18—THE ABRASION-RESISTANCE OF SOME WOVEN FABRICS AS DETERMINED BY THE ACCELEROTOR ABRASION TESTER

The use of an Accelerotor abrasion tester is discussed, and the abrasion-resistance of several plain-weave fabrics is shown to depend on the type of fibre. The materials are ranked in order of decreasing resistance to abrasion with carborundum, rubber, metal, and plastics abradants. Polyamide fibres have outstanding resistance and cellulose-ester and regenerated protein fibres poor resistance to abrasion. The order of resistance of other synthetic-polymer fibres, regenerated cellulosic fibres, and natural fibres is shown to alter slightly according to the nature of the abradant, the linear density of the fibre, and the sett of the fabric. The results are in general agreement with published data, but the resistance of polypropylene-fibre fabrics is lower than it was expected to be.

Microscopical examination of detritus confirmed that this consisted of small segments of complete fibre, which indicated that abrasion occurs by fibre breakage. A useful correlation is established between the specific strength and initial modulus of a fibre, or the energy of rupture of mechanically conditioned fibres, and the abrasion-resistance of a fabric.     

The Calibration of Air-flow Apparatus for the Determination of the Fibre Diameter of Wool

There is a general algorithm for the determination of practicable starting allocations of colours to the two sides of a 4 × 4 box pick-at-will loom, but its convenience in use varies greatly. An improvement is indicated, but a simpler and more efficient algorithm is suggested for the one-empty-box case, for which the general algorithm is least satisfactory.

Two of the constraints of weft patterning on such 4 × 4 box looms are examined, largely by using the general algorithm. First, the maximum number of practicable starting allocations is determined for any given number of weft colours and any smaller number of box-pairs. Next, it is shown that there is a possibility that a weft repeat may be unweavable with one shuttle per colour if the number of picks in the reduced repeat is not less than the number of shuttle boxes in use.

In contrast to the genera! case, if there is only one empty shuttle box, the box plan that minimizes the number of large box movements for a given weft repeat can rapidly be determined by using a microcomputer.     

10—THE USE OF FLUORESCENT STAINS FOR THE STUDY OF THE STRUCTURE OF ANIMAL FIBRES

An account is given of the use of fluorescence microscopy for the study of the structure of various animal fibres. Sections of wool, mohair, llama, cow-tail, and horse-tail fibres, which were either untreated or had had some chemical treatment, were stained with fluorescent stains; much more detail was shown by this technique than by other staining methods. Basic dyes (acridine orange, rhodamine B, rhodamine 3GO, and thioflavine T) stained the orthocortex and acid dyes (uranin and geranine G) the paracortex.     

38—THE EFFECT OF FIBRE ARRANGEMENT ON THE INDICATION OF THE AIR-FLOW APPARATUS FOR WOOL FINENESS

The air-flow fineness apparatus, long used in the measurement of the fibre diameter of wool tops, is finding a rapidly growing application in the determination of the fineness of samples of loose wool or corings. It is known that the indication of the instrument is sensitive to the arrangement of fibres in the plug and that a calibration made by using wools in the form of tops cannot be expected to hold for the same wools in a different form.

This paper reports an investigation into the shift in instrument indication produced by subjecting tops to a variety of treatments: cutting, coring, hand- and machine-washing, and passage through the Shirley Analyser. The treatments were applied singly or in certain combinations. In all cases, the treatment produced an apparent increase in mean fibre diameter, i.e., increased air-permeability, the magnitude of the increase rising with mean diameter. The change in apparent diameter is considered to arise from an increase in pore-size distribution in the fibre mass, which is the result of disordering the fibre arrangement. Disordering can be caused by various treatments.

The effect of a steaming treatment on tops was somewhat similar to that produced by the other treatments already mentioned.

The magnitude of the apparent shift in diameter is tabulated for the important cases.     

43—THE AIR-FLOW DIAMETER OF WOOL TOPS: THE EFFECT OF COEFFICIENT OF VARIATION

Differences between the results obtained for the fineness of wool tops measured by air-flow and projection-microscope methods can arise because the coefficient of variation of the measured top is different from that of the tops used to calibrate the air-flow meter. The validity of some assumptions implicit in the air-flow calibration is examined and a correction table for precise use of the air-flow meter calculated. The corrections range from ?2% at 16 μm to zero at 36μm.     

SOLUTION OF DIFFERENT HOLES SHAPE BORDERS OF FIBRE REINFORCED COMPOSITE PLATES BY INTEGRAL EQUATIONS

Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.     

15—A STUDY OF NEEDLED FABRICS. PART V: THE APPROACH TO THEORETICAL UNDERSTANDING

Needled fabrics are complicated structures, and an exact analysis of their mechanics is not yet possible. Understanding is approached through three routes. Firstly, the behaviour of a fully bonded web is used to predict the effects of orientation, and to estimate the upper limits of strength. These estimates may be reasonable if the network that actually exists at the breaking point is used in calculations. Needled fabrics can give a fairly high utilization of fibre strength. Secondly, the effects of slippage are discussed qualitatively, by analogy with the behaviour of spun yams. The influences of entanglement, fibre length, fibre fineness, and fibre friction are discussed. Thirdly, a quantitative analysis, with many approximations, of a much-simplified model is made. Despite the unsatisfactory nature of some of the assumptions, the predictions are in general accord with experimental results.     

Macro- and microdispersion of carbon black in liquid silicone rubbers

Abstract

A correlation between the online during mixing measured conductance of carbon black (CB) filled silicone rubber and macrodispersion of CB determined by optical microscopy and microdispersion analysed by AFM has been established. The online conductance is a suitable tool to characterise the effect of technological parameters (e.g. rotor type, speed, mixing temperature) and material parameters (matrix viscosity, CB type and content) on the macro- and microdispersion directly during the mixing process. Thus, a modified method of the online conductance measurement can be used as the in-process method for monitoring the production process of electrical conductive polymer materials with low viscosity, e.g. liquid silicone rubbers.     

Molecular level investigation into selective permeability of silicon based membranes with potential use in gas separation processes

Abstract

The effect of the modification of the molecular structure on the permeability coefficients of typical rubbery and glassy silane and siloxane polymers at different temperatures was experimentally investigated. It was shown that carbon dioxide had higher permeability coefficients than those of nitrogen and oxygen due to the higher affinity of the various polymers toward the gas molecules. In order to provide a detailed understanding into the effect of the molecular structure on the gas diffusion behaviour in polymers, molecular modelling of carbon dioxide diffusion in silicon based membranes was used. The polymer molecules were shown to have lower self-diffusion coefficients than the gas ones related to the small size of the gas molecules as compared to the large size of the polymeric segments, thus allowing the gas molecules to jump from one unoccupied site to another through a series of connected pores or channels within the polymeric matrix. Increasing the temperature was shown to have a proportional effect on the mean square displacement, possibly due to the increase in the kinetic energy available to the systems. At high temperatures, the glassy siloxane molecules had similar values for the mean square displacement to those of the gas molecules since the polymer in this case is in close proximity to its glass transition temperature. The presence of the alternating oxygen atoms in the main backbone of the polymeric chains led to higher values for the selfdiffusion coefficients for the siloxane polymers as compared to those of the silane polymers as a result of the change in the bond angle about the oxygen atom (~ 144°) as compared to the tetrahedral angle (~ 110°) about the silicon atoms.