37—THE AIR-FLOW FINENESS OF GREASY WOOL: INTER-LABORATORY TESTS OF A PROPOSED STANDARD PROCEDURE

An account is given of an inter-laboratory trial of a method of measuring the fineness of greasy wool by means of a Wira Air-flow Fineness Meter. Eight laboratories took part in two tasks: firstly, a calibration by each laboratory of its own air-flow meter in terms of internationally standardized wools; and, secondly, the measurement of the fineness of greasy-wool core samples by means of the specified method, which included a normal laboratory washing of the wool followed by opening on a wool-type Shirley Analyser.

As a result of the trial, the method was considered to be suitable for use by testing authorities, and tentative limits of precision of the method of measuring the fineness of greasy wool were established. The mean difference between any two laboratories ranged from 0.2 μm at 20-μm diameter to 0.5 μm at 28-μm diameter. This does not include sampling errors.     

36—THE EFFECT OF EXTRANEOUS MATTER ON THE INDICATED DIAMETER OF WOOL FIBRES AS MEASURED BY THE AIR-FLOW TECHNIQUE

The air-flow technique for the measurement of wool-fibre fineness has advantages over other methods because of its speed and convenience of testing. However, if the wool being tested is in the form of washed corings from greasy bales or corings from scoured bales rather than tops, the sample may contain impurities such as vegetable matter or sand and dust, and, although it is possible for such impurities to be removed, the treatment requires time and the continuous attention and judgement of a trained operator.

The effect of the presence of impurities on the indicated mean diameter of wool fibres is therefore a matter of some importance, and an account is given in this paper of an investigation undertaken to study this effect.

The theoretical basis of the influence of impurities on the indicated diameter is given, and it is shown that the experimental results are, in general, in agreement with the predicted values. Provided that the amount of vegetable matter present does not exceed 5% and coarse, sandy dirt is present to an amount not exceeding 1%, it is likely that the error in the indicated diameter resulting from the combined effects will fall in the range from 0 to +4.2%, i.e., the error would not exceed ±2.1% at the 95% probability level, which might be an acceptable figure for many purposes if an adjusted calibration were made.     

6—THE EFFECT OF ALKALINE AND ACID SWELLING AGENTS ON THE MECHANICAL PROPERTIES OF COTTON FIBRES

A study of the changes in mechanical properties of cotton brought about by sodium hydroxide, an iron tartrate complex in caustic soda (EWNN), cuprammonium hydroxide, and sulphuric, phosphoric, nitric, and perchloric acids has been made. Instead of choosing the normal mercerizing conditions with sodium hydroxide, different temperatures of treatment and of washing were studied to see what effect the condition had on the subsequent mechanical properties of the fibres. The variable studied with the other reagents was that of concentration, so that a distinction between interfibrillar and intrafibrillar swelling could be made. The main effect of swelling is to alter the extensibility of the fibre, and this has been analysed at different stages of loading up to break.     

19—A STUDY OF NEEDLED FABRICS. PART VI: THE MEASUREMENT OF PUNCHING FORCE DURING NEEDLING

An account is given of an investigation in which a small needle board was fitted to the compression cage of an Instron Tensile Tester and used to measure the forces developed during the penetration of a web by needles. The punching speeds were much lower than those in a needling machine. The effects of web weight, type of fibre, fibre length and fineness, density, a reinforcing base fabric, and punching speed were studied.     

Application of sessile drop technique (SDT) for study of reduction of FeO in slags: reduction by solid carbon as well as solute carbon

Abstract

With growing importance of smelting reduction processes, experimental research to understand reduction of FeO in molten slag and the foaming behaviour associated therein have assumed greater relevance. In a previous paper, experimental data on reduction of FeO in molten slag in a 30 kW capacity induction furnace have been reported. The present study used around 250 g slag in each experiment was concerned with influence of FeO concentration in molten slag and temperature on foaming and kinetics. The present paper describes a study on the same system carried out using the sessile drop technique (SDT) which, although it uses very small (～25 mg) sample size, is extremely versatile. Moreover, SDT allows one to actually see the reaction occur. An attempt has been made to correlate kinetic data obtained using the present set-up with the data where much larger sample sizes were used. Both solid carbon and solute carbon have been employed in reduction studies.     

Reaction rate and product morphology in carbon composite iron ore pellets with and without Portland cement

Abstract

The aim of this work is to study the reaction rate and the morphology of intermediate reaction products during iron ore reduction when iron ore and carbonaceous materials are agglomerated together with or without Portland cement. The reaction was performed at high temperatures, and used small size samples in order to minimise heat transfer constraints. Coke breeze and pure graphite were the carbonaceous materials employed. Portland cement was applied as a binder, and pellet diameters were in the range 5·6–6·5 mm. The experimental technique involved the measurement of the pellet weight loss, as well as the interruption of the reaction at different stages, in order to submit the partially reduced pellet to scanning electron microscopy. The experimental temperature was in the range 1423–1623 K, and the total reaction time varied from 240 to 1200 s. It was observed that above 1523 K the formation of liquid slag occurred inside the pellets, which partially dissolved iron oxides. The apparent activation energies obtained were 255 kJ mol^–1 for coke breeze containing pellets, and 230 kJ mol^–1 for those pellets containing graphite. It was possible to avoid heat transfer control of the reaction rate up to 1523 K by employing small composite pellets.     

