Modification of LLDPE using esterified styrene maleic anhydride copolymer: Study of its properties and environmental degradability

Linear low‐density polyethylene (LLDPE) was blended with decanol‐esterified styrene maleic anhydride copolymer (MDESMA) with an aim to enhance the environmental degradability of polyethylenes. Styrene‐maleic anhydride copolymer (SMA) was synthesized by precipitation polymerization, using benzoyl peroxide (BPO) as initiator. SMA was esterified with a long‐chain monoalcohol, n‐decanol, using methyl ethyl ketone (MEK) as solvent at 80°C to obtain monoesterified styrene‐maleic anhydride (MDESMA). Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA) were performed to characterize SMA and MDESMA. IR spectra of MDESMA showed a decrease in intensity of peak responsible for carbonyl absorption of a five‐membered ring anhydride group along with broadening of carboxyl O? H stretching peak. TGA showed two‐stage degradation for SMA and MDESMA. LLDPE was blended with MDESMA in single‐screw extruder and blends were characterized thermally by DSC and TGA. A single endothermic melting peak of LLDPE/MDESMA blend was observed. Films of the blends, formed by compression molding, showed an increase in modulus of elasticity but a decrease in elongation at break with increasing concentration of MDESMA. LLDPE/MDESMA blend compositions when kept in phosphate/citric acid buffer solution (pH ～ 8) showed initial weight gain because of water absorption and subsequently loss in weight due to dissolution of soluble component of blends. Film samples of blends kept for soil burial also showed similar behavior. Contact‐angle measurement of film samples of the blends showed an increase in value on soil burial, indicating degradation/dissolution of MDESMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 102–108, 2004     

Optimal Weld Parameters, Weld Microstructure, Mechanical Properties, and Hydrogen Absorption: An Effective Analysis

Weld bead-in-grooves were deposited on low alloy, high strength steel plates (ASTM A 517 Grade “F”) with a commercial flux-cored filler wire, Auto-MIG 420, at different welding conditions. Microstructure and mechanical properties of welds were characterized by means of optical microscopy, SEM, TEM, EPMA, microhardness measurements, tensile tests, and Charpy impact tests. Hydrogen content of weld metals in as-weld condition and after exposing in simulated service condition was measured by LECO Gas Analyzer. Microstructure of weld metals consisted primarily of lath martensite with small amount of M-A constituents (Martensite-Austenite alternating layers). For some particular welding conditions, such as higher heat input and lower preheat temperatures etc., acicular ferrite is observed with lath martensite. Welds consisting of acicular ferrite in the microstructure showed improved mechanical properties as well as lower hydrogen absorption. The study provides guidelines for selecting proper welding conditions, which results in lower propensity to absorb hydrogen during service, as well as better mechanical properties. Necessity of post-weld heat treatment processes, which is mainly performed to achieve toughness, may be reduced; consequently saving cost and time of the welding process.     

Electronic states of organic semiconductors vis-à-vis interactions between molecules in a submonolayer through time-restricted electrostatic assembly

We have made in-depth studies to revisit time-restricted layer-by-layer (LbL) electrostatic assembly process of a couple of organic molecules. The studies have been made in relation to electronic states of metal phthalocyanines. We show that by shortening dipping time for adsorption of the active molecules, mass adsorbed in each monolayer can be decreased and hence intermolecular spacing between the molecules can be increased. We have characterized the (sub)monolayers deposited on an electrode with scanning tunneling microscope tip to record tunneling current through the molecules. Results show that the highest occupied molecular orbitals and lowest unoccupied molecular orbitals, and also the difference between the orbitals, that is, the transport gap of the molecules in a (sub)monolayer depends on the dipping time of LbL assembly or molecule-to-molecule separation. We show that interactions between molecules in a monolayer decrease the transport gap of the metal phthalocyanines.     

Relationship between normal load and dynamic co-efficient of friction on rock-rubber wear mechanism

In this study, rubber compounds were produced in varying proportions of carboxylated acrylonitrile butadiene rubber (XNBR) and natural rubber (NR) and the parameters such as cure characteristics, wear behavior against various surfaces at different normal loads, and frictional works were tested. The tensile strength and dynamic co-efficient of friction of sample containing 80 wt.% of XNBR was high compared to other samples by 2% and 10% respectively. The results of XNBR and NR vulcanizates under normal pressure ranging from 43 to 118 kPa were reported. Based on these results the relationship between normal load and dynamic co-efficient of friction has been proposed. It was also observed that sample containing 80 wt.% of XNBR exhibits lesser volume loss than compared to other samples.     

Progressive cutting tool wear detection from machined surface images using Voronoi tessellation method

Tool condition monitoring by machine vision approach has been gaining popularity day by day since it is a low cost and flexible method. In this paper, a tool condition monitoring technique by analysing turned surface images has been presented. The aim of this work is to apply an image texture analysis technique on turned surface images for quantitative assessment of cutting tool flank wear, progressively. A novel method by the concept of Voronoi tessellation has been applied in this study to analyse the surface texture of machined surface after the creation of Voronoi diagram. Two texture features, namely, number of polygons with zero cross moment and total void area of Voronoi diagram of machined surface images have been extracted. A correlation study between measured flank wear and extracted texture features has been done for depicting the tool flank wear. It has been found that number of polygons with zero cross moment has better linear relationship with tool flank wear than that of total void area.     

