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The Physical Testing of Chemical Protective Clothing testing

2019-05-30 14:41
In terms of protective coveralls, Body Protection normally refers to protecting the skin from the harmful effects of chemicals– either liquids or solids. This bulletin focuses on the testing of the physical properties of the fabric that is used to make the coveralls but first we will look at the three Types of coverall generally available for protection against different levels of liquid chemical hazards. 
Each of these tests is carried out by independent specialist labs. These labs are independently assessed in order for their results to be accepted by the Notified Bodies who are authorized to issue a CE certificate for the finished coveralls. The results for each test are based on a classification system set out in EN 14325:2004. This classification system helps users select the most suitable coverall for their needs. CE certification gives users confidence that the coverall has been independently assessed as meeting the necessary Standards and that there are annual, independent checks of the production process to ensure that compliance with those Standards is maintained.
Trapezoidal Tear Strength and Tensile Strength:
These tests use the same piece of equipment to measure the strength of the coverall in Newtons. In many work situations machinery is used and there is a risk that fabric may get caught in the machine. These tests give an indication of how strong the fabric is in case a situation arose where the coverall needed to be freed from the machine.
Coveralls can easily be torn if caught on sharp edges, for example, and so these are very real practical demonstrations of the strength of the fabric. The tests are very similar in that a sample of fabric is held in a clamp at the top and bottom, and the clamps are then pulled apart to see how much strength is required to pull the fabric apart.
In the Trapezoidal Tear Strength test (EN ISO 9073-4) a sample of fabric 150mm x 75mm is cut & marked out with lines indicating where the sample is to be clamped (Figure 1). A small cut 15mm is made through the center (Figure 2). 
The sample is clamped in place along the non-parallel sides of the trapezoid with the cut half-way between the clamps. The clamps are pulled apart (Figure 3) until the fabric tears completely (Figure 4). But if the fabric has not completely pulled apart when the clamps are 64mm apart then at that point the mean strength is used for the result.
The Tensile Strength test – EN ISO 13934-1 - is very similar in principal but the size of the sample of fabric is 50mm x 250mm and no cut is made in the sample. As with the Trapezoidal Tear test this test is an assessment of the strength of the fabric.
Abrasive Resistance:
This test (EN 530) looks at the durability of the fabric because in real work situations workers often rub against other surfaces e.g. by kneeling, or elbows on workbenches. This can be a problem because:
? Abrasion can create holes which can cause inward leakage.
? Abrasion can result in linting and in applications such as paint spraying or in the pharmaceutical industry where clean rooms are often used, lint can be a problem.
In this test 4 circular samples of fabric are cut with a diameter of 14cm.
(Figure 5) Each sample is clamped onto the Martindale Abrasion machine and a downward pressure of 9kPa applied. The machine is set to carry out 10 rubs and the sample is then assessed. If there is no abrasion it is then set for a further 90 rubs i.e. 10 + 90 = 100 etc.
Classification is based on the lowest single result of the 4 samples that are tested.
Flex Cracking:
Measuring Flex Cracking is a way of assessing the flexibility of the fabric because in many industrial applications the work can be very physical and the coveralls need to be hard wearing. In work situations coveralls are worn for several hours at a time and during this time the fabric is flexed and creased many times through the natural movement of the wearer. It is important therefore to have a coverall made from a fabric that is not likely to crack and thereby create a weak point for penetration of potentially harmful dusts or liquids.
In this test samples of fabric 105mm x 50mm are clamped using metal cylinders at each end to make a roll. The center section of fabric is 36mm.
The “roll” is then fixed to a machine which has a rigid bottom row and a moveable top row (Figure 6).
During the test this top row moves up and down which causes the fabric to flex and crease. The machine is set to carry out 1000 flexes & then the sample is assessed. If there are no cracks it is then set for a further 1500 flexes i.e.1000 + 1500 = 2500 etc.
Puncture Resistance:
In many work situations coveralls may be at risk from being torn or punctured by sharp edges or tools. It is therefore important to measure the Puncture resistance of the fabric to ensure it meets minimum requirements.
A sample of fabric is clamped between two 10mm thick metal plates. Each plate has a hole in the center through which a spike is advanced on to and through the sample of fabric at a rate of 100 mm/min. The maximum force needed to puncture the sample is recorded. 


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