing. Samples were prepared with dicumyl peroxide crosslinking agent. The antioxidants used were (i) N, N’-diphenyl-1,4-phenylenediamine; DPPD, (ii) Tetrakis[methylene(3,5-di-tert-butyl hydroxyhydrocinnamate)]methane; Irganox, and (iii) Tris(2,4-di-tert-butylphenyl) phosphate; Irgafos. All of the antioxidants produced considerable improvement in the thermal-resistance. The most effective one was the combination of Irganox and Irgafos even though the continuous phase in these blends was low-density polyethylene.