ABSTRACT
Polypropylene is one of the fastest growing classes of thermoplastics. This growth is attributed to its attractive combination of low cost, low density, and high heat distortion temperature (HDT). The extraordinary versatility of unfilled virgin resin and reinforced polypropylene suits a wide spectrum of end-use applications for fibers, films, and molded parts. However, there always exist certain shortcomings in physical and chemical properties that can limit universal use of any given polymer resin. In packaging, for example, polypropylene resins have poor oxygen barriers, while low dimensional and thermal stability limits the scope of polypropylene composites in automotive applications. Most schemes to improve polypropylene gas barrier properties involve either addition of higher barrier plastics via a multilayer structure or surface coatings. Although effective, the increased cost of these approaches negates one big attraction for using polypropylene in the first place-economy. Currently, automotive and appliance applications employ glass or mineral-filled systems with loading levels ranging from 15 to 50 wt%. This approach improves most mechanical properties, but polypropylene’s ease of processing is somewhat compromised. Furthermore, the need for higher filler loading leads to greater molded part weight.
