PVC foamed products - unbalanced characterization of various auxiliaries (I)
The most commonly used stabilizers for PVC foamed products are lead salt stabilizer and calcium zinc stabilizer. With the increasingly stringent requirements for environmental protection and the increasingly high cost performance of calcium zinc stabilizer, the application of calcium zinc stabilizer has become more and more extensive.
If the stabilizer is too much, the foaming agent will decompose in advance, and the gas will overflow from the feeding hole and the vacuum hole.
2. External lubricant
Foaming products on the application of the most commonly used outside the lubrication of paraffin, PE wax, paraffin wax easy precipitation, so the general use of PE wax.
Insufficient external slip, temperature in zone 4 and 5 of the extruder is not easy to control, easy to overheat, large bubbles, string bubbles, yellowing and rough surface of the plate; The friction shear heat increases, causes the material decomposition, the surface becomes yellow, the paste;
Excessive external slip, poor plasticization, resulting in mold cavity scaling and product surface precipitation, easy to appear leucorrhea, uneven wall thickness and some symptoms in the surface irregular movement phenomenon;