The development of infrared spectrometer and its application direction in the coating industry

1 - Introduction
infrared spectroscopy (IR), also known as molecular vibration rotation spectra, is a molecular spectrum. The first generation of infrared spectrometers, which began to be used in the 1950s, were spectroscopic based on the dispersion of infrared radiation by prisms, which were made of alkaline metal halide crystals, which were easily moisture-absorbing, requiring strict constant temperature and humidity, low resolution, high cost and many disadvantages. With the development of grating engraving and engraving technology, infrared radiation in the 1960s completed spectroscopy through the diffraction of the grating, resulting in the second generation of infrared spectrometers
China
. Although it has the advantages of high energy, high resolution, cheap price and low temperature and humidity requirements for the instrument, the common disadvantage of these two generations of instruments is that scanning speed is slow, at least a few minutes to make a spectral map, far from meeting the needs of reaction dynamics research.
Fourier Transform Infrared Spectrometer was introduced in the 1970s. It is based on the principle of photocodych, the interferometr infrared spectrograph, unlike the dispersion infrared spectrograph based on the refraction and diffraction of light, known as the third generation infrared spectrometer.
when the Fourier infrared transformation spectrometer is used in a computer, its sensitivity is increased by 2 to 3 multispectral stages compared to the second generation grating spectrometer. Fourier transforms the characteristics of the infrared spectrometer as follows.
(1) Measures faster
the mirror scans once for about a second, while a scan contains information about all wavelengths of infrared light from the light source, hundreds of times faster than the dispersive infrared spectrometer. It can track fast in-place chemical reactions, can detect on-line gas chromatography and liquid chromatography separation samples, experimental chromatography and infrared spectrum.
(2) High sensitivity
Fourier transforms the original data measured by the infrared spectrometer when a beam of mixed light interferogram, the entire beam is detected at the same time, the signal strength is high. At the same time, the number of scans can be adjusted to increase the signal strength and noise ratio. Since the sample absorbs a certain value when the signal is absorbed, and the noise is random within a certain range, the signal of the average noise becomes weaker and weaker as the number of scans increases.
(3) Spectral peak positioning is accurate
Fourier Transform Infrared Spectrometer can make multiple measurements of the same sample at different times without the need to use reference sample measurements to determine the exact location of the spectral peak.
(4) high resolution
strong resolution between adjacent peaks, can reach 0- 5cm-1 or less.
(5) measurement range is wide
the spectrum of the entire infrared region (10,000 to 10 cm-1) can be studied by changing the appropriate split sensor and light source.
2 - Fourier Transform Infrared Spectrometer (FT IR) is evolving towards
- - FTIR is moving from a large research-grade instrument to a small penetration level, which is to meet the general daily infrared analysis, so that the price from extremely expensive gradually into low, to produce a series of different models of products to meet the requirements of different users. Another direction of development of FT IR is combination, which is divided into two ways: one is to expand the spectral range of the instrument itself. Replace light sources, beam splitters, detectors, etc. in the optical path and get information on the same FT IR in the full spectrum of 15000 to l0 cm-1 infrared. The operation of the replacement element is very simple, through the computer automatic lying and correction, in a few minutes can complete the replacement work, and ensure the reliability of the instrument. The second way is to connect other instruments or sample accessories to the spectrometer through various interfaces, so that the analytical samples get more information. Originally used as a GC union, the compositions in the GC can be analyzed directly for qualitative analysis. There is also an interface to connect the visible-UV terrometer to the same computer. In recent years, a thermal heavy interface has been developed, allowing FT IR to be used in a joint way with TGA to directly analyze the thermal weight loss components. In addition, FT IR is now able to use EGA (degassing analysis), LC (liquid chromatography), S FC (supercritical jet chromatography) and T LC (thin layer chromatography), which solves the problem of mixing sample separation and shortens the analysis cycle of mixed samples. In order to further expand the field of infrared spectroscopy analysis, to solve the problem of infrared analysis of trace samples and treatment samples, a large number of sample accessories have been developed in recent years. In addition to the earlier beam focuser, ATR, mirror reflection and other accessories, the recent emergence of light-acoustic spectral accessories, the use of light-acoustic effect, without the need for special samples can be analyzed difficult samples. Infrared microscopes are designed specifically for the effective analysis of trace and precious samples and are of special significance to the work of the Tribunal. As we all know, infrared analysis in the sample making process is the most taboo is water, in order to determine the composition of aqueous solution samples, designed a cylindrical body reflector, it can effectively analyze water quality samples like milk. In addition, there is a diffuse device that can obtain a good spectral map from trace samples, such as the analysis of micrograms of components in LC and TLC separation components. The automatic sampler can be automatically sampled 100 times without anyone operating. Work around the clock to improve laboratory efficiency.
