A method for testing the resistance to yellowing of glass fibers and articles thereof and a method for optimizing the same

Abstract

The application discloses a kind of glass fiber and its product yellowing resistance test method, comprising the following steps: measuring the initial chromaticity value L0 of sample to be detected * And b0 * ; sample to be detected is treated, and then the chromaticity value L1 after aging is measured * And b1 * ; the measured L0 * , b0 * , L1 * And b1 * Input into the yellowing determination expression constructed to obtain yellowing determination value, then compare the size of yellowing determination value and preset yellowing threshold and determine whether yellowing resistance is up to standard or yellowing resistance is not up to standard according to the comparison result;Compared with prior art, the aging yellowing of glass fiber and its product is detected more accurately and specifically;And by comparing the obtained yellowing determination value with the preset yellowing threshold, it is determined whether the glass fiber and its product yellowing resistance is up to standard or not, so that a quantitative use standard is formed, which is beneficial to the practical application of industry;And it has the characteristics of simple operation, clear evaluation standard and wide application range.

Description

Technical Field

[0001] This invention relates to the field of glass fiber testing technology, specifically to a method for testing the yellowing resistance of glass fibers and their products, and an optimization method thereof. Background Technology

[0002] Glass fiber and its products are widely used in construction, automotive, and electronics industries due to their excellent mechanical properties, electrical insulation, and heat resistance. However, during use, glass fiber and its products often exhibit yellowing under environmental conditions such as ultraviolet radiation, high temperature, and high humidity, affecting the product's appearance and some functional properties. Yellowing is usually caused by chemical changes in the material, which not only affect the product's appearance but may also affect its performance and lifespan in certain applications.

[0003] Therefore, the prepared glass fibers and their products need to be tested for yellowing. Existing methods use ultraviolet (UV) aging to detect yellowing in glass fibers and their products. Specifically, this involves simulating UV radiation on the glass fibers and their composites, and using a colorimeter or spectrophotometer to measure the color of the samples before and after aging. The values ​​in the L*a*b* color space are recorded, and the results are then processed using the formula... The color difference value ΔE is calculated. The larger the ΔE value, the more significant the color change. Specifically, the increase in the b* value directly reflects the sample's tendency to develop towards a yellowish hue.

[0004] The ΔE mentioned above is a comprehensive color change judgment and cannot make a targeted judgment on the yellowing of glass fiber and its composites. Judging the yellowing of glass fiber and its composites solely by the b* value only reflects the color change along the yellow-blue axis, rather than the actual commercial needs and visual perception of aging yellowing. Therefore, its accuracy is relatively poor. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for testing the yellowing resistance of glass fiber and its products and an optimization method thereof, so as to solve the problem that the existing technology does not have a relatively accurate measurement of the aging yellowing of glass fiber and its composite materials.

[0006] To achieve the above objectives, the first aspect of the present invention adopts the following technical solution: a test method for the resistance of glass fiber and its products to yellowing, comprising the following steps: Measure the initial colorimetric value L0 of the sample to be tested. * and b0 * ; The sample to be tested was subjected to an aging treatment, and then the color value L1 after aging was measured. * and b1 * ; The measured L0* b0 * L1 * and b1 * The yellowing determination value is obtained by inputting the constructed yellowing determination expression. Then, the yellowing determination value is compared with the preset yellowing threshold, and the yellowing resistance is determined to be up to standard or not up to standard based on the comparison result.

[0007] Furthermore, the expression for determining yellowing is: ; Wherein, T1 is the yellowing determination value.

[0008] Furthermore, the cutting specifications of the sample to be tested shall meet one of the following requirements based on the product shape: (1) For planar products, the sample to be tested is a square with a side length of not less than 30 mm and a flat surface; ensure that the spectrophotometer detection spot completely covers the sample and there is no light leakage at the edge; (2) For long strip products, the sample to be tested is not less than 100 mm in length and covers not less than 5 bundles of parallel fibers in width. The sample to be tested is placed on a black backing plate with a reflectivity of not more than 5% during measurement. (3) For short-cut fibers or powders, the sample to be tested is spread in a container with a thickness of not less than 0.5 mm and no visible gaps. By standardizing the cutting specifications of samples of different shapes, the consistency and repeatability of the test results are ensured.

[0009] Furthermore, the sample to be tested must be pretreated before the colorimetric value measurement. The pretreatment conditions are: constant temperature for 24 hours at 23±2℃ and 50±5% humidity.

