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A special plastic: TPX™

Polymethylpentene (PMP) is a special plastic produced by Mitsui Chemicals from Japan under the brand name TPX™.  It’s the polymer of 4-methyl-1-pentene. It is produced with a Ziegler-Natta catalyst. 

Polymethylpentene has a unique combination of properties

Pure poly (4-methyl-1-pentene) has a high degree of crystallinity, making it brittle and difficult to process. Therefore, another alpha olefine is usually used as a co-monomer in polymerization. Polymethylpentene has a unique combination of properties:

  • Very good Better than PMMA, PS and glass, among others.

TPX kunststof

  • High temperature resistance. The melting point of TPX is 230-240 °C. As a result, TPX has a better thermal deflection temperature than PC and PSU, among others.


TPX kunststof

  • Chemical resistance is significantly better than that of PSU, PES and PEI. PMP is comparable to PP in terms of chemical resistance.

harsen verschillende kunststoffen

  • Hydrolysis resistance is comparable with f.e. PSU, PES and PEI. Both steam and boiling water have virtually no effect on Mitsui TPX properties.
  • Mitsui TPX’s refractive index is also very low at 1,463, lower even than, for example,
  • For electric applications, Mitsui TPX is suitable thanks to its very good electrical insulation and the very low dielectric constant. The dielectric constant is even similar to PTFE and LDPE.


  • The surface tension of Mitsui TPX is similar to many fluoropolymers. This makes PMP extremely water repellent and offers very good release properties.

Grafiek met de oppervlaktespanning van verschillende kunststoffen

  • Mitsui TPX has a very low density, namely 833 kg/m3. Compared to PSU and PEI, this results in a weight reduction of >30%, compared to PES even almost 40%. This makes TPX, in addition to technology, also commercially very interesting as an alternative to PSU, PES and PEI. Mitsui TPX then offers a cost-saving of 80-130% for hot water applications.
  • In addition, Mitsui TPX offers excellent gas permeable properties for fruit and vegetable packaging. Of course, PMP is suitable for food contact applications.

TPX kunststof Mitsui


Thanks to this unique combination of properties, TPX is used in food packaging, microwave trays, laboratory glassware, cufats, cosmetic packaging, speaker cones, sonar housing, ultrasonic lenses, as well as packaging film, baking paper and various electronics applications.

Mitsui TPX is also used in CO2 lasers as a lens, as the material is transparent throughout the terahertz range and completely suppresses the ~10 μm radiation.

Contact us

Please contact Larry de Kleine or Epco Blessing for more information about TPX and other plastics solutions.