PSA D44 1221 Velvet Surface Materials - Scratch Resistance

The purpose of the standard “PSA D44 1221 Velvet-surfaced materials - Resistance to abrasion” developed by the French automobile company Renault is to determine the resistance to abrasion of finished parts. This method is applied to flock-sprayed, needle-pile and non-woven materials, such as woven and knitted materials that form the coating of appearance parts. The test can be performed on the material as new or after wear. This method should not be applied to materials where the abrasion blade is likely to damage the piano wire.

This test consists in rubbing a worn-out piano wire blade against a planar sample placed perpendicular to it and assessing the deterioration.

Major test equipment used in these tests includes:

• The metal frame is where the block support specimen is slid horizontally.
• The motor has the following characteristics and includes a block support sample for reciprocating motion: voltage 220 V, intensity 0,2 A, couples 0,6 Nm and maximum speed 1500 tr/min. This motor is equipped with a potentiometer that allows the speed to be varied between 2 and 100 revolutions per minute. Unless otherwise stated, this speed is regulated at 20 revolutions per minute (plus/minus 1 revolution), which is the load stated in the documentation. If necessary, this is adjusted using the potentiometer.
• The specimen support block is guided back and forth in the pass. It is connected to the engine by a connecting rod-crank standard system that includes the adjustment of the race. Unless otherwise specified, this race is set to 400 mm under a load of 20g plus/minus 40g. This block is equipped with a tool that enables the specimen to be fixed.
• The blade is fixed to a movable arm and is equipped with a spirit level. The height of the arm can be adjusted using nut A, which allows the unit to be raised. The blade can be blocked on the arm using nut B. The cutting edge of the blade is equipped with a 0,45 mm diameter piano wire made of extra hard steel. The piano wire is retained on the blade by tightening it from the side and can be replaced. If any deterioration occurs in the profile of the piano wire, it must be replaced.
• The overload or counterweight system is a mechanism that allows the load specified in the standard to be reached, close to plus/minus 20 gr. The maximum acceptable load of the device is limited to 3,2 kg.
• The meter is equipped with a process paragraph that allows the movement to be stopped automatically as soon as the prescribed number of passes (outgoing and returning = 2 passes) is fulfilled.

The following test equipment is also used in the tests:

• The cutting tool is a cutting tool such as cutting punches, saws, repair knives and similar equipment that allows the sample to be cut without damaging it.
• A conditioned room is a room maintained at a temperature of 23 degrees plus/minus 2 degrees and a relative humidity of 50 percent plus/minus 5 percent.
• Mono plate balance (accuracy close to 1 gram).
• Ruler (accuracy up to 1/2 mm).

Test samples should be representative of the scale to be characterized. In order to ensure this representation, the basic characteristics of the studied population must be revealed. Selection criteria for test samples must be stated in the test report in accordance with the A10 0156 standard. In case of doubt about sampling, the PSA Group should be contacted to learn the directives to be followed.

The procedure for exiting a race while testing is taking place includes the following steps:

• Instead of the sample, a sheet of paper is applied according to the dimensions of the sample and fixed on this support sample.
• A pencil of the undercut type (E) (e.g. 0,5 mm) is firmly fixed on the axis of the worn blade and perpendicular to the support sample, ensuring that only the tip of this pencil touches the plate.
• The tip of the pen is leveled for a load of 400 g plus/minus 20 g. The counter is reset to zero to initialize the device and perform three successive passes.
• The arm is noted and the distance (D) between the extreme points of the line drawn with the tip of the pencil is measured using a ruler.
• Race C (mm) = D - E should be 40 mm plus/minus 1 mm.
• If necessary, the crank level is adjusted and the procedure is repeated.

When preparing the sample, a sample plane of approximately 70 mm length and 40 mm width is taken using the tool. At least three samples are taken for each test in each direction (transverse and longitudinal). The samples are conditioned in the chamber for at least 2 hours. For parts with a support of a rigid type (e.g. wood, plastic) with a support thickness equal to or greater than 7 mm, when possible cutting, divide the part according to the directional thickness, making the value lower or equal to 5 mm. This preparation should not change the hardness of the complex in any case.

Among the numerous tests, measurements, analyses and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the “PSA D44 1221 Velvet surface materials - Resistance to scratching” standard with its trained and expert staff and advanced technological equipment.