A method for analyzing and evaluating the UV aging dynamics of organic resin coatings

Abstract

The present invention discloses an analysis and evaluation method for ultraviolet aging dynamics of an organic resin coating, comprising the following steps: S1: using an optically transparent material as a substrate, coating an organic resin on the substrate to prepare a sample; S2: using transmission infrared spectroscopy to measure the initial infrared absorption spectrum of the sample as a baseline, and determining the wave number and peak intensity of the characteristic spectrum peak characterizing the ultraviolet aging of the resin; S3: placing the sample under a standard ultraviolet light source for irradiation, and then measuring the infrared absorption spectrum of the sample, and describing the aging degree of the sample by the intensity change of the characteristic spectrum peak; S4: using the dose of ultraviolet irradiation as the horizontal coordinate and the intensity change of the characteristic spectrum peak as the vertical coordinate to draw a graph, and obtaining the dynamic law of the organic resin aging degree changing with the irradiation dose. The present invention realizes the evaluation and quantification of the ultraviolet aging of the resin, so that the analysis and evaluation are objective and systematic, and the consistency of the expression of the aging dynamics is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of coating evaluation, and belongs to the technical field of organic resin coating aging evaluation, and specifically relates to an analysis and evaluation method for ultraviolet aging dynamics of an organic resin coating. Background Art

[0002] Organic coatings are widely used in metal components in marine atmospheric environments. Organic resins are the main film-forming substances of organic coatings. They are prone to aging reactions under the influence of environmental factors such as light radiation, temperature, and humidity. Among them, the ultraviolet part of the sunlight spectrum has the most significant effect on the aging of resins.

[0003] At present, the most common UV aging accelerated test method for organic resin coatings basically adopts the standard direct UV radiation aging test. For example, as described in GB / T 23987, ISO 16474 or ASTM 154-05, the standard coating sample is placed in a UV aging box and subjected to accelerated aging treatment by the combined action of UV radiation and condensed water. After a specified period of UV irradiation, the changes in the resin's color, glossiness, degree of powdering and other property parameters are judged by visual observation, and the degree of resin aging is characterized by such explicit physical changes. For example, when the ISO 4628 standard stipulates the evaluation standards for various coating aging, on the basis of visual observation, a grading method is further used to grade the degree of change, quantity and size of coating defects, thereby evaluating the degree of aging of organic coatings. However, the above-mentioned currently commonly used organic coating UV aging evaluations are all qualitative detection methods. Although the operation is simple and easy to implement, the evaluation results are highly subjective and largely depend on the experience of the inspector. They are also easily affected by the state of the inspector himself and changes in environmental factors, and lack systematicity, objectivity and comparability.

[0004] The evaluation requirements for coatings are no longer satisfied with such simple qualitative judgments as whether the coating can be used, but it is necessary to know how long the coating can be used. Therefore, how to quantitatively characterize the degree of UV aging of organic resin coatings and then obtain the aging rate of organic coatings is of great engineering significance for the quantitative evaluation of organic coatings. Summary of the invention

[0005] The purpose of the present invention is to provide an analysis and evaluation method for the ultraviolet aging kinetics of an organic resin coating. The organic coating aging sample is prepared using a standard method (such as GB / T 23987). Based on the chemical reaction kinetics of the coating molecular structure during the ultraviolet aging process, the ultraviolet aging kinetics of the organic coating is systematically and quantitatively analyzed and evaluated, and the degree of ultraviolet aging of the organic resin coating is quantitatively characterized.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] The present invention provides a method for analyzing and evaluating the ultraviolet aging dynamics of an organic resin coating, characterized in that infrared spectroscopy is performed on organic resin samples that have been subjected to different ultraviolet irradiation times, the aging reaction of the sample and its aging degree are characterized according to the position and intensity changes of the spectrum, and a quantitative functional relationship between the ultraviolet aging reaction degree of the organic resin and the irradiation dose is obtained, thereby evaluating the ultraviolet aging performance of the organic resin.

[0008] Since organic resins generally undergo multiple aging reactions under ultraviolet radiation, and the aging reaction with the highest rate determines the service state and quality life of the organic resin, the aging reaction with the highest rate is used as the ultraviolet aging rate of the resin in the evaluation.

