Definitions

HOMOGENEOUS MATERIAL: Material where the electrical properties of the components (threads, layers) do not differ substantially from each other, or a material which contains an intimate blend of conductive fibres.

INHOMOGENEOUS MATERIAL: Material that contains small quantities of conducting threads, which are distributed discretely in a grid pattern throughout the material; or a material that is coated or laminated with polymeric or metallic materials where the electrostatic properties of the materials differ substantially from each other.

SURFACE RESISTANCE: The resistance in Ohms as determined by using specified electrodes placed on the surface of the material.

SURFACE RESISTIVITY: The resistance in Ohms between opposite edges of a square of the material, along the surface of the material.

Why part 1?

This standard is part of a series of test methods and requirements for electrostatic properties of protective clothing. Different parts of the standard are geared towards testing various qualities required for a variety of applications and materials.

Requirements:

Samples must be preconditioned in the following atmosphere for at least 24 hours prior to testing:

• Air Temperature 23 (+/-1)°C
• Relative Humidity 25 (+/-5)%

These conditions are designed both to create a standard set of testing conditions, and to replicate possible working environments. Relative humidity has a large impact on electrostatic build-up and the surface resistance of a fabric. As a general rule, the lower the RH, the better a fabric has to perform to dissipate the same level of charge.  This is good to keep in mind when comparing fabrics tested using various methods, as certain test procedures dictate a higher RH%

Due to the way this standard has been implemented, there are two units that the result can be measured in. (these are defined in the next section)

Firstly, Resistance. The requirement is that the resistivity shall be less than <2.5 x109

Secondly, Resistivity. This is actually calculated directly from the resistance, and for this unit the requirement is that the measurement shall be less than <5.0 x 1010

These requirements are for homogenous materials (that are the same construction all the way through a cross section of the fabric) for inhomogeneous materials, e.g. coated, or laminated, the requirement is that at least one surface shall comply with the requirement for homogeneous materials.

Why is anti-static treatment important?

Materials with poor electrical conductivity, such as the synthetic fibres found in Dailys products can through normal use of a coverall build up a static charge simply through the fabric rubbing against skin or under garments.

This can lead to a build-up of negative charge on the surface of the garment.  This can prove to be extremely hazardous in certain environments, especially flammable environments, where a sufficient static charge can lead up to an explosion! Also static charges can damage sensitive electronic components.

Therefore, it is important in these environments that action is taken against the build-up of static charge.  Many of the coveralls offered by Dailys are treated with an anti-static agent which facilitates the dispersal of static charge. It is important to note that garments with an anti-static finish must be correctly and continuously grounded via conductive safety shoes, floor and/or grounding cable. If the wearer has an anti-statically treated garment, but is not grounded, the wearer will remain charged.