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Epoxidised Natural Rubber – ENR

Producer: Muang Mai Guthrie
Polymer type Natural Rubber

Epoxidised Natural Rubber, ENR or Epoxyprene is a speciality polymer produced from natural rubber latex, cis 1.4 – polyisoprene, with epoxide groups randomly dispersed along the polymer backbone.

Two grades are available commercially from Muang Mai Guthrie Public Limited Company of Thailand, Epoxyprene 25 and Epoxyprene 50, indicating 25% and 50% epoxidation respectively.

General info

Muang Mai Guthrie Public Company Limited was established in 1996 as a joint venture between Muang Mai Rubber Company Limited and Malaysian Kumpulan Guthrie Berhad Company which has over 100 years of experience in the natural rubber production industry, and was itself the first commercial licensee for the production of Epoxidised Natural Rubber. The Company’s current facilities are strategically located in Southern Thailand in the heart of the natural rubber production region in the province of Suratthani. To achieve the consistent, high quality of ENR Epoxyprene, both the raw materials and final products are subjected to stringent tests at MMG’s fully equipped laboratories and ISO 9001:2000 certification by BVQI.

Epoxidation results in a systematic increase in the polarity and glass transition temperature; these increases are reflected in the vulcanised properties.

Property changes with increasing levels of epoxidation include:

  • an increase in damping
  • a reduction in swelling in hydrocarbon oils
  • a decrease in gas permeability
  • an increase in absorption of microwave energy
  • an increase in silica reinforcement
  • improved compatibility with polar polymers like polyvinyl chloride
  • reduced rolling resistance and increased wet grip

Epoxyprenes may be compression moulded, extruded and injection moulded employing standard formulations, particularly those associated with natural rubber. Due to its polar nature, Epoxyprenes can be heated using microwave energy and have been used as additives to increase the microwave heating rate of non-polar polymers.


Standard ENR specifications:
Epoxyprene 25Epoxyprene 50
Epoxide level [%] 25 ± 250 ± 2
Glass transition temp [C°]-47-24
Density [Mg/m3]0.971.2
Solubility parameter [(jm-3)0.5]17.418.2
Lovibond Colour4.53.5
Mooney viscosity70-10070-100