Renault D44 1900 Plastics - Marking Resistance (Scratch Resistance by Polishing)

The standard “Renault D44 1900 Plastics - Resistance to marking (resistance to scratching by polishing)”, developed by the French automobile company Renault, is intended to characterize the resistance to marking of plastics used in the composition of exterior body parts (bumpers) and interior trim parts (dashboards, rear shelves and similar areas);

The method described reproduces the effects obtained when plastic parts are rubbed together, come into contact with hard objects or come into frequent contact with occupants (e.g. dashboard accessories). This contact causes a local increase in gloss. Such parts may have a smooth or grained surface finish. Where necessary, they may have a decorative finish such as paint.

In principle, this test method consists of rubbing the surface of a flat sample against a metal wire attached to a marking tool. Marking the sample results in a change in the brightness of the area being tested. The sample is taken from a very flat area of ​​the part or a plate whose appearance is representative of the material to be analyzed. The tool is moved parallel to the surface of the sample and perpendicular to its length.

The marking device used in the tests consists of the following parts:

• Boyunduruk
• Hinged wire holder
• Metal wire used to rub the sample for the marking resistance test (steel wire of class SH or DH as defined in the table according to the French standard “NF EN 0,45-10270 Steel wire for mechanical springs - Part 1: Patented cold-drawn non-alloyed spring steel wire”, this wire is changed at least every 1 runs)

A testing machine is also used in the tests. An example of the machine is shown in the diagrams and photographs in the annex to the standard. The machine must be capable of moving forward and backward on the sample support with a movement amplitude of 40 mm and a speed of 0,02 m/s. It must be capable of applying a weight of 4000 g plus/minus 5 g to the marking tool. The total weight is a function of the sample width.

The following equipment is also used in the tests:

• Double-sided tape with thick adhesive (e.g. acrylic foam backing)
• Correction machine
• Air-conditioned room (set to 23 degrees plus/minus 2 degrees temperature and 50 percent plus/minus 5 percent relative humidity)
• Sliding calipers (accuracy of tenths of a millimetre)
• Gloss meter (compliant with standard Renault D25 1413 Paint coatings, plastics and rubbers - Gloss measurement (20 degrees, 60 degrees, 85 degrees))

When preparing the samples, flat samples are cut with a minimum length of 70 mm and a width of 20 mm plus/minus 1 mm, measured using a slide caliper. After cutting using a straightedge or other tool, the samples are carefully straightened. The edges of the surface to be marked should have a cross-section as shown in the figure given in the standard. The flatness of the sample in the width direction is verified using the edge of a ruler. Condition the samples in the chamber for at least 16 hours. The width of the tool should be greater than the width of the sample.

Tests are performed on five samples marked 1, 2, 3, 4, 5. The sixth sample is stored for reference.

When performing the tests, the initial brightness of the samples is measured according to the Renault D25 1413 standard (measurement angle 60 degrees). These brightnesses are assumed to be B01, B02, B03, B04, B05 and B0t, respectively.

Adhesive tape is applied to the back of the sample and the sample is attached to the mount shown in the figure:

• The position of the sample in relation to the marking tool should conform to the diagram in Annex 2.
• The marking should begin approximately 25 mm from one end of the sample.

The marking tool is prepared, 120 mm wire is cut, bent into the groove of the wire holder and attached using eccentric screws. The friction part of the metal wire should be perfectly linear.

The marking tool is attached to the end of the arm. The weight of the arm in grams is recorded as M0. The arm with the marking tool and weights is slowly brought onto the sample. The marking tool axis should be perpendicular to the length of the sample. The electric drive is operated so that the marking tool travels only once over the sample surface.

The gloss is measured on the samples marked 1 to 5 that have passed the marking test and on the reference sample according to the Renault D25 1413 test method. The values ​​obtained are assumed to be B1, B2, B3, B4, B5 and Bt, respectively.

B0t and Bt measurements are not used to express the results, they are used to ensure the measurement repeatability of the gloss test. After marking, samples with inhomogeneous surfaces are discarded. If necessary, the test is repeated to obtain at least 3 usable samples.

The absolute brightness changes of the sample, expressed in brightness units, are obtained from the formula given in the standard. The result of the measurement is the average of the absolute changes.

The relative brightness changes of each sample can be expressed as relative change using the formula given in the standard. The measurement result is the average of the relative changes.

In addition to the results obtained, the test report should include the reference of this test method, the sampling method, full references of the material tested, grain structure, colour, surface treatment, if any, and any procedural details not specified in this test method.

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 “Renault D44 1900 Plastics - Resistance to marking (resistance to scratching by polishing)” standard with its trained and expert staff and advanced technological equipment.