Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging and labeling, textiles (e.g., ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, transvaginal mesh and polymer banknotes. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.
Polypropylene has a relatively slippery "low energy surface" that means that many common glues will not form adequate joints. Joining of polypropylene is often done using welding processes.
In 2013, the global market for polypropylene was about 55 million tonnes.Polypropylene is the world's second-most widely produced synthetic plastic, after polyethylene.
Why not make pvc bio-degradable so that it can rot away？
PVC is mainly used in medium or long-life applications, for which its ability to resist natural degradation is a significant advantage.
When used in packaging, PVC is often chosen for its barrier performance and hence any process that would progressively impair this resistance would be counterproductive
Bio-degradable plastics are presented as one of the possible solutions to the problem of litter. The main products causing the litter problem are plastic carrier bags and plastic drink bottles. Neither of these products is made of PVC anymore, and hence PVC packaging is not actually a significant contributor to the plastic litter problem.