Large-eddy simulation of laser-induced surface-tension-driven flow

The turbulent flow inside a laser-generated molten pool is investigated by an adapted large-eddy simulation (LES) model that incorporates physical considerations pertaining to the solid-liquid phase change. A single-domain, fixed-grid enthalpy-porosity approach is utilized to model the phase-change phenomena in the presence of a continuously evolving solid/liquid interface. The governing transport equations are simultaneously solved by employing a control-volume formulation, in conjunction with an appropriate enthalpy-updating closure scheme. To demonstrate the performance of the present model in the context of phase-change materials processing, simulation of a typical high-power laser melting process is carried out, where effects of turbulent transport can actually be realized. It is found that the present LES-based model is more successful in capturing the experimental trends, in comparison to the k-ε-based turbulence models often employed to solve similar problems in contemporary research investigations.     

Studies of mechanical and moisture regain properties of methyl methacrylate grafted silk fibers

The mechanical properties such as the tenacity, breaking extension, initial modulus, elastic and work recovery, and stress relaxation behavior of methyl methacrylate (MMA) grafted silk fibers prepared under different conditions were measured and explained in terms of the relative dominance of the stress concentration, reduction in the interchain cohesion, and fiber matrix stiffening at different grafting percentages. The moisture regain characteristics of fibers grafted in the presence of different solvents were also studied and compared. The grafting of MMA on silk was found to improve the recovery properties significantly without affecting the stress relaxation behavior. The moisture regain studies indicate that moisture regain is reduced with increasing length of the grafted poly(MMA) chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 969–974, 2002; DOI 10.1002/app.10202     

Bovine pancreatic lipase.I.Isolation, homogeneity, and characterization.

Bovine pancreatic lipase was isolated in pure form by lyophilization of fresh bovine pancreas, extraction of the enzyme with sucrose solution, fractional precipitation with ammonium sulfate and acetone, followed by chromatography on Sephadex G-100. The specific activity of the purest lipase fraction was 1750 micromoles fatty acid, liberated in 30 min per milligram of protein, indicating a purification of approximately 473-fold, with an overall yield of about 42%. Homogeneity of the enzyme was confirmed by rechromatography on Sephadex G-100 as well as with the gel electrophoretic and ultracentrifugal techniques. The purified enzyme gave a typical protein ultraviolet absorption spectrum with maximum absorption at 276 nm and minimum at 252 nm. The purified enzyme exhibited a single pH optimum of 8.8 and an isoelectric point near pH 5.5. Its optimum temperature was 37 C, and its optimum substrate concentration was 10%. These properties resembled those of milk lipase.     

Effects of alkalization and fiber loading on the mechanical properties and morphology of bamboo fiber composites. II. Resol matrix

Resol resin composites reinforced with alkali‐treated bamboo strips were fabricated with a hand‐lay‐up technique. This study was aimed at the evaluation of the influence of the caustic concentration on the mechanical properties of bamboo‐strip‐reinforced resol composites with a constant 50% loading of the reinforcement. The treatment of bamboo fiber in a solution of sodium hydroxide with increasing concentration percentages resulted in more and more rigid composites; as a result, the strength and modulus values exhibited improvements. The maximum improvement in the properties was possibly achieved with 20% caustic treated reinforcements. An infrared study indicated the formation of aryl alkyl ether with ? OH groups of cellulose and methylol groups of resol. Beyond 20%, there was degradation in all the strength properties due to the failure of the mechanical properties of the reinforcement itself. A correlation was found to exist between the mechanical properties and the morphology that developed. Another set of composites with variable loadings of 20% alkali treated fiber (40, 50, and 60%) was fabricated, and a 60% fiber loading showed the best mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of phase modifiers on morphology and properties of thermoplastic elastomers prepared from ethylene propylene diene rubber and isotactic polypropylene

A series of thermoplastic elastomers (TPEs) were prepared from a binary blend of ethylene propylene diene rubber (EPDM) and isotactic polypropylene (iPP) using different types of phase modifiers. The influence of sulphonated EPDM, maleated EPDM, styrene‐ethylene‐co‐butylene‐styrene block copolymer, maleated PP, and acrylated PP as phase modifiers showed improved physico‐mechanical properties (like maximum stress, elongation at break, moduli, and tension set). Scanning electron and atomic force microscopy studies revealed better morphologies obtained with these phase modified EPDM‐iPP blends. The dependence of the phase modifier type and concentration was optimized with respect to the improvement in physical properties and morphology of the blends. Physical properties, dynamic mechanical properties, and morphology of these blends were explained with the help of interaction parameter, melt viscosity, and crystallinity of the blends. Theoretical modeling showed that Kerner, Ishai‐Cohen, and Paul models predicted the right morphology–property correlation for the prepared TPEs. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Analysis of Fatty Acid and Lignan Composition of Indian Germplasm of Sesame to Evaluate Their Nutritional Merits

