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<p>A pre-crosslinked (80% vulcanised) form of natural rubber (PA80) was blended with a medium-molecular-weight ethylene-propylene-diene elastomer (EPDM) in different proportions using a two-stage mixing process. The processability, morphology and thermomechanical properties of the blends were evaluated against an unmodified natural rubber/EPDM (NR/EPDM) blend to identify the optimum blend ratio suitable for extrusion applications. In the proposed PA80/EPDM blend system, extruded profiles with higher PA80 content exhibited smoother contours and lower die swell under the same processing conditions. A combination of ultra-fast and semi-ultra-fast accelerators in PA80/EPDM blends having comparable unsaturation levels resulted in faster and uniform vulcanisation. The viscosity mismatches existing between the blend partners were made minimal with sufficient pre-mastication of PA80. Hence, the thermomechanical properties, filler dispersion and morphological analysis of the PA80/EPDM blends showed satisfactory results, whereas the samples with adequate EPDM content (30 phr) resisted the ozone attack effectively. Therefore, PA80 can be considered a cost-effective substitute for EPDM profiles (30–50% replacement) without considerable property reduction.</p>

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Processability and thermomechanical properties of PA80/EPDM blends

  • 期刊论文

  • 发表日期：

    2026年4月23日

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  • Sujith Nadarajan,
  • Siby Varghese,
  • Shera Mathew

摘要

A pre-crosslinked (80% vulcanised) form of natural rubber (PA80) was blended with a medium-molecular-weight ethylene-propylene-diene elastomer (EPDM) in different proportions using a two-stage mixing process. The processability, morphology and thermomechanical properties of the blends were evaluated against an unmodified natural rubber/EPDM (NR/EPDM) blend to identify the optimum blend ratio suitable for extrusion applications. In the proposed PA80/EPDM blend system, extruded profiles with higher PA80 content exhibited smoother contours and lower die swell under the same processing conditions. A combination of ultra-fast and semi-ultra-fast accelerators in PA80/EPDM blends having comparable unsaturation levels resulted in faster and uniform vulcanisation. The viscosity mismatches existing between the blend partners were made minimal with sufficient pre-mastication of PA80. Hence, the thermomechanical properties, filler dispersion and morphological analysis of the PA80/EPDM blends showed satisfactory results, whereas the samples with adequate EPDM content (30 phr) resisted the ozone attack effectively. Therefore, PA80 can be considered a cost-effective substitute for EPDM profiles (30–50% replacement) without considerable property reduction.