[0010] Furthermore, the colorimetric values ​​were measured using a spectrophotometer, and the measurement conditions for the spectrophotometer were as follows: (1) Use a D65 standard light source; (2) The measuring aperture shall not be less than 4 mm; (3) Eliminate specular reflection light components; (4) Perform no less than 5 measurements on each sample to be tested and take the average of its color data; (5) The spectrophotometer is calibrated before use, and the deviation of the reflectance calibration value of its calibration white plate does not exceed 0.5%.

[0011] Furthermore, the aging treatment is ultraviolet aging, damp heat aging, or thermo-oxidative aging; The aging conditions for ultraviolet light aging are: UV-A band light source, irradiance 0.8-1.2 W / (m²·nm), temperature 50-70℃, and time 24-240 hours; The aging conditions for damp heat aging are: temperature 85±2℃, relative humidity 85%±5%, and time 168-1000 hours. The aging conditions for thermo-oxidative aging are: temperature 60-280℃, air velocity ≥1 m / s, and time 2 minutes to 240 hours.

[0012] Furthermore, the preset yellowing threshold is set in one of the following ways: (1) The upper limit of the yellowing determination value specified in the customer's technical agreement shall be adopted; (2) Based on the yellowing judgment value of qualified samples in the same batch, calculate the average value plus K times the standard deviation, where K is a positive integer not less than 2; (3) Based on historical data, select the critical value for yellowing judgment corresponding to the product performance failure. Set differentiated threshold standards for different application scenarios to make the evaluation results more practical and targeted.

[0013] The second aspect of this invention adopts the following technical solution: an optimization method for anti-yellowing of glass fiber and its products, comprising the following steps: (a) Provide a sample and test it using the test method described in the first aspect of the present invention. If it is determined that the anti-yellowing is not up to standard, then proceed to step (b). (b) Based on the formulation of the sample described in step (a), increase the amount of anti-yellowing agent by a preset increment to prepare a new sample; (c) The new sample prepared in step (b) is tested using the test method described in the first aspect of the present invention; (d) If the test result is determined to be unsatisfactory in terms of anti-yellowing, repeat steps (b) and (c) until a sample that meets the anti-yellowing standard is obtained.

[0014] Furthermore, in step (b), an upper limit is set for the amount of anti-yellowing agent; when the amount of anti-yellowing agent reaches the upper limit and the judgment result of step (c) is still unsatisfactory, the type of anti-yellowing agent is changed, and the modification and verification are repeated in step (a) or (b).

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The test method for the yellowing resistance of this glass fiber and its products is based on the initial colorimetric value L0. * and b0 * and the chromaticity value L1 after aging * and b1 *This system is designed to reflect changes in brightness and yellow-blue values ​​of surface organic matter in glass fibers and their products during the aging process, enabling targeted and more precise detection of yellowing during aging. Furthermore, by comparing the obtained yellowing determination value with a preset yellowing threshold, it determines whether the glass fibers and their products meet or fail to meet the yellowing resistance standard, thus establishing a quantitative standard that is beneficial for practical application in the industry. It also features simple operation, clear evaluation standards, and wide applicability. 2. The optimization method for anti-yellowing of glass fiber and its products is based on this test method, which provides the most direct technical guidance for material improvement quickly and effectively. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments: To address the sensitivity bias issue in the traditional ΔE method for assessing yellowing of glass fibers (e.g., the yellowing signal is obscured by optical interference in coated glass fibers), this invention, through systematic aging experiments, reveals that: (Brightness change) and The coupling effect of (yellow-blue axis variation) has a synergistic corrective effect on the determination of yellow discoloration, as shown in Table 1:

[0017] Table 1 Based on the above findings, an innovative proposal is put forward. T1 is used as the core indicator for determining yellowing, with a coefficient of 0.5 determined through orthogonal experiments. L9(3) is employed. 4 An orthogonal array was used to test four factors: k value (0.3 / 0.5 / 0.7), aging temperature (50℃ / 65℃ / 80℃), time (24h / 120h / 240h), and material type (alkali-free / high-alkali / basalt fiber). The results showed that the overall misjudgment rate was the lowest when k=0.5 (3.2%), which was significantly better than k=0.3 (8.5%) and k=0.7 (6.1%) (p<0.05). The following will use specific examples to illustrate this point.

