Subhas Ghosh

Impact of Nanoclay on Isothermal Cold Crystallization Kinetics and Polymorphism of Poly(l-Lactic Acid) Nanocomposites

Poly(L-lactic acid) (PLLA) intercalated nanocomposite films containing 1, 2, 5, and 10% organically modified montmorillonite (OMMT) have been synthesized by the solvent casting approach. The thermal characteristics, isothermal cold crystallization kinetics, and structural changes of neat PLLA and its nanocomposites during annealing were studied by using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. DSC observation showed that melting temperature and final crystallinity were not affected significantly with OMMT loading. PLLA films with increasing OMMT content exhibited higher crystallization rates than neat PLLA during annealing and suggested that the silicate platelets act as a nucleation agent during annealing. The effect of OMMT content on the isothermal crystallization kinetics of PLLA was analyzed using the Avrami equation. An Avrami constant of 1-2 was observed, suggesting that crystallization proceeds through one-dimensional growth with heterogeneous nucleation. FTIR investigation showed a band at 922 cm(-1) at all T(a), and no band at 908 cm(-1) suggested that all samples form α crystal regardless of OMMT content or T(a).

Antibacterial properties of cotton fabric treated with silver nanoparticles

In recent years nano‐sized particles have been focused on bacteriostasis. We investigated antimicrobial activities by applying two types of silver nanoparticles on cotton fabric. These are MesoSilver particles and silver chloride compounds (Silpure). Silver chloride, used in aqueous dispersion, is mixed with a monomer prior to the application on the fabric. MesoSilver is pure silver sub‐nanometer sized particles suspended in deionized water. Silpure solutions were padded and cured on cotton fabric. MesoSilver was padded onto the fabric followed by air drying. SEM images of Silpure‐ and MesoSilver‐treated fabric samples showed good particle dispersion on the fabric. EDX analysis was conducted to confirm the presence of silver particles on the fabric surface. Biological studies exhibited that no growth took place with zones of inhibition on both the treated samples; while the untreated samples did show bacterial growth. The Silpure sample exhibited excellent wash durability; however, the MesoSilver specimen did not.

Development of moisture vapour permeable waterproof cotton fabric by coating with blend of natural rubber latex and polyvinyl alcohol

Abstract Cotton fabric was coated with aqueous dispersion containing blend of natural rubber latex (NRL), polyvinyl alcohol (PVA) and starch following a knife-over-roll technique to produce moisture vapour permeable waterproof coating. Coating of cotton with a formulation containing NRL, 15% aqueous PVA and tamarind kernel seed powder as starch, in the ratio of 1:3: 0.3 in presence of a typical sulphur curing system, followed by drying of the coated fabric at 95 °C for 5 min and subsequent vulcanization at 120 °C for 2 h produced most balanced improvements in the properties of the coated fabric such as, waterproofness, breathability as revealed by moisture vapour transmission rate, coating adhesion, tensile properties, abrasion resistance and flex endurance. Incorporation of PVA makes the coating permeable to moisture vapour and such property is promoted further in presence of starch in the coating formulation. Examination of surface morphology of vulcanized coating by scanning electron microscopy revealed that poly vinyl alcohol crystals formed clusters of dimensions of only few microns in the rubber matrix. Such clusters of PVA served as conduits for transportation of moisture vapour through the film of NRL while acting as an effective barrier to liquid water droplets.

Study of chameleon nylon and polyester fabrics using photochromic ink

Abstract There is a growing interest in the development of chameleon textiles using chromic dyes (inks) for several uses, such as brand protection, responsive camouflage, ultraviolet (UV) sensors, and fashion apparel. However, their use is limited to very few colors and responsivity to color change in the spectral range. This investigation used two photochromic inks: magenta and turquoise. These inks change color when exposed to certain wavelengths of light. The magenta and turquoise photochromic inks belong to the naphthopyran and spironaphthoxazine classifications of dye, respectively. These plastisol inks were applied on the nylon and polyester fabrics using a screen-printing technique. The color-changing behavior of the printed fabrics was studied using a Hunter Lab Color Spectrophotometer after exposure to tungsten, fluorescent, UV, and sunlight. Each sample was subjected to five fade cycles to study the fading effects. The effects on the color changes of the magenta ink-printed fabrics were most intense under UV and sunlight, creating strong red colors with an increase in a-values, but only a small change in color was observed under fluorescent light. Turquoise ink-printed fabric exhibited very minor visible changes under UV and sunlight with a decrease in b-value. No significant effect on color changes and color strength was found after five fade cycles.