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The effect of increasing lamellar thickness in bulk polychlorotrifluoroethylene (PCTFE) by various methods (annealing and increasing time and temperature of crystallisation) on the parameters of theα andγ relaxations has been studied.

The dc conductivity of poly(sebacyl piperazine), a polyamide prepared from the secondary diamine piperazine, in which no NH groups are present and no hydrogen bonding can occur, has been examined and compared with that of a normal 610 polyamide. The results obtained point clearly to the conduction in the 610 polyamide being electronic below about 100°C but probably involving protons as well as electrons above this temperature. This is largely consistent with the findings of earlier work and clarifies the nature of conduction below about 80°C as being almost certainly electronic where previously it was in doubt. A definite and sometimes marked hysteresis in the conductivity was observed with regard to raising and lowering the temperature of the polyamides. This is explained in terms of the space-charge polarization developed in the materials at higher temperatures and which becomes clearly evident in their dielectric behavior. This shows the importance of discharging specimens at a sufficiently high temperature before making conductivity measurements. The polarization is a bulk and not an electrode effect, and it will probably depend to a marked extent on the morphology of the polyamides.

This paper describes the measurement of the kinetic coefficients of friction between guides and nylon yarns in relation to the speed of the running yarn, the tensions in the yarn, the materials of the guides and the smoothness of their surfaces, the twist in the yarns, titanium dioxide content and the effects of lubricants and sizes. The results show that for high-twist multifilament yarns the smoothest guides give rise to the lowest frictional forces. For low-twist multifilament yarns and monofilaments, guides with rougher surfaces are essential if the coefficients of friction are to be kept low.

A laboratory apparatus has been constructed to study the pilling of fabrics. Work was concentrated on nylon and nylon blended woven fabrics. The following variables were studied; nylon content, fibre denier and staple length, yarn twist, doubling yarns, ends and picks, type of weave, milling, heat-setting, dyeing, wetting and flexing. The effects of cropping and of applying certain chemical finishes, the forces required to remove pills from fabrics and the extent to which fibres were withdrawn from fabrics under a given load were also determined.The pilling results obtained with the laboratory apparatus correlated with those obtained from small-scale wearer trials. These trials showed that the pilling of a cloth varied considerably with its end-use and that large differences can occur between individuals wearing tbe same garment.Pilling is caused by protruding fibres which entangle when a fabric is rubbed. The magnitude of the pilling depends upon the number and lengths of protruding fibres and the ease w...

The relation between anomalous charging or discharging currents and ac dielectric behavior of a material is discussed together with the use of the Hamon approximation for calculating the loss factor from these currents.The validity of the assumption used in deriving the Hamon approximation is discussed with reference to the behavior of a material with a Cole-Cole distribution of relaxation times. An analytical derivation of the Hamon approximation which has appeared in the literature is described together with a discussion of the limits of its validity. A description of the experimental methods which have been used to measure these anomalous currents (dc transient technique) is given, and experimental data in the literature showing the continuity of the loci of relaxation processes and values of loss factor from the audio frequency region into the very low-frequency region (e.g., ${10}^{\ensuremath{-}4}$ to ${10}^{\ensuremath{-}2}$ cps) is discussed.Solids often have long relaxation times at ordinary temperatures and are then suitable for examination with the dc transient technique. Moreover, the components of loss due to relaxation and conduction may be separately determined using this technique, and this is an essential prerequisite to an understanding of the different mechanisms involved. When peaks in loss factor are obtained, all the usual dielectric information may be obtained---including distribution of relaxation times, activation energy and entropy for dipole orientation, and dipole-moment values for the structural units involved.

Many aspects of our physical understanding of the electrical properties of polymers are very limited, with consequent disagreement amongst research workers about their interpretation. Critical discussion of these differences can only be helpful, and a suitable forum was provided at the Polymer Physics Group's two day conference at UWIST in Cardiff on 18–19 September.

The dielectric α relaxation arising from segmental motion in polydimethylsiloxane and polyphenylmethylsiloxane has been studied in the audio frequency region and at lower frequencies using d.c. step response measurements.The macroscopic decay function for polyphenylmethylsiloxane conforms with the empirical relationship ϕ(t)= exp –(t/τ0)β, 0 < β⩽ 1.