Prosenjit Saha

Enhancement of tensile strength of lignocellulosic jute fibers by alkali-steam treatment.

The physico-chemical properties of jute fibers treated with alkali (NaOH) solution have been investigated in this study. The treatments were applied under ambient and elevated temperatures and high pressure steaming conditions. To the knowledge of these authors the influence of alkali-steam treatment on the uniaxial tensile strength of natural ligno-cellulosic fibers, such as jute, has not been investigated earlier. The results from this investigation indicate that a 30 min dipping of the fibers in 0.5% alkali solution followed by 30 min alkali-steam treatment leads to an increase in the tensile strength of up to 65%. The increase appears to be due to fiber separation and removal of non-cellulosic materials, which, in turn, resulted in an increased crystallinity.

A brief review on the chemical modifications of lignocellulosic fibers for durable engineering composites

A brief review has been presented on the existing methods to enhance the durability of lignocellulosic fibers (LCFs) for manufacturing composites for engineering applications. The free hydroxyl groups of the cellulose chains within LCFs tend to attract water molecules in moist environment, which may cause the fibers to swell and the cellulose chains to lose their integrity due to hydrolysis and oxidation imparted by the actions of biogenic enzymes or chemical factors, such as acidity, alkalinity, and salinity or UV irradiation. This study mainly highlights those technologies that present the modifications of cellulose main chain within the LCFs to improve the degradation resistance and mechanical strength. Detailed pros and cons of those chemical modifications have also been presented in this study with possible applications of the composites with special reference to durability.

Composition analysis and material characterization of an emulsifying extracellular polysaccharide (EPS) produced by Bacillus megaterium RB-05: a hydrodynamic sediment-attached isolate of freshwater origin.

Aims:  This work was aimed to isolate, purify and characterize an extracellular polysaccharide (EPS) produced by a freshwater dynamic sediment‐attached micro‐organism, Bacillus megaterium RB‐05, and study its emulsifying potential in different hydrocarbon media.

Effect of photodegradation of lignocellulosic fibers transesterified with vegetable oil

This study presents the assessment of resistance of raw and vegetable oil treated transesterified lignocellulosic fibers (LCFs) such as jute, and sisal against photo-induced oxidation and subsequent hydrolysis reaction by subjecting them to alternate cycles of irradiation of ultraviolet light (UV) of wavelength between 300 to 400 nm and spray of deionized water in an artificial accelerated weathering (AAW) test chamber over a duration of 500 hours. The extent of UV and moisture induced degradation has been evaluated by measuring the residual tensile strength and water absorption before and after AAW. The results indicate that at the end of the 500 h of exposure transesterified LCFs retained about 53 to 60 % of its initial tensile strength, whereas the corresponding retention for raw fibers was only about 14 to 20 %. Average water absorption for transesterified LCFs was increased to about 100–110 % (by weight) following AAW from a pre-exposure value of about 65–80 %. The corresponding average increase for raw LCFs was 300 % from 220 %, respectively. Although both raw and transesterified LCFs exhibited susceptibility to oxidation and hydrolysis following AAW, the resulting impact was found to be more pronounced for raw fibers.

Enhanced biodegradation resistance of biomodified jute fibers

A bio-catalyzed process has been developed for treating jute fibers to enhance their tensile strength and resistance against biodegradation. Lipolytic bacteria were used in the process to transesterify jute fibers by replacing hydrophilic hydroxyl groups within cellulose chains with hydrophobic fatty acyl chains. Transesterification of some of the hydroxyl groups within the fiber was confirmed with FTIR, UV-vis spectroscopy, (13)C solid state NMR, gas chromatography and analytical determination of ester content. Biomodified fibers exhibited remarkably smaller affinity to water and moisture and retained 62% of their initial tensile strengths after being exposed to a composting environment over 21 days. The corresponding figure for untreated fibers was only 30%. Efficacy of the process reported herein in terms of tensile strength and biodegradation resistance enhancement of fibers achieved after treatment appears to be comparable with similar chemical processes and better than the enzyme-catalyzed alternatives.

Biodegradation of chemically modified lignocellulosic sisal fibers: study of the mechanism for enzymatic degradation of cellulose

Abstract The susceptibility and characteristics of biological degradation of lignocellulosic fibers, such as sisal fibers, are presented in this study using a modified soil burial test (SBT) protocol. The biodegradation profile of untreated sisal fibers as well as of fibers treated with an alkaline emulsion of neem oil and phenolic resin was evaluated by estimating the enzymatic activities during the exposure of fibers to a soil/compost mix. Observation of the results indicated that biodegradation of the fibers was predominated by enzymatic hydrolysis of amorphous materials followed by degradation of crystalline cellulose. It was also evident that “oil-resin” treatment makes the fibers more resistant to biodegradation owing to the removal of amorphous materials, enhanced hydrophobicity, and possible chemical alteration of the surface hydroxyl groups of the fiber surface. This research aims to establish a systematic knowledge on the biodegradation profile of fiber components using a state-of-the-art protocol for SBT.

