This study explores the plasticizing effect of coconut oil (CO) on PLA for evaluating its suitability for flexible packaging. Changes in morphological, mechanical, thermal, rheological, barrier and optical properties of melt compounded Poly(lactic acid)-Coconut oil (PLA-CO) blend were investigated by varying the mixing ratio. Water vapor permeability of blends decreased by 58% at 7 wt % plasticizer content. The tensile strength showed a decreasing trend with increasing plasticizer percentage while the % elongation showed an increasing trend. At 7 wt % plasticizer content tensile strength decreased from 60 to 41 MPa and % elongation increased from 12% to 54%. Molecular weight (M n ) and onset of degradation (T onset ), upon 1 wt % plasticizer addition showed a reduction of 6% and 0.6%, respectively, which were well within permissible limits required for polymer processing. The melt flow properties of the blends were slightly improved (16%) upon 5 wt % addition of CO. Transparency of the PLA films was improved by addition of plasticizer. FTIR spectra of PLA-CO sample confirmed the interaction between PLA and coconut oil via hydrogen bonding. At higher loading, coconut oil shows very limited compatibility with PLA.
In this study, we successfully demonstrate single-step industrially scalable reactive extrusion of polylactic acid (PLA)/ cellulose nanocrystal (CNC)-based cast films which leads to reduced necking, improved processability, melt strength, and rheological behavior. PLA chains grafted onto CNCs, formed cross-linked gel-like structures of high molecular weight (M w ≈ 150−245 kDa), with varying grafting efficiency (14%−67%) or gel-fraction yield (16%− 69%), depending on the type of compatibilizers used. The reactively processed films show reduction in both oxygen properties (20%− 65%) and water vapor barrier properties (27%−50%), along with improved thermomechanical properties. These films finds potential applications for the storage of oil-and dairy-based products, which show shelf lives of ∼5 months and ∼2 weeks, respectively, and are within the standard migration limits, as per the set legislations. Therefore, the present study provides a novel, easily processable extrusion-based approach for manufacturing sustainable PLA/ CNC-based green and eco-friendly films with improved recyclability, biodegradability, and nontoxicity for potential applications as food packages on a commercial scale.
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