SU741116A1 - Method of determining oxygen-containing groups in oxidized polymer - Google Patents

Description

one

The invention relates to methods for studying polymers and can be used in laboratory practice to determine oxygen-containing groups in an oxidized or mechanically treated oxygen (air) polymer.

Known methods for determining oxygen-containing groups are mainly chemical (method of esterification, isocyanate method, method of titration, etc.) and spectral (IR spectroscopy UV spectrophotometry).

One of the most widely used methods at present is the method for determining oxygen-containing groups from the IR absorption spectra of fl. This method is universal, simple, low laborious. Determination of oxygen-containing groups by this method includes the preparation of various types (solutions or films of an oxidized polymer are used as samples), the acquisition of IR spectra, and the analysis of spectra based on reference data. The described method has a limited n1-gnny limit of sensitivity.

The closest technical solution to the present invention is a method for determining oxygen-containing groups by the IR absorption spectra at the deep stages of oxidation of polymers (at a relatively high concentration of 2).

Known methods are not sensitive enough.

The purpose of the invention is to increase the threshold sensitivity of the method for determining oxygen-containing groups in an oxidized polymer by IR absorption spectra without altering the instrumentation of the process and without increasing its labor intensity.

Claims (2)

This goal is achieved by dissolving the polymer under study in a hydrocarbon solvent having a low affinity to this polymer, obtaining and analyzing the infrared spectrum of low molecular weight polymer fractions that were dissolved in the process. The method is based on the fact that oxygen-containing functional groups formed in the polymer upon oxidation or in as a result of mechanical action in the environment of oxygen (air), are predominantly terminal. Therefore, their concentration in nizomolecular fractions, characterized by an increased concentration of the ends of the macromolecules, is always higher than in the gross polymer. Example 1. The proposed and known methods determined the presence of oxygen-containing groups in the SKMS-ZOARK rubber powder & a variety of rubber (average particle size 0.34 mm) obtained by mechanical grinding of the block rubber in a hammer cork at 2 ° C in an air atmosphere. In the determination of oxygen-containing groups by the proposed method, low molecular weight fractions were separated from the test gross polymer by dissolving it in a solvent having a low affinity with this polymer. N-hexane was used as a solvent. The dilution of SKMS-ZOARK in n-hexane at a temperature of 20 ° C is 8% (determined experimentally). Samples (films 30–35 microns thick) were prepared by Si casting a solution of low molecular weight polymer fractions in n-hexane on NaC substrates, followed by evaporation of the solvent. When determining the oxygen-containing groups according to known methods, the film of the studied gross polymer was prepared by casting toluene solutions of powdered rubber on a NaCE substrate (SKMS-ZOARK is almost completely dissolved in toluene). The IR spectra were obtained on an IKS22 instrument in the range of 5000-700 cm. Analysis of the IR spectra showed that the absorption corresponding to the presence of oxygen-containing groups (a clear absorption band of O, 25) was observed only 171O cm L.M.T. obtained by the proposed method. Obviously, the concentration of oxygen-containing groups in the gross polymer is so small that it cannot provide the level of absorption necessary for the fixation by the device upon detection of oxygen-containing groups by a known method. Example 2. By the proposed and known methods, the presence of oxygen-containing groups in SKMS-ZOARK powder rubber, obtained by mechanical grinding of SKMS-ZOARK rubber previously purified from antioxidant (by extraction with acetone), was determined. The sequence and nature of operations for obtaining IR spectra by the proposed and known methods was the same as in Example 1. The analysis of the obtained IR spectra showed that the absorption at 1710 cm in the gross-spectrum spectrum takes place (this is due to that the oxidation processes, when grinding cleared of antioxidant rubber, proceed with much higher intensity. However, the absorption band at 17 IU cm is weak, not sufficiently clear, its optical density is determined with a low accuracy of 0.11). In the IR spectrum obtained by the proposed method, the absorption band at 1710 cm is strong enough to determine the optical density with a high accuracy of UCN. The given examples show the advantage of the method over the known. The proposed method, firstly, allows determining the presence of oxygen-containing groups in an oxidized (mechanically treated in an oxygen environment) polymer when their total concentration (in the gross polymer) is very small and not sufficient for the appearance of noticeable absorption bands in the infrared. spectra; secondly, it increases the reliability of determining the absorption band in the IR spectra more intense. The application of the proposed method allows to increase the threshold sensitivity of the determination of oxygen-containing groups without increasing the sensitivity of the spectrophotometer and without increasing the complexity of the determination. Claims A method for determining oxygen-containing groups in an oxidized polymer by IR "absorption spectra, characterized in that, in order to increase the threshold sensitivity of the determination, the traced polymolecular polymer is dissolved in a hydrocarbon solvent having a low affinity for this polymer, is obtained and analyze the IR spectrum 57411166 low molecular weight 1. Analytical Chemistry Polymer polymer fractions KAIN G., t. 2, M., Mir, 1965i Istochiiki. information, 2. Wagap ae K-J.ppe, .Sci, 19b8, taken into account in the examination of j V. 12, no. 6, p. 1459-1469 (prototype) with. 244.