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What are the properties of glass fabric in epoxy insulation board?
2020-02-26

The important raw material of epoxy insulation board is glass fabric. What special properties does glass fabric have to meet the performance requirements of epoxy insulation board? We summarize the following points.

(1) Mechanical property

Glass fibric has a high tensile strength, and its strength is related to the fiber diameter, fiber length, and alkali content. The finer the fiber, the higher the strength, and the shorter the fiber, the higher the strength. The strength of the fiber increases with the decrease of the alkali content, and the strength of the fiber increases with the temperature of the glass melt when drawing the fiber, and increases with the speed of drawing and winding. The strength of glass fibric is greatly reduced after friction damage. The glass fibric is woven into a cloth. Although it is protected by a lubricant, the loss of glass strength is still large. The order of strength is: one weave and one pattern → twill → plain

(2) Permeability

Glass fibric is a cylinder without capillary structure, and the fiber itself cannot be penetrated by water and resin. In order to improve the penetrating ability, the surface area of the adsorption resin is increased. There are three measures. Pull the fiber very thin: increase the surface area of the same mass; reduce the twist of the yarn: the twist of the glass yarn has high twist, medium twist, low twist, and no twist. The filling resin increases. Laminated yarn twist is generally 40 ~ 110 twists / m, and non-twisted glass cloth is used; ③Density reduction: Density reduction is also to increase the void and increase the amount of resin filled. As the twist and density decrease, the strength of the glass fibric also decreases, but due to the increase in the resin penetration ability, the strength of the laminate increases instead.

(3) Dielectric property

The dielectric properties of glass fabric are related to the alkali content. Increasing the alkali content decreases the surface resistance and increases the dielectric loss. The effect of alkali is more significant under the condition of high temperature and humidity, but the dielectric strength of glass fibric is good.

(4) Thermal performance of glass fabric

The alkali-free glass fabric has high heat resistance, and its mechanical and electrical properties are stable below 200 ° C. Due to the lubricant on the surface of the glass fiber, the tensile strength of the glass cloth rises at 100 ~ 150 ° C. Because the lubricant is heated, the viscosity increases, which strengthens the friction protection effect on the fiber; at 150 ~ 200 ° C, the lubricant is further cured, and The tensile strength is the highest; after 200 ℃, the strength decreases due to thermal decomposition; 300 ℃ decreases to 80% of the original strength; 400 ℃ decreases to 55%; the 600 ℃ strength almost disappears. This loss of strength, which is much lower than the glass transition temperature, is related to the shrinkage caused by the ultra-rapidly formed fibers after heating. Thermal shrinkage is one of the characteristics of glass fibers. The heat shrinkage phenomenon of glass fiber (cloth) is very instructive for the production of laminated products. The combination of temperature and pressure during hot pressing should be noted. Practice has proved that the hot pressing temperature is higher than 170 ℃, and the internal temperature of thick products is nearly 200 ℃. If the pressure is not matched well, the strength will be greatly reduced. Attention should be paid to the change of steam pressure (high temperature to low temperature) during the hot pressing process and the pressure maintenance during cooling. Glass fiber performance is relatively stable below 200 ° C.

(5) Chemical resistance

Glass fibric is insoluble in organic solvents, has strong resistance to mildew, tapeworms, bacteria and decay, and is not affected by oils, most acids and corrosive vapors (except hydrofluoric acid and hot phosphoric acid).

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