Application of common analytical instruments in the research and development of coating resins

0 Introduction
In the process of research and development, production and application of resins for coatings, how to shorten the research cycle and avoid unnecessary losses is a matter of great concern to every person engaged in resin research and development, production and application. With the rapid development of instrument analysis methods, fully functional, computerized analytical instruments have been widely used. Also in the research and development, production and application of coating resins can also use these analytical instruments to obtain analytical data, and from these data to determine whether the design of the formula, production process is reasonable, product quality meets the requirements, so as to guide the research and development of coating resins, production and application purposes
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kinds of analytical instruments, but in the research and development of resins for coatings, production and application of a higher degree of application of the instrument mainly has chromatography, spectrometer, thermal analyzer. This paper will explain some specific examples of analysis, introduce several commonly used analytical instruments in the basic research of synthetic resin, reaction method research, applied research and raw material analysis, production process control, quality inspection of finished products and other aspects of the role.
1 chromatography
1. 1 Separation principle
chromatography is actually a physical separation technique. Using the difference in the distribution coefficients between the components in the mixture between the fixed phase and the flow phase, the separated components are separated in the fixed phase for different retention times, so that the different components are washed away from the flow phase in a certain order. This technique, which separates the components of a mixture by distributing differences between two phases, is called chromatography.
1. 2 Application range of various chromatography
Chromatography methods are available in a variety of types, generally divided into two categories according to the state of the flow phase: gas chromatography (flow phase is gas) and liquid chromatography (flow phase is liquid). Gel chromatography is a kind of liquid chromatography, but its separation principle is completely different from other chromatography, and to measure the relative molecular mass of polymer and its distribution as the main use, so it is often discussed separately.
1 is a different chromatography applicable to different relative molecular mass ranges.
1 shows that when using chromatography for analysis, the appropriate chromatography analysis instrument should first be selected according to the relative molecular mass of the sample.
1. 3 Gas Chromatography (GC)
1. 3. 1 Scope of application
to the general gas chromatography, in addition to the above requirements of relative molecular mass <400, should also be a good thermal stability of volatile organic compounds, generally refers to the boiling point ≤350 degrees C of the compound, that is, can vaporize the compound.
1. 3. 2 Application example
(1) Raw material inspection
GC is currently the best method for testing all types of volatile organic raw materials because it can quickly and efficiently separate and quantify compounds with boiling point ≤ 350 degrees C.
commonly used in (1) pure analysis of single solvents and mixed solvents: such as alcohols, ketones, ethers, esters, benzene solvents, heavy aromatic solvents, pine-saving oils, solvent gasoline, etc. (2) Purity analysis of reactive monosomes: e.g. various acrylic monogies used in the synthesis of acrylic resins, styrene; A variety of isocyanate monosomes, etc. Figure 2 is a GC diagram of acrylic hydroxyl propylene.
as shown in Figure 2, the peak reserved for 1.715 m in is acrylic hydroxypropylate, while the remaining peaks are the peaks of volatile impurities in the sample. This kind of analysis is the most common application of GC in the quality control of coating resin production, the method is mature, can carry out qualitative and quantitative analysis.
(2) water content (including trace and constant water content)
water content in various samples, GC is also the most convenient method. Generally choose the thermal conductivity detector, polymer microball as a fixed phase. In order to improve the accuracy of the analysis results, trace amounts of water in organic solvents generally use the legal quantity of external standard, with benzene-water saturation solution as the standard water sample. Constant water is mostly based on the internal standard legal quantity, isopropyl alcohol as the internal standard. Standard test methods have been developed, such as A131 1 in Appendix A in GB18582) 2001.
(3) Quality Control of the production process
The resin synthesis of volatile raw materials can be determined by tracking the content of the remaining raw materials or residual monosomes after the reaction, and the degree of reaction can be determined, according to which the rationality of the synthetic route can be judged. Such as synthetic acrylic resin, polyurethane pre-polymer, etc.
test method: At the beginning of the reaction, sampling determines the amount of the reaction to be tracked, sample the amount of the reaction at a certain interval of reaction time, and then calculates the conversion rate.
