Polymethylpentene (PMP) / TPX Plastic Recycling

Polymethylpentene (PMP) is a thermoplastic polymer of methylpentene monomer units. TPX is a commonly used trademark provided by Mitsui Chemicals. Other trademark names of PMP are Zeonex and Crystalor. TPX is a lightweight, high temperature polyolefin. It is commonly used for applications requiring low distortion of sound waves, and also for electrical insulating applications requiring high dielectric strength and low dielectric constant. Natural TPX is FDA compliant for use in food processing machinery.

Molecular formula - (C12H24)n

Density - 0.84 g/cm³

Melting point - 235°C (455°F)

Chemical and Physical Properties of TPX

The following are the chemical and physical properties of TPX:

  • Mechanical properties are comparable to polyolefins with higher temperature properties and higher creep properties
  • Can be formed by injection molding and blow molding
  • Crystallizes to 40%-60% and has gas permeability
  • Highly transparent with 90% transmission
  • Flammable and peelable
  • Low permeability to gases and good chemical resistance
  • Exceptional electrical and acoustical properties
  • Low specific gravity and low density
  • Good steam, heat and chemical resistance
  • Lowest specific gravity of any known thermoplastic
  • Low moisture absorption
  • Low refractive index and resin FDA compliant
  • Low dielectric properties and food sanitation properties

Manufacturing Process of TPX

Polymethylpentene is a 4-methyl-1-pentene based linear isotactic polyolefin that can be manufactured using the Ziegler-Natta type catalysis. The Ziegler– Natta catalyst is used in the synthesis of polymers of 1-alkenes (α-olefins).

The commercially available TPX grades are usually copolymers. TPX can be extruded and molded using injection molding or blow molding. As TPX does not absorb water /moisture, it is does not require drying before processing provided that it has been stored under normal conditions. To control or reduce decomposition of TPX, it is better to apply nitrogen-feeding at the hopper during molding process.

Applications of Virgin Material TPX

The following are the various uses of TPX:

  • Autoclavable medical and laboratory equipment
  • Microwave components and cookware, and gas permeable packaging
  • Lighting elements such as diffusers and lenses reflectors
  • Electric and electronic components, acoustical devices, antennas and release films
  • Loudspeaker diaphragms and sonar transducer covers
  • Lightweight structural parts, and cosmetic caps and tubes
  • Gas separating membranes
  • Mandrels and sheaths for rubber hose production
  • Animal cages and carrier films for ceramic slurry
  • Medical instrument cover and ultrasonic imaging equipment
  • LED molds and synthetic papers
  • Baking carton, food wraps and food preservation packs
  • TPX is a hard, solid material that can be mechanically-shaped into optical components such as lenses and windows

Environmental Impacts of TPX

TPX is considered as eco-friendly as it is halogen-free. However, any type of plastic in landfills takes several years to decompose and become an environmental hazard.

Recycling Process

The recycling code of TPX is 7. Type 7 plastics are made of a resin that does not belong to the other six types or a mixture of the six plastic types. Type 7 plastics such as TPX are not recycled often due to high recycling costs. It is advisable to reduce the usage of these plastics and when they have to be used, better re-use them rather than disposing or recycling them.

Sources

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