In order to prevent CPE from caking, the line label stipulates that no more than 5% calcium powder can be added to CPE as a spacer. The regular manufacturers use mostly ultra-fine light calcium carbonate, which has high fineness, good dispersion effect, and can effectively and evenly cover the surface of CPE particles, playing a good isolation and anti-caking role. Although it is true that there will be a little dust in the sensory touch, it does not affect the toughness, tensile strength, plasticizing performance and other indicators of CPE, and can be used with confidence.
In recent years, in order to fill up and reduce costs, some manufacturers began to use granular calcium as a CPE isolator, granular calcium is composed of 85% calcium carbonate, 10% stearic acid, 5% PE wax, coupling agent, plasticizer and other components. Because the particle calcium is small in dust in use, well camouflaged, it is not easy to detect, and some manufacturers fill a large number of them. Due to the large particle size and poor dispersibility after surface treatment of granular calcium, CPE particles can not be effectively coated and isolated, and can not play the role of anti-caking. Due to the large amount of granular calcium added, and containing stearic acid and other lubricant, it will delay the plasticization of PVC products, affecting the toughening effect of CPE, products are easy to brittle, easy to break, especially for the buckle plate, bellow, electrical threading pipe and other thin-walled products, more likely to lead to brittle products, but also appear on the surface of the product irregular white spots and other phenomena, which is not plasticized granular calcium. Because some CPE manufacturers add a large number of granular calcium, its specific gravity is different from that of CPE, CPE filled with calcium powder is not easy to mix, which results in a large difference in the content of calcium powder between the first packaged CPE and the later packaged CPE even if the CPE product comes out of the same reactor, and some calcium-free powder is close to the CPE pure material, and the CPE calcium content is different in the same batch number. This makes it difficult for users to determine the process, resulting in fluctuations in the quality of pipes, profiles, and gusset plates.
The use of granular calcium will make the impression of small dust in the sense and use of CPE, but it will actually affect the quality of CPE, so do not blindly judge the quality of CPE through the feel when choosing CPE, we must use scientific methods to identify and measure the calcium powder content of CPE.
Whether it is the addition of light calcium carbonate or the addition of granular calcium and heavy calcium, by detecting the calcium ion content of CPE, the added amount of calcium in CPE can be detected, which makes it difficult for CPE manufacturers to achieve the purpose of reducing costs by adding a large amount of calcium powder. In order to detect the calcium ion content of CPE and not detect adulteration, some manufacturers add other inorganic substances such as talc powder, for which the ash index and test method are added to the HG/T2704-2010 Chlorinated Polyethylene standard. By measuring the mass fraction of CPE ash, the amount of inorganic substances such as calcium carbonate and talc filled into CPE can be quantitatively understood.
Too much inorganic material filling in CPE will lead to delayed plasticization of PVC products, affect the toughening effect of CPE, and make products brittle and easy to break. Therefore, it is necessary to identify and measure the mass fraction of ash according to the scientific method in HG/T2704-2010.
