Cellulose Functionalized High Molecular Weight Stereocomplex Polylactic Acid Biocomposite Films with Improved Gas Barrier, Thermomechanical Properties

Abstract

This work presents a facile, solvent-free approach for the fabrication of PLA biocomposites, followed by melt extrusion process to prepare stereocomplex PLA films with excellent thermomechanical and gas barrier properties. The presence of stereocomplex crystallites improves the thermal properties of polylactic acid (PLA); however, the formation of stereocomplex crystallites is predominantly lesser compared to homocrystallites in case of high molecular weight poly(L-lactic acid) and poly(D-lactic acid) blend. Grafting of biofillers with polymer matrix chains may help in homogeneous dispersion and formation of stereocomplex crystallites. Henceforth, stereocomplex PLA was fabricated with cellulose microcrystals (CMC) as filler, after chemical modification by in situ ring opening polymerization of D-lactide. The stereocomplexation in the blend system was found to be enhanced by the extended molecular surface area provided by grafted CMC. As confirmed by morphological analysis, the modification of CMC drives the homogeneous dispersion into the matrix and reduction in the size of CMC in the range of ∼200 nm diameter. Increased melting temperature (∼209 °C) with no evidence of homocrystallites confirm the role of grafted CMC in the formation of stereocomplex crystallites by suppressing the development of homocrystals. The fraction of stereocomplex crystallites was found to be 100% when analyzed using X-ray analysis. The enhanced stereocomplexation in the composites resulted ∼96% improvement in the tensile strength in comparison to pristine PLLA/PDLA blend. Interestingly, the oxygen permeability and water vapor permeability were reduced by ∼25% and ∼35%. The improved thermomechanical properties of the biocomposites through enhanced stereocomplexation may comply with the requirement for high temperature engineering and packaging applications.

Effect of silk nano‐disc dispersion on mechanical, thermal, and barrier properties of poly(lactic acid) based bionanocomposites

“…Lattice planes of PLA can be clearly seen in the diffraction spectra with peaks at 14.9°, 16.8°, and 19.9° . XRD analysis shows peak broadening at 16.8° and shifting to lower 2θ values, indicating possible intercalation of CSNs.…”

“…PLA‐based composites fabricated using biofillers are sparsely represented currently. The influence of different biofillers such as cellulose, starch, cellulose nanocrystals, chitosan, gum, sucrose palmitate, silk on the thermomechanical and permeation properties of PLA have been examined.…”

Crystallization kinetics, morphology, and hydrolytic degradation of novel bio‐based poly(lactic acid)/crystalline silk nano‐discs nanobiocomposites

“…From the perspectives of resource and environment, biodegradable polymers have been on the focal point to address the predicament caused due to unruly utilization of conventional polymers like polyethylene, polyethylene terephthalate, and polypropylene, etc . Poly(lactic acid) (PLA) has shown a lot of promise because of its convenient biodegradability and analogous mechanical properties and melting temperature to many traditionally used polymers . In last two decades, synthesis, crystallization kinetics, morphology, mechanical properties, and biodegradability of PLA has been investigated in detail .…”

“…On the contrary, organic fillers like cellulose, starch, chitosan, etc. are abundant, low‐cost, renewable, and biocompostable making them clear favorites …”

“…1 Poly(lactic acid) (PLA) has shown a lot of promise because of its convenient biodegradability and analogous mechanical properties and melting temperature to many traditionally used polymers. 2 In last two decades, synthesis, crystallization kinetics, morphology, mechanical properties, and biodegradability of PLA has been investigated in detail. 3,4 Utilization of organic and inorganic fillers have often been utilized to improve the material properties of PLA to distend its applicability.…”