PVC because of the high cost performance, is widely used in the material, but the white sole often can appear the phenomenon of pale yellow, especially the summer high temperature weather change color, to prevent the sole color yellow, should first clear the reason of the color yellow, then suit the remedy to the case.
One, precipitate out. Because the shoes with a large amount of plasticizer (generally in the 60 ~ 100 PHR), and liquid plasticizers (especially chlorinated paraffin, liquid paraffin, white oil, etc.) and the compatibility of PVC is not very good, when the temperature rises, it is easy to precipitate to the surface of material, cause the sole yellowed.
Solution: use the plasticizer with high molecular weight and PVC compatibility, such as polyester plasticizer; Use high order calcium powder to increase dispersibility and oil absorption value; Reduce the use of stearic acid soap and stearic acid lubricants, and change the use of polyol ester lubricant; Use part 2 and 3 tree powder to increase the oil absorption value; ACR resin is added to improve the plasticizing uniformity and reduce the surface density.
Secondly, lead pollution. Summer high temperature, the use of lead salt stabilizer, powder for three salt two salt, etc., especially under the condition of high temperature, with sulfur lead pollution will occur (such as packing carton) or can be called sulfur pollution, yellow color.
Solution: change the use of PVC shoe special lead salt stabilizer or replace the sole calcium zinc stabilizer; Reducing contact sulfur; Reduce storage temperature, etc.
Third, lack of stability. The lack of stability of PVC will result in the process of turning from white to yellow and brown until the conversation becomes dark. Stability is divided into light stability, thermal stability and oxygen stability.
Solution: change to high quality stabilizer or increase the use of stabilizer; An appropriate amount of uv absorbent; Add antioxidants and so on.