(4) quality analysis of the finished product
whether the residual volatile monosome in the synthetic resin meets the relevant standards or the requirements of the unit of use, GC analysis can obtain satisfactory results. The most typical examples are the national standard for coating samples of the limit of tribenzene content, free TD I limit, synthetic resin emulsion residual monosome limit, etc. are using GC analysis.
specific test methods can be found in the following standards: GB 18581) 2001 interior decoration material solvent-based wood coating hazardous substances limit: tribenzene content determination; GB /T18446) 2001 gas chromatography to determine unresponsive toluct toluene diocyanate (TDI) monomers in aminomethylate pre-polymers and coating solutions; H J/T201) 2005 environmental mark product certification technical requirements: water-based coatings, volatile organic compounds (VOCs), benzenes, halogenated hydrocarbons; GB/T20623) 2006 Architectural Coatings Emulsion: The Sum of Residual Monosomes.
In fact, many test method standards for GC analytical coatings and raw materials for coatings have been developed at home and abroad, such as ISO 11890) 2B2000 paint and varnish - determination of volatile organic compound (VOC) content (Part 2): gas chromatography; ISO10283B1997 color paint and varnish with paint-polycyanate resin monosomediocyanate determination. The American Society for Material Testing (ASTM) has more standards, which are listed here.
1. 4 High-efficiency liquid chromatography (HPLC)
The biggest difference between H PLC and gas chromatography is that the flow phase is liquid. High boiling point, medium relative molecular mass, heat-prone organic compounds, strong polar compounds, ion-type inorganic compounds, biologically active biomoleuries can be analyzed. It is generally believed that organic compounds with a relative molecular mass of less than 2,000 can be analyzed using liquid chromatography. However, due to its high operating costs (flow phase for a variety of chromatography levels of liquid), the operation of cumbersome, limited applications in the coatings industry.
, but for some high boiling point and strong polar organic compounds in synthetic coating resins, HPLC analysis and testing is a convenient, fast and accurate method. such as polyols (three (2- hydroxyethyl) isocyanate (THEIC), trihydroxymethyl propane, etc.), polyaccharides (benzoic acid, etc.), polyethylene polyamines (diethylene triamine, triethylene tetamine, tetraethylene pentaamine, etc.); Heat-prone polymerization compounds (acrylamide and N-hydroxymethylene acrylamide, etc.); Additives (phthalates, additives with relative molecular mass between 300 and 2,000, etc.); The amount of blockers in various acrylic monomers, etc.
1. 5 Gel Chromatography (GPC)
Gel Chromatography is a kind of liquid chromatography, the separation principle is different from other chromatography, is separated by the size of the molecular volume, so it is also known as the volume of chromatography. The relative molecular mass of the sample can be found with the help of GPC/Correction Curve 0. Includes the number of relative molecular mass M n, the mass of relative molecule mass Mw, the dispersion coefficient of the dispersion of the sample of the expressive polymer A: A s Mw/M n
1. 5. 1 Determining the significance of relative molecular mass and its distribution
The strength, mechanical properties, thermal stability, processability and solution properties of polymers are closely related to the average relative molecular mass and distribution of polymers. The film-forming substances of coatings are basically polymer polymers, and their relative molecular mass and distribution data play an important role in studying and guiding formulation design, selecting the best synthesis process, and further studying and improving the physical properties, construction properties and control product quality of coating resins. As a result, GPC is widely used in synthetic resins.
1. 5. 2 Application examples
(1) determination of relative molecular mass and its distribution
assay of relative molecular mass and its distribution are the most common uses of GPC. From the relative molecular mass distribution curve, we can know the average relative molecular mass value and dispersion degree of various statistics.
