Poly (lactic acid)/modified gum arabic (MG)based microcellular composite foam: Effect of MG on foam properties, thermal and crystallization behavior.

The article demonstrates a simple and innocuous method for fabrication of poly (lactic acid) (PLA)/modified gum arabic (MG)based hydrophobic, microcellular, highly porous and interconnected composite foam. The observed density of the composite foams was remarkably reduced by ~86% in comparison to PLA granules. Further, there was noticed an increase in cell density and a decrease in cell size due to the addition of MG nanofiller. The thermogravimetric analysis (TGA) of developed foam showed no significant effect of MG in maximum degradation temperature (Tmax). Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) investigations suggested the plasticizing effect of MG nanofiller in the PLA matrix. The hydrophobicity of fabricated foam was found to increase with an increase in loading of MG and an increment of ~20° in contact angle was observed for highest loading of MG (3%) in comparison to neat PLA foam. Further, an increase in the surface area up to ~60% and a decrease in pore diameter up to ~53% were observed for PLA/MG based foam by porosimetric investigations. Based on this investigation, the fabricated PLA/MG based foams have the potential for specialized applications as an alternative to non-degradable petro-based foams in various fields of life.

Thermal degradation behaviour and crystallization kinetics of poly (lactic acid) and cellulose nanocrystals (CNC) based microcellular composite foams.

The current investigation addresses the thermal degradation and non-isothermal crystallization behaviour of the fabricated poly (lactic acid) foam (nPLA) and poly (lactic acid) (PLA)/cellulose nanocrystal (CNC) based foams at three different loadings of CNC (i.e. 1%, 2% and 3%) as PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 having highly porous, interconnected and microcellular morphology. The formation of various gaseous products at two different conversions (α = 0.3 and α = 0.7) are investigated by using thermogravimetric analyser hyphenated Fourier transmission infrared spectroscopy (TGA-FTIR) analysis in isothermal condition. Effect of porosity and CNC reinforcement towards thermal degradation and crystallization of the PLA is thoroughly investigated by using mercury intrusion porosimetry (MIP). "Model-free" and "modelistic" approaches like Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sinouse (KAS), Kissinger and Augis & Bennet have been utilized for non-isothermal degradation kinetics of the fabricated foams. Non-isothermal melt crystallization kinetics of fabricated foams reveals that both primary and secondary crystallization process taking place. The apparent activation energy calculated from FWO are ~175.8 kJ/mol, ~198.6 kJ/mol, ~175.5 kJ/mol and ~174.7 kJ/mol for nPLA, PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 respectively. It is also observed that at higher conversions, complex three dimensional diffusion mechanism of degradation might be taking place in accordance with Criado plots.

Biodegradable poly (lactic acid)/Cellulose nanocrystals (CNCs) composite microcellular foam: Effect of nanofillers on foam cellular morphology, thermal and wettability behavior.

This article addresses the elegant and green approach for fabrication of bio-based poly (lactic acid) (PLA)/cellulose nanocrystal (CNCs) bionanocomposite foam (PLA/CNC) with cellular morphology and hydrophobic surface behavior. Highly porous (porosity >80%) structure is obtained with interconnected pores and the effect of CNCs in the cell density (Nf) and cell size of foams are thoroughly investigated by morphological analysis. The thermo-mechanical investigations are performed for the foam samples and almost ∼1.7 and ∼2.2 fold increase in storage modulus is observed for the compressive and tensile mode respectively. PLA/CNC based bionanocomposite foams displayed similar thermal stability as base PLA foam. Detailed investigations of decomposition behavior are studied by using hyphenated thermogravimetric analysis-fourier transmission infrared spectroscopy (TGA-FTIR) system. Almost ∼13% increment is observed in crystallinity at highest loading of CNCs compared to neat counterpart. To investigate the splitting and spreading phenomenon of the wettability of the samples, linear model is used to find the Young's contact angle and contact angle hysteresis (CAH). Besides, ∼6.1 folds reduction in the density of PLA and the nanocomposite foams compared to PLA carries much significance in specialized application areas where weight is an important concern.