Traditional hollow blow molding technology is mainly used for thermoplastics. However, with the development of molten core hollow molding technology, thermosetting plastics can also be made into high-performance hollow products. This new technology enables thermosetting plastics to form hollow products similar to thermoplastics, which have higher strength, hardness, air tightness and surface gloss.

Process principle and flow

Principle

Melted core hollow molding technology is based on the difference in physical properties between thermosetting plastics and core materials at specific temperatures. Within a certain temperature range, thermosetting plastics first appear in a molten state, and then undergo a chemical reaction to transform into an insoluble and infusible solid. In contrast, the metal material used for the core melts at this temperature and becomes a liquid substance. Using this principle, a low-melting-point alloy core that is consistent with the internal shape of the desired hollow container can be manufactured and placed in a female mold, combined with injection molding, extrusion, pressing or reaction injection, to achieve hollow molding of thermosetting plastics.

Process

The molten core blow molding method can be classified according to the plasticization method of the raw materials, including injection molding, extrusion molding, compression molding or reaction injection molding. The specific operation steps are as follows: First, install the pre-made fusible core into the female mold and ensure that the core is firm. Next, preheat the mold until it reaches the required temperature. Then, add the material and apply pressure to gradually increase the temperature so that the material fills the entire cavity. When the cavity is filled, continue to heat up to the solidification temperature of the material, which causes the plastic part to harden while the core begins to melt. The molten core flows into the mold through a specially designed channel and regenerates into a new fusible core. Finally, after waiting for the plastic part in the mold to cool, the mold can be opened to take out the finished product.

Key points of production control

Temperature control

Temperature control is crucial in the molten core blow molding process. In the first stage of pressurization and heating, the temperature range of the material melt flow must be accurately grasped and maintained for a period of time to ensure that the material fully fills the cavity. After the cavity is filled, the temperature should be raised and solidified quickly so that the plastic part can harden and the core can melt. If the temperature is too low, the molding cycle will be extended, the plastic part will not harden enough, the core will not be able to melt completely, and the discharge port may be blocked; on the contrary, if the temperature is too high, the plastic part may be burned, discolored, and bubbles may be generated, and even waste products may be generated.

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