With the promotion of silicone sealant production technology and the intensification of competition between enterprises, some manufacturers use white oil instead of dimethicone oil as a plasticizer for silicone sealers in order to reduce costs. The use of a large amount of white oil instead of silicone oil in silicone sealants has the consequence of greatly reducing many properties of silicone sealants, such as weather resistance, high and low temperature resistance, and the performance of high-performance silicone sealants. As a result, the performance and service life of the previously highly durable, high-performance silicone sealant are greatly reduced. After this kind of white oil sealant is used in engineering, it has poor aging resistance, large volume shrinkage, and is prone to cracking, brittleness and hardening of the sealant, which affects the sealing and appearance of the curtain wall and even causes serious engineering accidents.

Dimethicone is a colorless and odorless transparent liquid, its molecular formula is mainly composed of dimethylsilicon, and its structure is very similar to that of the base polymer of silicone sealants, so it has good compatibility with the base adhesive. Dimethicone oil is odorless, non-toxic, non-volatile, and has good chemical stability. With little viscosity change over a wide temperature range, high boiling point and low freezing point, it can be used for a long time in the range of -50 ~ 200°C. Dimethicone has good electrical properties, especially in various frequency ranges. It has low surface tension and excellent shear resistance. Due to these properties, dimethicone is particularly suitable for use as a plasticizer and thinner in silicone sealants.

In the application of silicone sealant, considering the needs of construction, it is often necessary to adjust the viscosity of the sealant, reduce the viscosity of the adhesive, improve the construction fluidity and lubricity of the adhered object, so dimethyl silicone oil is selected as a plasticizer. At the same time, the addition of plasticizer can also improve the comprehensive properties of the cured adhesive layer, and improve the impact resistance and fatigue resistance of the adhesive joint.

On the other hand, the addition of plasticizers can also have an impact on the other properties of silicone sealants. Generally, with the increase of plasticizer dosage, the tensile strength of silica gel will gradually decrease, and the elongation at break will gradually increase. The reason for this is that the addition of non-reactive dimethicone plasticizers reduces the number of junctions between the polymer molecular chains, resulting in a decrease in cross-linking density and ultimately a decrease in tensile strength. In addition, the decrease of cross-linking density reduces the stiffness of the three-dimensional structure, and the molecules are prone to slip, resulting in an increase in elongation at break. In addition, it was also found that with the increase of plasticizer dosage, the adhesive strength of silicone generally decreased. The reason is that the plasticizer used is a non-reactive plasticizer, which has a dilution effect on the active molecules of silica gel, which will cause the number of active groups per unit volume to decrease.

In order to adapt to the larger-scale development of construction in the future and maintain the market growth of silicone sealants, enterprises should continuously improve product quality, enhance sustainable development capabilities, and jointly adhere to industry self-discipline and standardize the market. Dimethicone oil has been widely used in silicone sealants as a plasticizer, and the performance of silicone sealants will be greatly reduced by replacing silicone oil with white oil. In engineering use, the use of white oil sealant should be refused, and silicone oil sealant should be selected.

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