Titanium ester coupling agent manufacturers inform everyone of the precautions when using silane coupling agents.
According to the principle of chemical reactions, silane can only exert its coupling effect under hydrolysis conditions, but this does not mean that water must be added to the system. The water adsorbed and bound in the material and the water vapor in the air can usually meet the requirements for hydrolysis. Whether silane is pre hydrolyzed depends on specific conditions.
2. Hydrolyzed silane usually has poor stability and short shelf life, so it should be used now rather than stored for a long time. If the silane solution has obvious viscosity increase and gel like suspended precipitation, it means that most silane is invalid due to self polymerization, and this silane solution can no longer be used.
3. The solvent for silane is usually water, alcohol, or a mixture thereof, without deionized water, but never water containing fluoride ions. Alcohol is a cheap and non-toxic mixture of ethanol and isopropanol, but it easily reacts with aminosilane and cannot be used as a solvent. Toluene and ether are also alternative solvents.
4. The concentration of silane in aqueous solution should not be too high, usually below 5%, otherwise the self polymerization rate of silane hydrolysate will be significantly accelerated, which can easily cause solution stratification and affect use and storage.
5. The aqueous solution of aminosilane is generally alkaline and can be hydrolyzed directly without the need to add acid as a catalyst. However, amino silane dissolves in water and releases a large amount of heat of dissolution, so it is important to avoid burns. Non amino silane generally needs to be hydrolyzed at pH 3-5, and weak acids such as formic acid and acetic acid are usually used to adjust the pH value. However, the hydrolysis of silane must be accompanied by sufficient stirring, which can last up to 12 hours.
Below are the general principles for choosing silane coupling agents from manufacturers of titanium ester coupling agents.
The hydrolysis rate of silane coupling agents is determined by the silicon energy group Si-X, while their reactivity with organic polymers is determined by the carbon functional group C-Y. Therefore, it is very important to choose suitable silane coupling agents for different substrates or processing objects.
The manufacturer of titanium ester coupling agent said that the selection method is mainly based on experimental pre selection, which should be carried out on the basis of existing experience or rules. For example, generally speaking, unsaturated polyesters can choose vinyl, epoxy, and methacryloyloxysilane coupling agents; Polyurethane should choose amino silane. Epoxy resin should be epoxy resin or amino silane; Phenolic resin should use amino or urea based organosilane; The olefin polymer should be vinyl organosilane. Sulfur vulcanized rubber should be a hydrophobic organosilane coupling agent. The adhesion between heterogeneous materials is influenced by a series of factors such as wettability, surface energy, interfacial layer and polar adsorption, acid-base interactions, interpenetrating networks, and covalent bond reactions.
Therefore, manufacturers of titanium ester coupling agents remind everyone that experimental pre selection is sometimes not accurate enough, and it is necessary to comprehensively consider the composition of the material and its sensitivity to the reaction of silane coupling agents. To improve hydrolysis stability and reduce modification costs, trialkylsilane can be mixed into silane coupling agents. For difficult to stick materials, polymers crosslinked with silane coupling agents can also be used. When silane coupling agents are used as thickening agents, they mainly form chemical and hydrogen bonds with polymers; Wetting and surface energy effects; Improve the crystallinity, acid-base reactions, and generation of interpenetrating polymer networks of polymers.