Precipitation and Blooming Causes and Solutions of PVC Foamed Sheets
After long-term production and competition of PVC foam board, foam board formulations commonly used in the market are basically positioned, and the types of raw materials are basically determined.
The reason is very simple. Materials with good compatibility with PVC materials will certainly not precipitate under the appropriate dosage. Only materials with poor compatibility with PVC materials will precipitate when the amount exceeds the critical value. Precipitation is bound to cause more Frost phenomenon.
The commonly used additives for PVC foam sheet include lead salt/calcium zinc stabilizer, yellow white foaming agent, foaming regulator, stearic acid, 60,316A, PE wax, calcium stearate, light calcium carbonate, etc.
The foaming regulator has the best compatibility with PVC, which can promote the melting and plasticization of PVC, form a gelled structure on the network, increase the brightness and brightness, and even reduce the precipitation of materials.
Stearic acid, calcium stearate, 60, 316A are internal lubricants, especially 316A molecules with hydroxyl, compatibility is relatively good, 60 is an ester lubricant, compatibility is also good, stearic acid Slightly special, when the temperature is low, the internal lubrication is mainly used. If the temperature is too high, the temperature will be partly changed to external lubrication and even precipitated. The calcium stearate is easy to form a film on the surface of the equipment. .
PE wax is a high melting point lubricant with poor compatibility with PVC. It can form a film between metal and PVC molecules at high temperatures to prevent blocking. Stabilizer is one of the most important auxiliary agents for PVC. Most of the stabilizers are composite stabilizers. In order to reduce costs, some manufacturers add paraffins, polyols and other small molecules to them, not only with PVC. Poor capacitive, it is easy to cause precipitation.
To avoid the occurrence of precipitation, we can take the following measures. First, a variety of lubricants (low-medium, high-melting, internal and external slip agents) are used in coordination to complement each other to make up for deficiencies. Secondly, in the case of ensuring non-sticking mode Minimize the amount of external lubricants, minimize the amount of internal lubricants to ensure fluidity and plasticization; Third, the selection of stabilizers, try to choose high quality and high price, do not understand can find our platform; fourth , adding a small amount of ultra-fine silica will have a certain improvement in the precipitation.
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