Types and characteristics of silicone release agent
1. Pure silicone oil release agent:
When the demoulding system can't contact water, organic solvent, silica and emulsifier, silicone oil can be directly used as demoulding agent and applied on the surface of the mould with soft leather or cloth. The main silicone oils suitable for demoulding agent are dimethyl silicone oil, methyl phenyl silicone oil, hydroxyl silicone oil, alkoxy silicone oil, long chain alkyl silicone oil and polyether. Silicone oil, sulfhydryl silicone oil, aminoalkyl silicone oil, phenol alkyl silicone oil, etc.
Dimethyl silicone oil was first used as demoulding agent and has been widely used in rubber, plastic moulding and precision casting industries. Its demoulding effect increases with the increase of viscosity, but its spreading and affinity to the surface of the die are not as good as low-viscosity silicone oil. Both requirements should be taken into account when selecting dimethyl silicone oil.
If solvent is allowed, dimethyl silicone oil can be diluted to 0.2%~5.0%(volume dispersion) solution and coated or sprayed to form film on the surface of the die. The solvent used for dilution shall be determined by the temperature of the die. When used in the mould with temperature below 100 C, it is better to select low boiling point solvents such as toluene and xylene; when used in the precision casting mould with higher temperature, it is better to select petroleum solvents with higher boiling point; in order to facilitate small-scale use, the solution can be loaded into a pressurized sealed tank and sprayed on the mould when used. Surface. It should be pointed out that although dimethyl silicone oil demoulding performance is excellent, after demoulding silicone oil more or less migrates to the surface of the product, which will cause trouble to the products that need to be bonded or printed. Therefore, the dimethyl silicone oil on the surface should be cleaned before the next process.
When the silicone resin in dimethyl silicone oil can significantly improve the demoulding durability, and the demoulding effect of high adhesive resins (such as polyurethane, epoxy resin, etc.) is more satisfactory.
Using dimethyl silicone oil containing OH or OR as demoulding agent, especially when shared with other components, good demoulding effect and durability can be obtained.
When methyl phenyl silicone oil is used as release agent, on the one hand, it is allowed to be used at higher temperature; on the other hand, the effect and durability of the release are obtained. Long chain alkyl (carbon atom number 8-16) silicone oil can be used as polyurethane internal release agent, which can obtain good finishing, printing and products without affecting their printability.
2. Solution release agent:
Silicone oil and additives are usually dissolved in organic solvents to produce 5%-50% of the product (volume fraction of silicone oil). As mentioned above, depending on the application of release agent, low boiling point solvents such as petroleum ether and trichloroethylene can be used as release agent for low temperature (< 100 C) mould, and high boiling point solvents such as petroleum solvent should be used for high temperature mould. Solution release agent is mainly used in situations where water is not suitable and the mould is not cooled. When casting, it can be easily sprayed or brushed on the surface of the mould. The silicone oil film left after solvent evaporation has demoulding effect. It is suitable for the moulding of rubber, plastics and resins, as well as for the casting of shell moulds. Solvent release agent has the advantages of fast volatilization of solvent, no cooling of mould and dedusting and decontamination. The biggest disadvantage is that it is easy to use less, so it is necessary to strengthen the use of site ventilation and fire prevention measures. According to the application requirements, it can be prepared from high viscous silicone oil or mixed with various solid Micro-powders such as MQ silicone resin, polymethylsilsesquioxane, mica powder, talc powder, clay and silica.
Reference: Synthesis and Application of Silicone Products