Blending of Natural Rubber/Recycled Ethylene-Propylene-Diene Monomer: Cure Behaviors and Mechanical Properties

Abstract

In this article, blending of natural rubber with recycled ethylene-propylene-diene monomer (R-EPDM) was studied. The comparative studies of cure behaviors, mechanical properties and morphology of natural rubber/recycled ethylene-propylene-diene monomer (NR/R-EPDM) and natural rubber/ethylene-propylene-diene monomer blends (NR/EPDM) were carried out. Results indicated that the maximum torque (M_H), minimum torque (M_L), scorch time (ts₂) and cure time (tc₉₀) of NR/EPDM increased with increasing virgin EPDM in the weight ratio of the blend. Similar observation was also obtained for NR/R-EPDM blend except for the M_L and ts₂ which exhibited the opposite trend. SEM micrographs proved that the incorporation of R-EPDM up to 30 phr in the blends exhibited high roughness surface and matrix tearing line. Meanwhile, the micrographs of NR/EPDM blends showed a reduction in crack path with increasing virgin EPDM content, which led to less resistance for crack propagation and therefore, resulted in low tensile strength.

Keywords:

• Cure behaviors
• Mechanical properties
• Morphology
• Recycled ethylene-propylene-diene monomer

ACKNOWLEDGMENT

One of the authors (H. Nabil) gratefully acknowledges the personally financial support under Graduate Assistant Scheme and Postgraduate Research Grant Scheme (PGRS) provided by Institute of Postgraduate Studies (IPS), Universiti Sains Malaysia (Account Number: 1001/PBAHAN/8045014), and the research grant of Exploratory Research Grant Scheme (ERGS), Ministry of Higher Education (MOHE), Malaysia (Account Number: 203/PBAHAN/6730066) for the great support.

Notes

NR = Natural rubber.

EPDM = Ethylene-propylene-diene rubber.

R-EPDM = Recycled ethylene-propylene-diene rubber.

ZnO = Zinc oxide.

SA = Stearic acid.

TBBS = N-tert-butyl-2-benzothiazyl sulfonamide.

T-5% = The temperature at 5% weight loss. T-50% = The temperature at 50% weight loss. T-80% = The temperature at 80% weight loss. T_{max I} = The temperature at first peak of decomposition. T_{max I} = The temperature at second peak of decomposition.

M_H = Maximum torque.

M_H–M_L = Torque difference.

ts2 = Scorch time.

tc90 = Curing time.

CRI = Cure rate index.