Comparative Study of the Processing Conditions Required for Pla and Pet Polymers

This paper presents a comparative study of the thermal, mechanical, chemical and surface properties of the biodegradable polymer polylactic acid (PLA) and the petroleum based polymer polyethylene terephthalate (PET). The study shows how the material properties of these two polymers influence the processing conditions used during manufacture. The polymer properties were compared using differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, gel permeation chromatography and tensile testing. Significant differences were observed between PLA and PET with respect to both their mechanical and thermal properties. The melting temperature of PLA, as determined by DSC, was ~100C lower than that of PET. This lower melting temperature influenced the selection of parameters used in polymer extrusion and injection moulding. The glass transition temperature of PLA (60C) was also considerably lower than that of PET (77C), influencing the processing conditions used in thermoforming and heat sealing.