Interlaminar fracture toughness of a plain weave flax/epoxy composite

ABSTRACT

In recent decades, flax fibre has become a popular natural resource as reinforcement in polymeric composites. However, the pure mode characterisation of flax fibre composites is rather limited. Furthermore, the mixed-mode delamination is not yet available. Nevertheless, delamination behaviour is important to be characterised as it is a major problem in composite laminates. This study examined the delamination behaviour of a woven flax/epoxy composite. Specimens were tested using mode I double cantilever beam, mode II end-notched flexure and mixed-mode I+II single leg bending tests. Results showed that the mode I, mode II and mixed-mode I+II fracture toughness were 363.23, 962.17 and 649.06?N?m^?1, respectively. When the fracture toughness values were fitted using Benzeggagh–Kenane criterion, it was found that the best-fit material parameter η was attained at 0.88. This information is useful to estimate the variation of fracture toughness with the mode ratio. Finally, through scanning electron micrographs, it was noticed that fibre/matrix debonding was the major fracture mechanism in all loading modes. In conclusion, the findings from this study suggested that the composite was suitable to be used for structural applications under mixed-mode loading.     

Morphology and Mechanical Properties of Normal Blends and In-Situ Microfibrillar Composites from Low-Density Polyethylene and Poly(ethylene terephthalate)

In this work, normal blends, microfibrillar blends and composites were prepared from low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) in 85/15 and 75/25 w/w% ratio in the presence and absence of a compatibilizer polyethylene grafted with maleic anhydride (PE-g-MA). The microfibrillar composites (MFCs) were prepared using extrusion – drawing – isotropization technique. The morphology development of the microfibrillar blends and composites was studied using scanning electron microscopy (SEM). The presence of 5 wt% PE-g-MA compatibilizer affected the continuity of the fibrils differently in 75/25 and 85/15 w/w% microfibrillar blends. In the case of normal blends the addition of compatibiliser reduced the size of the dispersed PET phase. The presence of PET microfibrils improved the tensile properties of the microfibrillar composites. The normal blends exhibited a relatively ductile failure during tensile loading in comparison with the microfibrillar composites. The microfibrillar nature of the dispersed phase was found to improve the stiffness of the composite rather than their impact strength.     

Studies on the effect of anions of various lithium salts in PEMA gel polymer electrolytes

This research synthesized graft copolymers of chitosan‐g‐poly(N‐isopropyl acrylamide) (CS‐g‐PNIPAAm) by UV‐initiated free‐radical polymerization of NIPAAm monomer to CS selectively at the C‐6 position of pyranose ring. First, amino groups in CS were protected by reaction with phthalic anhydride (PA) to form PACS. The degree of phthaloylation was carefully controlled to ensure that most amino groups were protected, and only a very small amount of hydroxyl groups were reacted. In the second step, the vinyl functional group was introduced to the PACS by reaction with a vinyl compound containing an isocyanate group (3‐isopropenyl‐αα′‐dimethylbenzyl isocyanate), through the urethane linkage with hydroxyl groups at the C‐6 position. The phthaloyl groups were then removed by hydrazine to recover the amino groups in CS. Finally, PNIPAAm was grafted to the vinyl CS at the C‐6 position by UV‐initiated free‐radical polymerization. The synthesized CS‐g‐PNIPAAm copolymers were confirmed to have a structure of an AB‐crosslinked graft copolymer. Respectively, these copolymer hydrogels exhibited pH‐ and thermal‐responsive swelling properties in an aqueous solution due to their CS and PNIPAAm components. The test of cell viability with L929 fibroblast revealed that the CS‐g‐PNIPAAm copolymers having a grafting ratio lower than 1.7 had cellular compatibility as good as pure CS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dielectric and thermal response of poly[(vinylidene chloride)‐co‐acrylonitrile]/poly(methyl methacrylate) blend membranes

Poly(methyl methacrylate) was mixed with poly[(vinylidene chloride)‐co‐acrylonitrile] (Saran‐F) and lithium perchlorate in tetrahydrofuran to make polymer blend systems. Solvent‐free membranes with various blend ratios were prepared using a solution casting technique. Impedance analysis was used to study the electrical response of the polymer membranes, which shows that the 50:50 wt% blend ratio polymer membrane has a low bulk resistance and high dielectric constant at room temperature and hence high ionic conductivity. The dielectric behaviour was analysed using dielectric permittivity and electric modulus of the samples. The conductance spectra follow the universal power law variation. Structural analysis confirms the amorphous nature and functional group analysis confirms the miscibility. The decomposition temperature of the membranes was determined using thermogravimetric analysis. © 2014 Society of Chemical Industry     

