Akhilesh Kumar Pal

Nanoamphiphilic Chitosan Dispersed Poly(lactic acid) Bionanocomposite Films with Improved Thermal, Mechanical, and Gas Barrier Properties

This article demonstrates the synthesis of lactic acid oligomer-grafted-chitosan (OLLA-g-CH), a nanoamphiphilic molecule, by in situ condensation polymerization and its effective use as a nanofiller for improvement in multiple properties of poly(lactic acid) (PLA) films, essential for stringent food packaging applications. Fourier transform infrared spectroscopy (FTIR) analysis shows the presence of amide-ester bond at 1539 cm(-1), which confirms the structural grafting of OLLA chains with chitosan molecules. This nanoamphiphilic OLLA-g-CH molecule act as surfactant containing hydrophilic chitosan head and hydrophobic OLLA tails with average size in the range of ∼2-4 nm. Prepared PLA/OLLA-g-CH bionanocomposite films appear with uniform dispersion of nanoamphiphilic OLLA-g-CH molecules with self-assembled micelles having size as low as ∼20 nm and as high as ∼150 nm with core-shell morphology in PLA matrix. This nanofiller is found very effective toward significant reduction in oxygen permeability (OP) by ∼10-fold due to the reduction in solubility of oxygen molecules and improvement in crystal nucleation density due to availability of nanonucleating sites. Ultimate tensile strength (UTS) of PLA/OLLA-g-CH bionanocomposite films are relatively comparable to that of PLA, however, elongation at break is improved significantly. The onset of thermal degradation of PLA/(OLLA-g-CH) films is also found comparable to that of PLA film. The glass transition temperature (Tg) of bionanocomposites is decreased by more than 18 °C with increase in OLLA-g-CH loading, which indicates the improved plasticization characteristics of PLA matrix. The crystallization kinetics suggest nonthree dimensional truncated spherical structures, which is controlled by the combination of thermal and athermal instantaneous nucleations. POM analysis suggested that the spherulite growth of PLA is improved significantly with the addition of OLLA-g-CH. The reduction in Tg of PLA with improvement in elongation at break and multifold reduction in oxygen permeability offers this bionanocomposite films, a promising candidate for stringent food packaging applications.

Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films

In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol-1 respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis.

Theoretical and analyzed data related to thermal degradation kinetics of poly (L-lactic acid)/chitosan-grafted-oligo L-lactic acid (PLA/CH-g-OLLA) bionanocomposite films

The theoretical and analyzed data incorporated in this article are related to the recently published research article entitled “Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films” (http://dx.doi.org/10.1016/j.ijbiomac.2016.11.024) (A.K. Pal, V. Katiyar, 2016) [1]. Supplementary information and data (both raw and analyzed) are related to thermal degradation kinetics and explains various model fitting and is conversional methods, which are used in this research work to enhance the knowledge about degradation behaviour of PLA/CH-g-OLLA bionanocomposite system. Non-isothermal degradation kinetics of such polymeric system was proposed using Kissinger, Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa and Augis and Bennett models to estimate the activation energies (Ea) and R2 values.

Chitosan dispersed PLA films for high gas barrier applications: An industrially viable approach

A films for use as greenhouse covers, mulch films and silage film are a film market in excess of 350 million pounds in North America. There is a large recycling market for these films after their use in agriculture but much of these films still end up in landfill or as litter.This paper will discuss the physical properties of various biopolymers in relationship to the application needs of agricultural mulch films. The ability to recycle, compost or bio-digest these biopolymer based mulch films will be discussed in relation to their petroleum based counterparts that are presently used.The focus will be on the use of the biopolymer film waste as a replacement or a supplement to the use of and need for food waste in composting and biogas production.The percentage of food waste in the raw materials to be composted or anaerobically digested directly effects the time necessary for composting and the speed of biogas production. With food waste supplies and sources being variable, the use of biopolymer based agricultural films as a supplement to the food waste could add predictability and increased production to the composting and biogas industries.

Effects of Amphiphilic Chitosan on Stereocomplexation and Properties of Poly(lactic acid) Nano-biocomposite

This article demonstrates an elegant approach for the fabrication of high heat-stable PLA using an industrially viable technique i.e. melt extrusion, which is quite challenging due to the higher viscosity of poly(lactic acid) melt. scPLA has been fabricated by melt extrusion of PLLA/PDLA using nano-amphiphilic chitosan (modified chitosan, MCH) which has been synthesized by grafting chitosan with oligomeric PLA via insitu polycondensation of L-lactic acid that possibly increases the molecular surface area and transforms it into nano-amphiphilic morphology and in turn lead to the formation of stereocomplex crystallites. The effect of MCH loading on the structural, morphological, mechanical and thermal properties of PLLA/PDLA have been investigated. The modification of chitosan and formation of stereocomplexation in PLA has been confirmed by FTIR and XRD techniques, respectively. Heat treatment has also laid a significant effect on the stereocomplexation and the degree of crystallinity of stereocomplex crystallites has been increased to ~70% for 1.5 wt % MCH content with the absence of homocrystals. The heat deflection temperature is found to be more than 140 °C for the biocomposite with 1.5% MCH in comparison to ~70 °C for pristine scPLA. The biocomposites display significant improvement in UTS and Young’s modulus.

Effect of Dicumyl Peroxide on a Poly(lactic acid) (PLA)/Poly(butylene succinate) (PBS)/Functionalized Chitosan-Based Nanobiocomposite for Packaging: A Reactive Extrusion Study

Nanobiocomposites with balanced mechanical characteristics are fabricated from poly(lactic acid) (PLA)/poly(butylene succinate) (PBS)blend at a weight ratio of 80/20 in association with varying concentrations of functionalized chitosan (FCH) through reactive extrusion at a temperature of 185 °C. The combined effect of FCH and dicumyl peroxide (DCP) showed insignificant change in tensile strength with a remarkable increase in % elongation at break (∼45%) values. Addition of DCP also caused increase in the molecular weight (Mw ∼ 22%) of the PLA/PBS/1DFCH nanobiocomposite, which is attributed to the cross-linking/branching effect of FCH on the polymers. The interfacial polymer–filler adhesion is also improved, which is observed from the field-emission scanning electron microscopy images of PLA/PBS/1DFCH. For PLA/PBS/1DFCH, the crystallization rate and nucleation density of PLA are increased because of cross-linked/branched structures are developed, which acted as nucleating sites. Therefore, the present work facilitates a simple extrusion processing with a combination of balanced thermal and mechanical properties, improved hydrophobicity (∼27%), and UV-C-blocking efficiency, which draw the possibility for the utilization of the ecofriendly nanobiocomposite in the packing of UV-sensitive materials on a commercial level.