TY - JOUR
TI - Influence of time and room temperature on mechanical and thermal degradation of poly(lactic) acid
AU - Karamanlioglu Mehlika
AU - Alkan Ümit
JN - Thermal Science
PY - 2019
VL - 23
IS - 11
SP - 383
EP - 390
PT - Article
AB - Poly(lactic) acid, PLA, is a compostable thermoplastic which degrades fast  under composting conditions of microorganisms, high humidity and  temperatures. However, PLA degrades slowly below its glass transition  temperature and in low humidity, hence, when used as short-shelf life  product containers and not disposed to composting systems, PLA may cause  environmental pollution. Therefore, when not disposed to proper waste  management systems, the effect of long incubation time at room temperature  on mechanical and thermal properties of PLA is the main concern of this  study. To determine the effect of room temperature on semi-crystalline PLA  degradation at a low humidity percentage, PLA films (PLA2) were kept at room  temperature for 5 years at 40±10% humidity. Some PLA films (PLA3) were  pre-treated at 55°C under dry conditions for 1 year and then kept at room  temperature for 4 years. Influence of incubation time and temperature on PLA  degradation was evaluated by mechanical, thermal analyses and by  Fourier-Transformation Infrared Spectroscopy Analysis (FTIR) and compared  with the initial PLA samples (PLA1). Mainly mechanical properties of PLA  were affected by incubation temperature and time since 68% tensile strength  loss was observed in PLA3 samples which were pre-treated at 55ºC and 34%  decrease in tensile strength was observed in PLA2 samples. Thermal behaviour  of PLA was also influenced by incubation time and temperature as degree of  crystallinity decreased 2 and 5% in PLA2 and PLA3 samples, respectively.  Deformation of CH bonds and amorphous phase degradation were revealed by  FTIR analyses in PLA2 and PLA3 samples.