Propylene polymers, also known as polypropylene, is a thermoplastic polymer used in a wide variety of applications. It is an addition polymer made via chain-growth polymerization from the monomer propylene. Polypropylene can be produced in a variety of structures giving rise to applications including packaging and labeling, textiles, plastic parts and reusable containers of various types, laboratory equipment, automotive components, and medical devices. It is a white, mechanically rugged material, and is resistant to many chemical solvents, bases, and acids.
Traditionally, three manufacturing processes are the most representative ways to produce propylene polymers:
Hydrocarbon slurry or suspension: Uses a liquid inert hydrocarbon diluent in the reactor to facilitate the transfer of propylene to the catalyst, the removal of heat from the system, the deactivation/removal of the catalyst as well as dissolving the atactic polymer. The range of grades that could be produced was very limited. (The technology has fallen into disuse).
Bulk slurry (or bulk): Uses liquid propylene instead of liquid inert hydrocarbon diluent. The polymer does not dissolve into a diluent but rather rides on the liquid propylene. The formed polymer is withdrawn and any unreacted monomer is flashed off.
Gas-phase: Uses gaseous propylene in contact with the solid catalyst, resulting in a fluidized-bed medium.
Polypropylene is a major polymer used in nonwovens, with over 50% used for diapers or sanitary products where it is treated to absorb water (hydrophilic) rather than naturally repelling water (hydrophobic). Other interesting non-woven uses include filters for air, gas, and liquids in which the fibers can be formed into sheets or webs that can be pleated to form cartridges or layers that filter in various efficiencies in the 0.5 to 30 micrometer range. Such applications occur in houses as water filters or in air-conditioning-type filters. The high surface-area and naturally oleophilic polypropylene nonwovens are ideal absorbers of oil spills with the familiar floating barriers near oil spills on rivers.
Its most common medical use is in the synthetic, nonabsorbable suture Prolene, manufactured by Ethicon Inc. Polypropylene has been used in hernia and pelvic organ prolapse repair operations to protect the body from new hernias in the same location. A small patch of the material is placed over the spot of the hernia, below the skin, and is painless and rarely if ever, rejected by the body. However, a polypropylene mesh will erode the tissue surrounding it over the uncertain period from days to years. Therefore, the FDA has issued several warnings on the use of polypropylene mesh medical kits for certain applications in pelvic organ prolapse, specifically when introduced in close proximity to the vaginal wall due to a continued increase in a number of mesh-driven tissue erosions reported by patients over the past few years. Most recently, on 3 January 2012, the FDA ordered 35 manufacturers of these mesh products to study the side effects of these devices.