What is PTFE microporous film? What is the waterproofing principle of PTFE microporous membrane? What is the waterproof principle of PTFE composite fabric? The price of PTFE composite fabric
What is PTFE microporous film? What is the waterproofing principle of PTFE microporous membrane? What is the waterproof principle of PTFE composite fabric? Price of PTFE composite fabric
PTFEWaterproof mechanism of microporous membrane
In the capillary tube formed by the micropores of the polytetrafluoroethylene film , the liquid-gas interfacial tension of the meniscus surface will be added to the capillary liquid column. According to the Lapus equation, the additional pressure P is:
P=YLG (1/p1+1/p2)
Formula: YLG Surface energy or liquid-gas interfacial tension at the interface between liquid and gas, usually called surface tension, 200CWater is 0.0725N/M;
P1, P2 Curvature of the two axial directions of the curved surface Semimenstrual period.
For cylindrical capillary holes, p= P1= P2 Then there is: P=2yLG/ P Because: p=r/cos In the formula: r-capillary equivalent semi-radius; θ-the advancing contact angle between the inner wall of the capillary and the liquid, the value of PTFE is 1180. P is positive outward, so we have: P =2yLGcos / r
From the above formula, it can be found that the influence of polytetrafluoroethylene The main factors that determine the resistance of microporous films to water pressure are the diameter r of the micropores and the contact angle. When 900﹤ ﹤1800, the larger it is, the higher the water pressure resistance is. The advancing contact angle between the inner wall of the micropores of the polytetrafluoroethylene microporous film and water is 1180, the receding contact angle is 910, and the contact angle is 1040 is the largest among various materials; the smaller r, the higher the water pressure resistance. The micropore diameter of PTFE microporous film is very small, only a few tenths of a micron. Therefore, the water pressure resistance is very high, and the hole diameter is smaller than that of small raindrops, which cannot directly penetrate.
In addition, the surface energy of PTFE microporous film is very Low, the contact angle of water on the surface of the PTFE microporous film is around 1200, so its wettability is extremely poor; the PTFE film itself has a certain mechanical strength and is slightly weak when subjected to pressure. The holes are not easily squeezed, which is beneficial to improving water pressure resistance.
Theoretically, water pressure resistance has nothing to do with film thickness, but in practice On the other hand, the thinner the film thickness, the lower the mechanical strength, which can cause a decrease in waterproofness.
The calculation results also show that when the capillary is in a vertical position, The influence of gravity caused by the height of water accumulation on the film surface (the same order of magnitude as the thickness of the PTFE microporous membrane) can be ignored.
What is obtained is a polytetrafluoroethylene film The micropores in are simplified to the cylindrical capillary model formula. The formula shows that when the advancing contact angle between the inner wall of the capillary tube and the liquid is greater than 900, the water entering the capillary tube is subject to the liquid-gas interfacial tension to form an additional outward pressure. Therefore, to make water pass through the micropores, a force greater than the resistance caused by surface tension is required. When r=1um, the calculated P is about 72.5kPa, that is, less7.2mThe external pressure of the water column can make water pass through the capillary pores;��That is to say, for a polytetrafluoroethylene microporous film with a hole diameter of 1um, the theoretical pressure resistance value is 72.5kPa. Considering that the micropores in the PTFE microporous film are not actually a straight channel, but the channels form a network structure within the film, the actual test value should be greater than the calculated value from the theoretical model.
This article is excerpted from [China Composite Fabrics Networkwww.tpu-ptfe.com] Please indicate when reprinting.
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