Interpretation of national standard for ecological wood decorative board
There are two national standards for WPC materials currently, they are B/T24137-2009 《WPC decorative board》 and GB/T24508-2009 (WPC floor), which regulated the WPC floor's terms,definition, classification, requirements, testing methods, marks, packing, transportation, storage,applicable to floor that is processed by the mixture of wood and fibers.Another standard that is Is being submitted for approval--《WPC for building template》, stipulates the WPC floor's terms,definition, classification, requirements, testing methods, marks, packing, transportation, storage,applicable to building floor that is processed through extrusion and molding procedures.
Here we'll focus on the related requirements in standard 《WPC decorative board》. This standard is applicable to decorative WPC materials and decorative lines processed through all kinds of processing methods, with content including terms,definition, classification, requirements, testing methods, marks, packing, transportation, storage etc.
Classifying by production technology and main categories---by the surface treatment, there are non-decoration WPC decorative board, veneer decorative WPC board, and painted decorative WPC board. Classifying by the use of places, there are outdoor decorative WPC floor and indoor decorative WPC floor. Classifying by the resistance to artificial weathering performance, there are class I, class II and class III decorative WPC floor.
A. General technological requirements and testing methods
General technological requirements is the fundamental requirements for decorative WPC floor, including appearance, quality, size, deviation,physical features, limit of harmful substances and fire performance.
Appearance and quality. Requirements differ according to different surface treatment.The standard regulates the maximum allowable range for forbidden appearance defects and allowable appearance defects. For the chromatic aberration, normally visually test is performed. But due to individual differences, testing errors are inevitable,while this test is a very important procedure. To avoid this problem, the buyer and seller should negotiate and agree on the contract for the different chromatic aberration according to different decorative effects.
Size and deviation.
Due to the difference in the shape and size of decorative WPC floor, this standard only regulates on the length, width and edge angle deviation. Testing method: GB/T19367.1 《artificial board》, the width, thickness, and length testing.
B. Physical features
Physical features are very important features for decorative WPC board, determining the product quality. There are 14 testing items, below is a introduction for the testing method and necessity of the testing for main testing items.
1. Moisture content: moisture content has very big influence on other mechanical properties of the WPC decorative board. If the product contains too much water, it will get mildew, directly affect its use of performance and beauty.
Testing method is the item 4.3 in GB/T 17657－19991, test 3 samples. After cutting, weigh the samples with 0.01g accuracy balance, avoiding the moisture content changes during cutting and weighing process. After weighing, put the samples into air convection drying box at (103±2)℃ to dry till quality is constant. Then cool the dried samples in the dryer, preventing absorbing water from the air. Weigh after cooling. Calculate the moisture content according to the quality difference before and after drying.
2.Bending strength and modulus of elasticity:
During the production and transportation, WPC decorative board will be affected by the bending force, the bending strength and modulus of elasticity reflects the rigidity of materials. Testing method is the item 4.9 in GB/T 17657－1999, bending strength is tested by the load value when samples are destroyed. Modulus of elasticity is tested according to the strain curve, calculated according to the strength relative to 10% and 40%.
Due to the special shape of some WPC materials, especially some hollow products with reinforcement inside, its inner structure and cross section is closely related to the bending strength. If testing the bending strength by taking its solid part on surface, the cross section shape will be damaged, failing to reflect the product bending strength, only getting the material strength. Therefore, the standard regulates the samples should be taken in the length direction when testing the bending strength, and in principle the samples thickness should be the same as product thickness. Take samples at the direction parallel to the squeeze direction, try not to destroy the product structure. In this way, the product modulus of elasticity will be better reflected.
3. Stability of size
This item is to test the size changes of WPC materials when put in environment of different temperature and moisture. If the WPC decorative board's processing technology is not suitable, causing stress in the inside of board and defects, then during using the board(especially in high temperature), sizes will change, affecting the decorative effect.
Testing method: Deal with the samples in (23±2)℃ and relative moisture at (50±5)% Constant temperature and humidity box environment for (96±4)h. The accuracy of length should be set at 0.01mm. When testing any samples for the second time, test at the same position,. When samples are taken out at certain environment, all the testing must be finished in 5 minutes.
