Summary: Recently, many peers and clients have consulted about poor sealing of doors and windows, problems such as leaking rain on rainy days, wind entering on windy days, loud noise from street facing windows, and excessive dust on windows. In fact, the sealing of doors and windows is a very systematic overall issue. If there is an appeal problem, one can consider whether the sealing strip effectively meets the sealing design requirements of doors and windows. The most problematic issue is whether the quality of the sealing strip has aged. Many people think that the sealing strip I chose is made of * * material - EPDM sealing strip, which is definitely not a problem, but in reality it is not.

In 2018, our company conducted a survey, testing, and analysis of the EPDM sealing strips currently on the market, and the result was only four words: "Chaos is rampant", with chaotic prices and quality. After a short period of use (1 to 3 years), quality issues such as hardening, lack of elasticity, and surface stickiness of the sealing strip may occur due to material aging. In fact, the service life of high-quality EPDM sealing strips will not be less than 20 years. Products that have problems in a short period of time are actually low-cost, poorly made products. But even high-quality products will gradually age over time until their sealing performance deteriorates, which is an irreversible law of any substance.

Many people do not know the fundamental reason for the aging of EPDM sealing strips. The following article will conduct an internal mechanism analysis of the aging problem of EPDM rubber strips.

1. The effect of heat

Raising the temperature can cause thermal cracking or cross-linking of EPDM rubber products. But the basic function of heat is still activation. Improving oxygen diffusion rate and activating oxidation reaction to accelerate rubber oxidation reaction rate is a common aging phenomenon - thermal oxidative aging.

2. The function of oxygen

Oxygen undergoes a free radical chain reaction with rubber molecules in rubber, causing molecular chains to break or over crosslink, resulting in changes in the properties of EPDM rubber products. Oxidation is one of the important causes of rubber aging.

3. The reason for light

The shorter the light wave, the greater the energy. The high-energy ultraviolet radiation has a destructive effect on rubber. Ultraviolet radiation can not only directly cause the breakage and cross-linking of rubber molecular chains, but also generate free radicals in rubber due to the absorption of light energy, triggering and accelerating the oxidation chain reaction process. Ultraviolet radiation has a heating effect. Another characteristic of light action (different from heat action) is that it mainly occurs on the surface of rubber. Samples with high adhesive content will exhibit network cracks on both sides, known as "outer layer cracks".

4. The role of ozone

Ozone has much higher chemical reactivity and greater destructiveness. It also causes molecular chain breakage, but the effect of ozone on rubber varies depending on whether the rubber deforms or not. When used as rubber for deformation (mainly unsaturated rubber), cracks appear in the direction of stress, known as "ozone cracking"; When applied to deformed rubber, only an oxide film is formed on the surface without cracking.

5. The role of water

The role of water has two aspects: EPDM rubber products are prone to damage when exposed to humid air, rain, or immersion in water. This is because water-soluble substances and water droplets in the rubber are extracted and dissolved by water. Caused by hydrolysis or absorption. Especially under the alternating action of water immersion and atmospheric exposure, it will accelerate the damage of rubber. But in some cases, moisture does not have a destructive effect on rubber, and even has a delaying effect on aging.

6. Other reasons

Chemical media, valence metal ions, high-energy radiation, electricity, and biological factors can also accelerate the aging of EPDM rubber products.