The injection molding method for plastic thermoforming machines is suitable for both thermoplastic and thermosetting plastics.

Rigid thermoplastic and thermosetting plastics can both be produced using injection molding machines. If producing thermosetting plastics, the machine requires minor modifications. Specifically, the nozzle of the injection molding machine needs to be replaced with a larger one, and the backstop ring should also be changed, as the backstop ring is used to prevent plastic from flowing back.

Rigid thermosetting plastics are rarely used in Huangyan nowadays; I've hardly ever heard of them. A decade or so ago, I did hear about them, particularly in the reflectors of our car lights and in some bread machines and ovens, where thermosetting materials were used. However, they are now used less frequently, as many have been replaced by thermoplastic plastics.

Rigid plastics are麻烦 and costly. I'm not sure about the price of rigid materials, but they are definitely more expensive than standard PP. Rigid plastics cannot be crushed and reshaped for production. If defects occur and waste is produced, it becomes unusable; once crushed, they cannot be melted down again. In contrast, thermoplastic plastics can be crushed and reused, shredded and reused over and over. Moreover, many rigid materials require surface treatments like painting, electroplating, and so on. Waste products might end up being scrapped.

Injection molding machines used for producing thermosetting materials are typically older machines that have been modified. They are favored for their ease of production and minimal need for adjustment. They are heated by mold heaters with no water channels, so they are usually older machines that are simply modified for the purpose of manufacturing thermosetting plastic products.