Testing, testing: Shear Test

In this month’s Testing, testing, we look at the Shear Test; what it’s for and how it’s done.

What is it used for?

The test is used to assess the shear strength of an adhesive on textile or resilient floorcoverings.

 How it’s done:

  1. Six samples of the floorcovering measuring 50mm x 100mm are bonded to a piece of plywood of the same dimensions- the bond area measures 50mm x 50mm.
  2. During the test period, half of the samples are kept at a constant temperature of 23°C for 28 days.
  3. After this time period, the lateral shear force it takes to pull the floorcovering from the plywood must measure at least 400 newtons per millimeter (N/mm).
  4. The other half of the samples are kept at a temperature of 50°C for 42+7 days, to represent a floorcovering being on the floor for 12 months.
  5. The floorcoverings are then ‘pulled’ off the plywood using a tensometer.

 What’s next?

The lateral shear force it takes to pull the floorcovering from the plywood is measured and has to have reduced by less than 25% in between the two sets of readings, to pass the test.