, the current FT IR is moving in the direction of increasing productivity and expanding the scope of analysis. In the future, the analytical laboratory will need only to purchase an FT IR that can be online with the above instruments and have sufficient sample accessories, i.e. it will basically meet the requirements of the analysis of organic matter, and it will be the most powerful tool of the
organic analysis laboratory.
3 - FT IR Spectroscopic Analysis Application Directions in the coating industry
- - Coatings are organic substances in a flowing or powdery state that can be evenly and firmly covered on the surface of an object and are dried and cured to form a tough continuous coating film that protects and decorates the object being applied to increase its durability and aesthetics. Early coatings were made of vegetable oil and lacquer from lacquer trees, so they were called paint. Contemporary due to the continuous progress of science and technology, the development of petrochemical industry, more and more applications of synthetic resin to make paint, so that the paint's product structure, performance, variety of quality have undergone fundamental changes, the scope of application is more extensive, almost replaced vegetable oil, so the name of the paint is more accurate.
with the development of market economy, foreign paint products into the domestic market in large numbers, on the whole, China's paint industry and foreign advanced level of the gap is obvious. In order to narrow this gap, in the increasingly fierce market competition occupies a place, enterprises are paying more attention to the development of new products and the introduction of technology digestion and absorption; At the same time, coating production and application enterprises also pay more attention to the quality management of coating products. To this end, the application of modern analytical methods must be strengthened. Although there are many methods to achieve the above-mentioned purposes, but the infrared spectrometer because of the high characteristics of most substances, the sample can be solid, liquid, gas, not subject to the state of the subject, organic, inorganic, polymerized stations, etc. can be measured, easy to analyze and operate, fast and so on, thus becoming the preferred analytical instrument for coating analysis. Huang Ning used an infrared spectrometer to analyze and identify the various parts of the PVDF fluorocarbon coating, and how to determine the content of PVDF resin in the coating, and illustrate it by example. Using an infrared spectrometer to analyze the curing process of polyurethane coatings, Shen Hao, Yu Quansheng, and Li Xiaolan analyzed the curing process of polyurethane coatings, measured their curing degree and curing speed at 120 - and determined that their curing conditions were 120 - 􀀂 30min. Based on the results of infrared spectral analysis, the experience formula for calculating the curing speed of polyurethane coatings is derived. Fey za Karasu and others studied the photo-trigger polymerization of polyfunte acrylates with real-time Fourier Transform Infrared Spectrometers, in which 2-ton ketones ithropoacetic acid and 2-(pyrethyl methoxygen) ton ketones were used as single-group photoretic triggers. These single-group natural triggers fade in the air. The total fade irradiation time of 2-ton ketones ithion acetic acid and 2-(methyl methyl) ton ketones was 240s and 540s, respectively.
FT IR Spectroscopic Analysis Application Directions in the Coatings Industry:
3-1 - Development of existing software packages
(1) Development of quantitative analysis packages and utilization of near-infrared zone multivestity information. The most commonly encountered hydroxyl, amino hydroxyl groups in the coating substations, often overlap in areas 3600 to 3200 cm-1. The development of quantitative analysis software package, the use of curves to be legal, guidance method, and even the use of refrouting and other methods can make the mixing peaks separate, quantitative analysis of resin table or curing process of hydroxyl, ammonia changes. Using the multi-frequency information of hydroxyl and amino in the near-infrared region, it is also expected to solve the quantitative problem of this kind of official group.
