Analysis and evaluation of laboratory comparison test results of internal bonding strength of MDF
Release date: February 15, 2022 browse: 2377 times
Abstract: the internal bonding strength is an important index to measure the processing performance of non veneer wood-based panels. In this paper, the results of the inter laboratory comparison activities carried out for the project of the bonding strength in the medium density board are comprehensively analyzed and evaluated by using the h-value test method and the classical statistical method, and some suggestions are put forward for the specific operation of the determination method of the bonding strength in the medium density board.
The internal bonding strength is an important index to measure the processing performance of non veneer wood-based panels. The measurement results of internal bonding strength are not only determined by the factors of the sample itself, such as density, density deviation, moisture content, sizing amount, hot pressing process, etc., but also affected by some external factors, such as inspection equipment, inspectors, and the specific operation details in the test process, such as the number of universal joints used in the tensile test, the interval between sticking the sample and carrying out the tensile test The sizing amount and uniformity of hot melt adhesive when sticking samples, and some of these specific operation details are not clearly described in gb/t17657-2013 “test methods for physical and chemical properties of wood-based panels and decorative wood-based panels” and other relevant standards. Therefore, it is necessary to often carry out comparative analysis of laboratory comparison tests, monitor the quality of laboratory testing activities and sustainability, eliminate non-conforming factors in the quality link in time, and formulate corresponding remedial measures to ensure the accuracy of test results.
Aiming at the laboratory comparison activities of the bonding strength in the medium density board, the author uses the h-value test method and classical statistical method to comprehensively analyze and evaluate the results, and puts forward some suggestions on the inspection of the bonding strength in the medium density board in combination with the daily inspection work.
1 test content
1) Comparison sample: medium density board, taken from a large medium density board finished product warehouse in Guangdong, the density is 0.71g/cm3, and the density deviation in the board is -1.4%, +1.4%.
2) Comparison unit: 4 laboratories, with laboratory codes of a, B, C and D.
3) Comparison item: internal bonding strength.
4) Test method: according to “6.7 determination of internal bonding strength” in gb/t11718-2009 medium density board. Each laboratory measured 8 data, and the results were accurate to 0.01Mpa.
5) Sample preparation and distribution: saw the internal bonding strength test piece on the selected medium density board, which is 100mm away from the board edge when sawing, and the size of the test piece is 50mm × 50mm, the number of sawn test pieces (> 120 pieces). After sawing, mix well, seal and place in a constant temperature and humidity chamber with a temperature of (20 ± 2) ℃ and a relative humidity of 60% – 70% for balance treatment for 3 days.
Four samples (more than 20 samples each) are randomly selected for uniformity test and stability test. After the uniformity sample test, one sample is randomly selected from each of the four samples every two days for stability test, a total of 8 tests. The remaining samples are randomly divided into 4 parts (10 samples for each, and 8 samples for each laboratory during the test) for sealed packaging, which is multi sealed with food grade tin foil and food grade self sealing polyethylene bags. After subcontracting, it shall be kept in a constant temperature and humidity chamber until it is sent. After the samples were distributed to the laboratories, the four laboratories tested the samples the next day after receiving them, and the stability test continued.
6) Evaluation method: F test method is used to evaluate the uniformity of samples; T-test method was used to evaluate the stability of samples; The comparison results were evaluated and analyzed by h-value test and classical statistical method.
2 results and analysis
2.1 uniformity and stability analysis
See Table 1 for the test results of internal bonding strength of 4 uniformity verification samples. Experience shows that the test values of the internal bonding strength of MDF from the same sample population obey the normal distribution, and the normal distribution curve of the internal bonding strength fitting measured for the uniformity verification of the test according to the ratio is shown in Figure 1. Therefore, F test (one-way ANOVA) can be used to verify the uniformity of the samples. The results are shown in Table 2. It can be seen from table 2 that the F value of one-way ANOVA is 1.2632, and the p value is 0.306, in which the F value is less than the f critical value (f0.05 (3,28) =2.9467), and the p value is greater than 0.05, which indicates that when the significance level is 0.05, the bonding strength test samples used in this comparison meet the uniformity requirements.
Table 1 measured value of bonding strength in uniformity verification sample MPa
Sample No 1# 2# 3# 4# 5# 6# 7# 8# average value
Group 1 zero point six four zero point six zero zero point five eight zero point six zero zero point five eight zero point five two zero point five nine zero point five eight zero point five nine
Group 2 zero point five nine zero point five six zero point five seven zero point six two zero point five four zero point five five zero point six two zero point six one zero point five eight
Group 3 zero point five nine zero point five nine zero point five eight zero point six three zero point six four zero point five six zero point six two zero point six one zero point six zero
Group 4 zero point five eight zero point five three zero point five seven zero point five five zero point six two zero point five six zero point six zero zero point five eight zero point five seven
Total average / / / / / / / / zero point five nine
Table 2 test results of internal bonding strength f of uniformity verification samples
Source of difference Sum of squares of residuals freedom mean square F value P value F critical value
Intergroup zero point zero zero three four seven five three zero point zero zero one two one point two six three two zero point three zero six zero two point nine four six seven
In group zero point zero two five six seven five twenty-eight zero point zero zero zero nine
total zero point zero two nine one five zero thirty-one
Samples were randomly selected from 4 samples used for Uniformity Inspection and then tested for internal bonding strength to verify its stability. According to cnas-gl03 guide for evaluation of uniformity and stability of capability verification, the stability of this comparison test is tested by using the independent sample t-test in the double population. The results are shown in Table 3 ~ 4.
It can be seen from the calculation results that the T value in the four groups is less than the t critical value (t (0.05, 14) =2.14), which indicates that when the significance level is 0.05, the internal bonding strength of the MDF used for this comparison meets the stability requirements. In conclusion, the bonding strength test samples used in this comparison have good uniformity and stability, and the results submitted by various laboratories can be statistically analyzed.如无特殊说明，文章均为本站原创，转载请注明出处。If there are no special instructions, the articles are original, if you want to use or reproduce, please indicate the original source www.plywoodinspection.com,If you find that our articles infringe on your copyrights and interests, please email us at firstname.lastname@example.org in time and we will delete it at the first time.