PVC is widely used in shoe materials because of its high performance-price ratio. However, white soles often change color and turn yellow, especially in high temperature weather in summer. In order to prevent the soles from changing color and turning yellow, we should first identify the reasons for the color and turn yellow, and then apply the right medicine to the case.
First, precipitation. Because there are a lot of plasticizers (generally 60~100PHR) added to the shoe material, but the compatibility of liquid plasticizers (especially chlorinated paraffin, liquid paraffin, white oil, etc.) with PVC is not very good. When the temperature rises, it is easy to precipitate to the surface of the shoe material, resulting in yellowing of the sole.
Solution: use plasticizers with high molecular weight and good compatibility with PVC, such as polyester plasticizers; Use high mesh calcium powder to increase dispersion and oil absorption value; Reduce the use of
Stearic Acid soap and stearic acid lubricant, and replace with polyol ester lubricant; Use some type 2 and 3 resin powder to increase oil absorption value; Add ACR resin to improve the uniformity of plasticization, make the surface compact and reduce the exudation.
Second, lead pollution. When the temperature is high in summer, lead salt stabilizers, especially powdered trisalt and bisalt, are used. When the temperature is high, lead pollution or sulfur pollution, yellowing and discoloration will occur when sulfur elements (such as packaging cartons) are encountered.
Solution: use
Lead Salt Stabilizer for PVC shoes or calcium and zinc
Stabilizer for soles; Reduce exposure to sulfur; Reduce storage temperature, etc.
Third, the stability is insufficient. Insufficient stability of PVC will lead to the process from white to yellow to red to brown, and then the conversation will turn black. Stability is divided into light stability, thermal stability and oxygen stability.
Solution: replace with high-quality STABILIZER or increase the amount of stabilizer; Add an appropriate amount of ultraviolet light absorber; Add antioxidants, etc.