[0018] Example 1 Step 1: Take fiberglass cloth for electronic substrates and cut it into 30*30mm squares. Maintain a constant temperature of 23±2℃ and 50±5% for 24 hours. Use an X-Rite Ci62 (Ci6x series) spectrophotometer with an 8mm aperture light-proof clamp. Preheat the spectrophotometer for 30 minutes and calibrate according to standards. Measure the initial colorimetric value b0. * =1.48, L0 * =92.11 (average of 5 measurements).

[0019] Step 2: Place the tested fiberglass cloth in an ultraviolet aging chamber. The aging conditions in the ultraviolet aging chamber are set as follows: UV-A band light source, irradiance 0.8-1.2 W / (m²·nm), temperature 50℃, and time 120 hours.

[0020] Step 3: After aging, the fiberglass cloth is kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours, and the color value b1 after aging is measured using a spectrophotometer. * =3.21, L1 * =90.27 (average of 5 measurements).

[0021] Step 4, L0 * b0 * L1 * and b1 * Substitute into the yellowing determination expression ( In the calculation, the yellowing judgment value T1=2.65, T1<3 (product failure value, determined based on the lower limit of the decrease in tensile strength after wet heat aging in historical data), and it is determined that this glass fiber cloth meets the yellowing resistance standard.

[0022] Example 2 Step 1: Take untwisted roving (2400TEX wind power fiberglass), cut it into 150mm long segments, and lay 10 segments flat on a black backing board with a reflectivity of no more than 5%. Maintain a constant temperature of 23±2℃ and 50±5% for 24 hours. Use an X-Rite Ci62 (Ci6x series) spectrophotometer with a light-leakage prevention clamp (8mm aperture). Preheat the spectrophotometer for 30 minutes and calibrate according to standards. Measure the initial colorimetric value b0. * =3.98, L0 * =85.57 (average of 5 measurements).

[0023] Step 2: Place the tested glass fiber in an ultraviolet aging chamber. The aging conditions in the ultraviolet aging chamber are set as follows: UV-A band light source, irradiance 0.8-1.2 W / (m²·nm), temperature 60℃, and time 240 hours.

[0024] Step 3: After aging, the glass fiber is kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours, and the color value b1 after aging is measured using a spectrophotometer. * =5.9, L1 * =80.27 (average of 5 measurements).

[0025] Step 4, L0 * b0 * L1 * and b1* Substitute into the yellowing determination expression ( In the calculation, the yellowing judgment value T1=4.57, T1<7 (product failure value, determined based on the lower limit of the epoxy peak reduction in the infrared spectrum of the glass fiber organic layer after ultraviolet aging in historical data), and it is determined that this glass fiber meets the yellowing resistance standard.

[0026] Example 3 Step 1: Epoxy pultruded sheets (the epoxy pultruded sheets are at least 100mm in length and cover at least 5 bundles of parallel fibers on a width, placed on a black backing with a reflectivity of no more than 5%) are kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours. A Taishuang TS7X spectrophotometer with a 4mm platform test aperture is used. The spectrophotometer is preheated for 30 minutes and calibrated according to standards. The initial colorimetric value b0 is measured. * =7.41, L0 * =80.55 (average of 5 measurements).

[0027] Step 2: Place the tested epoxy pultruded sheets in a damp heat test chamber. The aging conditions in the damp heat test chamber are set as follows: temperature 85±2℃, relative humidity 85%±5%, and aging time 240h.

[0028] Step 3: After aging, the pultruded sheet was kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours, and the color value b1 after aging was measured using a spectrophotometer. * =11.12, L1 * =77.86 (average of 5 measurements).

[0029] Step 4, L0 * b0 * L1 * and b1 * Substitute into the yellowing determination expression ( In the calculation, the yellowing judgment value T1 is 5.05, T1>3.5 (product failure value, obtained by adding 3 times the standard deviation to the mean T1 value after wet heat aging of qualified samples in the batch), and it is determined that the yellowing resistance of this epoxy pultruded sheet is not up to standard.

[0030] Because T1 is greater than the failure value, the formulation of the epoxy pultruded sheet was readjusted (the epoxy pultruded sheet includes 100 parts epoxy resin (E-51), 85 parts methyltetrahydrophthalic anhydride (MTHPA), 1 part accelerator (BDMA), 0.6 parts antioxidant (1010), and 310 parts glass fiber). The amount of antioxidant in the formulation was increased by 20% (i.e., the amount of antioxidant was increased to 0.72 parts), and a new epoxy pultruded sheet was prepared. Steps 1-4 were repeated on the new epoxy pultruded sheet, and the yellowing judgment value T1 was calculated to be 3.06, T1 < 3.5. The new epoxy pultruded sheet was judged to meet the yellowing resistance standard.