Enrichment of glutaminase production by Bacillus subtilis RSP‐GLU in submerged cultivation based on neural network—genetic algorithm approach

BACKGROUND: Owing to the importance of glutaminase in biotech product production, its production with isolated Bacillus subtilis RSP‐GLU (MTCC 9727) was investigated. Fermentation factors play an important role in product enhancement. Hence, glutaminase production was optimized using an artificial neural network (ANN) coupled genetic algorithm (GA). RESULTS: A ‘6–12–1’ topology ANN was constructed to identify the nonlinear relationship between fermentation factors and enzyme yield. ANN‐predicted values were optimized for glutaminase production using a GA. The overall mean absolute predictive error (MAPE) and the mean square errors (MSE) were observed to be 0.00125 and 1.77 and 0.002 and 3.06 for training and testing, respectively. The goodness of neural network prediction (coefficient of R²) was found to be 0.996. The maximum interactive impact on glutaminase production was noted with rpm versus medium volume. The use of ANN–GA hybrid methodology resulted in a significant improvement (47%) in glutaminase yield. CONCLUSION: Five different optimum fermentation conditions out of 500 revealed maximum enzyme production. Glutaminase enzyme production in this Bacillus subtilis RSP‐GLU is strongly influenced by aeration of the fermentation. A hybrid ANN‐GA effectively identifies the different fermentation conditions for optimum production of enzyme in a given large set of conditions. Copyright © 2009 Society of Chemical Industry     

Statistical optimization of anticholesterolemic drug lovastatin production by the red mold Monascus purpureus

Lovastatin (HMG-CoA reductase inhibitors), is an important anticholesterolemic drug which inhibits the conversion of HMG-CoA to mevalonate in the biosynthesis of cholesterol. Plackett–Burman statistical screening of 12 media components and subsequent optimization of significant parameters by response surface methodology for the biotechnological production of lovastatin by Monascus purpureus MTCC 369 was studied. In this study, the statistical analysis of Plackett–Burman experimental results showed that the medium components glucose, peptone, MnSO₄·H₂O, NaCl and NH₄Cl as the significant components influencing the lovastatin production. The most significant medium components, glucose, peptone and MnSO₄·H₂O which have confidence level of more than 95% were further optimized using a full factorial central composite design of the response surface methodology. Maximum lovastatin production of 97.5 mg l^?1 was obtained after 14 days of fermentation period in the optimized medium containing, glucose, 52.61 g l^?1 peptone, 16.65 g l^?1; NH₄Cl, 1 g l^?1; KH₂PO₄, 1 g l^?1; yeast extract, 3 g l^?1; K₂HPO₄, 1 g l^?1; KNO₃, 0.5 g l^?1; MgSO₄·7H₂O, 0.2 g l^?1; MnSO₄·H₂O, 0.418 g l^?1; NaCl, 0.5 g l^?1; CaCl₂·2H₂O, 0.1 g l^?1 and FeSO₄·7H₂O, 0.001 g l^?1 at 30 °C and 120 rpm. The production of lovastatin by M. purpureus MTCC 369 in the optimized medium was found to be four times higher than the basal medium in the submerged fermentation. The statistical experimental design serves as an efficient tool for screening large number of variables with minimum number of experiments and optimizing the significant variables for enhancing the production of lovastatin.     

Novel Proton-Conducting Polymer Electrolytes Based on Poly(Vinylidene fluoride-co-hexafluoropropylene)–Ammonium Thiocyanate

The polymer electrolytes composed of poly(vinylidene fluoride-co-hexafluoropropylene) with various concentration of ammonium thiocyanate salt have been prepared by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis and Fourier transform infrared spectroscopy. The highest conductivity has been found to be 6.5?×?10^?3?S?cm^?1 at 343?K for 25?wt% ammonium thiocyanate. The temperature-dependent conductivity of polymer electrolyte follows Arrhenius hopping relation. Thermogravimetric analysis has been used to ascertain the thermal stability of the polymer electrolytes. Atomic force microscopy analysis predicts the roughness parameter of the sample with higher conductivity.     

