The gel chromatograph () combines independent innovation with international advanced technology and key components, and its product performance is leading domestically. This equipment is mainly used for the detection of molecular weight and molecular weight distribution of waterborne and oily high molecular polymers. And qualitative and quantitative analysis of sugars, alcohols, fatty acids and lipids. Gel chromatography (), also known as gel chromatography, is a fast and simple separation analysis technique developed in the early 1960s. Due to its simple equipment and convenient operation, it does not require organic solvents. High molecular weight has a high separation effect. Gel chromatography is also known as size exclusion chromatography. main application: 1 in the application of polymer production and use process a . Selection of production process The choice of process will directly affect the molecular weight of the product and its distribution. Therefore, analyzing the molecular weight distribution of different processes provides the basis for selecting the best process. The effects of three different production processes, such as tank type, tank type continuous and tower continuous polymerization, on the molecular weight distribution of polycarbonate were studied by gel chromatography. It can be seen from the figure that the polymerization products of the three different processes have little difference at the high molecular weight tail end, but the PC-62 (1) column type continuous polymerization sample has the highest molecular weight content and wide distribution. This process needs improvement. b. Control and Monitoring of the Polymerization Process Samples were continuously sampled during the polymerization reaction by gel chromatography to determine the effect of polymerization conditions on the molecular weight distribution of the product. For example, polyvinyl chloride often has microgels that affect its physical and solution properties. What is the microgel related to? Abdel-Alim used gel chromatography to study the effect of polymerization temperature on the content of polyvinyl chloride microgels. From the molecular weight distribution curve in the figure, the molecular weight greater than 8.5×105 is the microgel fraction. It can be seen that the lower the polymerization temperature, the higher the content of the microgel. When the polymerization temperature is 70 ° C, the microgel has almost no It is. Therefore, with the monitoring of gel chromatography, the microgel of the product can be controlled. c. The detection polymer during processing degrades during processing due to heat, oxygen and mechanical action. Gel chromatography was used to study the degradation of polymer during extrusion molding. The experiment was simple and rapid. It can be used to observe the difference in molecular weight and distribution of the center and surface of the sample strip under different extrusion conditions. It is impossible to do it. The figure below is a comparison of the molecular weight distribution of different parts of the polystyrene sample strip after 50% extrusion at 160 °C by gel chromatography. As can be seen from the figure, during the extrusion process, the average molecular weight of the sample decreases, and the molecular weight of the sample column surface degrades faster than its center. d. The polymer material is broken during the use of the polymer material during use due to the action of light, heat and oxygen. Hendrickson studied the aging process of polystyrene. The molecular weight distribution of polystyrene (Mw= 2.67×105, Mw/Mn = 1.08) samples after aging for 2×103 hours in the aging chamber was analyzed by gel chromatography. . It can be seen from the figure that after aging, the molecular weight distribution is broadened, the molecular weight of 40% is still in the range of the original sample, the molecular weight of 49% is lower than the molecular weight of the original sample, and the molecular weight of 11% is larger than the original sample. The molecular weight range, which may be due to the incorporation of polystyrene molecules. Gel chromatography not only examines changes in the molecular weight of the aging process but also provides data for the study of aging mechanisms. e. Product quality inspection Poly 2,6-dimethylphenyl ether (PPO) is blended with PS, ABS, etc. to form an excellent engineering plastic (MPPO). The impact strength is related to the low molecular weight content of PPO. Therefore, by measuring GPC, the quality of the product can be checked. 2 composition and analysis of high polymer and oligomer In the analysis of the polymer or monomer content in the polymer, the polymer was previously separated from the monomer or the auxiliary by extraction, and then quantitatively determined by spectroscopy or chromatography. The gel chromatography can be carried out simultaneously for the above separation and analysis, so it is convenient. Analysis of monomer content: Separation of small molecular compounds: Kato et al. used a microgel TSK-gel column with a flow rate of 0.6 ml / min, tetrahydrofuran as a rinse, and separation of polyethylene glycol oligomers within 2 h. 3 copolymer analysis In addition to the molecular weight distribution, the copolymer also has a polydispersity of composition. In the past, the composition analysis of the copolymer was troublesome. First, classification was carried out, and then each fraction was measured by spectroscopy, chromatography, etc., which was time consuming and inaccurate. The composition and molecular weight distribution of the copolymer can be determined quickly and simultaneously by gel chromatography. For a copolymer in which one component has UV absorption and the other component has no UV absorption, Tung uses a gel chromatogram with UV and differential double detector to determine the composition distribution of styrene butadiene rubber as shown in the following figure. It can be seen that the molecular weight distribution is wide but The composition distribution is relatively uniform. Insect net greenhouse also known as plant and vegetables greenhouse net. Used for prevent the insect fly into the greenhouse during the plant growing, and cover the plants. Key off the approaches that the pests (adult insect) breeding. 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Polyvinylcarbazole is an organic photoconductive material, and the presence of residual monomers can affect the useful life of the material. Ye Meiling used gel chromatography to determine the residual monomer content simply and accurately. The polymer solution containing the monomer is first separated through a chromatographic column to obtain two peaks of a polymer and a monomer as shown below. Using the external standard method, a calibration line of known monomer concentration is produced. Then, the peak height of the monomer was measured, and the content of the monomer was determined by a calibration line, and the minimum detection amount was 0.03%.
Similarly, the determination of the polymer content in the mixed solution can be carried out. At this time, a column with a small pore size is selected, so that the polymer is all discharged at the permeation limit, and a symmetrical narrow peak is obtained to facilitate quantitative calculation. The content of polyacrylamide in the oilfield wastewater was successfully analyzed by gel chromatography, and the minimum detectable amount was 0.1×10-6 (0.1 ppm).