Resistance to surface wear

 

 

Principle
The test measures the ability of the decorative surface of the laminate under test to resist abrasive wear-through to the sub-layer. Abrasion is achieved by rotating a specimen in contact with a pair of loaded cylindrical wheels covered with abrasive paper. The wheels are positioned so that their cylindrical faces are equidistant from the specimen’s axis of rotation but not tangential to it. As they
are turned by the rotating specimen they abrade an annular track on the specimen’s surface. The numbers of revolutions of the specimen required to cause defined degrees of abrasion are used as measures of resistance to surface wear. This test is not applicable to flooring grade laminates.

Materials
a. Calibration plates of rolled zinc sheet, (Taber S-34 or equivalent)
b. Abrasive paper strips
c. Double-sided adhesive tape, required only if the abrasive paper has no adhesive backing.

Apparatus
a. Test machine, as specified in ISO 9352.
b. Conditioning chamber, in accordance with EN ISO 291, with a standard atmosphere of (23 ± 2) °C, relative humidity (50 ± 5) %.

Test specimens
Each specimen shall be a piece of the laminate under test, shaped to fit the type of clamping device used. It will usually be a disc of diameter about 130 mm, or a square of about 100 mm with its corners rounded to give a diagonal of about 130 mm, and it will usually have a hole of diameter 6 mm in its center. Three specimens shall be prepared.

Preparation of specimens and abrasive paper
a. Clean the surface of the specimens with a non-hazardous organic solvent which is miscible with water. Using a suitable marker pen, mark the surface of each specimen with two lines mutually at right angles so that the surface area is divided into quadrants.
b. Precondition the specimens and the abrasive strips for at least 72 h in the conditioning atmosphere before testing. After preconditioning seal the paper strips in suitable polythene bags (maximum 10 strips per bag) until required for immediate use.

Procedure
a. Preparation of abrasive wheels
Bond a strip of preconditioned unused abrasive paper (see 10.2.2) to each of the rubber covered wheels, using either the adhesive backing, if present, or the double-sided adhesive tape. Ensure that the cylindrical surface is completely covered, but without any overlapping of the abrasive paper.
b. Calibration of abrasive paper
Prepare two abrasive wheels with preconditioned unused strips of abrasive paper from the batch to be used for testing. Clamp a zinc plate (see 10.2.1) in the specimen holder, start the suction device, set the revolution counter
to zero, lower the wheels and abrade the zinc plate for 500 revolutions. Wipe the zinc plate clean and weigh to the nearest 1 mg. Replace the abrasive paper on the wheels with preconditioned unused strips from the same batch, clamp the same zinc plate in the specimen holder, lower the abrasive wheels and operate the suction device. Abrade the zinc plate for an additional 500 revolutions, then wipe it clean and reweigh it to the nearest 1 mg. Its loss in mass shall be (130 ± 20)
mg. Any batch of abrasive paper which causes a loss in mass of the zinc plate outside this permitted range shall not be used for testing.
c. Abrasion of specimen
Perform the test immediately after removal of the specimen and calibrated abrasive paper from the preconditioning atmosphere.
Prepare two wheels with preconditioned unused abrasive paper from the same batch previously approved by calibration. Fit the wheels to the machine and set the revolution counter to zero.

Clamp the specimen in the holder, ensuring that the surface of the specimen is flat. Lower the abrasive wheels on to the specimen, start the suction device and begin abrading the specimen. Examine the specimen for wear after each 25 revolutions and examine the abrasive paper for clogging with abraded particles. Replace the abrasive paper if it becomes clogged, or after 500 revolutions, whichever happens first. Continue the test in this way until the initial wear point (IP) is reached. Record the number of revolutions and resume the test until the final wear point (FP) is reached. Record the number of revolutions again.
The initial wear point (IP) is that point at which the first clearly recognisable wear-through of the print, pattern or plain colour appears and the sub-layer becomes exposed in three quadrants. The initial wear point is reached when there are areas of at least 0,60 mm2 wear-through in two quadrants and
an area of 0,60 mm2 wear-through becomes visible in a third quadrant.
The sub-layer for printed patterns is the background on which the pattern is printed; for plain colors it is the first sub-layer of different colour 1) 2).
The final wear point (FP) occurs in the case of a patterned laminate when about 95 % of the pattern is removed in the abraded area, and in the case of a plain-color laminate when an under layer of a different color is exposed over about 95 % of the abraded area.

Expression of results
Calculate the wear resistance, expressed as a number of revolutions, for each specimen using the following equation:
The initial wear point (IP) for the sample under test shall be the average of the IP values obtained on the three specimens.
The resistance to surface wear of the laminate under test shall be the average of the wear resistance values obtained on the three specimens, rounded to the nearest 50 revolutions