[0009] More specifically, the method for analyzing and evaluating the ultraviolet aging dynamics of an organic resin coating of the present invention is characterized by comprising the following steps:

[0010] S1: using an optically transparent material as a substrate, coating the organic resin on the substrate, and preparing several groups of samples;

[0011] In order to conduct infrared spectrum testing, the coating thickness needs to be controlled at a relatively thin scale, and the dry film thickness should not exceed 15 microns, preferably not more than 5 microns; and then the curing treatment is carried out according to the curing parameters of the organic resin;

[0012] The optically transparent material is an infrared transparent material, such as infrared transparent optical glass, infrared transparent ceramics, alkaline earth-halogen compound crystals, calcium fluoride crystal infrared transparent window sheets, etc., preferably calcium fluoride crystal infrared transparent window sheets;

[0013] S2: using transmission infrared spectroscopy to measure the initial infrared absorption spectrum of the sample before ultraviolet irradiation as a baseline, and determining the wave number and peak intensity of the characteristic spectrum peak characterizing the ultraviolet aging of the organic resin;

[0014] S3: After the samples are irradiated under a standard ultraviolet light source for different time periods, infrared absorption spectra of the samples are measured by infrared spectroscopy. After deducting the baseline obtained in S2, the intensity change of the characteristic spectrum peak is used to describe the aging degree of the samples;

[0015] S4: Draw a graph with the dose of ultraviolet radiation as the horizontal axis and the intensity change of the characteristic spectrum peak of the sample as the vertical axis; wherein the dose of radiation is the product of the radiation intensity and the radiation time; fit the data to obtain the kinetic law of the change of the aging degree of the organic resin with the radiation dose as the ultraviolet aging kinetic rate of the sample.

[0016] The UV aging process of organic resin coatings is related to the wavelength of UV light, the temperature and humidity of the environment. Therefore, during the aging evaluation process, the wavelength of UV light should be kept consistent with the evaluation environment parameters.

[0017] The present invention has the following beneficial technical effects:

[0018] The present invention realizes the evaluation and quantification of resin ultraviolet aging, so that the analysis and evaluation have objectivity and systematicity; the radiation dose is used as the independent variable, including two related variables of radiation intensity and time, so as to ensure the consistency of the expression of aging dynamics and avoid the influence of the change of radiation intensity on the evaluation of the resin's anti-ultraviolet aging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The UV aging kinetic curve of the bisphenol A epoxy resin in Example 1.

[0020] Figure 2 UV aging kinetic curve of the alkyd resin in Example 2. DETAILED DESCRIPTION

[0021] Those skilled in the art should recognize that the present embodiment is only used to illustrate the present invention, and is not used to limit the present invention. Any changes or modifications to the embodiment within the scope of the present invention are within the scope of the claims of the present invention.

[0022] Example 1

[0023] A method for analyzing and evaluating the ultraviolet aging dynamics of an organic resin coating, characterized in that it comprises the following steps:

[0024] S1: Using a calcium fluoride crystal infrared-transmitting window as a substrate, bisphenol A epoxy resin brand DER332 and curing agent 1,3-bis(aminomethyl)-cyclohexane were mixed evenly in a stoichiometric ratio, coated on the substrate and cured to obtain a coating sample. A total of 3 groups of samples were prepared, each group had 5 samples, and the coating dry film thickness was about 5 microns;

[0025] S2: The initial infrared absorption spectrum of each group of samples before ultraviolet irradiation was measured by transmission infrared spectroscopy as a baseline; for the resin described in Example 1, the initial infrared absorption spectrum was 1510 cm -1 The vibration peak intensity of the benzene ring (stretching vibration) at the wave number is used as the characteristic peak to characterize the aging of the resin. As the resin ages, its vibration peak intensity gradually decreases;

[0026] S3: After each group of samples were placed under a standard ultraviolet light source for different irradiation times, the transmission infrared spectroscopy was used to measure the -1The intensity of the vibration peak at the wave number, after deducting the baseline obtained by S2, is used to characterize the aging degree of the coating sample by the intensity difference of the vibration peak;

[0027] S4: The radiation dose is taken as the horizontal axis, and the coating sample is measured at 1510 cm -1 The vibration peak intensity difference at the wave number is plotted as the ordinate, such as Figure 1 As shown; wherein the irradiation dose is the product of the irradiation intensity and the irradiation time; the curves of each spectral peak are fitted by the least square method (the peak intensity difference adopts the arithmetic mean of 3 parallel samples), and the aging kinetics of the resin as a function of the irradiation dose are obtained:

[0028] Y=aX 2 -bX-c

[0029] Where Y is the intensity difference of the characteristic peak of resin aging, which characterizes the degree of resin aging; X is the ultraviolet radiation dose, which is the product of the radiation intensity and the irradiation time; a, b, and c are constants, which are 10 -8 , 0.0002, 0.0182; the tangent line at any point on the kinetic curve is the instantaneous aging rate of the resin under the corresponding radiation dose, that is, 2aX-b.

