[serial] paint inspector, I want to say to you (2) - Determination of nonvolatile content, have you done it right?

Nonvolatile content, which is defined as the mass fraction of the residue obtained by volatilization of the sample under the specified test conditions The nonvolatile content of the sample is not an absolute quantity, and its value depends on the weighing amount of the sample, the heating temperature and time used in the determination and other factors At present, the national standard for paints and related products is GB / T 1725-2007 for the determination of non-volatile matter in paints, varnishes and plastics The common wrong operations in the test process are as follows: ◆ before sampling, the test sample is not fully stirred evenly, and the sample is not representative Especially for some coating products that are easy to be layered and precipitated, such as zinc rich primer, micaceous iron paint, etc., this operation will lead to large deviation in the test results, and the test results cannot be reproduced ◆ when weighing and taking samples, dip them into the test dish with a glass bar or wooden bar, etc this operation can not ensure that the samples taken are evenly distributed, especially for the color paint samples containing pigments and fillers ◆ for volatile samples, if the reduction method is not used to weigh the samples, if the direct weighing method is used to weigh the volatile samples, the measurement value will be inaccurate due to solvent volatilization during the weighing process, resulting in large deviation of the test results ◆ the solvent contained in the sample is not easy to volatilize when the sample is not fully spread in the test pan after weighing and baking, which will lead to high test result value Error figure the correct operation of the above operation is as follows: ◆ weigh the sample immediately after the test sample is fully stirred evenly ◆ when weighing the sample, use a spoon (or a device that can ensure that the uniform sample is obtained) to take the sample and put it into the test dish ◆ after the volatile sample is stirred evenly, put it into a small dropper, and weigh the sample with the decrement method ◆ after weighing the sample, spread the sample completely or as far as possible in the test pan For the high viscosity sample or easy skinning sample, use a metal wire (use an unpainted paper clip) and the pan to weigh together to flatten the sample When the test accuracy is high, a small amount of diluent can be used to dilute and disperse the viscous sample Have you done these operations correctly? Related wonderful articles (click on the title to read) [serial] coating inspector, I want to say to you (1) - from the feeling caused by the assistant of the experiment w cleaning the windowsill [guide] coating inspector, I want to say to you (3) - "fine" operation, reading "degree", how can we do the coating "fineness" test?