An investigation of multilayer nanocomposite polypropylene film for food packaging applications

Many food packaging applications require multilayer polymer structures to provide properties necessary for freshness and shelf-life. Retort processing is a steam sterilization process that is currently utilized for military rations which are packaged in an aluminum foil quad-laminate in order to obtain required barrier properties and shelf-life. Polypropylene (PP) was compounded with 7.5% montmorillonite layered silicate (MLS) and a compatibilizer and then extruded to produce blown and cast films. The monolayer PP/MLS films were first investigated and found to have significant improvement in thermal, barrier and mechanical properties over the neat PP films. The retort process did not negatively affect the monolayer PP/MLS films. Then an experimental five layer structure consisting of PP and ethylene co-vinyl alcohol (EVOH) was co-extruded and investigated as a possible replacement for the current retort packaging. The multilayer neat PP-EVOH and PP/MLS-EVOH films however, did not maintain barrier or mechanical properties after the retort process.