[0030] Example 2

[0031] A method for analyzing and evaluating the ultraviolet aging dynamics of an organic resin coating, characterized in that it comprises the following steps:

[0032] S1: Using a calcium fluoride crystal infrared-transmitting window as a substrate, the alkyd resin (BD-3380) to be evaluated is coated on the substrate, and a coating sample is prepared after coating and curing (self-drying at room temperature). A total of 3 groups of samples are prepared, each group of samples has 3 parallel samples, and the coating dry film thickness is about 5 microns;

[0033] S2: The initial infrared absorption spectrum of each sample before UV irradiation was measured by transmission infrared spectroscopy as a baseline; for the resin described in Example 2, the initial infrared absorption spectrum was 1735 cm -1 The vibration peak of the hydroxyl group (alcohol ester bond) at the wave number is used as the characteristic peak to characterize the aging of the resin. The intensity of the vibration peak gradually decreases with the aging of the resin;

[0034] S3: After each group of samples were placed under a standard ultraviolet light source for different irradiation times, the infrared spectroscopy was used to measure the infrared spectroscopy of each group of samples at 1735 cm -1 The intensity of the vibration peak at the wave number, after deducting the baseline obtained by S2, is used to characterize the aging degree of the coating sample by the intensity difference of the vibration peak;

[0035] S4: The radiation dose is taken as the horizontal axis, and the coating sample is measured at 1735 cm -1The vibration peak intensity difference at the wave number is plotted as the ordinate, such as Figure 2 As shown; wherein the irradiation dose is the product of the irradiation intensity and the irradiation time; the curves of each spectral peak are fitted by the least square method (the peak intensity difference adopts the arithmetic mean of 3 parallel samples), and the aging kinetics of the resin as a function of the irradiation dose are obtained:

[0036] Y=aX 2 -bX-c

[0037] Where Y is the intensity difference of the characteristic peak of resin aging, which characterizes the degree of resin aging; X is the ultraviolet radiation dose, which is the product of the radiation intensity and the irradiation time; a, b, and c are constants, which are 6x10 -8 , 0.0001, 0.0006; the tangent line at any point on the kinetic curve is the instantaneous aging rate of the resin under the corresponding radiation dose, that is, 2aX-b.

Claims

1. A method for analyzing and evaluating the ultraviolet aging dynamics of an organic resin coating, characterized in that: The following steps are involved: S1: using an optically transparent material as a substrate, coating the organic resin on the substrate, and preparing several groups of samples; S2: using transmission infrared spectroscopy to measure the initial infrared absorption spectrum of the sample before ultraviolet irradiation as a baseline, and determining the wave number and peak intensity of the characteristic spectrum peak characterizing the ultraviolet aging of the organic resin; S3: After the samples are irradiated under a standard ultraviolet light source for different time periods, infrared absorption spectra of the samples are measured by infrared spectroscopy. After deducting the baseline obtained in S2, the intensity change of the characteristic spectrum peak is used to describe the aging degree of the samples; S4: Draw a graph with the dose of ultraviolet radiation as the horizontal axis and the intensity change of the characteristic spectrum peak of the sample as the vertical axis; wherein the dose of radiation is the product of the radiation intensity and the radiation time; fit the data to obtain the kinetic law of the change of the aging degree of the organic resin with the radiation dose as the ultraviolet aging kinetic rate of the sample.

2. The analysis and evaluation method according to claim 1, characterized in that: The dry film thickness of the organic resin coating should not exceed 15 microns.

3. The analysis and evaluation method according to claim 1, characterized in that: The dry film thickness of the organic resin coating should not exceed 5 microns.

4. The analysis and evaluation method according to claim 1, characterized in that: The optically transparent material is one of infrared-transmitting optical glass, infrared-transparent ceramics, alkaline earth-halogen compound crystals, and calcium fluoride crystal infrared-transmitting window sheets.

5. The analysis and evaluation method according to claim 1, characterized in that: The optically transparent material is a calcium fluoride crystal infrared transparent window.

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