Saurindra N. Maiti

Poly (L-lactic acid)/layered silicate nanocomposite blown film for packaging application: thermal, mechanical and barrier properties

In an attempt to alleviate the global solid waste disposal problem and to reduce the dependence on petroleum-based plastics for packaging materials, biodegradable and compostable thermoplastic polymers are required. Polylactic acid (PLLA) is a highly versatile biodegradable polymer derived from 100% renewable resources. Three types of PLA nanocomposites containing 1, 3 and 5 phr of nanoclay were compounded in a co-rotating twin screw extruder, to study the effect of nanoclay content on film processibility of composites as well as properties of blown films. Differential scanning calorimetry CDSC) showed that the cold crystallization and melting temperatures were influenced by the presence of nanoclay. The thennogravimetric analysis (TGA) showed increase in the decomposition temperature for all of the nanocomposites. Mechanical properties of the nanocomposite film showed that the elongation (%) increased up to 3 phr of clay whereas tensile strength and modulus increased only up to 1 phr of the nanoclay. N anocomposite films showed an improvement in oxygen barrier and water vapor barrier in comparison to the neat PLA up to 3 phr of nanoclay.

Effect of surface treatment of jute fibers on the interfacial adhesion in poly(lactic acid)/jute fiber biocomposites

Jute fibers have immense potential to be used as natural fillers in polymeric matrices to prepare biocomposites. In the present study jute fibers were surface treated using two methods: i) alkali (NaOH) and ii) alkali followed by silane (NaOH+Silane) separately. Effects of surface treatments on jute fibers surface were characterized using fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analyses. Further, the effects of surface treatments on jute fibers properties such as crystallinity index, thermal stability, and tensile properties were analyzed by X-ray diffraction method (XRD), thermo gravimetric analysis (TGA), and single fiber tensile test respectively. The effects of surface treatment of jute fibers on interphase adhesion between of poly(lactic acid) (PLA) and jute fibers were analyzed by performing single fiber pull-out test and was examined in terms of interfacial shear strength (IFSS) and critical fiber length.

Crystallization, Morphological, and Mechanical Response of Poly(Lactic Acid)/Lignin-Based Biodegradable Composites

ABSTRACT Green/bio-based composites of poly(lactic acid) and lignin were prepared by melt blending in a twin-screw extruder. Thermal and mechanical properties, phase interaction, and morphology of the composites have been investigated. Fourier transform infrared studies elucidated the existence of intermolecular hydrogen bonding between poly(lactic acid) and lignin. Scanning electron microscopy studies revealed an extent of diffused phase boundaries between poly(lactic acid) and lignin which also indicated significant interaction between them. Tensile properties showed significant increase over neat poly(lactic acid) with lignin loading (0–0.28 volume fraction) which further justified using theoretical models. Izod impact strength decreased with lignin content. GRAPHICAL ABSTRACT

Fabrication of super tough poly(lactic acid)/ethylene-co-vinyl-acetate blends via a melt recirculation approach: static-short term mechanical and morphological interpretation

The mechanical properties such as tensile strength, tensile modulus, elongation-at-break and impact strength of poly(lactic acid) (PLA)/ethylene-co-vinyl-acetate copolymer (EVA, vinyl acetate content 50 weight percent) blends were evaluated at EVA volume fractions ranging from 0–0.35. The tensile properties were compared using several theoretical models. The blends lost little of their tensile strength and modulus while elongation-at-break was simultaneously enhanced. Efficient dispersion of EVA in PLA using a micro compounder in which there is provision for melt recirculation significantly improved the Izod impact strength making the blends super tough. The phase miscibility, two phase morphology, fibrillation and interparticle distance were studied using scanning electron microscopy (SEM). The blend is a two phase system where the particle size is enhanced upon an increase in the concentration of the blending copolymer. The normalized values of the relative elongation-at-break and Izod impact strength were enhanced significantly in accordance with the crystallinity, 33 fold (53.73 kJ mm−2) at a 0.35 volume fraction of EVA, which indicated softening of the system with enhanced toughness.

Effect of surface treatments of jute fibers on the microstructural and mechanical responses of poly(lactic acid)/jute fiber biocomposites

Poly(lactic acid) (PLA)/jute fiber (70/30 w/w) biocomposites were prepared by melt mixing PLA with untreated, NaOH treated and (NaOH + silane) treated jute fibers in a twin screw extruder. The effects of surface treatment of jute fiber were examined at the matrix–fiber interface by Fourier transform infrared spectroscopy (FT-IR) which confirmed the formation of hydrogen bonds and covalent bonds between PLA and jute fibers. Polarized light optical microscopy (PLOM) images showed improved transcrystallinity at the matrix–fiber interface while scanning electron microscopy (SEM) showed matrix covered fiber surfaces in the case of composites reinforced with surface treated jute fibers. Addition of untreated jute fibers in PLA increased the tensile strength and modulus, while composites reinforced with surface treated jute fibers exhibited higher mechanical properties. Dynamic mechanical analysis (DMA) results showed enhanced storage moduli in the case of surface treated jute fiber reinforced composites.

