YICHUN CITY KEYUAN CHEMICAL INDUSTRY CO,.LTD
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One, calcium zinc, lead salt stabilizer advantages and disadvantages.
1. Lead salt stabilizer.
Good thermal stability, especially long-term thermal stability;
Electrical insulation and weather resistance;
Good processing performance is suitable for various processes;
Color aberration, cannot be used for transparent products!
2. Calcium and zinc stabilizer.
Thoroughly solve the sulfur lead pollution phenomenon; A small amount of lead in the material can be combined with the sulfur in the air, especially at high temperature and humidity.
Good switching adaptability; If you use lead salt stabilizers, replacing other stabilizers may cause cross-contamination, but calcium and zinc stabilizers can help.
Light weight, can increase the mineral filler appropriately, reduce the cost.
2. Precautions for use of calcium and zinc stabilizer:
Confirm the green environmental protection of the stabilizer formula; It is necessary to pay attention to whether the content of heavy metals (lead, cadmium, tin and barium) can meet the requirements of new national standards.
Calcium zinc stabilizer has a strong lubrication effect, and more external lubricant should be added.
The thermal stability of calcium zinc stabilizer is weaker than that of lead salt, the processing window is narrower and the control requirement is higher.
The operation process pays attention to the cleaning cycle, and the calcium and zinc stabilizer lubricants are more abundant, which can easily lead to the increase of precipitation, thus affecting the cleaning cycle. For larger scale production, we need to select the stabilizer. If it is a self-stabilizing agent, it needs to cooperate with the lubricating effect of PE wax or oxidized wax. Moreover, the vacuum degree can be strictly controlled to reduce the precipitation and prolong the time of mold cleaning.
The formulation of good stabilizer and appropriate dosage have little effect on the appearance, material performance and aging resistance of the product.
3. Lubrication and use characteristics of calcium and zinc stabilizer.
In the process of replacing the lead salt stabilizer with calcium and zinc stabilizer, the process parameters should be adjusted properly, and in the end, it is necessary to achieve the material performance and plasticity of the materials we need. It should be noted, of course, that calcium and zinc stabilizers use more lubricant than lead salts. Please look down.
First, we need to understand the main components of stabilizers:
Lead salt: 3 pbo ・ PbSO4 (inorganic salt)
The reason why stearic acid is also taken is to give us a better understanding of the influence of the composition of calcium and zinc stabilizers on the lubricity.
It has been said that to maintain the plasticization uniformity of PVC resin requires both internal and external lubrication, and the external energy is transferred evenly to the PVC resin, while stearic acid ACTS as an internal lubrication.
Calcium stearate, zinc stearate and stearic acid are similar in structure, with charged calcium ions and zinc ions. How to understand the ions with charge, to say the polarity is actually the attraction of charge. The charge of calcium and zinc ions greatly enhances its polarity, and it is important to know that the polarity of calcium stearate and zinc is the strongest in PVC commonly used lubricants. Gives it stronger affinity with PVC resin, so as to eliminate or decrease the PVC resin particles within the layers of the attraction of the ionic bonds, pushing PVC intertwine chain segment is easy to spread, the formation of the sliding layer of high viscosity, friction heat production, the mechanical power transmission of high efficiency, speed up the material to heat up, triggering plasticizing resin transition. Lead salt itself has no such effect.
In other words, calcium and zinc stabilizers have a stable effect and shorten the plasticizing time, which can promote plasticization. If the original use of lead salt stabilizer, using calcium zinc stabilizer, use the same lubricant in (including stabilizer) in the premise, can produce qualified products with lead salt, with calcium zinc can promote material plasticizing ahead of time, may not discharge phenomenon.
Solution: pay attention to the dosage of stearic acid, can use less, less reasonable external lubricant selection, increase the dosage of external lubricant, delay the plasticizing, use less heat conditions allow lubricant. Strictly control the performance of other materials.
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