Novel polymer composites from waste ethylene-propylene-diene-monomer rubber by supercritical CO2 foaming technology.

In this study, a composite has been prepared by mixing waste rubber, such as ethylene-propylene-diene-monomer and low-density poly ethylene foaming, with supercritical carbon dioxide. In order to optimise the foaming process of the waste ethylene-propylene-diene-monomer–low-density poly ethylene composite, the variations of pressure and temperature on the foamed Microcell formation were studied. As indicated in scanning electron microscope photographs, the most uniform microcellular pattern was found at 200 bar and 100 °C using 30% by weight of waste ethylene-propylene-diene-monomer. Carbon dioxide could not be dissolved uniformly during foaming owing to extensive cross-linking of the waste ethylene-propylene-diene-monomer used for the composite. As a result the presence of un-uniform microcells after foaming were observed in the composite matrix to impart inferior mechanical properties of the composite. This problem was solved with uniform foaming by increasing the cross-link density of low-density poly ethylene using 1.5 parts per hundred dicumyl peroxide that enhances composite tensile and compressive strength up to 57% and 15%, respectively. The composite has the potential to be used as a foaming mat for artificial turf.

Processing and characterization of electrospun trans-polyisoprene nanofibers

Abstract The method of manufacturing nanofibers using the electrospinning technique from trans-polyisoprene (TPI) is presented in this study, possibly for the first time. The process parameters such as solution concentration, applied voltage, distance and feeding rate for electrospinning were investigated and optimized with respect to fiber morphology, as observed from scanning electron microscopy (SEM) photomicrographs. Smooth and uniform nanofibers were found to generate at the optimum conditions with 1% melt concentration, 15 kV of voltage, tip-to-collector distance (TCD) of 15 cm and injection rate 4 ml/h. The physicochemical properties of pure TPI and electrospun TPI fibers were characterized by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) analysis. Both DSC and FTIR characterization results show predominant transformation of TPI crystalline structure from the β form to the α form upon electrospinning.

Fixed bed column study for water defluoridation using neem oil-phenolic resin treated plant bio-sorbent

Fluoride has both detrimental and beneficial effects on living beings depending on the concentration and consumption periods. The study presented in this article investigated the feasibility of using neem oil phenolic resin treated lignocellulosic bio-sorbents for fluoride removal from water through fixed bed column study. Results indicated that treated bio-sorbents could remove fluoride both from synthetic and groundwater with variable bed depth, flow rate, fluoride concentration and column diameter. Data obtained from this study indicated that columns with the thickest bed, lowest flow rate, and fluoride concentration showed best column performance. Bio-sorbents used in this study are regenerable and reusable for more than five cycles. The initial materials cost needed to remove one gram of fluoride also found to be lower than the available alternatives. This makes the process more promising candidate to be used for fluoride removal. In addition, the process is also technically advantageous over the available alternatives.

Electrospun chitosan/polycaprolactone-hyaluronic acid bilayered scaffold for potential wound healing applications

Fabrication of mechanically stable, biocompatible bilayered polymeric scaffold consisting of chitosan(CS)/polycaprolactone(PCL) and hyaluronic acid(HA) using less toxic solvent system is presented in this study. Electrospinning technique to make the scaffold was used followed by morphological, physiochemical and mechanical characterizations. Average fiber diameter of CS/PCL-HA bilayered scaffold was found 362.2 ± 236 nm which is in the range of collagen fiber found in the extracellular matrices. Enhanced swelling, degradation, hydrophilicity and water vapour transmission rate were found for the bilayered scaffold compared to that of the PCL and CS-PCL scaffolds. Antimicrobial property evaluation revealed reduction in bacterial adhesion on bilayered scaffolds. Invitro studies with vero cells [kidney epithelial cell, extracted from African Green Monkey (Chlorocebus sp.)] confirm enhanced proliferation, growth and migration of vero cell on the bilayered CS/PCL-HA scaffold to that of PCL and CS/PCL scaffolds. Novelty of this study includes the use of HA for mechanically stabilized scaffold with acceptable biological properties for wound healing applications.