(2) multi-part quantitative analysis software package, it is expected to improve the efficiency of coating analysis. General coatings in addition to containing inorganic pigments, fillers, paint-based and additives to form a complex organic mix, separation is very difficult, especially the use of very small amounts of additives difficult to quantify, easy to lose, multi-group quantitative software package is expected to solve such complex problems.
(3) developed spectroscopic retrieval procedures to help us accumulate spectra of polymers and additives commonly encountered in the coatings industry, providing the basis for long-term work in the future. Make full use of the standard map in the instrument spectrum library, quickly find the unknown spectral map, gradually get rid of the working state of manual
improve the efficiency.
(4) the development of multi-component qualitative software packages, in fact, how to use good differential spectral tools, this differential spectromet technology is also quite difficult, the mixture system should have a certain information base, the user's correct analysis and judgment will put forward higher requirements.
3- 2 - In association with other instruments
(1) and GC for reaction dynamics studies. For example, in the process of co-polymerization reaction, the exact content of the components in the co-polymerization product is analyzed quantitatively by measuring the aggregation rate of each monomer in the process of co-polymerization with GC. It can be learned that the use of GC is an important means of analysis.
(2) with T GA to effectively determine the exact composition of each weight loss in the paint mix. The use of thermal balance can also measure the proportion of each part of the paint, for color paint can also measure the color base ratio and so on.
(3) is used in association with TLC and is mainly used to analyze coatings. The organic mix in the coating is directly qualitatively identified by FTIR after TLC separation, simplifying the analysis procedure and shortening the analysis time.
3- 3 - Develop applications for a variety of sample accessories
(1) infrared microscopes through which the operator can observe small samples that are not visible to the naked eye. For example, the multi-layer coating film under the microscope, can push the coating one by one into the sample optical path test infrared spectra, avoiding the difficult stripping work, especially for car accidents, crime tools on the micro coating analysis has brought great convenience and reliability. The nearest infrared microscope can not only do the transmission spectrum of the sample, but also do the reflection spectrum, prevent the substrate interference with the coating, and make an ideal spectra layer by layer.
(2) acoustic spectroscopy attachments usually do not require sample making, and putting the sample directly into the photosonic pool can make a spectrogram, making it ideal for highly scattered surfaces or optically opaque samples. For example, paint dry film and high-polyp balls, etc., can also be used to analyze pigment surface treatment agents. By adjusting the frequency of sound waves, it enters different depths of the sample. Even two different varnishes can be coated together to form a dry film can be measured separately. Therefore, for the analysis of such difficult samples, the optical and acoustic spectroscopy is of great significance.
(3) reflective attachment in a cylinder is characterized by the ability to make water-like samples. High concentrations of water have no effect on spectral analysis, which is necessary for the study of water-based coatings. For water-based coatings, strong absorption of water appears in the infrared spectra due to the combination of water, masking the absorption peak of the parts. If the water-based coating is made into a dry film, the molecular structure changes, the spectral defense rate also decreases, it is difficult to identify, making sample analysis very difficult. Reflective attachments in cylinders are expected to solve such problems.
addition to the above three sample accessories, there are mirror reflection, immersion reflection, AT R, light focuser, etc. have their own characteristics, coating analysis is also very useful.
4 -
, with the rapid development of FT IR, infrared spectroscopic analysis is more and more widely used in laboratories. Because it can be used with a variety of instruments, sharing a computer operation, in fact, reduce the laboratory equipment investment. Also because it has a high degree of characteristics on most substances, the sample can be solid, liquid, gas, not limited by the state of the object under test, organic, inorganic, polymerized benches, etc. can be measured, easy to analyze and operate, fast and so on. To this end, it will play a greater role in the coatings industry.