Polymethylpentene (PMP), also known as poly(4-methyl-1-pentene). It is used for gas-permeable packaging, autoclavable medical and laboratory equipment,

microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

components, and cookware. It is commonly called TPX, which is a trademark of Mitsui Chemicals.

Production

Polymethylpentene is a 4-methyl-1-pentene-derived linear isotactic

polyolefin A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...

and is made by Ziegler–Natta type

catalysis Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

. The commercially available grades are usually copolymers. It can be extruded and moulded (by injection moulding or blow moulding).

Physical properties

Polymethylpentene melts at ≈ 235 °C. It has a relatively low

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

(0.84 g/cm³) among plastics and is transparent. It has low moisture absorption, and exceptional acoustical and electrical properties. Its properties are reasonably similar to those of other

s, although it is more

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. ...

and more gas permeable. The polymer also has a high thermal stability, excellent

dielectric In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric ...

characteristics and a high chemical resistance. The

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

line phase has a lower

than the

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...

phase.

Optical properties

In comparison to other materials being used for operating in THz range, TPX shows excellent optical properties with a wavelength independent

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

of 1.460±0.005 between visible light and 100~GHz. While having a very good transmission in the THz area, TPX also shows a very wide transmission range spreading from UV to THz.

Applications

*Applications include sonar covers, speaker cones, ultrasonic transducer heads, and lightweight structural parts. It is also FDA compliant for use in

food processing Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing takes many forms, from grinding grain into raw flour, home cooking, and complex industrial methods used in the mak ...

machinery. Polymethylpentene is often used in films and coatings for gas-permeable packaging. *Because of its high

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

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 An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—semiconductors and electrical conductor, conductors—con ...

. *TPX is a hard, solid material, which can be mechanically shaped into various optical components like

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

es and

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent ma ...

s. It 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.

References

* 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)

External links

Mitsui Chemicals, Inc.Tydex J.S.Co. - Manufacturer of polished TPX lenses and windows
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