PP properties for automotiva parts

The development of automobile industry is accompanied by the increase of interaction between people and cars. For this, people have higher and higher requirements for corresponding spare parts and materials.

1. Requirements for scratch resistance

Polypropylene, the raw material of automobile interior decoration parts, is relatively low in hardness. Therefore, some parts are easy to be scratched, scratched or kicked during the use of users. Over time, the surface of the parts is obviously white and very ugly. Therefore, polypropylene material must have scratch resistance.

Specific requirements: under the action of a certain load, draw 20 lines vertically on the surface of the sample with the specified knife, and then evaluate the brightness change of the marked position. Generally, the brightness change shall not exceed 1.5, i.e. △ L ≤ 1.5. The commonly used loads are 5N and 10N. Different loads can be selected according to the use part of the part or whether it is painted or not.

2. White mark resistance

When polypropylene decorative parts are assembled or subjected to external forces such as bending and impact, they often turn white, and with the passage of time, the white mark will further expand, affecting the beauty of the interior. This is what we usually call stress whitening. In order to avoid stress whitening, polypropylene material must also have stress whitening resistance.

Specific requirements: under a certain height, conduct ball drop impact test on the sample, then evaluate its brightness change and record it. After a period of time, evaluate the brightness change of the impacted part again; Then store the sample at high temperature and re evaluate the brightness change of the sample after the specified time.

3. Heat aging resistance

Due to its own structure, polypropylene material is easy to be oxidized by oxygen in the air. Especially when it is affected by light and heat, it will accelerate aging and destroy its physical and mechanical properties. It affects the service life of parts. Therefore, polypropylene materials must have the properties of heat and oxygen aging.

Specific requirements: as an interior part, it shall at least meet the requirement of no pulverization for 400 hours under the condition of 150 ℃. The experiment can use the whole part, or the part can be cut into splines and carried out in the drying oven.

4. Emission performance

People have higher and higher requirements for the air quality of automotive interior. Therefore, in order to ensure a good automotive interior environment, as interior parts, without exception, they must meet the four requirements of emission performance. The emission performance of interior trim includes odor test, formaldehyde content determination, condensation composition and total carbon emission.

Specific requirements: odor score ≤ 3, formaldehyde content ≤ 10mg / kg; Condensation composition ≤ 2mg, total carbon content ≤ 50 μ gC/g。

5. Requirements for light aging resistance

When the door is opened, the parts that users can see directly can be directly or indirectly exposed to the sun. In order to avoid discoloration, deformation and other defects caused by sunlight, the raw material itself must have the performance of light aging resistance.

Specific requirements: firstly, determine the degree of exposure to sunlight according to the specific use position of the parts, that is, whether to directly or indirectly, and then determine the exposure cycle. Under certain irradiation intensity (UV), temperature, humidity and other conditions, after a certain exposure period, the change of color fastness of the sample is required to be no more than 4 (evaluated by gray level), or △ e ≤ 1.7.

6. Anti tacking performance

With the wide application of polypropylene materials in automotive interiors, new problems have also been exposed. In the atmospheric exposure, precipitates are produced on the surface of polypropylene parts, and sticky phenomenon occurs at the same time, and the luster of the surface of parts has also changed. Therefore, polypropylene material must have the characteristics of anti sticking.

Specific requirements: simple thermal aging, sunlight simulation and ordinary interior light aging experimental conditions can not reproduce the sticky phenomenon, which can only be verified under more appropriate light aging conditions.

7. Good antistatic performance

It can be observed that after the car is used for a period of time, the surface of some parts often adsorbs dust. After a long time, the dust is not only not removed, but also getting dirtier and dirtier, which is difficult to clean. This is caused by static electricity. Polypropylene is a non-polar polymer, which has good electrical insulation and is not affected by humidity, so it is easy to produce static electricity.

Over time, the above problems will appear. Serious static electricity will also produce impact and even sparks. Therefore, polypropylene materials should also have antistatic properties. Antistatic property can be measured by surface resistance and other indicators.

8. Requirements for hand feel

When getting on and off the bus, passengers have more and more contact with cars. Take the hard plastic center console as an example. Every time they touch it, it is hard, and there are even some hands on the edge. The corresponding high-end cars usually use solid wood or piano baking paint. In contrast, they stand out. At present, car enterprises mostly promote plastic lining materials, This soft plastic feels much better.