Polypropylene (PP) is a thermoplastic polymer (a polymer molded above a given temperature and returns to the solid state upon cooling) used in many applications such as labeling and packaging, textile (e.g. thermal underwear, carpets and ropes), plastic parts, stationery, reusable containers, loudspeakers, polymer banknotes, laboratory equipment and automotive components. It is resistant to many acids, chemical solvents and bases. They are resistant to alkali and organic solvents and does not absorb water and water solutions which are destructive to metals.
Polypropylene is a polymer prepared catalytically from propylene which differs from HDPE by having an isostatic replacement of a hydrogen atom by a methyl group on alternate carbon atoms in the main chain. Although largely unreactive chemically the presence of the methyl groups makes it slightly more susceptible to attach from strong oxidizing agents than HDPE. A major advantage is its higher temperature resistance. It makes it particularly suitable for items such as trays and instrument jars that have to be sterilized frequently for use in a clinical environment. Polypropylene is a translucent material with excellent mechanical properties and it has gradually replaced polyethylene for many purposes.
Benefits of Polypropylene
It is used in the everyday applications because it is semi-flexible. Its melting point is high compared to other plastics. For this reason it is excellent for use in food containers where temperatures can raise to high levels- such as dishwashers and microwaves. Its melting point temperature is 320 degrees F, hence its application in hot containers but should not be used in temperatures higher than 230° F (127° C).
The following are the other benefits of polypropylene:
· It doesn’t absorb water like many other plastics. It is naturally hydrophobic but can be chemically treated to be hydrophilic in porous filtration applications.
· It contains an elastic constituent which provides it with a rubber-like element and makes a way for new uses like bottles and film.
· It does not weaken or mold in the presence of mold, bacteria or other destructive elements. Polypropylene will handle sterilization over and over again where other plastics will not.
· It has low probability of shattering and absorb significant damage before breaking, even though it is not strong compared to other plastics like polyethylene. Polypropylene is more rigid than polyethylene.
Chemical Properties and Uses
Understanding polypropylene is of significance as it differs completely from other types of the plastic products. Its quality properties allow it to be used effectively in the everyday use, especially in situations where a non-toxic and a non-staining material is needed. Its cost is not high. It offers the best alternative to the other plastics as it doesn’t contain BPA which is unsafe for food packaging because it leaches into the food products causing health hazards. Its electric conductivity is low making it suitable for electronic products. As a result of these advantages, polypropylene is used in many American homes.