New requirements for O-ring PTFE coatings

2021-09-28   Pageview:123

1. Automatic assembly
Rubber parts must be processed so that they can be separated without problems and the assembly process can be carried out smoothly.

2. Silicone-free and paint wetting free
In painting technology, all rubber parts must be treated to ensure paint adhesion.

3. Reduce friction
Depending on the application area, stick-slip phenomena and high separation forces should be prevented.

4. Chemical resistance
Swelling and dissolution of rubber parts should be prevented.

 

 

 

 

 

 

 

 

 

 

The gelatinized surface layer is the outer layer of the film. When it starts to solidify, the viscosity will increase, and there is also a viscosity gradient. The viscosity of the surface layer is higher than that of the inner layer, which significantly reduces the tendency to allow bubbles to burst. The coating formula tends to form a highly viscous, anti-sagging surface coating film. This is an airtight surface condensed film.

Through the surface transfer and the electrostatic repulsion between the inner and outer layers of the coating film, they have a self-healing ability. The overall viscosity delays the speed of bubbles gathering and migrating to the surface, making it difficult for bubbles to burst. On the basis of the basic characteristics or influencing factors proposed by Gibbs to explain the thermodynamic stability of foam, Berger and Gast studied the surface properties of some water-based paints that are difficult to defoam. They discussed the blistering phenomenon of water-based coatings, which was stabilized due to the following five factors: ①surface potential; ②surface transfer; ③surface state: ①surface viscosity; ⑤overall viscosity

Defoaming mechanism
1. Natural defoaming
The essence of foaming is unstable. Its destruction is first to rise from the inside of the liquid to the liquid level, and then go through the redistribution of bubbles, the thinning of the film thickness and the rupture of the film to achieve natural defoaming.
When a bubble rises from the inside of the liquid to the liquid surface, according to S to ks’ law, its rising speed is proportional to the square of the bubble radius and inversely proportional to the viscosity of the liquid.
V~
(3-5) This means that for bubbles of the same size, the higher the cat degree of the liquid, the slower its rising speed. For a specified liquid system, its viscosity is fixed, and the rising speed of large and polyethylene wax bubbles is fast. Small bubbles rise slowly, so large bubbles are helpful to eliminate.

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