40—SELF-CROSS-LINKING IN HEATED KERATIN

An account is given of an investigation of the influence of dry heat on wool keratin. It is shown by three different chemical techniques that cross-linking occurs up to a temperature at which the amino-acid decomposition becomes marked. Although Iysinoalanine and lanthionine are shown to be formed, these amino acids do not appear to be major contributors to the cross-linking of the heated protein.

The covalent binding of the ?-amino group of lysine was determined quantitatively, and, from the results obtained, it is deduced that this group is involved to a large extent in the formation of cross-links.

On the basis of these findings, it is postulated that amide cross-links are formed through the ?-amino group of lysine by reaction with carboxylic side chains of aspartic or glutamic acids or their amide derivatives.     

Cathodic protection of UNS C71500 heat exchanger tubes in sulphide polluted Arabian Gulf sea water

Abstract

A laboratory investigation using a specially designed circulating test rig has been undertaken to study the feasibility of achieving complete cathodic protection of UNS C71500 heat exchanger tubes in sea water applications by means of sacrificial carbon steel anodes. The results have indicated that the galvanic current distribution covered the entire 6 m length of the tube. However, the presence of sulphide ions as pollutants in the sea water shifted the galvanic potentials of the tubes to less active potentials and affected the development of the protective films that normally form.     

The multiple roles of interfacial tension in fluid phase equilibria and fluid–solid interactions

The tension at the interfaces separating the three phases of matter is a unique property in that it can reveal a great deal of information about the phases in contact, including the direction and extent of mass transfer of components, their proximity to equilibrium, the nature of fluids distribution relative to one another, the contact angle, and the spreading and adhesion behavior of liquids on solid surfaces. In this paper we examine, with supporting experimental data, the multitude of roles played by interfacial tension in establishing (1) the phase behavior characteristics of solubility, miscibility, and the associated mass transfer mechanisms in multicomponent fluid systems, (2) the nature of fluids distribution in gas–oil–water systems in porous solid substrates and (3) the spreading and adhesion characteristics in solid–liquid–liquid systems through dynamic contact angles.     

43—THE INTRODUCTION OF AMIDE AND ESTER CROSS-LINKS INTO WOOL

An account is given of the examination of carbodiimides and ethyl chloroformate as cross-linking agents for wool. The level of cross-linking was estimated from the extent of swelling of the treated wool in formic acid. Carbodiimide treatments resulted in the condensation of amino and carboxyl side chains to give amide cross-links; ester cross-links were also formed by condensation of hydroxyl and carboxyl side chains, Hydroxylamine treatments, which cleaved the ester but not the amide cross-links, were used to estimate the relative abundance of the two types of cross-link. N-Hydroxysuccinimide strongly promoted the cross-linking of wool with carbodiimides, most of the extra cross-links introduced being esters.

The treatment of wool with ethyl chloroformate introduced relatively few cross-links. The main reactions are believed, on the basis of indirect evidence, to be esterification of carboxyl side chains and conversion of amino side chains to urethanes.     

14—COMPARISON OF THE FELTING PROPERTIES OF LOOSE WOOL FIBRES,WORSTED-SPUN YARN,AND KNITTED FABRIC

When the felting properties of loose wool, yarn, and fabric are compared, before and after chemical modification, only a poor relationship is found between the felting rates of all three assemblies. It is therefore impossible to predict the effect of a particular treatment on a fabric by applying the same conditions of treatment to the loose wool. A very detailed study of a particular treatment is necessary before loose-wool felting can be used for prediction purposes.     

Finite element modelling of tungsten inert gas welding of aluminium alloy 2024

Abstract

A finite element model to predict the evolution of stress and distortion for a bead on plate tungsten inert gas (TIG) weld in aluminium alloy 2024 plate is described. The thermal model was calibrated against thermocouple measurements, and the mechanical model was validated against direct measurements of residual strain made using synchrotron X-ray diffraction. Particular attention has been paid to the clamping arrangement, the transfer of heat between the plate and the copper backing plate, and the selection of appropriate thermal history dependent mechanical properties. The validated model has been used to determine the optimal arrangement for 'low stress no distortion' welding using laser heating applied to both sides of the joint line ahead of the TIG torch. In this manner it is predicted that the peak longitudinal tensile stresses in the weld region can be reduced to 15% of their normal values.     

