BILITEN Knowledge Sharing: Those inconspicuous small accessories for car lights

Author: BILITEN

2025-05-09

Introduction:

Automobile lights are easily polluted by rain, oil, dust and other dirt in driving environments such as rain, high and low temperatures. Simple protection can easily affect the parts by splashing water, humidity, etc., reducing performance. The negative pressure formed by the temperature drop will absorb pollutants, causing fogging and parts failure. Rainwater infiltration will also cause some parts to oxidize and rust, lose function, and increase the safety of the car and maintenance costs.
At this time, the breathable film of the headlight plays a relatively important role.

Necessity of using breathable film for automobile lights

Many important parts of cars need to be protected by waterproof and breathable films that are waterproof, dustproof, corrosion-resistant, resistant to environmental climate change and have excellent breathability to ensure reliable performance, long service life, high stability and reduced maintenance costs.

For car headlights, fogging is easy in rainy days or high humidity environments. For some structures that are directly connected to the atmosphere, negative pressure will bring in moisture when the lights are turned off, making the fogging more serious and damaging the components. Breathable products can quickly disperse the fog and provide protection.

For other lamps such as fog lights and tail lights, although the light-emitting components have low power, the space is small, and products with good breathability and high protection performance are also required.

The waterproof and breathable principle of the breathable film of automobile lights

Based on the principle of pressure balance

During the use of the headlight, due to temperature changes, the air inside the headlight will expand and contract, causing the internal pressure to change. The breathable film allows air to enter and exit the headlight under the action of pressure difference, so that the internal pressure of the headlight is balanced with the external environmental pressure. When the internal pressure is higher than the external pressure, the air will be discharged through the breathable film; when the internal pressure is lower than the external pressure, the external air will enter, avoiding the situation where water vapor or dust is sucked into the headlight due to pressure imbalance.

Based on the microstructure of the material (taking the common ePTFE as an example)

Micropore size difference: The breathable film of the headlight is mostly made of expanded polytetrafluoroethylene (ePTFE), which has billions of micropores. These micropores are about 700 times larger than air molecules, allowing air molecules to pass through these pores freely, thereby realizing the breathable function and ensuring that the air inside and outside the headlight can be exchanged and the pressure is balanced. At the same time, micropores are about 20,000 times smaller than water droplets, which makes it impossible for water droplets and other liquid water to enter the interior of the headlight through the micropores, achieving a waterproof effect.

Based on the effect of surface tension

There is surface tension on the surface of the liquid, which makes the surface of the liquid tend to shrink and minimize the surface area of the liquid. When water droplets come into contact with the breathable membrane, due to the extremely small size of the micropores, the surface tension will cause the water droplets to form a hemispherical shape at the entrance of the micropores, making it difficult to enter the micropores.

There are mainly the following types of car light breathable membranes in terms of product form and structure:

1. Waterproof breathable membrane: It is a thin film with a microporous structure, and the most common material is expanded polytetrafluoroethylene (ePTFE). It can prevent moisture and dirt from entering the interior of the car light, while allowing gas to pass freely, which can effectively prevent fogging and condensation inside the car light, such as the waterproof breathable membrane 6812 of the ES682 and ES673 models of Weils.
2. Waterproof breathable valve: It is usually installed in the car light housing, and contains a waterproof breathable membrane inside. While ensuring the sealing of the car light, it allows air to circulate, which can adjust the temperature and pressure inside the car light and maintain the stability of the internal environment of the car light.
3. Waterproof breathable plug: It is used to fill the holes on the car light housing. The waterproof breathable membrane inside can prevent moisture and dirt from entering the interior of the car light through the holes, while maintaining ventilation and air permeability inside the car light, so that the pressure inside and outside the car light is balanced.

Based on the functional characteristics and application scenarios, the breathable film for headlights can be divided into the following categories:

1. High-permeability breathable film: Suitable for parts such as headlights that have high requirements for heat dissipation and ventilation. It can quickly dissipate fog and heat to ensure that the performance of the headlights is not affected in high-temperature environments or after long-term use.
2. Adhesive breathable film: With adhesive backing, it is easy to install in the corresponding position of the headlight and can be firmly pasted.
Ultra-thin breathable film: For fog lights, turn signals and other lamps with narrow space, ultra-thin breathable film can provide good waterproof and breathable performance without taking up too much space.

Summary

In the future, the design of car lights will develop in the direction of "slenderer, more transparent, and more functional integration", which will bring new challenges to the waterproof and breathable properties of car lights, and will also be a test for the car light manufacturing industry.

BILITEN has been deeply involved in the research and development of car headlights for many years, and has strict selection criteria for car light breathable membranes. If it is not heat-resistant, it will not be used; if it is not wear-resistant, it will not be used; if it is not breathable, it will not be used; if it is not waterproof, it will not be used. The fog lamp products that are being developed and produced use waterproof and breathable membranes, and there are special requirements for size and thickness to ensure the waterproofness and breathability of the fog lamps.

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