Bond strength of laminated films between poly(lactic acid)based cast films and metalized cast polypropylene films

摘要

This research was carried out to study the feasibility to use biodegradable poly(lactic acid)(PLA)in flexible packaging films,which they were usually laminated with metalized cast polypropylene(MCPP)film in order to reduce oxygen permeability and could be microwaveable.Since PLA was too brittle,two types of polymers;poly(butylene adipate-co-terephthalate)(PBAT)and polyethylene glycol(PEG),were blended and extruded into cast films in the weight ratios of 5,10,and 15 wt%.The prepared blend films were laminated with MCPP films using a commercial polyurethane adhesive.Mechanical and thermal properties of the blend films were investigated by tensile testing and differential scanning calorimetry.The bond strength of the laminated films was analyzed.It was found that the glass transition temperatures of PLA in the PLA/PEG blends were dramatically reduced attributed to the plasticizing effect,however,they were not changed in the PLA/PBAT blends.As a result,tensile strength of the PLA/PEG films was reduced significantly with respect to PEG content.The laminated films of PLA/PBAT blend and MCPP had higher bond strength than those of PLA and MCPP or PLA/PEG and MCPP.The transparent PLA/PBAT 95/5 wt% was the best formula that could replace poly(ethylene terephthalate)for laminated film.