Which material is best for car lampshades?

  • October 10, 2018
  • Categories: Blog

Generally speaking, the car lamp is composed of mirror, lens, light source, electronic circuit, and installation accessories. PC, PP, ABS, PMMA and a few other plastic materials are the main plastic materials for automobile lampshade. But do you know how to choose these materials?

Why the car lampshade material is plastic?

There are many reasons for this. Plastic is more elastic than glass, not a severe impact on the downstream buffer will not be easily broken, even if broken on the road to passers-by animals and so on do a lot of damage. The weight is light, and the plastic lampshade is about 0.5 kg lighter than the glass lampshade. Corrosion resistance, impact resistance, high transparency, good insulation, low heat conduction, good mechanical properties, strong plasticity, easy molding, and processing.

Application of plastic in car Lampshade

1. PC (polycarbonate)

PC (Polycarbonate wiki) is widely used in automotive lampshades. According to the relevant data, PC series materials account for about 50% (weight ratio) of plastic materials in headlamp shades. In the lampshade, PC is mainly used in the lens and external light of the headlamp shade and fog lampshade.
So why the material is PC but not others? PC, polycarbonate, has excellent impact and transparency, good mechanical and electrical insulation, wide use temperature, high dimensional stability and high creep resistance. The internal structure of the lampshade results in a certain temperature difference in different parts, and the temperature of some mirrors and rings may reach 100 °to 190 ℃, so PC and PC-HT are generally selected in the selection of materials.

2. PP (polypropylene)

Most of the PP used in automotive lampshades is modified PP, which accounts for about 30% (weight ratio) of plastic materials. For example, the rear cover of the rear lampshade, the trim plate and the wire harness guide slot (PP-T20), the and the rear cover of the headlamp shade, are generally used in PP. At present, PP is the main material of headlamp shade.
PP has strong electrical insulation and chemical corrosion resistance and good fatigue resistance. It has the highest mechanical properties and heat resistance in general plastics. In addition, compared with other plastics, it also has price advantages.

3. PBT/PET

PBT and ASA modified with glass fiber can be used as the of fog lampshade. The mechanical properties are similar to PA,POM, the friction coefficient is small, the self-lubricity is good, the thermal stability and chemical stability are good, the electrical insulation is excellent, the rigidity and hardness are high, the impact is good, the dimensional stability is high, and the heat resistance is good.

4. PA

The PA used in the lampshade is usually the common screw adjustment in the PA and GF, lampshade or the bracket uses PA6 and GF or PA66 and GF. Aromatic PA has higher heat resistance and strength than ordinary PA, and some aromatic PA and glass fibers will also be used in some important regulating structures and internal supports in the lampshade.

5. PMMA

PMMA, commonly known as acrylic or organic glass, is a highly transparent amorphous thermoplastic material. The optical properties are excellent, the transmittance is 90% to 92%, the refractive index is 1.49, the weather resistance is good, the surface hardness is high and the comprehensive properties are excellent. It is mainly used as optical transparent products. The light guide material of the outer distribution light of the tail lampshade and the inner atmosphere lampshade of the car.

Why is the headlight of the car use the PC instead of the PMMA?

Both PC and PMMA have high transparency and good machining characteristics, but there are some differences in the application of lights. First of all, in heat resistance temperature, PC can generally reach 130 ℃, while PMMA is only about 100 ℃. Secondly, the toughness of PC material is better, while PMMA material is very brittle and fragile by impact. Finally, the unit price PC is higher than PMMA, and the liquidity when it is formed is not as good as that of PMMA. In general, the lampshade of the headlamp shade is PC, which is mainly due to the high illuminance of the headlamp shade, the large amount of heat emitted, and in front of the whole vehicle, which requires a material that is both heat-resistant and impact-resistant. The lampshade of the rear tail lampshade is generally PMMA, in addition to the cheap factors. The rear tail lampshade is generally a single machine energy signal lampshade combination, which requires red and transparent two colors. So PMMA with good liquidity is the best choice.

6. ABS、PC/ABS

In the field of car lampshades, ABS is generally used after being modified with PC material, and the proportion of PC content in ABS is determined according to the difference of operating temperature and impact performance. ABS, PC/ABS is generally used for rear lampshade and decorative plate.

7. BMC, PEI, PEEK, PPS, LCP and other materials

The mirror of the vehicle light mainly uses the materials such as BMC and PET. The BMC is a new material which has the advantages of thermosetting plastics and reinforcing engineering plastics. Injection molding can be uniform flow at a same time, and it can be molded once in a very short time. It also has high rigidity and strength, good molding shrinkage and dimensional accuracy stability. Based on the above characteristics of BMC, the mirror of headlamp shade generally uses BMC. The main function of the headlamp shade is to illuminate the road in front of the vehicle and ensure the normal running of the vehicle. The mirror can emit two kinds of light shapes: near light and far light, and the near light should have clear dividing line and high illuminance, so the good molding shrinkage and dimensional accuracy stability of BMC can meet this point.

The rear tail lampshade is generally made of PET, PC and other materials or directly formed from the lampshade nave. The rear tail lampshade is a combination of signal lampshade function, and the dimensional accuracy is not as high as required by the headlamp shade. However, if the reflector can be seen directly from the lampshade cover, the reflection surface on the mirror must be beautiful and must ensure the unique light shape after lighting.

The development trend of lampshade material

In the future, the lampshade will develop towards the trend of simplicity, lightweight, high heat resistance and environmental protection. For the selection of materials, the following three points are the key points to strengthen in the future:

  1. Lens material, so that the light effectively uniform scattering, high light dispersion;
  2. Heat dissipation, infrared material can be used as headlamp shade or fog lampshade;
  3. The weathering resistance of external lampshades has been gradually changed from 3 years to 5 years, and the material (coating) is required to have better weathering resistance and temperature resistance.

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