Views: 0 Author: Site Editor Publish Time: 2021-07-19 Origin: Site
Silicone sealant in the application process needs to bear the displacement of the joint width caused by the external environment. This requires that silicone sealant has a good ability to withstand joint displacement, and can withstand the change of joint width for a long time without cracking. However, in the context of the current price of raw materials, there are quite a lot of silicone rubber products filled with white oil on the market. They attract users with low price, but in actual use, various performance decline is very obvious, and can not meet the requirements of the corresponding standard of sealant, which brings serious quality problems and even safety risks to users.
What is white oil?
White oil, commonly known as paraffin oil, white oil and mineral oil, is produced by regular pressure and pressure fractionation of crude oil, solvent extraction and dewaxing, and hydrorefining (Fig. 1). It is mainly a mixture of saturated naphthenes and paraffins. See Figure 1 for details. It has good oxidation stability, chemical stability, light stability, colorless, tasteless, non-corrosive fiber fabric.
The production process of white oil mainly includes sulfur trioxide refining and hydrorefining.
(1) At the end of the 19th century, foreign countries began to produce white oil, using concentrated sulfuric acid or fuming sulfuric acid sulfamation method, the white oil produced by this method is unstable in quality, low yield, large raw material loss, acid consumption is also large, a large number of acid residue is difficult to deal with, environmental pollution is very serious. Later, sulfur trioxide sulfonation technology appeared, which greatly reduced the acid consumption and improved the yield of white oil, but the environmental pollution problem was still not solved.
(2) In the early 1960s, hydrorefining technology began to be applied to white oil production. Hydrorefining technology has low environmental pollution, high yield and stable quality of white oil, and can produce high-viscosity and high-grade white oil. Since then, the quality and output of white oil have been improved by leaps and leaps.
Why do some manufacturers want to add white oil in silicone glue?
Core main reason: reduce costs and gain more benefits. Due to the high price of dimethyl silicone oil, as the sealant industry market competition is white-hot, some manufacturers in order to reduce costs, starting from plasticizer, using white oil instead of dimethyl silicone oil as a silicone sealant plasticizer, made of silicone rubber is known as "white oil glue".
White oil as a plasticizer can not only increase the gloss of silicone sealant, but also improve the extrusion speed, and the price of silicone sealant is lower than that of dimethylsilicone oil as a plasticizer. But white oil is made up of small molecule saturated alkane, low molecular weight, volatile, as plasticizers added to the silicone sealant, with the passage of time, will completely evaporate from the silicone sealant or leakage, thus losing the effect of plasticizer, eventually led to the hardness of the silicone sealant has increased dramatically, serious embrittlement occurs, even cracking phenomenon.
From the surface, these low-cost "white oil" and not filled with white silicone sealant is not much different, some products even do a good appearance, very bright, curing speed is fast, early curing mechanical properties are good. However, with the extension of use time, the difference between "white oil filled sealant" and silicone sealant without white oil will gradually appear.