Basudam Adhikari

Reclamation and recycling of waste rubber

Abstract One of the various problems which mankind faces as it enters into the 21st century is the problem of waste disposal management. Since polymeric materials do not decompose easily, disposal of waste polymers is a serious environmental problem. Large amounts of rubbers are used as tires for aeroplanes, trucks, cars, two-wheelers etc. But after a long run when these tires are not serviceable and discarded, only a few grams or kilograms of rubber (

Isolation and characterization of fish scale collagen of higher thermal stability

Collagen is the most abundant protein found in animal body and widely used for biomedical and pharmaceutical applications. However, its applicability is severely limited due to high cost. Fish processing waste, which otherwise cause serious environmental pollution, is a promising cost effective collagen source. In the present study, collagen was isolated from scales of Labeo rohita (Rohu) and Catla catla (Catla). It is first time that these species are used as sources of collagen. Thermo-gravimetric analysis (TGA) revealed maximum demineralization achieved after 48h of EDTA treatment of intact scale. The isolated protein was confirmed as collagen by different physico-chemical techniques like FTIR, SDS-PAGE, and CD. Further amino acid analysis corroborates isolation of type I collagen. A major characteristic of obtained collagen was found to have denaturation temperature (T(d)) of 36.5 degrees C, which is promising as an advantage for biomedical application due to closeness in T(d) to mammalian collagen.

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.

Improvement in mechanical properties of jute fibres through mild alkali treatment as demonstrated by utilisation of the Weibull distribution model

Chemically modified jute fibres are potentially useful as natural reinforcement in composite materials. Jute fibres were treated with 0.25%-1.0% sodium hydroxide (NaOH) solution for 0.5-48 h. The hydrophilicity, surface morphology, crystallinity index, thermal and mechanical characteristics of untreated and alkali treated fibres were studied.The two-parameter Weibull distribution model was applied to deal with the variation in mechanical properties of the natural fibres. Alkali treatment enhanced the tensile strength and elongation at break by 82% and 45%, respectively but decreased the hydrophilicity by 50.5% and the diameter of the fibres by 37%.

Polyaniline as a gas-sensor material

ABSTRACT Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.

Collagen scaffolds derived from fresh water fish origin and their biocompatibility

Collagen, a major component of native extracellular matrix, has diverse biomedical applications. However, its application is limited due to lack of cost-effective production and risk of disease transmission from bovine sources currently utilized. This study describes fabrication and characterization of nano/micro fibrous scaffolds utilizing collagen extracted from fresh water fish origin. This is the first time collagen extracted from fresh water fish origin was studied for their biocompatibility and immunogenicity. The nano/micro fibrous collagen scaffolds were fabricated through self-assembly owing to its amphiphilic nature and were subsequently cross-linked. In vitro degradation study revealed higher stability of the cross-linked scaffolds with only ~50% reduction of mass in 30 days, while the uncross-linked one degraded completely in 4 days. Further, minimal inflammatory response was observed when collagen solution was injected in mice with or without adjuvant, without significant dilution of sera. The fish collagen scaffolds exhibited considerable cell viability and were comparable with that of bovine collagen. SEM and fluorescence microscopic analysis revealed significant proliferation rate of cells on the scaffolds and within 5 days the cells were fully confluent. These findings indicated that fish collagen scaffolds derived from fresh water origin were highly biocompatible in nature.

Reclaiming of rubber by a renewable resource material (RRM). III. Evaluation of properties of NR reclaim

Sulfur-cured filled natural rubber (NR) is successfully reclaimed by using a renewable resource material (RRM) and diallyl disulfide (DADS), which is the major constituent of RRM. Reclaiming of NR vulcanizate was carried out at 60°C for 35 min in an open two-roll mixing mill. Evaluation of the properties of NR reclaim was carried out by mixing it with virgin rubber in various proportions. The cure characteristics and mechanical properties of the virgin NR/ reclaim NR blend were studied. With increase in the proportion of reclaim rubber (RR) in virgin NR/ reclaim NR blend scorch time and optimum cure time decrease. To increase scorch time N-cyclohexylthiophthalimide as prevulcanization inhibitor (PVI) was added in NR/RR (50/50) blend. It was found that use of 40% NR reclaim with virgin rubber resulted 83% retention of tensile strength of that of the virgin NR vulcanizate. Effect of carbon black loading was studied in NR/RR (50/50) blends. Tensile properties and swelling value of different NR/RR blends were evaluated before and after aging.

Synthesis and characterization of lignin–HTPB copolyurethane

Abstract Lignin–HTPB copolyurethanes have been synthesized from hydroxyl terminated polybutadiene (HTPB) and varied quantities of lignin and toluene diisocyanate. IR spectroscopy and estimation of isocyanate groups have established the formation of HTPB polyurethane and lignin–HTPB copolyurethane. The crosslink density, sol fraction, diffusion coefficient, mechanical properties and X-ray crystallinity of lignin–HTPB copolyurethane have been measured and compared with those of HTPB polyurethane. Tensile strength improvement of lignin–HTPB copolyurethane was observed up to 3-wt.% lignin incorporation. High hydroxyl value of lignin has been found responsible for the decrease in tensile strength with the increase in lignin content of lignin–HTPB copolyurethane.

Lignin-modified phenolic resin: synthesis optimization, adhesive strength, and thermal stability

Lignin-modified phenolic resin has been prepared by replacing phenol with lignin at different weight percentages. The resin synthesis was optimized by varying the molar ratio of phenol to formaldehyde, the concentration of sodium hydroxide, and the reaction time by measuring parameters such as the gelation time, flow time, solids content, pH, and specific gravity. The thermal stability of lignin-modified phenolic resin was studied by DSC, TGA, and isothermal analysis, and it was found that lignin-modified phenolic resin is thermally more stable than pure phenolic resin. The adhesive strength of lignin-modified phenolic resin was determined by the lap-shear method, which showed that the lignin-modified resin retains 78% of the adhesive strength for wood-wood systems and 86% of the adhesive strength for Al-Al systems.

Sustained release of antibiotic from polyurethane coated implant materials.

Implant associated infections are of increasing importance. To minimize the risks of implant-associated infections recent biomedical strategies have led to the modification of the medical device surfaces. The modifications are in the terms of increasing surface biocompatibility and decreasing bacterial adherence, which can be achieved by applying a coating of biocompatible polymer onto the said surfaces. Entrapping anti-infective agents in a polymer matrix provides an approach to kill bacteria and combat the possibility of any residual infection. We have prepared a biodegradable polyester urethane coat for implant materials, which have the property to accommodate antibiotics within itself. These polyurethane coating materials were characterized by FTIR spectroscopy, swelling property in SBF, gravimetric analysis, drug release, and biocompatibility study. Drug release rates, bacterial colonization and morphological features were also evaluated to predict and understand the antimicrobial activity of these delivery systems. Drug release characteristics were investigated and the physico-chemical mechanisms of the delivery were discussed. Results suggest that the polyester urethane can be used as an implant coating material and can be used as a matrix for the sustained delivery of anti-infective agent.