Introduction and Progress of Phenolic Extrusion Molding Process

Phenolic resin has significant characteristics such as flame resistance, low smoke release, and low content of toxic gases, making it widely used in various fire and flame retardant applications. However, how to use phenolic resin in the pultrusion molding process has been a process technology issue that has attracted widespread attention from the domestic and foreign fiberglass industry in the past decade. Here is a brief introduction to the latest developments in phenolic extrusion technology.

In theory, the pultrusion molding process is relatively simple. The types of reinforcement materials used are relatively wide, and can be fiber like, woven or felt like. The components can be glass fiber, aramid fiber, carbon fiber, or other fiber materials.

Reinforcement materials usually use continuous feeding methods, such as the use of untwisted roving yarns and the continuous feeding of fibers from the frame. During pultrusion molding, the fibers first pass through a hot forming mold with the same size as the fiberglass product, and then enter a pulling mechanism. There is a glue groove between the yarn frame and the molding mold, in which pre prepared resin is placed. After the fibers are impregnated with resin, they are arranged through a guiding device and then enter the molding mold.

On the guide device, there is a circular hole or slit used to remove excessive resin adhered to the fibers. The temperature distribution of the forming mold is carefully designed to ensure that the resin has completed the curing process when the pultrusion material leaves the rear port of the mold. In front of the pulling mechanism and cutting machine, there is an air cooling section to cool the extruded products with higher temperatures

According to relevant reports, a new form of process arrangement for the pultrusion process has emerged. This new arrangement involves injecting a mixed resin into the front end of the molding mold under pressure. This new form of pultrusion process not only eliminates the need for resin impregnation tanks, but also maintains the reinforced material in a dry state before injection into the mold. This process method is also known as the "injection pultrusion process" (IP).

This injection pultrusion process method has two advantages:

① The resin group distribution material is relatively accurate and can be continuously measured using a metering pump to avoid errors caused by manual mixing;

② The resin impregnation tank has changed from an open form to a fully enclosed form, greatly reducing the possibility of resin splashing and improving the working environment of the extrusion process.

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