A Laboratory Protocol to Assess the Electrostatic Propensity of Protective-clothing Systems

Abstract

The ability to predict the electrostatic propensity of textile systems has been an elusive goal for many years. Some small-scale test methods previously reported were found to be inadequate for certain conditions. One of the most serious problems is poor correlation between test measurements and the values of electrostatic discharges from a clothed person in real-life situations.This paper describes the development of a laboratory protocol to evaluate the electrostatic properties of clothing sy.stems. Four small-scale tests were evaluated and compared in order to select a protocol that could best assess the static propensity of protective-garment systems worn by workers in hazardous environments under dry conditions. Several two-layer fabric systems that included non-FR (non-fire-retardant) cotton, as well as thermal-protective fabrics of aramid fibre/carbon, aramid fibre/PBI (polybenzimidazole) fibre, aramid fibre/FR viscose, and FR cotton, were tested. Experiments were conducted at room temperature and 0% and 20% relative humidity (r.h.). Fabrics were evaluated in terms of both peak discharge potentials and charge decay. These peak potentials and charge decays were compared with data from human-body experiments, and significant coefUcients of determination (/f') of up to 0.99 were found when results from difTerent tests were regressed on human-body data.It therefore .seems that measuring peak discharge potentials and charge decays from charged-fabric .systems and peak discharge potentials from a capacitor hy using a battery of test methods can be sufficient to assess, with high accuracy, the static behaviour of garment systems in real-life conditions.

Comments on methods for charge decay measurement

“…A modification has been proposed to the above approach [10] to try to simulate the risk from the charging of an unearthed person's body while wearing personnel protective clothing. An isolated pick up disc has been mounted as a backing support for the sample with 220pF capacitance to earth.…”

“…Several methods for measurement of 'charge decay' are described in 'standard' documentation and in published literature [3][4][5][6][7][8][9][10][11][12]. The methods are very different, do not in general agree with each other and in general do not provide the information likely to be useful for uninitiated or unskilled users because they are susceptible to the construction of the materials tested.…”

Elektrostati̇k Boşalim İçi̇n Etki̇n Bi̇r Yaklaşim; Esd Koruyucu Gi̇ysi̇ Ve Öneri̇len Gi̇ysi̇ Topoloji̇si̇ni̇n Performans Anali̇zi̇

“…İletken malzeme 2 boyutlu analiz sonucu, Poliimid (ε r =3,5) Maksimum yük düzleminde elde edilen voltaj değeri (V), 5 Gelecek çalışmalarda, bu çalışma kapsamına alınmamış senaryolarda analizlerin gerçekleştirilmesi; giysinin yıkanması ile iletken malzemede oluşacak paslanma, yalıtkan malzemeden oluşacak aşınma vb. etkilerin ESD koruyuculuk özellikleri üzerinde etkilerinin incelenmesi hedeflenmektedir.…”

“…1950-2000 yılları arasında yapılmış olan çalışmalar, ESD'nin gerçekten de soğuk ve düşük rutubetli ortamlarda bir ceketin veya süveterin hızlı bir şekilde giyilmesi/çıkarılması, bir laboratuvar önlüğünün hızlı bir şekilde bir iskemlenin üzerine bırakılması gibi olağan hareketler sonucunda bile oluşabildiğini göstermiştir [3][4]. Farklı davranış tiplerinin veya cisimlerin neden olduğu ESD etkileri literatürde ilgi görmüş olup; genelde ölçüm sonuçlarından elde edilen bulgulara göre nem miktarı, Tablo 1'de de görüldüğü üzere oluşan gerilimi etkilemektedir [5]. Örneğin polietilen döşeme üzerinde yürüme, yüksek nemde 250V gerilime sebep olurken bu değer düşük nemde 12000V'a kadar çıkmaktadır.…”

“…Tablo 1. Farklı davranış/hareket tiplerinin veya cisimlerin neden olduğu ESD etkileri [5]. (ESD effects resulting from different actions and motion types [5])…”