Immobilization and the conformational study of phospholipid and phospholipid-protein vesicles

The present work demonstrates the immobilization of phospholipids and phospholipids-protein vesicles on solid substrate by simple drop-cast technique. We have also studied the structural and conformational transition of protein (OVA) molecules when they are loaded in immobilized vesicles of DPPC. High-resolution FE-SEM imaging is used to study the structural aspects of the immobilized vesicles of DPPC and OVA loaded DPPC. FTIR analyses of amide bands are being used to inspect the extent of the conformational transitions of β-sheet to α-helix of OVA in immobilized DPPC vesicles. Immobilized OVA-DPPC vesicles provide the structure of individual OVA molecule attached with DPPC, without aggregation amongst them.     

Revisiting Stress Corrosion Cracking of Steel in Caustic Solutions for Developing Cracking Susceptibility Diagrams for Improved Applicability

Stress corrosion cracking tests were conducted using Bayer solutions of different chemistry at different temperatures for extraction of alumina from bauxite ores. The validity of the commonly used caustic cracking susceptibility (CS) diagram for steels exposed to plain caustic solutions was assessed by testing the notched and precracked specimens. This study presents first results toward the development of a model susceptibility diagram for actual Bayer solutions, and for improved applicability of the traditional plain caustic diagram. For mechanistic understanding of caustic cracking, tests were also carried out under imposed electrochemical conditions.     

Comparison of performances of five prospective approaches for the multi-response optimization

The Taguchi method of experimental design is widely used for optimization of process performance. However, this method has been developed to optimize single-response processes. But, in many situations, the engineers are required to determine the process settings that can simultaneously optimize multiple responses. In the recent past, researchers have proposed several systematic procedures for multi-response optimization. Most of these methods use complicated statistical/mathematical models and are, therefore, not easily comprehendible to the engineers who do not have a strong background in mathematics. Only a few methods, e.g. weighted signal-to-noise (WSN) ratio, Grey relational analysis, multiple-response signal-to-noise ratio, VIKOR (VlseKriterijumska Optimizacija I Kompromisno Resenje in Serbian), and weighted principal component methods, use relatively simpler procedures. In this paper, the computational procedures for these five methods are standardized. Three sets of experimental data are analyzed using these standardized procedures and the predicted optimization performances of the five methods are compared. The results show that no method can give better optimization than the WSN method.     

Controlled and modified atmospheres influence chilling injury,fruit quality and antioxidative system of Japanese plums (Prunus salicina Lindell)

Our objective was to compare the effects of controlled atmosphere (CA) and modified atmosphere packaging (MAP) on fruit quality, chilling injury (CI) and pro‐ and antioxidative systems in ‘Blackamber’ Japanese plums. Matured fruit were stored for 5 and 8 weeks at 0–1 °C in normal air, CA‐1 (1% O₂ + 3% CO₂), CA‐2 (2.5% O₂ + 3% CO₂) and MAP (~10% O₂ and 3.8% CO₂). CA was more effective than MAP in retention of flesh firmness and titratable acidity during cold storage. Fruit stored in CA‐1 showed reduced CI and membrane lipid peroxidation after 5 and 8 weeks of cold storage. Low O₂ atmospheres appeared to limit the generation of reactive oxygen species (ROS) and their efficient scavenging through the concerted action of superoxide dismutase and peroxidase. The role of ascorbate–glutathione (AsA–GSH) cycle in the regulation of oxidative stress was also studied during and after storage in different atmospheres. In conclusion, optimum CA conditions delayed fruit ripening and CI through augmentation of antioxidative metabolism and suppression of oxidative processes.     

Structural and thermal characterization of macro-branched functional terpolymer containing 8-hydroxyquinoline moieties with enhancing biocidal properties

Novel polyfunctional acetyl and hydroxyl bearing functional terpolymer (HQFCA) derived from 8-hydroxyquinoline (HQ), 4-chloroacetophenone (CA) and formaldehyde (F) has been synthesized by complex condensation polymerization in the presence of an acid catalyst. The structure and morphology of terpolymer were elucidated by FTIR-ATR, one-dimensional NMR (¹H NMR, ¹³C NMR and DEPT-135 experiment), two-dimensional NMR (HSQC and TOCSY), pyrolysis GC–MS, gel permeation chromatography (GPC), nitrogen absorption, and optical microscopy (OM). Principal pyrolysis products generated from HQFCA units were 8-hydroxy-5,6-dimethylquinoline, 8-hydroxy-2-methylquinoline and 4-chloroacetophenone. This reactive terpolymer can be used as synthons for exchange membrane preparation and biomedical coating applications.