Epoxy resin is a kind of high molecular polymer, which is widely used in coatings, composites, adhesives and other industrial applications. Its properties are affected by its purity and composition, especially the chlorine content. This article will focus on the organochlorine in epoxy resin, its determination method, and its effect on the properties of epoxy resin.
Organic chlorine and its classification
The chlorine in epoxy resins can be divided into organochlorine and inorganic chlorine according to their existing forms. Organochlorine is a kind of heteroterminal group in epoxy resins, and has various existing forms in epoxy resins. It can be divided into two categories:
Active chlorine: also known as easily saponified chlorine or hydrolyzable chlorine.
Inactive chlorine: The opposite of active chlorine is chlorine that is not easily saponified or hydrolyzed.
When the content of organochlorine exceeds 0.01mol/100g, it will affect the curing reaction of the epoxy resin, resulting in a decrease in the mechanical properties, insulation properties, and water resistance of the coating. Therefore, from the perspective of application, the lower the content of organochlorine in the epoxy resin, the better. But as the content of organochlorine decreases, the cost of epoxy resin will also increase accordingly.
Determination of organochlorine
A special method has been developed for the determination of organochlorine in epoxy resins, especially easily saponified chlorine. The core principle of this method is to use the concentration of chloride ions generated by acidification reaction and detect them by potentiometric titration.
The specific measurement steps are as follows:
1. For non-glycidyl ester epoxy resins, mix the sample with a 2-butoxyethanol solution of sodium hydroxide and react at room temperature for 2 hours.
2. For glycidyl ester epoxy resins, mix the sample with a methanol solution of sodium hydroxide and react at 50 ℃.
3. Next, the above mixture is acidified and titrated with silver nitrate standard titration solution. By this method, we can accurately determine the concentration of easily saponified chlorine in epoxy resins.
4. It should be noted that in order to ensure the accuracy of the determination, the inorganic chlorine content in the tested sample needs to be corrected in accordance with the provisions of GB 4618.1-2008.
Effects of organochlorine
The properties of epoxy resins are largely influenced by their composition and purity. In particular, organochlorine, although its content is relatively low, has a significant impact on the properties of epoxy resins.
First of all, organochlorine affects the curing reaction of epoxy resin. The curing reaction is the key process of epoxy resin from liquid state to solid state, which is directly related to the final mechanical properties, insulation properties, and water resistance of the resin.
Secondly, the presence of organochlorine can lead to incomplete dehalogenation of hydrogen in epoxy resins, which results in the presence of compounds such as 1,2-chloroethanol in epoxy resins, which are one of the main factors affecting the performance of epoxy resins.
summarize
Epoxy resins are widely used in a variety of industrial applications. In order to ensure its performance and stability, it is particularly crucial to determine and control the organochlorine in them. With the development of science and technology, the determination technology of organochlorine in epoxy resins has become more and more perfect, which provides us with more efficient and accurate methods to ensure the quality and performance of epoxy resins.
