The analysis method of unsaturated polyester is to use the polyester in the resin and the dilute cross-linking agent sharply, then saponify the ester group, and then separate the acid and alcohol parts, and then use the qualitative method or quantitative method to determine.
The method of separating the polyester from the cross-linking monomer from the resin is mainly to use a liquid that is insoluble in polyester (such as petroleum ether) to precipitate the polyester from the monomer solution.
In order to separate the two parts of acid and alcohol in the polyester, the precipitated polyester can be dissolved in benzene or acetone again, and saponification reaction is carried out with an anhydrous alcohol solution of about 0.5mol/L. The potassium salt of dibasic acid is insoluble and can be separated from the solution by filtration. The filtrate contains polyhydric alcohols, which can be reserved for further use. The alcohol component can be identified by infrared spectroscopy. The isolated dibasic acid can be further analyzed qualitatively or quantitatively. Paper chromatography can also be used to identify alcohol and acid components.
In addition, ammonium chloride can be used as a catalyst to reflux with benzylamine. The resulting dibenzylamine is used to separate the saturated and unsaturated components with a selective solution, and then identified and determined with an infrared spectrometer. If there is only a small amount of polyester, the untreated resin can also be directly analyzed by infrared spectroscopy.
For the cured resin, ammonium chloride can also be used as a catalyst to degrade it with benzylamine, or with KOH in benzyl alcohol. Then the structure and composition are determined by spectroscopic analysis.
In recent years, proton nuclear magnetic resonance has been used to study the composition and structure of the resin, which can quickly analyze the resin and clarify the components contained in the resin