Subhas Ghosh

Bio: Subhas Ghosh is an academic researcher from Eastern Michigan University. The author has contributed to research in topics: Coating & Dendrimer. The author has an hindex of 9, co-authored 20 publications receiving 280 citations.

Impact of nanoclay on isothermal cold crystallization kinetics and polymorphism of poly(L-lactic acid) nanocomposites.

Abstract: 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 nuc...

A study of antimicrobial property of textile fabric treated with modified dendrimers

Abstract: Dendrimers have been used as a vehicle to develop the antimicrobial properties of textile fabrics. We have taken advantage of the large number of functional groups present in the regular and highly branched three-dimensional architecture of dendrimers. In this study, the poly(amidoamine) (PAMAM) G-3 dendrimer was modified to provide antimicrobial properties. Following a procedure similar to what is suggested in the literature, PAMAM (G3) with primary amine end groups was converted into ammonium functionalities. The modification was then confirmed by FTIR and 13 C-NMR analysis. Dendrimers have unique properties owing to their globular shape and tunable cavities, this allows them to form complexes with a variety of ions and compounds; and also act as a template to fabricate metal nanoparticles. AgNO 3 -PAMAM (G3) complex as well as a MesoSilver-PAMAM (G3) complex were formed and these modified dendrimers were characterized by a UV-Visible spectrophotometer to study the complex formation. Modified dendrimers were applied to the Cotton/Nylon blend fabric. SEM and EDX analysis were performed to study the dispersion of silver nanoparticles onto the fabric. An antimicrobial test of the treated-fabric against Staphylococcus aureus exhibited significant biocidal activities for each type of modified-dendrimer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 716-722, 2010.

Structure development of poly(L-lactic acid) fibers processed at various spinning conditions

Abstract: Poly(L-lactic acid) (PLA) filaments were spun by melt-spinning at 500 and 1850 mm−1, and further drawn and heat-set to modify the morphology of these PLA filaments. PLA yarns were characterized by wide-angle X-ray diffraction (WAXD) and sonic method. WAXD reveals that PLA yarns spun at 500 mm−1 are almost amorphous while the PLA filaments spun at 1850 mm−1 have about 6% crystallinity. This is different from PET filaments spun at the same speed that have almost no crystallinity. Both drawn- and heat-set PLA filaments showed much higher crystallinity (60%) than do as-spun fibers produced at 500 and 1850 mm−1 speed, which is also higher than the usual heat-set PET yarns. It appears that crystalline orientation rapidly reaches a value in the order of 0.95 at 1850 mm−1 and that drawn- and heat-set yarns have almost the same crystalline orientation values. Molecular orientation is relatively low for as-spun PLA yarn, and molecular orientation increased to ∼0.5 after drawing or heat–setting or both. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1210–1216, 2006

Ultrasonic sealing of polyester and spectra fabrics using thermo plastic properties

Abstract: A study of polyethylene terephthalate (PET) and spectra fabric's ultrasonic sealing (welding) potential was conducted using both continuous and discontinuous ultrasonic welding machines. The effects of two important welding parameters such as weld pressure and weld time were investigated on the fabric's bond strength. Depending on the thermal property of the polymer, a certain level of temperature rise during sealing is required to soften the fibers, to facilitate the development of rows of welding points between the fabric layers. This happens under the compaction due to weld pressure. The gaps between the points are so narrow that the rows appear to be a complete sealing of the layers. Excessive melting under weld pressure, to create melt bonding caused polymer degradation and poor bond strength. Scanning Electron Microcopy images and the temperature measurements at the fabric's interface were used to examine the bond locations of the fabric. Differential Scanning Calorimetry analyses of PET and spectra fabrics have been used to examine the thermal behavior of the ultrasonic sealed material. Adequate seam strength was achieved under certain conditions of sealing for both the fabrics using both continuous and discontinuous methods of operation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

Abstract: Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers.

Chemical Insights into Antibacterial N-Halamines.

Abstract: Microbial contamination arising from pathogens poses serious threats to human health and in recent decades has presented an unprecedented challenge to antibacterial research. Of the various antibacterial agents that effectively kill pathogens, halogen-based antibacterial compounds have been successful in eliminating harmful pathogen-associated diseases and are becoming the most popular disinfectants. As a significant subcategory of halogen antibacterial agents, N-halamines have drawn increasing research interest into their chemistry and practical applications. N-Halamines have many advantages over other antibacterial agents, including effectiveness against a broad spectrum of microorganisms, long-term physicochemical stability, high structural durability, and the regenerability of their functional groups, with corresponding renewal of their antibacterial properties. This review examines recent progress and research trends in both theoretical and experimental studies of N-halamines, with the aim of providi...

Strain-Induced Molecular Ordering in Polylactide upon Uniaxial Stretching

Abstract: This study deals with the tensile drawing behavior of a polylactide material containing 4% of d-stereoisomer units, in the amorphous state. The draw temperature domain spanned from the glass transition to the onset of thermal crystallization, namely 70−100 °C. The stress−strain curves exhibit a strain-hardening strongly sensitive to the draw temperature regarding both the onset and the slope of the phenomenon. A detailed structural investigation reveals that various strain-induced phase changes take place depending on the draw temperature. For Td = 70 °C, a mesomorphic form develops from the strain-oriented amorphous chains, starting at a strain level e ≈ 130%. In the case Td = 90 °C, a well-defined crystalline phase grows beyond the strain e ≈ 250%. In the midtemperature range, i.e. Td = 80 °C, both the mesomorphic and the crystalline phases are generated in parallel. In all cases, the final weight content of ordered phases at rupture was roughly 30%, irrespective of their form. The observed evolution wi...