"Overview of technical and commercial aspects of static and textiles" M. J. D. Dyer - DuPont 1 Westbury Lodge Close, Pinner, HA5 3FG Tel/Fax: 0181 868 4584

The application of static control with textile materials covers a broad product and market base from general apparel wear and work clothing to specialised industrial applications such as carpets, conveyor belts, filtration, car upholstery and FIBCs.

A broad overview will be made of the market for ‘Antistatic’ textile materials.

The required ‘antistatic’ performance from the textile material will vary according to the end-use application and the level of protection required.

From the end-user position, ‘antistatic’ performance will relate only to the conditions required for a particular working environment.

We are faced with the questions:

Is it possible to define ‘antistatic’ performance by a single test or test method?

Is it possible to define the performance of the textile material in isolation without defining its performance within an end-use system of application?

"Evaluating apparel used in static sensitive environments" Paul Holdstock (British Textile Technology Group, Manchester)

The presence of static electricity on apparel materials causes problems in a wide variety of industrial and domestic situations. For many of these situations there are national and international standards describing test methods for evaluating the static propensity of apparel most of which are based on simple assumptions about charge dissipation mechanisms, However, a simplistic approach is at odds with the complex nature of much of today's apparel. Electrically inhornogencous fabrics containing conducting fibres in numerous configurafions are becoming increasingly commonplace and these cannot be evaluated by simple resistance measurements alone.

A more thoughtful approach to materials testing is discussed together with a description of some test methods used at BTTG. Most of the test procedures are quite straight-forward and require only basic measuring instruments - electrostatic fieldmeters, voltmeters, oscilloscopes, etc. Tests discussed include charge decay time, charging behaviour, electrostatic discharging behaviour and body voltage measurement. In some cases one test is all that is required to evaluate a material for a particular end use. In others, more than one method may be required in order to gain a better understanding of the material. The approach to testing is sophisticated in the sense that tests are tailored to the requirements of the end user so that laboratory results can be better related to the actual in-use performance of apparel.

"Studies of charge transfer, peak voltage and charge decay on a variety of materials" John Chubb - John Chubb Instrumentation, Unit 30, Lansdown Industrial Estate, Gloucester Road, Cheltenham, GL51 8PL, UK.(Tel: +44 (0)1242 573347 Fax: +44 (0)1242 251388 email: jchubb@jci.co.uk)

Studies are described relevant to the proposition that combination of measurement of charge transfer with measurement of initial peak surface voltage and the rate of surface voltage decay provides a general way to assess materials in terms of the maximum surface voltage able to arise and the time for which the influence of charge and surface voltage remain locally available to create risks from static electricity.

"Measurement of electrostatic discharges using the transmission line probe" J. M. Smallwood (Electrostatic Solutions Ltd, 14 Courtland Gardens, Bassett, Southampton, SO16 3PP)

Electrostatic discharges are extremely fast events in which the electrical current waveform can have sub-nanosecond risetimes, peak currents of tens of amps and be over in nanoseconds. To measure such a discharge, a very fast measurement system with bandwidth of the order 1GHz is required, and a digitising rate of more than 1Gsample/s is preferred.

"Controlling static in cleanroom garments" Nigel Slater (CCA Ltd, Northolt Drive, Bolton, BL3 6RE)

Static is an ever present problem in cleanroom manufacturing operations. This discussion looks braodly at the construction of cleanroom garments and fabrics and considers existing methods of trying to avoid problems with static. Ideas and concepts are proposed for the future.

"Assessment of Electrostatic Behaviour Under End-Use-Like Conditions" Peter Ehrler, Gabriele Schmeer-Lioe (Institut fur Textil und Verfahrenstechnik, Denkendorf)

The electrostatic behaviour of textiles is not only of interest in evaluating and minimising the risks associated with electronic damage and with explosions, but also as a functional property of textiles. Textiles designed for personal protective clothing and for clean room clothing very often contain conductive yarns to control the electrostatic behaviour.

The assessment of electrostatic behaviour of such materials requires other test methods in addition to electrical resistance measurements. Several years ago a test method was developed by ITV to simulate the typical end-use conditions for garments: they become charged by rubbing and separating from other materials. This method for the determination of the triboelectric behaviour will be presented.

The ageing process of the triboelectric behaviour of multiple use garments, which begins with the first wash treatment and the influence of the washing detertgents on the triboelectric behaviour will be discussed.

"A New Method for Evaluating Electrical Resistivity of Textile Assemblies" Pellumb G. Berberi (Polytechnic Univenity of Tirana, Department of Physics, Tirana, Albania)

Abstract: A new multiple-step method for measuring electrical resistance of textile assemblies is proposed that takes compressional properties of the assembly into consideration. A new parameter is introduced to describe electrical resistivity of textile materials as the limit resistivity of a compressed fiber-assembly. This new definition approaches the measured resistance of the textile assembly as something similar to the volume resistivity of a rigid homogeneous material. Experiments carried out with different kinds of fiber assemblies clearly show that the electrical resistivity so defined is an inherent characteristic reflecting the electrical properties of fiber material and is independent of sample form (fabric, yarn, fiber)

"The control of body voltages getting out of a car" John Chubb - John Chubb Instrumentation, Unit 30, Landown Industrial Estate, Gloucester Road, Cheltenham, GL51 8PL, UK.(Tel: +44 (0)1242 573347 Fax: +44 (0)1242 251388 email: jchubb@jci.co.uk)

Getting out of a car can easily create body voltages up to 15kV and give a very noticeable shock when the car or earth is touched. Studies are reported of body voltage measurements for a number of people with various clothing and a number of different seat surfaces. It is clear that body voltage measurement and recording is required with a fast response (1/4s or better). It is shown that body voltage can be effectively limited to below shock levels by choice of seat material. The next steps will be identification of the features of seat fabric for reliable, long term and economic achievement of low body voltages for the normal range of clothing and environmental conditions. A test protocol has been developed which gives fairly consistent body voltage values on repeated testing.

"Conducting Polymers for the Production of Antistatic Textiles and Packaging Materials" P Kathirgamanathan, J Antipan Lara, S Ravichandran, M. J Toohey (Electrical, Electronic and Information Engineering, South Bank University, London, SE1 0AA, UK)

Elimination or prevention of static build-up on textiles and packaging materials is of great importance both in defence and industrial environment. We have developed solvent processable conducting polymers which are amenable for the treatment of fibres, fabrics, tubes and sheets. The surface resistance can be controlled to any pre-determined value either by molecular engineering or dilution with a variety of resin systems. Surface resistance in the range 10^{6} -10^{10} ohms can easily be achieved. We have also developed vapour phase coating methods to give a coating thickness of 100 nm - 500nm which give surface resistance in the range 10^{8} - 10^{10} Ohms.

Surface resistance and charge decay measurements will be described in detail.