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Polymethylpentene (PMP) is a thermoplastic polymer of methylpentene monomer units. It is used for gas permeable packaging, autoclavable medical and laboratory equipment, microwave components, and cookware. It is commonly called TPX, which is a trademark of Mitsui Chemicals.
Polymethylpentene is a 4-methyl-1-pentene based linear isotactic polyolefin and is made by Ziegler-Natta type catalysis. The commercially available grades are usually copolymers. It can be extruded and molded (by injection molding or blow molding).
Polymethylpentene melts at ≈ 235 °C. It has a very low density (0.84 g·cm³) and is transparent. It has excellent chemical resistance, low moisture absorption, and exceptional acoustical and electrical properties. Its properties are reasonably similar to those of other polyolefins, although it is more brittle and more gas permeable.
In comparison to other materials being used for operating in THz range, TPX shows excellent optical properties with a wavelength independent refractive index of 1.460±0.005 between visible light and 100~GHz.
- Applications include sonar covers, speaker cones, ultrasonic transducer heads, and lightweight structural parts. It is also FDA compliant for use in food processing machinery. Polymethylpentene is often used in films and coatings for gas permeable packaging.
- Because of its high melting point and good temperature stability, polymethylpentene is used for autoclavable medical and laboratory equipment, microwave components, and cookware.
- It is also often used in electrical components e.g. LED molds because it is an excellent electrical insulator.
- TPX is a hard, solid material, which can be mechanically shaped into various optical components like lenses and windows. Also specifically TPX is used in CO2 laser pumped molecular lasers as an output window because it is transparent in the whole terahertz range and totally suppresses the ~10 µm pump radiation.
- Krentsel B.A., Kissin Y.V., Kleiner V.I., Stotskaya S.S. Polymers and Copolymers of Higher a-Olefins, Hanser Publishers: New York, 1997.
- H. C. Raine, J. Appl. Polym. Sci. 11, 39 (1969).
- Mitsui Chemicals Co., Properties of Standard TPX Grades, 2004.
- FDA CFR Title 21 Sec. 177.1520 Olefin polymers (C) 3.3b for TPX(4-methylpentene-1-based olefin copolymer)