An attempt was made to individually analyze a germplasm collection of 54 indigenous Indian sesame cultivars for fatty acid and lignan composition of their seed oil by gas chromatography and high performance liquid chromatography, respectively. The entries varied in their fatty acid and lignan composition. The mean percentage contents of palmitic, stearic, oleic, linoleic and α‐linolenic acids ranged between 10–22, 5–10, 38–50, 18–43 and less than 1 whereas sesamol, sesamin and sesamolin scored between 3–37, 27–67, 20–59 of the total percentage of lignan, respectively. The highest percentage of α‐linolenic acid (ALA) was obtained in Var‐9 (1.3 % of the total fatty acids). Among the lignans, high sesamin content is considered to be significant, particularly in terms of long shelf life and nutraceutical value of sesame seed oil. The study has broadened our understanding related to differential biochemical composition of the rich sesame germplasms, thereby providing us with a useful groundwork for identifying potential targets and suitable cultivars for genetic engineering approaches to be undertaken in order to improve the nutritional quality of sesame oil, which in turn would be beneficial towards human health.     

A facile synthesis of a novel three‐phase nanocomposite: Single‐wall carbon nanotube/silver nanohybrid fibers embedded in sulfonated polyaniline

A three‐phase water‐soluble nanocomposite of single wall carbon nanotube/silver nanoparticle hybrid fibers embedded in sulfonated polyaniline has been synthesized by a simple chemical solution mixing process. The nanocomposite has been characterized by high resolution electron microscopy, X‐ray diffractometry, FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Optical and electrical characteristics of the nanocomposite have been determined by UV–vis absorption spectroscopy, photoluminescence spectroscopy, and four‐probe electrical conductivity measurement. A surface plasmon absorption band obtained around 460 nm indicates the presence of silver nanoparticles in the composite. The optical band gap calculation for sulfonated polyaniline vis‐a‐vis the nanocomposite supported the conductivity measurement. Over 1300 times increase in DC electrical conductivity has been observed for the three‐phase nanocomposite, with a filler loading of 20 wt %, at 306 K. This observation could be explained by Mott's variable range hopping model considering a three‐dimensional conduction. Such a nanocomposite has immense potential for use as a cathode material in lithium‐ion batteries and supercapacitors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41692.     

Miscibility and fracture toughness of thermoplastic polyurethane/poly(vinyl chloride)/nitrile rubber ternary blends with special reference to the blend composition

Ternary blends of thermoplastic polyurethane and a poly(vinyl chloride)/nitrile rubber blend were investigated in this work. The blends, with weight ratios of 100/0, 80/20, 40/60, 60/40, 80/20, and 0/100, were prepared via melt blending. Dynamic mechanical analysis showed that the blends with ratios of 20/80 and 80/20 were miscible, whereas the 40/60 and 60/40 blends were partially miscible. IR spectroscopy studies showed shifts in the peaks due to specific interactions in the blends. The blends showed degradation behavior between the blend components. The fracture toughness was investigated with the J‐integral by the locus method; the components and the miscible blends had good fracture toughness, whereas the other blends had lower toughness. Similar behavior was observed for the tensile properties. Scanning electron microscopy studies showed the morphological variations in the blends. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1763–1770, 2005     

Mechanical and dynamic mechanical studies of epoxy/VAc‐EHA/HMMM IPN–jute composite systems

Epoxy [50:50 mixture of Di‐Glycidyl Ether of Bis‐Phenol A (DGEBA) and Epoxidized Novolac (EPN)] was solution blended with Vinyl Acetate‐2‐ Ethylhexylacrylate (VAc‐EHA) resin in aqueous medium, in varying weight fractions, with Hexamethoxymethylmelamine (HMMM) as a crosslinker and data was compared with a control. The present work was aimed to optimize the tensile strength, dynamic mechanical strength, impact strength, and toughness by preparing a blend followed by jute composites of a semi‐ and full interpenetrating network (IPN). In control experiments epoxy alone was crosslinked (semi‐IPN), whereas the DGEBA‐EPN and VAc‐EHA/HMMM were crosslinked separately (full‐IPN), using jute as the substrate for making composites. Composites of full‐IPN systems of epoxy/VAc‐EHA system had higher moduli and UTS than the semi‐IPN systems. Dynamic mechanical study showed that full‐IPN systems have higher T_g values than semi‐IPN systems. The impact strength increases with increasing proportions of VAc‐EHA copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 958–963, 2004