[0031] If, when the amount of antioxidant in the formula is increased by 20%, reaching the maximum amount of antioxidant in this formula, the calculated yellowing judgment value T1=4.26, and the epoxy pultruded sheet is judged to be substandard in terms of yellowing resistance. At this time, further increasing the amount of antioxidant will have a significant impact on other properties of the epoxy pultruded sheet. In this case, it is necessary to consider changing the type of antioxidant (for example, replacing the antioxidant with: 0.3 parts of high-temperature resistant card antioxidant (1076) + 0.3 parts of auxiliary antioxidant (168), and then prepare a new epoxy pultruded sheet; repeat steps 1-4 on the new epoxy pultruded sheet, and calculate the yellowing judgment value T1=2.98. When T1<3.5, the new epoxy pultruded sheet is judged to be qualified in terms of yellowing resistance, and the formulation optimization of the epoxy pultruded sheet is completed.

[0032] Example 4 Step 1: The worn glass fiber was placed at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours. The layer thickness in the culture dish was 5mm, with no visible gaps between the fibers. A Konica Minolta CM-5 spectrophotometer with a 4mm measuring aperture was used and calibrated according to standards. The initial colorimetric value b0 was measured. * =1.92, L0 * =90.32 (average of 5 measurements).

[0033] Step 2: Place the tested worn glass fiber together with the petri dish in a damp heat test chamber. The aging conditions in the damp heat test chamber are set as follows: temperature 85±2℃, relative humidity 85%±5%, and aging time 1000h.

[0034] Step 3: After aging, the pultruded sheet was kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours, and the color value b1 after aging was measured using a spectrophotometer. * =3.16, L1 * =83.86 (average of 5 measurements).

[0035] Step 4, L0 * b0 * L1 * and b1* Substitute into the yellowing determination expression ( In the calculation, the yellowing judgment value T1=4.47, T1<6 (product failure value, obtained by adding 3 times the standard deviation to the mean T1 value corresponding to the impact strength of the reinforced PA6 composite material after wet heat aging of qualified samples in the batch), and it is determined that the wear glass fiber meets the yellowing resistance standard.

[0036] Example 5 Step 1: Take short-cut glass fibers and incubate them at 23±2℃ and 50±5% humidity for 24 hours. The short-cut glass fibers are laid in a petri dish to a thickness of 10mm, with no visible gaps between the fibers. A Konica Minolta CM-5 spectrophotometer with an 8mm measuring aperture is used, calibrated according to standards before use. The initial colorimetric value b0 is measured. * =1.32, L0 * =91.05 (average of 5 measurements).

[0037] Step 2: Place the tested glass fiber in a hot air oven. The aging conditions in the hot air oven are set as follows: temperature 280℃, air velocity ≥1 m / s, and time 240 hours.

[0038] Step 3: After aging, the glass fiber is kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours. The color value b1 after aging is measured using a spectrophotometer after the flat sample preparation is completed in Step 1. * =5.15, L1 * =90.36 (average of 5 measurements).

[0039] Step 4, L0 * b0 * L1 * and b1 * Substitute into the yellowing determination expression ( In the calculation, the yellowing threshold T1 was 4.18, and T1 < 6 (this threshold was confirmed in consultation with the customer). Therefore, the glass fiber is deemed to meet the yellowing resistance standard.

[0040] Example 6 Step 1: CFRT-PP sheet (0.2mm thickness, 65% glass fiber content) was kept at a constant temperature of 23±2℃ and 50±5% for 24 hours. The CFRT-PP sheet was measured using a Konica Minolta CM-5 spectrophotometer with a 4mm aperture, calibrated according to standards before use. The initial colorimetric value b0 was measured. * =-1.25, L0 * =48.8 (average of 5 measurements).

[0041] Step 2: After the CFRT-PP sheet that has been tested is covered with a PTFE film, it is placed in a hot air oven. The aging conditions in the hot air oven are set as follows: temperature 210℃, air velocity ≥1 m / s, time 5min.

[0042] Step 3: After aging, the glass fiber is kept at a constant temperature of 23±2℃ and humidity of 50±5% for 24 hours. The color value b1 after aging is measured using a spectrophotometer after the flat sample preparation is completed in Step 1. * =-0.54, L1 * =48.56 (average of 5 measurements).