Effect of ZnO nanoparticles on the electrospinning of poly(vinyl alcohol) from aqueous solution: Influence of particle size

Recently, interest in nonwoven mats composed of fibers manufactured by drawing polymer solutions or melts with suspended nanoparticles has been growing due to exciting opportunities for use in biomedical applications. Poly(vinyl alcohol) (PVA), due to its biocompatibility, and zinc oxide (ZnO), due its antibacterial activity, present one interesting combination for the manufacture of nonwoven fiber mats for potential use as wound dressings. Therefore, we have investigated the electrospinning of aqueous PVA solutions with suspended ZnO nanoparticles. ZnO nanoparticles of three different diameters (20, 70, and 100 nm) were used in the study. Interestingly, we found that increasing the diameter of suspended ZnO nanoparticles was accompanied by a decrease in the diameter of the electrospun fibers. Fourier transform infrared spectroscopy indicated that the ZnO nanoparticles were merely suspended in the aqueous PVA solution without any chemical bonding between the ZnO nanoparticles and the PVA chains. Shear rheometry of the suspensions indicated that, over the relevant range of shear rates, all of the samples exhibited essentially Newtonian behavior. However, the viscosity increased with a decrease in the diameter of the ZnO nanoparticles. We suggest that the effect of the nanoparticles on the diameter of the electrospun fibers is through their effect on the viscosity of the suspension from which the fibers are drawn. Finally, as was expected, increasing the electric field strength led to a gradual decrease in the diameter of the electrospun fibers. POLYM. ENG. SCI., 54:1969–1975, 2014. © 2013 Society of Plastics Engineers     

Shape engineering vs organic modification of inorganic nanoparticles as a tool for enhancing cellular internalization

ABSTRACT: In nanomedicine, physicochemical properties of the nanocarrier affect the nanoparticle's pharmacokinetics and biodistribution, which are also decisive for the passive targeting and nonspecific cellular uptake of nanoparticles. Size and surface charge are, consequently, two main determining factors in nanomedicine applications. Another important parameter which has received much less attention is the morphology (shape) of the nanocarrier. In order to investigate the morphology effect on the extent of cellular internalization, two similarly sized but differently shaped, rod-like and spherical, mesoporous silica nanoparticles were synthesized, characterized and functionalized to yield different surface charges. The uptake in two different cancer cell lines was investigated as a function of particle shape, coating (organic modification), surface charge and dose. According to the presented results, particle morphology is a decisive property regardless of both the different surface charges and doses tested, whereby rod-like particles internalized more efficiently in both cell lines. At lower doses, whereby the shape-induced advantage is less dominant, however, charge-induced effects can be used to fine-tune the cellular uptake as a prospectively "secondary" uptake regulator for tight dose-control in nanoparticle-based drug formulations.     

An instrument for the measurement of customer perceptions of quality management in the software industry: An empirical study in India

Most of the available literature on quality management is based on management’s perception; few studies examine critical issues of quality management from the customer’s perspective, especially in the software industry. In order to gain an insight into what customers expect from a product/service, an analysis of quality management from customer’s point of view is essential. Such an understanding would help the managers to adopt strategies that can enhance the satisfaction level of their customers. The present study highlights the critical factors of quality management in the software industry from the customer’s perspective. Six critical factors are identified: and an instrument, comprising these factors, is developed and validated so as to measure the customer’s perception of quality management in the software industry. George Issac is an Assistant Professor in Mar Athanasius College of Engineering, Kothamangalam, India. He holds a B.Sc (Engg.) degree in Mechanical Engineering from Kerala University, and M.Tech and Ph.D degrees in Management from IIT Madras. His research areas are TQM and Organizational Behavior. He has published articles in the area of quality management in journals such as Total Quality Management and Business Excellence, and Quality Management Journal of American Society for Quality. Chandrasekharan Rajendran is a Professor of Operations Management in the Indian Institute of Technology Madras. His research interests are in TQM, Scheduling and Simulation. He has published several articles in international journals. He has publications in the area of TQM in journals such as Total Quality Management, International Journal of Production Research, International Journal of Service Industry Management, International Journal of Bank Marketing, and Journal of Services Marketing. He serves as referee for many journals. He is a recipient of the Alexander von Humboldt Fellowship of Germany. R.N. Anantharaman is a Professor of Management in the Indian Institute of Technology, Madras. His research interests are in TQM, Organizational Behavior and Industrial Psychology. He has published several articles in international journals. He has published research articles in the area of TQM, HRM Practices, Change Management, etc., in Journals such as Total Quality Management, International Journal of Production Research, International Journal of Bank Marketing, International Journal of Service Industry Management, Journal of Services Marketing, International Journal of Human Resource Management, and Journal of Transnational Management Development.