Vacuum water absorption rate of rubber and plastic insulation materials

Vacuum water absorption rate of rubber and plastic insulation materials

Vacuum absorption is usually used to characterize the water absorption properties of rubber and plastic insulation materials. Therefore, when immersed in water, water is only accumulated in the pores in which the surface is cut and in a small number of openings. Since the pores are small, water does not easily fill the pores, but under a certain degree of vacuum, water can quickly enter the pores. GB/T17794 stipulates that when the degree of vacuum is 85KPa, for a certain period of time, the ratio of the mass of water inhaled by the material to the mass of the material when it is not absorbed is called vacuum water absorption. The vacuum water absorption rate must be less than or equal to 10% (mass water absorption). The smaller the vacuum water absorption rate, the higher the bubble closure rate of the material and the better the insulation performance of the material.

Closed foam material refers to a material with a closed cell ratio of more than 90%. Therefore, if it is immersed in natural water, water is very difficult to enter its structure. In order to quickly test the water absorption rate of the material, the laboratory must provide testing. With a vacuum system, the vacuum water absorption rate is much higher than the water absorption rate under natural conditions.

The oxygen index of rubber and plastic insulation materials is also an important indicator, which indicates the content (percentage) of oxygen in the laboratory when the material is burned. In general, the higher the measured oxygen index, the better the fire resistance of the material. Smoke density refers to the concentration of smoke produced when an object is burned. For rubber and plastic materials, the higher the oxygen index, the harder it is to burn and the safer it is. According to the provisions of GB8627-1997, when testing the smoke density, it is tested with propane gas as gas. The rubber and plastic materials with high oxygen index have high ignition point and relatively large amount of smoke after combustion, so their MSD (smoke) The density level) is also larger.