1. Scope and Description
This method is applicable to the sampling of paints, varnishes and related products in order to obtain an appropriate number of representative samples . Sampling is the first step in testing, and the correctness of sampling directly affects the accuracy of testing results. For products that are not applicable to this method, sampling should be carried out according to the product description or the method agreed between the supplier and the purchaser.
2. Product type
According to the characteristics and physical properties of coating products, they can be divided into the following types of products.
Type A. Fluids with a single homogeneous liquid phase, such as varnishes and thinners.
Type B. A liquid consisting of two liquid phases, such as an emulsion.
Type C. A fluid consisting of one or two liquid phases together with one or more solid phases, such as paints and latex paints.
Type D. Viscous, consisting of one or more solid phases with a small amount of liquid phase, such as putty, mastic and pigment paste prepared with oil or varnish, also includes viscous resinous substances.
Type E. In powder form, such as powder coating.
3. Sample container
Depending on the type of product, the following containers are available: metal cans with unpainted interiors; brown or clear sealable glass jars; paper or plastic bags.
For liquid samples, the containers used should be colorless or brown glass bottles or metal cans. For slurries, liquid-solid mixtures, or solids, wide-mouth metal cans or glass bottles should be used. In any case, the containers need to be clean and dry, and the containers and their lids should be of a material that does not contaminate the sample.
4. Sampling instruments
In order to ensure that the sampling device is not corroded by the product and can be easily cleaned, it can be made of stainless steel, brass or glass, and it should have a smooth surface and no sharp inner corners or grooves. Sampling equipment should also have the function of making the product mix as uniform as possible and taking out a representative sample.
5. Initial inspection procedures for sampled products
(1) Check the appearance of the barrel and record the appearance defects or visible leakage of the barrel. If the leakage is serious, it should be discarded.
(2) When opening the packaging barrel, the outer packaging and dirt should be removed, and the lid of the barrel should be opened carefully without disturbing the product in the barrel.
(3) The initial inspection procedure for Class A and B fluid products <D visual inspection.
a. Crust. Record whether the surface is crusted and the extent of the crust, such as soft, hard, thick, or thin. If there is a crust, separate and remove it along the inner wall of the container, and record the difficulty of removing the crust.
b. Consistency. Record whether the product is thixotropic or gelled.
Note: Both thixotropic and gelled paints and varnishes are jelly-like, but the consistency of thixotropic samples will be significantly reduced by stirring or shaking, while gelled paints and varnishes cannot be reduced in consistency after stirring.
c. Layering, impurities and sedimentation. Check the stratification of the sample for visible impurities and sediment, and record it. @well mixed. Gels or products with dry and hard precipitates that cannot be mixed uniformly cannot be used for testing. In order to reduce the loss of solvent, the operation should be carried out as soon as possible. Remove the crust, if the crust has been dispersed and cannot be completely removed, it should be sieved to remove the crust
Skin. For products with precipitation, a stirring device can be used to fully mix the sample. Products with hard precipitates can also use a mixer. If there is no agitator or the sediment cannot be agitated, pour the flowing medium in the bucket into a clean container. Shovel up the sediment from the bottom of the container with a spatula. After crushing, pour the flow medium back into the original bucket several times and mix thoroughly. If it still cannot be mixed evenly according to this method, it means that the precipitate has dried hard and cannot be used for testing.
(4) Check whether there are any abnormal phenomena such as abnormal color, large or hard agglomeration and foreign matter in the initial inspection procedure of Class E powder products, and record them.
6. Sampling
(1) Sampling of storage tanks or tank trucks For A, B, C, and D products, after stirring evenly, select a suitable sampler to sample from the upper part of the container (1/10 from the liquid surface), the middle (55 from the liquid surface) /10) and the lower part (9/10 from the liquid surface) take the same amount of samples at three different levels for remixing. After stirring evenly, take two samples of 0.2-0.4L each and put them into the sample container respectively. The sample container should leave about 5% of the gap, cover it tightly, and clean the outside of the sample container, and prepare it immediately. sign.
(2) The sampling of the production line should take the same amount of samples from the discharge port at an appropriate time interval, mix and stir evenly, then take two samples of 0.2-0.4L each and put them into containers respectively. About 5% of the gap should be left, and the cap should be tightly sealed, and the outside of the sample container should be wiped clean, and marked immediately.
(3) Sampling of barrels (cans, bags, etc.) According to the number of samples specified in this method, select a suitable sampler, take the same amount of samples from different parts of the barrels that have been pre-inspected, mix them evenly, and take two parts each. 0. 2-0. 4L of the samples were put into the container, the sample container should leave about 5% of the gap, tightly closed, and clean the outside of the sample container, and mark it immediately. (4) Sampling of powder products According to the number of samples specified in this method, select a suitable sampler, take the same amount of samples, use the quartering method to take out 4 times the minimum amount required for the test, put them into two containers respectively, cover them Strictly, make a sign immediately. 7. Refer to national standard GB/T 3186-2006, national standard GB/T 10111-2008.
