This work reports reactive extrusion of polylactic acid based cellulose nanocrystals (PLA-g-CNC) using cross-linking agent dicumyl peroxide (DCP) in presence of different fillers through one-step twin-screw extrusion cum film casting process. The different nanofillers used such as nanosilica, nanoclays, carbon nanofibers, alumina nano powder etc. and vegetable oils with saturated and unsaturated fatty acid compositions acts as a compatibilizer in improving the grafting efficiency. Presence of such nanofillers lead to enhanced compatibilization between hydrophobic PLA and hydrophilic CNCs, alongwith remarkable improvement in its structural and physical properties. This is possibly due to formation of branched and cross-linked structures in PLA during reactive-extrusion process, which hindered the problems related to thermal-cum-shear induced degradation of PLA during processing. 1H Nuclear magnetic resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopy studies confirms the grafting between methine (-CH) groups of PLA with methylene groups(-CH2) of CNCs through formation of C–C bridge, the extent of grafting efficiency however depends on the inherent properties of the nanofiller used. The mechanism of chemical grafting during reactive-extrusion was confirmed from chemical analysis which suggests that the radicals generated on CNCs surface instantaneously reacts with amorphous PLA chains thereby shielding the sulphate and hydroxyl groups of CNCs and forming a thin layer of PLA grafted onto CNCs. Moreover, the presence of fillers especially the inorganic nanofillers helped in improving the dispersion and the biobased nano-filers shows enhanced grafting percentages. PLA-g-CNC films with different nanofillers are capable of forming transparent films with improved dimensional characteristics compared to films extruded through traditional approach. Presence of DCP alongwith the nanofillers led to enhancement in molecular weight-average (Mw) and number-average (Mn) of fabricated nanocomposites the percentage increment depends upon the nanofiller type. Thermo-mechanical studies suggests that the grafted CNCs act as an efficient reinforcing agent, which is evident from decreased filler effectiveness coefficient values. Therefore, this study provides an alternative strategy to select the appropriate nanofillers through which the crystallization and thermo-mechanical properties can be finely tuned during the industrial scale extrusion cum film processing.

Reactive extrusion of polylactic acid/cellulose nanocomposite films: Crystallization and thermo-mechanical studies

254th National Meeting (2017)

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