Application Of NMR In Polyester Analysis--Testing For Composition And Hydroxide Value Of Polyester

In this paper, the qualitative and quantitative ananlysis of the polyesters were studied by advanced techniques of NMR. The main works and conclusions of the paper are as follows.1. The common raw materials for the synthesis of the polyesters were measured by NMR. The peaks were assigned. On the basis of their chemical shift values in theH and ' C spectra of the raw materials, the database was established.2. Typical polyesters were synthesized by using common raw materials of polyester. The synthesized polyesters were measured by NMR. The peaks in their 1H and 13C spectra were assigned. The database of the synthesized polymers was created.3. Four kinds of known polyester were selected to check the quantitative accuracy of 1H spectrum. The results showed as long as the peak which was used to calculate the contant of the component in polyester was uncovered and the the contant of the component is more than 5mol percent in polyester, the relative error was lower than 10 percent.4. Two unknown polyesters were measured by several techniques of NMR. According to the measured data of 1H spectrum, 13C spectrum, H-H COSY spectrum, HSQC spectrum , HMBC spectrum and the database , the composition and sequence of the polyester were obtained. The ratio of diacid units and diol units and their different connecting manner were also gotten.5.The chemical shift of terminal hydroxy a-H in 1H spectra was studied firstly, then a method to measure the contant of hydroxyl value was established. The method is through the testing result of a-H which was measured by internal standard method (styeren is as the internal standard) to get the hydroxy value of polyester. The relative error of this method is lower than 1% and the precision is ±0.2.On all accounts, the database of chemical shifts ( δ H and δ C) of the polyestersand raw materals were established. According to the database and several techniquesof NMR , Two unknown samples were analyzed and got the composition and sequence.These are very useful for the analysis of unknown polyesters quickly and truly. At the same time, the internal standard method of measuring hydroxy value by NMR was established. This method is simple and accurate, what's more, it can be used to measure the samples which can't be measured by chemical method and get the good results.