Melt rheology and elasticity of natural rubber—ethylene–vinyl acetate copolymer blends

The melt rheology of blends of natural rubber (NR) and ethylene–vinyl acetate copolymer (EVA) has been studied with reference to the effects of blend ratio, cross-linking systems, shear stress, and temperature. When EVA formed the dispersed phase, the viscosity of the blends was found to be a nonadditive function of the viscosities of the component polymers at lower shear region, i.e., a positive deviation was observed. This behavior has been explained based on structural buildup of dispersed EVA domains in the continuous NR matrix. The effect of the addition of silica filler on the flow characteristics of the blends has been investigated. The melt elasticity parameters such as die swell, principal normal stress difference, recoverable shear strain, and elastic shear modulus of NR–EVA blends were also evaluated. © 1993 John Wiley & Sons, Inc.     

A Heavy Lift Planning System for Crane Lifts

This paper presents the work done toward developing a computerized heavy lift planning system (HELPS) for planning crane lifts. Initially, a survey of the industry was carried out to define the heavy lift planning process and identify the developments necessary to improve the process. This survey identified eight tasks in the lift planning process. Based on these tasks, a logical framework representing the planning process was developed. The scope of the current work was limited to developing a tool for planning three of these tasks. A visualization environment—Walkthru—was selected to implement the heavy lift planning system. Although Walkthru provided many of the features required for the system, critical functions had to be added. The developmental work for this study focused on (1) developing a shell that could control the visualization environment and related files to provide seamless access to the library of cranes and (2) providing features to perform critical lift planning functions. The resulting prototype system was tested on sample lifts, and all the functions worked as designed.     

Natural Rubber/Acrylonitrile Butadiene Rubber Blend Membranes: Vapor Permeation Properties

Natural rubber (NR)/Acrylonitrile butadiene rubber (NBR) blend membranes, prepared by using dicumyl peroxide as the crosslinking agent, were tested for their vapor permeation characteristics. The permeation studies were conducted using three chlorinated hydrocarbons, viz. dichloro methane, chloroform, and carbon tetrachloride. The effects of the blend ratio, compatibilizer, penetrant size, and temperature on the vapor permeability of the membranes were investigated. The permeability of the blends was found to decrease with an increase in the NBR content, which has been attributed to the inherent solvent resistant nature of NBR. The permeation behavior of compatibilized blends was compared with those of the uncompatibilized blends. The separation efficiencies of the membranes were also tested using chloroform/acetone mixtures to complement the observations from the vapor permeation experiments.     

Heat source problem of thermoelasticity in an elliptic plate with thermal bending moments

The principal aim of this article is to investigate the thermoelastic problems on an elliptical plate in which interior heat sources are generated within the solid, with compounded effect due to sectional heating and boundary conditions of the Dirichlet type. The analysis is based on the small-deflection theory of the elliptical plate and performed in the elliptical coordinate system. In addition, the intensities of bending moments, twisting moments, etc., are formulated involving the Mathieu and modified functions and their derivatives. The analytical solution for the thermal stress components is obtained in terms of resultant forces and resultant moments.     

Studies on energetic compounds part 15 : Transition metal salts of NTO as potential energetic ballistic modifiers for composite solid propellants

Abstract

The combustion of hydroxyl terminated polybutadiene (HTPB) - ammonium perchlorate (AP) composite solid propellants has been studied using transition metal (Mn, Fe, Co, Ni, Cu and Zn) salts of 5-nitro-2,4-dihydro-3H-1,2,4-triazole-3-one (NTO) as energetic burning rate additives. The steady burning rate (r) was considerably enhanced with Cu(NTO)₂ and Fe(NTO)₂ whereas moderately enhanced with Zn(NTO)₂ and Co(NTO)₂ at low concentration (2% by wt.). Activity of these salts has been observed during isothermal decomposition of AP at 260°C. The values of ignition delay (t_iJ), ignition temperature (T_ign.) and activation energy for ignition (E?) for AP has also been lowered when these salts are added to it at 2% wt. concentration. The processing parameters as well as mechanical properties of the propellants with Cu(NTO)₂ as additive have been studied in detail. The r of the propellants (both highly aluminized and less aluminized) with Cu(NTO)₂ as additive at various concentrations, has been determined at high pressures, also shows its activity during combustion, The condensed phase activity of Cu(NTO)₂ during propellant decomposition has also been studied using TG-DTG techniques.     

Spectroscopic studies of gel-grown lanthanum malonate crystals

Lanthanum malonate crystals were grown by single tube ionic diffusion through silica gel. The crystallinity of the grown crystals was analyzed by powder X-ray diffraction studies. Fourier transform infrared spectroscopy (FTIR) and fourier transform (FT) Raman studies confirmed the presence of functional groups in the title compound. The optical band gap energy of the material was extracted from diffuse reflectance spectrum.     

Effect of aggregate gradations on properties of porous friction course mixes

This paper presents the study on effect of aggregate gradation on the mix design and performance properties of porous friction course (PFC) mixes. Six aggregate gradations were tested with due consideration to gradations specified for PFC or similar mixes by different agencies around the world. The PFC mixes were characterized for volumetric properties, permeability, unaged and aged abrasion loss, moisture susceptibility, and rutting resistance. The results were statistically analysed to identify the factors that significantly influence the properties of PFC mixes. Findings of the study clearly indicate that the gradations specified by various agencies will have significant effect on the design properties of PFC mixes, thus they are different. It also, helps in framing the Master aggregate gradation band for PFC mixes. Generally, permeability property is considered to be an optional parameter in the design. However, the findings of the present study recommended considering the permeability as one of the prime parameters in the design of PFC mixes.     

Development of whey‐fruit‐based energy drink mixes using D‐optimal mixture design

The study deals with two whey‐fruit‐based energy drink mixes developed using freeze drying. D‐optimal mixture design with 2 factors at 5 levels was used for the optimisation of ingredients. The responses studied were overall acceptability and acidity of the formulations. The whey/grape juice and whey/pomegranate juice ratios selected on the basis of response analysis was 49:51 and 40:60, respectively. The energy drinks were freeze‐dried and packed in paper/Al foil/polythene (PFP) pouches were stored at ambient temperature as well as 37 ^○C. Periodic evaluation revealed that whey‐grape and whey‐pomegranate energy drink mixes had a shelf life of 9 and 8 months, respectively. The addition of caffeine at 200 ppm level did not impart any adverse change in sensory quality.     

Electrical properties of iron phthalocyanine thin film device using gold and aluminium electrodes

The electrical conductivity of FePc thin film sandwich structures using gold and aluminium electrodes has been investigated for the freshly prepared devices and device after exposure to oxygen for 30 days. Current density-voltage characteristics of the devices in the forward bias showed an ohmic conduction in lower voltages and a space charge limited conduction (SCLC) controlled by a single and an exponential trapping levels at two different ranges of applied voltages. The hole concentrations are obtained as P _o = 3.92 × 10¹⁶ m⁻³ with a hole mobility μ = 5.81 × 10⁻⁶ m⁻¹ V⁻¹ s⁻¹. In the SCLC region a discrete trap level of 1.88 × 10²¹ m⁻³ is found at 0.66 eV followed by an exponential trap distribution of P _e = 4.63 × 10⁴⁶ J ⁻¹ m⁻³ at N _t(e) = 2.23 × 10²⁶ m⁻³. From the current limitations in the reverse bias, the conduction is identified as an electrode limited Schottky type of conduction. In the oxygen-doped samples, both in the forward and reverse bias the order of currents are much enhanced and a transition from the ohmic conduction to a space charged conduction is observed.