What should be prepared before injection molding of TPR?

According to the characteristics and supply conditions of TPR material, generally before molding, the appearance and process performance of TPR material should be tested. TPR pellets often contain varying degrees of moisture, solvents, and other volatile low-molecular substances. Especially, TPR with hygroscopic tendency always has moisture content exceeding the limit allowed for processing.

Therefore, drying treatment must be carried out before processing, and the moisture content must be measured. Under high temperature, the moisture content of TPR is required to be below 5%, or even 2% to 3%. Therefore, a vacuum drying oven at 75°C to 90°C is commonly used for drying for 2 hours.

The dried material must be properly sealed and stored to prevent the material from reabsorbing moisture from the air and losing the drying effect. Therefore, using a drying hopper can continuously provide dried hot material to the injection molding machine, which is beneficial for simplifying operations, maintaining cleanliness, improving quality, and increasing injection rate. The loading capacity of the drying hopper is generally 2.5 times the hourly material consumption of the injection molding machine.

Before the initial use of a newly purchased injection molding machine, or when changing products, replacing raw materials, changing colors, or discovering decomposition in the plastic during production, the barrel of the injection molding machine needs to be cleaned or disassembled and cleaned. The barrel cleaning generally uses the heating barrel cleaning method. The cleaning material is generally plastic raw material (or plastic recycled material). For TPR material, the new material being processed can be used to replace the transition cleaning material.