Cold bonded ore–coal composite pellets for sponge ironmaking Part 1 Laboratory scale development

Abstract

There is a need for the development of efficient industrial processes to use iron ore fines of high grade. Attention is particularly drawn to rotary kiln sponge ironmaking technology using lump iron ore, where productivity is low and energy consumption high compared with gas based processes. Fundamental studies carried out elsewhere indicate that the reduction of lump iron is accelerated if a limited amount of carbonaceous material is incorporated in the agglomerate of iron ore fines. Based on these considerations, cold bonded ore–coal composite pellets have been developed for sponge ironmaking in a rotary kiln. These composite pellets were tested in the laboratory and found to reduce very quickly, compared with lump iron ore. Composite pellets were also tested in an 8 t/day rotary kiln sponge iron plant giving enhanced productivity and lower coal consumption, and these results will be presented in Part 2 of this paper (next issue).     

Modification of epoxy resin by polysulfone to improve the interfacial and mechanical properties in glass fibre composites. I. Study of processes during matrix/glass fibre interface formation

The rheology of epoxy resin-polysulfone blends and wetting at the blend/glass fibre interface have been studied. Measurements were made in a rotary viscometer and in a modified Wilhelmy apparatus. It was shown that none of the blends investigated revealed non-Newtonian behaviour in the range of shear rates used. The viscosity of the blends increased as polysulfone content increased. Introduction of hardener resulted in a significant increase of the blends viscosity up to 2-3 orders of magnitude. Rheological tests suggested that 15 wt% polysulfone was the highest concentration useful for obtaining composites by solvent-free impregnation technique. These tests suggested that the structure of the cured epoxy-polysulfone blends depended on the modifier concentration. The structures of the blends differed for the blends containing 5 wt% polysulfone and 10-15 wt% polysulfone. All the blends (with the hardener) required at least 30 min at 180°C to achieve final values of the mechanical properties such as storage and loss moduli, loss tangent and complex viscosity. For all epoxy resin-polysulfone/glass fibre systems a complete wetting of the fibres was observed. Surface tension vs. polysulfone content dependency was found to be nonadditive. Surface tension measured was minimal for epoxy resin-5% polysulfone blend, while for other systems the values were close to that of epoxy resin. Modification of epoxy resin by polysulfone did not change the kinetics of the fibres wetting by the blends.     

Adhesion characteristics of plasma surface treated carbon/epoxy composite

The load transmission capability of adhesive joints can be improved by increasing the surface free energy of the adherends with surface treatments. In this paper, suitable plasma surface treatment conditions for carbon/epoxy composite adherend were investigated to enhance the strength of carbon/epoxy composite adhesive joints using a capacitively coupled radio-frequency plasma system. Effects of plasma surface treatment parameters on the surface free energy and adhesion strength of carbon/epoxy composite were experimentally investigated with respect to gas flow rate, chamber pressure, power intensity, and surface treatment time. Quantitative chemical bonding analysis determined with XPS (X-ray photoelectron spectroscopy) was also performed to understand the load transmission capabilities of composite adhesive joints with respect to surface treatment time.     

Adhesion characteristics of carbon/epoxy composites treated with low- and atmospheric pressure plasmas

Although an adhesive joint can distribute load over a larger area than a mechanical joint, requires no holes, adds very little weight to structures and has superior fatigue resistance, it requires careful surface preparation of adherends for reliable joining and low susceptibility to service environments. The load transmission capability of adhesive joints can be improved by increasing the surface free energy of the adherends with suitable surface treatments. In this study, two types of surface treatment, namely the low pressure and the atmospheric pressure plasma treatment, were performed to enhance the mechanical load transmission capabilities of carbon/epoxy composite adhesive joints. The suitable surface treatment conditions for carbon/epoxy composite adhesive joints for both low and atmospheric pressure plasma systems were experimentally investigated with respect to chamber pressure, power intensity and surface treatment time by measuring the surface free energies of the specimens. The change in surface topography of carbon/epoxy composites was measured with AFM (Atomic Force Microscopy) and quantitative surface atomic concentrations were determined with XPS (X-ray Photoelectron Spectroscopy) to investigate the failure modes of composite adhesive joints with respect to surface treatment time. From the XPS investigation of carbon/epoxy composites, it was found that the ratio of oxygen concentration to carbon concentration for both low and atmospheric pressure plasma-treated carbon/epoxy composite surfaces was maximum after about 30 s treatment time, which corresponded with the maximum load transmission capability of the composite adhesive joint.