LY/T 3138-2019Wood products method for assessment of colour fastness to artificial light (English PDF)

6.1 Sample size

The sample size shall meet the requirements of Table 1.

Table 1 Sample size requirements

In millimeters

Length width thickness 100.0 20.0 ~ 30.0 1.0 ~ 2.0 Note. Samples of other sizes can be made according to the requirements of the instrument.

Take 6 color measurement points on each sample, each color measurement point is marked with a circle with a diameter of 12 mm, see Figure 1.

Figure 1 Schematic diagram of color measurement point location

6.2 Moisture content of the sample

The moisture content of the sample is (12 ± 2)%.

6.3 Quantity requirements

Three samples were randomly selected from each sample.

7.1 Test device

Fix the sample and the blue wool standard on the test stand in the xenon light attenuation instrument, and cover half of the blue wool standard with opaque tin foil.

Samples were exposed to light at an irradiance of 42 w/m², a black standard temperature of 65 ° C, and a relative humidity of 55%.

7.2 Test process

According to the requirements of Figure 1, the material color index (L *, a *, b *) of each point before exposure was measured, and the average value (L * 0, a 0, b

0) As the sample

Initial wood color index, accurate to 0.01.

From time to time during the test, remove the blue wool standard sample, lift up the foil, and check the light effect of the blue wool standard sample. When the blue wool standard

2 When the degree of discoloration reaches level 3 of the gray sample card, record the exposure time and irradiation amount at this time, measure the material color index of each point on the sample, and average Value (L * 1, a 1, b

1) The color index for the first test is accurate to 0.01.

Continue to expose the blue wool standard sample 4 to the same degree of discoloration as the gray sample card 4 and record the exposure time and the amount of radiation.

Material color index of each point, take the average value (L * 2, a 2, b

2) The color index for the second test is accurate to 0.01.

When the degree of discoloration of the blue wool standard sample 6 reaches the gray sample card level 4, or the color difference produced by the most light-resistant sample reaches (3.4 ± 0.4) Within the range, terminate the test, record the exposure time and exposure, determine the material color index of each point on the sample, and take the average value (L * 3, a 3, b

Used as the material color index for the third test, accurate to 0.01.

8.1 Color Difference Calculation

Calculate the color difference between the original sample and the sample processed by the color fastness test. The color difference is calculated according to the formula of 5.1.3 in GB/T 7921-2008.

(11) To proceed.

delta E * ab = [(deltaL *) 2 (deltaa *) 2 (deltab *) 2] 1/2 in the formula.

deltaL

deltaa

deltab

The value of t is 1, 2, or 3.

8.2 Grade Evaluation of Lightfastness and Color Fastness

8.2.1 Evaluate the lightfastness and color fastness of the sample according to the blue wool standard sample the light fastness grade of the sample was evaluated in accordance with the provisions of Table 2.

The sample with the color difference index delta E * ab >=3.8 measured for the first measurement of the material color index is rated as Grade 1; 3.0 <= delta E ab < 3.8, rated 2 Level; delta E * ab < 3.0, to be rated as level 3 or above.

For the sample to be rated as grade 3 or higher in the first measurement, delta E * ab >= 2.0 in the second measurement is rated as grade 3; 1.4 <= delta E ab < 2.0, Rated as 4; delta E * ab < 1.4, to be rated as 5 or more.

In the second measurement, the sample to be rated as grade 5 or higher, delta E * ab >= 2.0 in the third measurement, and rated as 5; 1.4 <= delta E ab < 2.0, the rating is 6; delta E * ab < 1.4, the rating is 7;

Table 2 Grades of light fastness and color fastness based on blue wool standards

Color difference value (delta E * ab) delta E * ab < 1.40 1.4<= delta E * ab < 2.0 6 delta E * ab < 1.4 b, delta E * ab >=2.0 1.4<= delta E * ab < 2.0 4 delta E * ab < 3.0 a , delta E * ab >=2.0 3.0<= delta E * ab < 3.8 2 delta E * ab >=3.8 Color difference value for the first measurement.

Color difference measured at the second measurement.

Color difference value for the third measurement.

8.2.2 Evaluation of light fastness and color fastness grades of samples based on gray sample cards According to the requirements of Table 3, according to the color change value (delta E * ab) measured before and after exposure to the sample, the color corresponding to the color fastness level of the gray sample card the difference value (delta E * ab) is evaluated. If the color difference value between the sample and the original is equivalent to the color difference value of a certain level of the gray sample card, the test Color fastness grade. When the color difference between the sample and the original is in the middle of two levels of the gray sample card, it can be determined as the middle level, such as 4-5 or 2-3. Only when there is no difference in visual perception between the sample and the original sample, can it be set as 5 grade.

Table 3 Grades of light fastness and color fastness of samples according to gray sample cards

Color difference value (delta E * ab) delta E * ab < 0.40 5 0.40<= delta E * ab < 1.25 4-5 1.25<= delta E * ab < 2.10 4 2.10<= delta E * ab < 2.95 3-4 2.95<= delta E * ab < 4.10 3 4.10<= delta E * ab < 5.80 2-3 5.80<= delta E * ab < 8.20 2 8.20<= delta E * ab < 11.60 1-2 delta E * ab >=11.60 1