Silica gel alias: Silicic acid gel. It is a highly active adsorbent material and an amorphous material. Its chemical formula is mSiO2. nH2O. It is insoluble in water and any solvent, non-toxic, odorless, stable in chemical properties, and does not react with any substances except strong alkali and hydrofluoric acid. Different types of silica gel have different micropore structure due to different manufacturing methods. The chemical composition and physical structure of silica gel determine that it has many other characteristics which are difficult to be replaced by other similar materials: high adsorption performance, good thermal stability, stable chemical properties, high mechanical strength, etc. Silica gel is classified according to its pore size: macroporous silica gel, coarse pore silica gel, B-type silica gel, fine pore silica gel, and the like.
Dissolution method for silica gel: Silicone rubber solvent has excellent water resistance and is insoluble in water, but it can be dispersed in water in subdivided form. Some silicon rubber is still soluble in some non-polar solvents (most of which are swelling), which can be dissolved first and then emulsified into emulsion, and the solvent can be evaporated out.
General rubbers such as common neoprene, nitrile rubber, natural rubber, synthetic natural rubber, butyl rubber, etc., have a large molecular weight, and need to be reduced in molecular weight by melting rubber to be dissolved in an organic solvent. Different glues have different solvents depending on their polarity.
Polyurethane is also a rubber, but it is formed by physical crosslinking. Linear or differentially branched polyurethane resins generally require aprotic, highly polar solvents such as DMF, DMAc, and NMP.
Characteristics of rubber dissolution: Solid unvulcanized rubber can be dissolved in some organic solvents, but as a polymer material, its dissolution process is significantly different from that of solid low molecular materials. First, the dissolution process is slow and cannot be accomplished in a flash like a low molecular material. Second, the whole process is divided into two phases: first swelling and then dissolution.This time needed is particularly long.
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