Identification of Hydrocarbon Components Generated by Transformation Processing of Cast Polypropylene Employed for Combining with Other Plastic Films

Abstract

In many packaging applications, next to the traditional custom of bi-oriented polypropylene (BOPP) there is an increasing use of polypropylene easily extrudable in film form, commonly known as cast polypropylene (CPP). More precisely, the combined structures BOPP-CPP unite the good barrier properties of the BOPP with those of tenacious weldability and tear resistance typical of the CPP. The operational conditions of extrusion and the raw materials adopt for forming these two kinds of film are not identical: sudden changes in temperature and the contemporaneous presence of propylene-ethylene units involve the formation of characteristic by-products of paraffinic nature (e.g. 2,3,4-trimethyl-pentane) and olefin nature (e.g. 2,4-dimethyl-1-heptene) in the CPP. They appear then like characteristics “markers” of CPP film destined to have a welding layer function; by the way their concentrations are very low (less than 0,5mg/m2) and their effect is practically absent in terms of anomalous odors that may be found on the packing.