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Scratch resistance test performance and influence of modified plastics معدات اختبار

Author: Released in:2022-12-07 Click:31


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With the rapid development of China\'s economy, cars are becoming more and more popular, and car inspections are also being systemized and standardized. The scratch resistance test is an important indicator for the quality control of automotive interior and exterior plastic parts. Here, Shanghai Qianshi mainly introduces the principle of the scratch resistance test, the classification of the scratch effect, and its performance and influence.

Automotive decorative parts should be selected according to their function, application environment and conditions required for production and shaping, combined with the characteristics of plastic raw materials. suitable raw materials. Polymer materials are widely used in the automotive industry, but parts made from polymer materials are prone to severe scratch damage, making itscratch problem the main research object. The scratch damage experiment of polymer materials is conducted Analysis, the influence of material and structural composition on scratches was evaluated.

Principle of plastic scratch resistance test

The basic principle of plastic scratch resistance test is scratching The rubbing head works with a certain pressure on the surface of the sample and the scraper head and the test sample move at a certain speed relative to each other. The trajectory is generally a straight line or a circle. When the material is not strong enough to withstand external scratches, plastic deformation occurs and the surface of the material is damaged. destroy. According to the basic principle of the scratch test, factors such as the scratch head, the load (pressure), and the relative motion state of the sample and the scratch head fundamentally determine the method of the scratch resistance test. First of all, hThe material, shape and size of the crab head are the key factors to determine the scratch test method. Different tests generally correspond to different crab heads. Common scraper heads are hemispherical or spherical steel materials, which meet certain hardness requirements after heat treatment, with a diameter of 1mm, 0.75mm or 0.5mm; second, the load is the pressure exerted by the scraper head on the surface of the material. It is also a very critical parameter characterizing the severity of the test. Different scratch resistance test methods have different load methods, such as weight load, lever load and compression spring load, etc.; Conditions, the state of the relative movement of the scraper head and the material, such as speed and stroke, are relatively minor parameters. In the early scratch resistance test, manual operation was mostly used, and the test speed consistency could notare guaranteed. However, with the continuous development of instrumented scratch resistance test equipment, the test speed can be kept constant in principle, and the repeatability and reproducibility of the test can be improved. improve.

Effect of material and surface parameters on scratch performance

Polymeric material scratch Performance experiments and we felt the need to use finite element digital simulation technology as a tool was high. The influence of the surface parameters of the molecular material, so the influence of the melon barn performance according to the surface parameters of the material is as follows: First, the influence of Poisson in the material on the scratching of the material is negligible. The scratch performance of polymer materials is not necessarily related to the elastic modulus of the material, but the material with the larger elmodulus of elasticity is more influenced by the scratch resistance under the influence of temperature. Increasing the yield of the material can reduce plastic deformation and improve the scratch resistance of the material. The smaller the coefficient of friction of the surface of the polymer material, the better the scratch performance. The surface structure of polymer materials has a great influence on the coefficient of friction, and its shape can be changed to improve the scratchability of the material. However, the texture of the surface can play a good role in hiding scratches, which has a great reference value for repairing the surface of the car. In the analysis of material and surface parameters, it is very important to strengthen the material composition of scratch resistance.

Factors Affecting Scratch Resistance

Referring to the scratch resistance of plastic,many technicians will always think of the surface hardness of the material. "Sturdy enough is king". In fact, that is not the case. Over the last 20 years, a large number of studies have shown that it is still an elusive luxury to completely solve this problem.

Due to the great diversity of knowledge about scratch resistance, there are also various factors that influence the scratch resistance. Such as the mechanism of scratch fracture, the effect of load and scraper shape, test temperature, viewing angle, polymer viscoelasticity, stress hardening, sample color, surface texture, treatment method, light scattering, tensile yield stress, compressive yield stress and many more. Taking ASA resin as an example, using the ASTM D7027 scratch resistance test method with increasing load, the resin has undergone three processes of groove deformation, periodic micro-cracks and plow marks during the scratching process. When the groove deformation starts atthe pressure generated by the normal load exceeds the compressive yield stress of the material itself, causing the surface of the material to collapse and the scratch depth curve and the material surface curve to begin to deviate. As the depth of the groove increases, it reflects light adjusted to the human eye, so that the appearance of scratches is visually perceived. This process is usually between the two stages of groove deformation and periodic cracking. When the applied normal stress increases to a certain extent, the tensile stress applied to the surface of the material parallel to the scraping direction at the rear end of the scraper head will increase by an order of magnitude, resulting in the formation of cracks. For ductile materials, it usually appears as fish scales, while for brittle materials, it appears as microcracks. At the later stage of taxationIn addition, a huge tensile stress perpendicular to the scraping direction, due to the puncture and the slippage of the front end of the scraper, will have a cutting effect on the material accumulated in front of it, and the scraper will penetrate further into the resin. and scraping material.