PVC foaming products - unbalance characterization between various additives

1. Stabilizer

The most widely used stabilizers in PVC foaming products are Lead Salt Stabilizer and calcium zinc stabilizer. With the increasingly stringent requirements of environmental protection and the higher performance-price ratio of calcium zinc stabilizer, the application of calcium zinc stabilizer has become more and more extensive.

Insufficient stabilizer, yellowing of board surface, large brittleness of paste and products, reduced strength and low foaming rate;

If there is too much stabilizer and the foaming agent decomposes in advance, the gas will overflow from the feeding hole and vacuum hole, and the cavity structure will crack or shrink;

2. External lubricant

The most widely used external lubricants on foaming products generally include Paraffin Wax and PE WAX, which are easy to precipitate, so PE wax is generally used.

The external slip is insufficient, and the temperature in zone 4 and zone 5 of the extruder is not easy to control, and it is easy to overheat. The plate surface has blisters, blisters, yellowing, and rough surface; The friction shear heat increases, causing material decomposition, yellowing and paste on the plate surface;

Excessive external sliding and poor plasticization lead to scaling in the inner cavity of the mold and precipitation on the surface of the product, which is prone to leucorrhea, uneven wall thickness and irregular movement of some symptoms on the surface;

3. Internal lubricant

Common internal lubricants include Stearic Acid, 60, monoglyceride, 316, etc.

Insufficient internal lubrication, poor dispersion of materials, uneven plasticization, difficult to control the thickness of the product, thin middle and both sides of the foam board, white band, adhesion to the mold cavity and local overheating may also occur;

Too much internal lubrication, brittle foaming products, reduced heat resistance, and changed to external lubrication under a certain temperature and melt pressure, resulting in unbalanced lubrication;