Control of Mounting Torque for Specimens in Abrasion-testing

The application of N-methoxymethyl-nylon to pre-chlorinated set wool inhibits felting shrinkage and stablizes the set to withstand machine-washing and tumble-drying. The methyoxymethyl groups in the resin appear to form covalent methylene cross-links between the resin and the wool.     

Synthesis and properties of polyester-based TPUs prepared by solution polymerisation

Abstract

The polyester based thermoplastic polyurethane elastomers (TPUs) were prepared by one-step solution polymerisation to obtain a product with completely linear molecular structure and with excellent solubility. The synthesis technique was determined by investigation of the influence of solvent and catalyst on the viscosity of the reaction system and the mechanical properties of the resulting product. The effects of the molecular structure on the mechanical, damping and crystallisation properties of TPUs were studied in terms of the type of diisocyanate, mass fraction of hard segment, type and molecular weight of soft segment, and type of chain extender. The structure and morphology of TPUs were characterised by FTIR, GPC and AFM analysis. There was microphase separation in the molecules of TPU, in which the hard-segment phase was dispersed in the soft-segment phase.     

Ureidosilanes on E-glass fibres: deposition and surface characteristics

The behaviour of methoxy- and ethoxy-ureidosilanes deposited onto E-glass fibres from both organic and aqueous solutions is reviewed. γ-Ureidopropyltri(m)ethoxysilanes are used as coupling agents for paints to metal surfaces, but they have not found much use as coupling agents for E-glass fibres. On metal surfaces, the silane is deposited with the ureido-functional group outermost, available for reaction with a paint/polymer matrix. On E-glass surfaces, however, unless specific conditions are employed, ureidosilanes tend to deposit with a highly cross-linked siloxane surface. The silanol groups condense not only with silanols of adjacent silanes and the E-glass surface, but also with aluminium hydroxides leached from the E-glass surface. This forms a highly cross-linked aluminosiloxane outer layer. The aluminosiloxane forms at all pHs between 4 and 10, and also when a range of organic deposition solvents is used. ²⁹Si-NMR results are presented which illustrate the high level of condensation; silane to silicate binding via the amino group was not detected. A small proportion of Si—O—Si (silane-glass) bonds was inferred, indicating that a small number of sparsely distributed Si—O—Si links bound the silane to the surface. Electrokinetic analysis of the surfaces confirmed patchy deposition with a siloxane outer surface. Using AFM and ab initio calculations, it was estimated that the patchwise deposition of the silane was in the form of bilayers (or multiples of bilayers). The bilayer structure consisted of siloxane outer layers, with the inner ureido layers forming hydrogen bonds. A graphical fit using the mole and volume fractions of silane and organic solvents confirmed the various types of siloxane surfaces as deposited from different organic solvents. Chlorinated solvents tended to produce a ureido outer surface, which was condensed, but solventswollen; deposition from alcohol and acetone resulted in a siloxane surface. Toluene and THF both produced minimally condensed ureido surfaces, which were easily removed by washing with methylene chloride.     

The Effect of Resin Matrix Composition on Mechanical Properties of E-glass Fiber-Reinforced Composite for Dental Use

The effects of resin matrix composition including bis-phenol-A-diglycidyl dimethacrylate (bis-GMA)-methyl methacrylate (MMA) based or urethane dimethacrylate (UEDMA)-triethylene glycol dimethacrylate (TEGDMA) based composition and storage conditions on the mechanical properties of E-glass fiber-reinforced composites (FRCs) were studied. Three experimental groups ('Exper 1', 'Exper 2', 'Exper 3') with differing UEDMA to TEGDMA ratio in the matrix together with a control group ('Control') based on bis-GMA–MMA resin matrix were prepared by light-curing. The storage conditions for each group were dry storage at room temperature for 24 h and 30- and 60-day immersion in deionized (DI) water at 37°C, which further divided each group into three subgroups. For all the four composition groups, mechanical properties including hardness, flexural strength and modulus in both three-point and four-point bendings were tested (n = 6), together with water sorption and solubility study (n = 6) and fracture site scanning with a scanning electron microscope (SEM). The experimental specimens were relatively strong and stiff in three-point bending compared to previous research. The same specimens in three-point bending had a lower flexural modulus and fractured at higher flexural stress than in four-point bending. According to the SEM images after fracture, some resin matrix was still bound to the fiber surface, showing cohesive–interfacial fracture type and relatively stable matrix–fiber adhesion. According to comprehensive analysis, the control group showed superior mechanical performance in most of the tests.