Titanate coupling agent manufacturers tell you the precautions for using silane coupling agents and how to choose them
Titanate coupling agent manufacturers tell you the precautions for using silane coupling agents.
1. According to the principle of chemical reaction, 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 in the material and the water vapor in the air can usually meet the requirements of hydrolysis. Whether or not the silane is prehydrolyzed depends on the specific conditions.
2. Hydrolyzed silanes usually have poor stability and short shelf life, so they should be used now instead of long-term storage. If the silane solution has obvious viscosity increase and gel-like suspension precipitation, it means that most of the silane has failed due to self-polymerization, and this silane solution can no longer be used.
3. The solvent of silane is usually water, alcohol or their mixture, without deionized water, but never use water containing fluoride ions. Alcohols are cheap and nontoxic ethanol and isopropanol, but they react easily with aminosilanes and cannot be used as solvents. Toluene and diethyl ether are also alternative solvents.
4. The concentration of silane in the aqueous solution should not be too high, usually below 5%, otherwise the self-polymerization speed of silane hydrolyzate will be significantly accelerated, which will easily cause solution stratification and affect use and storage.
5. The aqueous solution of aminosilane is generally alkaline and can be directly hydrolyzed without adding acid as a catalyst. However, aminosilane dissolves in water and releases a lot of heat of dissolution, so care should be taken to avoid burns. Non-amino silanes generally need to be hydrolyzed at pH 3~5, and the pH value is usually adjusted with weak acids such as formic acid and acetic acid. However, the hydrolysis of the silane must be accompanied by adequate agitation for long periods of up to 12 hours.
The following titanate coupling agent manufacturers tell you the general principles for choosing silane coupling agents.
The hydrolysis rate of the silane coupling agent is determined by the silicon energy group Si-X, and the reactivity with the organic polymer is determined by the carbon functional group C-Y. Therefore, it is very important to select the appropriate silane coupling agent for different substrates or processing objects.
The titanate coupling agent manufacturer said that the selection method is mainly pre-selection through experiments, which should be carried out on the basis of existing experience or rules. For example, in general, vinyl, epoxy and methacryloxy silane coupling agents can be selected for unsaturated polyesters; amino silanes should be selected for polyurethane. Epoxy resin should be epoxy resin or amino silane; phenolic resin should be amino or urea-based organosilane; olefin polymer should be vinyl organosilane. The sulfur vulcanizate should be a hydrophobic organosilane coupling agent. The adhesion between dissimilar materials is affected by a series of factors such as wettability, surface energy, interfacial layer and polar adsorption, acid-base interaction, interpenetrating network and covalent bond reactions.
Therefore, titanate coupling agent manufacturers remind everyone that the experimental pre-selection is sometimes inaccurate, and it is necessary to comprehensively consider the composition of the material and its sensitivity to the reaction of the silane coupling agent. In order to improve the hydrolysis stability and reduce the modification cost, trihydrocarbyl silane can be mixed into the silane coupling agent. For difficult-to-stick materials, a silane coupling agent-crosslinked polymer can also be used. When the silane coupling agent is used as a tackifier, it mainly produces chemical bonds and hydrogen bonds with the polymer; wetting and surface energy effects; improve the crystallinity of the polymer, the acid-base reaction and the formation of the interpenetrating polymer network.