Effects of SEBS-g-MA copolymer on non-isothermal crystallization kinetics of polypropylene

AbstractThe non-isothermal crystallization kinetics of pure PP and PP/SEBS-g-MA blends up to volume fraction, Φd (0–0.50) was studied by differential scanning calorimetry at four different cooling rates. Crystallization parameters were analyzed by Ozawa and Liu models. The Ozawa model fits in the PP/SEBS-g-MA blends and indicates the effect of SEBS-g-MA copolymer on the crystallization process of polypropylene. Augis–Bennet model has been used to calculate activation energy, ∆E, during non-isothermal crystallization process. The value of ∆E decreased with SEBS-g-MA due to flexibility of SEBS-g-MA by which movements of chains of PP become easier.

Correlation of Tensile Properties With Crystallization Parameters of PP in PP/Ag Composites

Crystallization properties of polypropylene (PP) in PP/Ag composites were estimated from differential scanning calorimetry (DSC) and wide-angle x-ray diffraction studies. The effect of Ag powder and its surface modification with a titanate coupling agent on rates of nucleation and growth of crystallization, crystallite size distribution, and crystallinity was determined from crystallization exotherm peaks. Crystallinity and tensile properties such as modulus, yield strength, and breaking elongation decreased with Ag concentration. Linear correlations were obtained with tensile and crystallization parameters in both types of composites.

Nonisothermal crystallization and microstructural behavior of poly(ε-caprolactone) and granular tapioca starch-based biocomposites

ABSTRACT The nonisothermal crystallization behavior of poly(ε-caprolactone) (PCL) in the presence of varying concentrations of granular tapioca starch (GTS) was studied. Various crystallization parameters were studied by differential scanning calorimeter at four different cooling rates and these parameters were analyzed using Jeziorny, Ozawa, and Liu models. Kissinger method was used to estimate the activation energy (ΔE) of the PCL/GTS composites. The ΔE results suggested that the speed of crystallization was inhibited by GTS particles. Polarized light optical microscopy suggests formation of spherulite structure in PCL and PCL/GTS composites while no evidence of nucleation by GTS particles was observed.

Post-yield fracture correlations to morphological and micromechanical response of poly(ε-caprolactone)-based biocomposites

The present work investigates the effect of jack wood flour (JWF) content on the fracture toughness, tensile, impact, and morphological behavior of the prepared green biocomposites. From 0 to 35 wt% (volume fraction (Φ f) = 0–0.34) of JWF was incorporated as a reinforcing biodegradable filler into poly(ε-caprolactone) (PCL) matrix by melt compounding in a twin screw extruder. The tensile modulus increases by 80.48% at the highest Φ f = 0.34, though marginal increment (13.71%) in the yield strength was registered. A sharp reduction in notched Izod impact strength (85%) was observed with increasing JWF content. The fracture toughness of the prepared biocomposites based on post-yield fracture mechanics concept was investigated by essential work of fracture (EWF) methodology. Incorporation of JWF into PCL matrix diminishes the EWF (w e), while increasing the non-essential work of fracture (βw p). In the biocomposites, principally two mechanisms governed the fracture deformation. Large JWF particles act as stress concentration points and favor the crack initiation, while the smaller particles favor fibrillation which arrests the crack propagation enhancing the parameter βw p at lower concentration of JWF. Freeze-fractured surfaces show a degree of phase adhesion at lower Φ f of JWF. The phase adhesion parameter obtained from micromechanical analysis of tensile properties suggesting the mechanical interlocking and interaction between PCL and JWF.

Surface Treated Jute Fiber Induced Foam Microstructure Development in Poly(lactic acid)/Jute Fiber Biocomposites and their Biodegradation Behavior

Poly(lactic acid) (PLA)/jute fiber biocomposites with: i) untreated jute fiber, ii) NaOH treated jute fiber, and iii) (NaOH+silane) treated jute fibers were prepared by melt extrusion process. Microcellular foaming of the injection molded samples was carried out by using single stage batch process. The effects of jute fiber content as well as that of matrix-fiber phase adhesion, in composites with surface treated jute fibers, on the foam microstructure were studied. Further, water absorption, thickness swelling, and biodegradation behavior of the foamed biocomposites were studied and correlated with their foam microstructures. It was observed that on increasing jute fiber content in PLA/JFU biocomposites, cell density increased from 6.5×107 to 8.1×107, while the cell size and expansion ratio decreased from 40 to 23 μm and 2.41 to 1.45, respectively. Again, on increasing the extent of the jute fiber surface treatment in the biocomposites, cell size and expansion ratio increased from 40 to 78 μm and 2.41 to 2.80 respectively. This study also revealed that the rate of biodegradation accelerated with increase in the jute fiber content in the biocomposites while the same retarded with increase in the extent of jute fiber surface treatment.