The standard “VW PV 3930 Abrasion in humid, hot climate (outdoor)”, developed by the Volkswagen automobile company, describes a procedure for testing the ageing behavior (e.g. change in color and gloss) of plastics, elastomers, convertible fabrics and paint and similar coatings when exposed to air and sunlight. This procedure is carried out by artificial abrasion in a humid, hot climate.
For certain applications, ageing criteria may consist of changes in mechanical properties or cracking. Therefore, additional tests may be required in addition to visual assessment and color and gloss measurements. These tests may include, for example, tensile tests, determination of impact strength, determination of hardness, and microscopic examinations.
During this procedure, the samples are irradiated using a xenon arc light and are periodically moistened. The spectral radiation components of the xenon arc light are adapted to the ultraviolet and visible light in the global radiation by means of filters. The tests on the instruments are carried out according to Method A of the standard “ISO 4892-2 Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon arc lamps” or according to Method A of the standard “ISO 16474-2 Paints and varnishes - Methods of exposure to laboratory light sources - Part 2: Xenon arc lamps”. Each of the test conditions defines an annual cycle related to the average ultraviolet (UV) radiation dose (300 nm to 400 nm) in humid, hot climatic zones.
Light exposure devices used in tests must comply with ISO 4892-2 or ISO 16474-2 standards or have been tested by means of comparison tests with existing systems in this standard. To ensure comparable test results between the supplier and the purchaser, the type of device to be used in each specific case should be selected in consultation with the materials development and materials engineering departments.
The weathering conditions should be taken from the table given in the standard. To ensure compliance with the test temperatures, the test devices should be installed in a temperature-stabilized test chamber (18 degrees to 25 degrees) as specified by the manufacturer. The use of flatbed devices is only permitted for testing entire parts or components (e.g. headlights) after agreement with the purchaser's materials development and materials engineering departments.
Samples shall be taken from a representative point on the finished part to be tested or from test panels produced under production conditions with the same surface (e.g. coating, grain, coating structure) and shall be documented by photographs. Samples shall be as flat and of equal thickness as possible. The sampling direction of the reference sample and associated samples shall be marked in a weatherproof manner (e.g. by cutting a notch on the side of the sample considered to be the top). For coated samples, the coating thickness shall be determined and documented.
The sample size depends on the maximum test surfaces that can be compressed into the original sample carriers.
Filter systems should be checked and cleaned regularly.
The end point of the weathering cycle is achieved after a test period/irradiation dose specified in the table. In order to ensure a uniform irradiation intensity, it must be checked and corrected regularly with a measuring device suitable for this purpose. The irradiation device must be calibrated with a radiometer according to the manufacturer's specifications. The maximum operating time of the lamps specified by the manufacturer must be observed. However, the operating time can be extended by performing calibration measurements with suitable systems.
To avoid deposits on the samples that may make evaluation difficult, distilled or deionized, silicate-free water with a conductivity of not more than 0,2 µS and an evaporation residue of not more than 1 ppm should be used. Spray water should be drained directly and not returned to the reservoir.
For a given ultraviolet (UV) radiation intensity and radiation dose, the end of the wear cycle is reached after a certain test period. To ensure uniform radiation intensity, it should be checked regularly with a suitable measuring device. Radiation devices should be calibrated with a radiometer according to the manufacturer's specifications.
Before evaluation, the sample should be measured cleaned and uncleaned. In coated samples, an area should be reserved for cross-cut testing in the cleaned area. Approximately 1/3 of the sample should be left uncleaned for later analysis.
High gloss surfaces must be cleaned in accordance with this standard. If cleaning is not sufficient, the previously cleaned area must be polished with polishing cotton and a specific polish. Other surfaces such as grained or matt surfaces must also be cleaned in accordance with this standard. Hard coating systems may only be cleaned to remove dirt but must not be polished.
Our organization, which has been trying to support businesses from every sector with its wide range of testing, measurement, analysis and evaluation studies for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services in accordance with the "VW PV 3930 Wear in humid, hot climates (outdoors)" standard are also provided to businesses.
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