The cover photo describes the scheme of the twin screw extruder for the preparation of thermoplastic starch (TPS). As discussed by M. Paula Guarás, this screw extrusion process is very advantageous for the preparation of TPS films with improved mechanical and water vapor absorption properties in any industrial processing line for plastic packaging products.
Morphological, structural, thermal and degradation properties of polylactic acid-waxy maize starch nanocrystals based nanocomposites prepared by melt processing
Pooja Takkalkar, Mahalaxmi Ganapathi, Maha Al-Ali, Nhol Kao*, Gregory Griffin
Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, 3000, Australia
Adv. Mater. Lett., 2019, 10 (3), pp 170-177
Publication Date (Web): Dec 31, 2018
Copyright © 2019 VBRI Press
Currently used petroleum-based polymers have adversely affected the environment in various ways, mainly due to their non-biodegradability. This undesirable aspect of commercial polymers led to increased interest in the research area of biodegradable polymer nanocomposites. Polylactic acid (PLA) based nanocomposites, with three different loadings of waxy maize starch nanocrystals (WSNC) as nanofiller (1, 3 and 5 wt%), were melt-blended in a Haake Rheomix. The morphological, structural, thermal and abiotic degradation characteristics of the prepared PLA-WSNC nanocomposites were studied to determine the effects of adding WSNC at different loadings in PLA. The results indicated that WSNC were dispersed uniformly at lower loadings (0-3 wt%) and agglomerated at higher loadings (5 wt%) within the PLA matrix. All PLA-WSNC nanocomposites were found to be stable over the processing temperature range of 25-220 ºC. In addition, there was no considerable change in the glass transition temperature and the melting point of the nanocomposites. Though, the cold crystallization temperature was reduced with the increase of WSNC loadings. The abiotic degradation studies, used as an initial screening tool, indicated that WSNC can accelerate the degradation process of PLA. As a result, the degradation rate was improved for all the PLA-WSNC nanocomposites. The PLA-WSNC-3 wt% was found to be the optimum concentration to enhance the crystallinity and morphological property of PLA, and beyond that the properties were affected by agglomeration.
Polylactic acid, waxy maize starch nanocrystals, melt processing.