[0043] Step 4, L0 * b0 * L1 * and b1 * Substitute into the yellowing determination expression ( In the calculation, the yellowing judgment value T1 = 0.83, T1 < 1.2 (this threshold was confirmed in consultation with the customer). Therefore, this CFRT-PP sheet is deemed to meet the yellowing resistance standard.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A test method for the resistance of glass fiber and its products to yellowing, characterized in that, Includes the following steps: Measure the initial colorimetric value L0 of the sample to be tested. * and b0 * ; The sample to be tested was subjected to an aging treatment, and then the color value L1 after aging was measured. * and b1 * ; The measured L0 * b0 * L1 * and b1 * The yellowing determination value is obtained by inputting the constructed yellowing determination expression, and then the yellowing determination value is compared with the preset yellowing threshold. Based on the comparison result, it is determined whether the yellowing resistance meets the standard or not. The expression for determining yellowing is: ； Wherein, T1 is the yellowing determination value; The preset yellowing threshold is set in one of the following ways: (1) The upper limit of the yellowing determination value specified in the customer's technical agreement shall be adopted; (2) Based on the yellowing judgment value of qualified samples in the same batch, calculate the average value plus K times the standard deviation, where K is a positive integer not less than 2; (3) Based on historical data, select the critical value of yellowing judgment corresponding to the product performance failure.

2. The test method for the yellowing resistance of glass fiber and its products according to claim 1, characterized in that, The cutting specifications of the sample to be tested shall meet one of the following requirements based on the product shape: (1) For planar products, the sample to be tested is a square with a side length of not less than 30 mm and a flat surface; (2) For long strip products, the sample to be tested is not less than 100 mm in length and covers not less than 5 bundles of parallel fibers in width. The sample to be tested is placed on a black backing plate with a reflectivity of not more than 5% during measurement. (3) For short-cut fibers or powders, the sample to be tested is spread in a container with a thickness of not less than 0.5 mm and no visible gaps.

3. The test method for the yellowing resistance of glass fiber and its products according to claim 1, characterized in that, Before performing the colorimetric value measurement, the sample to be tested must be pretreated. The pretreatment conditions are: constant temperature for 24 hours at 23±2℃ and 50±5% humidity.

4. The test method for the yellowing resistance of glass fiber and its products according to claim 1, characterized in that, The colorimetric values ​​were measured using a spectrophotometer, and the measurement conditions for the spectrophotometer were as follows: (1) Use a D65 standard light source; (2) The measuring aperture shall not be less than 4 mm; (3) Eliminate specular reflection light components; (4) Perform no less than 5 measurements on each sample to be tested and take the average of its color data; (5) The spectrophotometer is calibrated before use, and the deviation of the reflectance calibration value of its calibration white plate does not exceed 0.5%.

5. The method for testing the yellowing resistance of glass fiber and its products according to claim 1, characterized in that, The aging process is ultraviolet light aging, damp heat aging, or thermo-oxidative aging. The aging conditions for ultraviolet light aging are: UV-A band light source, irradiance 0.8-1.2 W / (m²·nm), temperature 50-70℃, and time 24-240 hours; The aging conditions for damp heat aging are: temperature 85±2℃, relative humidity 85%±5%, and time 168-1000 hours. The aging conditions for thermo-oxidative aging are: temperature 60-280℃, air velocity ≥1 m / s, and time 2 minutes to 240 hours.

6. An optimization method for preventing yellowing of glass fiber and its products, characterized in that, Includes the following steps: (a) Provide a sample and test it using the test method as described in any one of claims 1-5. If it is determined that the anti-yellowing is not up to standard, then proceed to step (b). (b) Based on the formulation of the sample described in step (a), increase the amount of anti-yellowing agent by a preset increment to prepare a new sample; (c) The new sample prepared in step (b) is tested using the test method described in any one of claims 1-5; (d) If the test result is determined to be unsatisfactory in terms of anti-yellowing, repeat steps (b) and (c) until a sample that meets the anti-yellowing standard is obtained.

7. The method for optimizing the anti-yellowing properties of glass fiber and its products according to claim 6, characterized in that, In step (b), an upper limit is set for the amount of anti-yellowing agent. When the amount of anti-yellowing agent reaches the upper limit and the judgment result of step (c) is still unsatisfactory, the type of anti-yellowing agent is changed, and the modification and verification are repeated in step (a) or (b).

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