GLOSSARY
PENETRATION Penetration is the movement of a chemical, hazardous substance or micro-organism through porous materials, seams, pinholes or other imperfections in a protective glove material at a non-molecular level. CHEMICAL DEGRADATION Chemical degradation of a glove occurs where exposure of the material to a chemical agent causes the loss of one or more of its original physical qualities. Signs of chemical degradation may include softening, swelling, brittleness, loss of flexibility, weakness, tackiness, disintegration etc. Resistance to degradation is measured as a loss of tensile strength. The loss of 30% tensile strength upon exposure to a chemical defines the maximum useful life of the glove. Resistance to degradation is usually rated on a five point scale from Excellent to Not Recommended. PERMEATION OF CHEMICALS Permeation occurs where a chemical or hazardous substance passes through an intact glove by diffusion, this can occur even if the glove is undamaged. Permeation is inversely proportional to thickness and is often expressed as a qualitative rate ie: fast, medium, slow and zero in addition to the breakthrough time. BREAKTHROUGH TIME Breakthrough time is the time it takes for a chemical or hazardous substance to pass through a glove and be detected on the inside surface of the material. It is measured in minutes and is derived from static tests carried out on a specimen cut from a glove. The test is carried out according to a standard method in EN 374- 3. Thicker gloves made from the same material will have a longer break-through time since breakthrough time is directly proportional to the square of the thickness. Breakthrough times are specific to the glove tested and gloves of the same material and thickness from different manufacturers can have different breakthrough times. This can be as a result of numerous factors including, differences in raw materials and their content in the finished product, as well as the degree of cross- bonding.
Breakthrough times are therefore effectively only ‘guides’, not hardand fast exposure times. Contaminated reusable gloves should always be washed and contaminated disposable gloves changed as soon as reasonably practicable. It is particularly important that re-usable gloves are thoroughly washed after use since residual chemicals may continue to permeate through the material in storage between ‘uses’. Where contact with chemicals has occurred gloves of any description should always be disposed off before the breakthrough time has been reached or if there is any reason to suspect the gloves integrity. In some cases gloves may even need to be discarded before the total in-use-time exceeds the breakthrough time, if permeation through to the inner surface can continue after the glove is washed.
114 I PERSONAL SAFETY EQUIPMENT CATALOGUE VOL 2
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