Home  > Technical Support > Molding Technology > Molding Technology for DURAFIDE(R) PPS

6. Safety Precautions

Content Introduction Molding Conditions Use of Regrind Mold Design
  Mold Shrinkage and Dimensional Accuracy Safety Precautions Molding Defects Countermeasures


6. Safety Precautions


There is no danger in molding DURAFIDE® so long as the general safety rules of molding operation are observed. However, like other plastics, DURAFIDE generates decomposed substances when heated to a very high temperature. If ventilation is inadequate, such decomposed substances store up and may cause hazardous health conditions. So, suitable ventilation is highly recommended.

In order to prevent thermal decomposition, gas emission and pressure build up in the cylinder, do not raise the resin temperature over 360°C

When molding is interrupted for a long time, the material in the cylinder must be thoroughly purged out and the temperature lowered to below 280°C.

Before feeding pellets or starting the screw, allow sufficient time for cylinder heating and wait until the temperature reaches at least 300°C.

Operators must wear protective goggles (especially when purging). And also wear gloves when handling a hot molds. When the molding operation is interrupted, withdraw the injection unit to prevent the material in the nozzle section from solidifying by contact with the mold.

 

 


7. Handling of Natural Color Grades


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.

 

 


Content Introduction Molding Conditions Use of Regrind Mold Design
  Mold Shrinkage and Dimensional Accuracy Safety Precautions Molding Defects Countermeasures