In dry heat test, samples are divided into 2 groups( each with longitudinal and transverse samples). Put samples in group 1 into (70±2)℃ air convection drying box, making sure the air is circulating. Take out after treating for (24±1)h, put into drying box for 1h, then double measure the length at the first measure position. For high moisture test, put samples of group 2 into (40±2)℃, relative moisture 90%～95% constant temperature and humidity box, take out after treating for (96±4)h. Clean the water in surface with absorbent gauze, then double measure the length at the first measure position. Calculate the size stability according to the testing results.
4. The surface screw holding capability:
Determination the force required to pull out the self tapping screw into a certain depth of wood plastic decorative plate screw. Testing method as item 4.10 in GB/T 17657－1999. On the longitudinal direction, at 40mm away from the center line, use a ∮(2.7±0.1)mm bit to drill a 19mm depth hole, then screw in the screws at depth of (15±0.5)mm, the bit and screws must be perpendicular to the board. After screwing the screw, start the pulling nail test immediately. The touching surface of the fixture and sample should be perpendicular to the center line. Nail pulling speed of 15mm / min, is the most vigorous screw holding the screw pulled out, the exact number to 10N.
5. Thickness swelling:
Determine the specimen after pre-absorption with increased thickness than the thickness of the absorption. Plastics are hydrophobic, but has a strong water-absorbing wood fiber. Wood fiber after absorbing water thickness swell rapidly, the size becomes large, causing twisting deformation of the product. If wood decorative plate processing or recipe unreasonable, can also cause swelling in thickness after absorbing products, and even into the film off. Test methods prescribed by 17657-1999 GB / T 4.5 conduct, all immersed in water samples 72h, six specimens tested. The test piece was immersed in a pH 7 ± 1, a temperature of (20 ± 2) ℃ tank, the specimen surface is perpendicular to the horizontal plane and maintained above the lower surface of the specimen, the specimen surface and the bottom of the tank to have a certain distance between the specimen to have a certain gap, so that it can expand freely. Soaking time after the completion of the specified product based on the standard soaking, remove the specimen, wipe the surface attached to the water, in the original measure its thickness measurement points. Measurements must be completed within 30min. Thickness swelling and water absorption as the ratio of the thickness before the thickness difference before and after absorbing water absorption thickness.
6. Peel strength, surface bonding strength and film adhesion: This 3 project is to detect three different finishes of wood finishes and decorative plates binding matrix. Detection methods were based on: LY / T 1279-2008, GB / T 15102-2006 and GB / T 15036.2-2001.
7.Freeze-thaw performance: decorative wood panels to determine resistance to freeze / thaw environment. WPC outdoor decorative plates will inevitably experience rain, freezing and thawing state, if it will lead to improper processing products in the freeze-thaw cycles experienced a serious decline in product performance. At room temperature the test piece as a whole is removed completely immersed in water 24h, then at a temperature of -29 ℃ ± 1 ℃ frozen 24h, and finally the test pieces were taken at room temperature is placed in 24h. This process is composed of a heat cycle, and then repeat the process twice. After three freeze-thaw cycles to complete, whether visual surface cracking, bubbling and other changes. While the bending strength after freeze-thaw cycle test sample, calculated flexural strength retention.
8.Anti-artificial weathering: the specimen into the xenon lamp aging me, time after irradiation is determined by the provisions of the specimen under xenon lamp irradiation and rain cycling conditions, the flexural strength of the specimen and the color change. According to GB / T 16422.2 provisions, the test pieces were placed in the chamber xenon arc lamp exposure, another specimen shading saved. Blackboard test chamber temperature (63 ± 3) ℃, relative humidity (65 ± 5)%, water cycle: Each spray time: 18min ± 0.5min, dry period between two water: 102min ± 0.5min, depending on the grade of material, after the exposure time corresponding to the termination of the test. Grey card assessment specimen provided by GB250 color grade, with the specimen in poor light fastness rating represents the sample.
9.Harmful substances (formaldehyde emissions and heavy metal content): WPC may produce formaldehyde pollution in the process, in the process of wood-plastic composite materials will be used in some of the additives, the introduction of heavy metals, heavy metals may cause material excessive levels. Formaldehyde emission testing according to GB18580-2001 standard dryer assay, soluble heavy metals in accordance with the provisions of GB18584-2001.
10.Fire performance:
Due to the large wood decorative panel wainscoting and ceiling area, such as the use of its fire performance can not be missing. When measured with indoor decorative wood panels with fire performance should be consistent with GB8624 "building materials and products of combustion performance rating" appropriate level of requirements.