International Organization for Standardization (ISO) has developed standards for testing resins for coatings:
ISO 13885 paint and varnish paint base - gel chromatography, Part I: Tethydrofuran as a gonorrhea; Part II: Methamphetamine is a gonorrhea; Part III: Water is a gonorrhea.
when analyzing a sample with LC (including GPC), the sample should be completely dissolved in the flow phase, so choose which flow to consider accordingly its solubility to the sample.
commonly used resins for coatings, such as acrylate resins, acrylic resins, epoxy resins, amino resins, polyurethane resins, hydrocarbon polymers, nitroculose, etc., as well as some raw materials such as greases, additives, etc. can be used as flow phase.
(2) Quality Control the relative molecular mass and distribution of
film resin is one of the important factors affecting its quality performance, so product quality can be controlled by measuring the relative molecular mass and distribution of resin.
3 shows the relative molecular mass and distribution determination of HDI trimers. Table 1 shows the average relative molecular mass and dispersion coefficient of HDI trimers in 4 batches.
GPC spectral of H DI trimers in
4 batches
the average relative molecular mass and dispersion coefficients of HD I triple polymers in 4 batches

GPC method for quality control, first of all to determine a good performance and suitable for the intended use of the material, with which to determine the GPC's standard spectral map, and then compare the spectrum of each production batch, to achieve rapid quality control. This method of comparing the relative molecular mass distribution curve is very practical for the quality control of the training product and can be used as the quality inspection method of the batch product.
(3) storage stability
changes in mass during sample storage can also be observed by measuring relative molecular mass and its distribution. These situations are often not easily detected by traditional quality control methods, and GPC can help solve such problems.
(4) Synthesis Process Research
Has been reported in the article ≤ 2) , using GPC to determine the relative molecular mass and distribution of polymers, can be used to show the distribution of lyonum and other compositions in crosslinking reactions relative molecular mass distribution, check whether the reaction is thorough. In fact, these studies take materials with different reaction times during testing, measure their relative molecular mass and distribution, and then analyze the measurements to adjust resin formulations and synthesis processes accordingly.
qualitative analysis of the components of the base material (5)
Since GPC is a chromatography method, it has the function of separation, so it is also a complementary means when the expressive modified resin is mixed or co-clustered. Figure 4 is the GPC analysis of the epoxy silicone resin system.
GPC spectrogram of an epoxy silicone resin system
the sample is analyzed as an epoxy silicone resin system using infrared spectroscopy. However, infrared spectroscopy is not easy to determine whether it is physical mixing or chemical change, GPC analysis shows that the physical mixture of the two resins.
above, the choice of chromatography to analyze the sample research, mainly depends on the relative molecular quality of the sample being analyzed and the purpose of analysis. If it is a volatile compound, and the boiling point is ≤ 350 degrees C, and to analyze its composition and content, the general choice of gas chromatography; If it is not easily volatile, the thermal stability is poor, and the relative molecular mass of < 2000 compounds, the choice of liquid chromatography to analyze its composition and content>;
2 spectrometers
commonly referred to as spectrometers refer to mass spectrometers, MRI spectrometers, infrared spectrometers and ultraviolet spectrometers, these four spectrometers are currently the most important method of organic compound structure identification. However, due to the solubility of resin-like polymers, in fact, more infrared spectrometers are used in the structural analysis and reaction pathology of resins used in coatings. This is because the infrared spectrum is highly characteristic of most substances, the measured sample can be solid, liquid and gas, not limited by the state of the object under test, organic, inorganic, polymer, etc. can be measured and can reflect the absorption of the organ group, so it can be from the change of the reactive organ group reaction structure research, but also suitable for the curing of the coating film.
2. 1 Infrared spectroscopy (IR)
2. 1. 1 Basic Principles
infrared spectroscopy is based on the interaction between infrared electromagnetic radiation and chemical substances, thus studying the relationship between the frequency of infrared characteristic clusters and molecular structure.
wavelengths of the infrared spectrum range from 0.78 to 1,000 um, and are divided into near-infrared, medium-infrared and far-infrared, depending on the frequency range measured.
the spectrum measured by each band of the infrared spectrometer and its range of application