When molding a natural color grade, pay attentions to notes below.
When molding a natural color grade, pay attentions to notes below. When raw material pellets or molded products, etc. are exposed to direct sunlight, fluorescent lamps, mercury vapor lamps or a high-temperature atmosphere, they will discolor in a relatively short time. Hence they should be stored away from such environments.
Meanwhile, to reduce discoloration when molding, pre-drying conditions should be kept constant. In addition, considering the volume balance of the material retained in the molding machine, any changes in shot volume of the molding machine or the number of mold cavities during the molding must be avoided by all means.
The recommended screw shape is either a low shear type or standard type. High shear-type screws generate more heat and sometimes cause discoloration.
When using nitriding-treated screws, cylinders and nozzle parts, grayish discoloration is liable to occur, so the use of chromium treatment is recommended.
It occasionally happens that in pellets, black spots called "black specks" are included. This is due to discoloration of PPS by heat during the manufacture process of our company. Our company is making every effort to minimize as far as possible such occurrence by improvements in the process, but at present the specks cannot be entirely eliminated. Please take this into account in use. Further, depending on conditions, it should be noted that specks might also occur during the molding process. In addition, there is a possibility that a colored product of high brightness discolors like the natural color grades.