RTM process principle and technical characteristics

2022-08-18 18:56:14

RTM process principle and technical characteristics

1 RTM process principle

RTM (Resin transfer molding), also known as resin transfer molding or resin die-casting, refers to a process technology in which a low-viscosity resin flows and infiltrates a reinforcing material in a closed mold and solidifies it. Forming process (liquid composite molding).  The pressurized liquid output by the resin and catalyst dose pump according to the ratio is mixed evenly in the static mixer, and injected into the closed mold where the preformed reinforcement has been reasonably laid. Seal and tighten, and allow the resin to flow freely, then cure. 

2 RTM process technical characteristics

It can be seen from the RTM process principle and process that the RTM molding process has the following main characteristics:

RTM is a closed-mold molding process. The infiltration of reinforcement and resin is accomplished by the rapid flow of pressurized resin in a closed mold cavity, rather than manual infiltration in hand lay-up and spraying process, but not prepreg Process and expensive mechanized infiltration in the SMC process, is a low-cost, high-quality semi-mechanized fiber/resin infiltration method.

The RTM molding process adopts the reinforcement preform technology similar to the shape of the product. Once the fiber/resin infiltration is completed, it can be cured. Therefore, a low-viscosity fast-curing resin system can be used, and the RTM mold can be heated to further Improve production efficiency and product quality.

Reinforcing material preforms in the RTM molding process can be prepared from chopped strand mats, fiber cloths, wrinkle-free fabrics, three-dimensional knitted fabrics, and three-dimensional braided fabrics. According to the performance requirements, selective reinforcement, local reinforcement, hybrid reinforcement and the use of pre-embedded and sandwich structures can give full play to the performance designability of FRP/composite materials.

The closed-mould resin injection method of the RTM molding process can greatly reduce the toxicity of harmful components of the resin to the human body and the environment, and meet the increasingly strict restrictions on the volatilization concentration of harmful gases such as styrene in the advanced industry (the volatilization of styrene in the operation workshop is less than 20ppm). ).

·The RTM molding process generally adopts a low-pressure injection process (injection pressure <4kg/cm2), which is conducive to the preparation of a complex overall structure with large size, complex shape and double-sided light.

·RTM molds can choose different grades of molds such as polyester molds, epoxy molds, nickel-plated surface molds, alloy molds, aluminum molds, and steel molds according to the requirements of production scale, which greatly reduces costs.

·The design of RTM molding mold must consider the flow of resin, which has great technical difficulty. When the production volume is large (more than 20,000 pieces/year), the economic benefit of RTM technology production is lower than that of highly automated SMC, LPMC and GMT technologies.

From the above-mentioned characteristics of the RTM molding process and the comparison with other molding processes, it can be seen that the production efficiency and economy of the RTM process are between the low-efficiency, low-cost molding process and the high-efficiency, high-cost molding process. In the production scale of 1000-20000 pieces, the best economic benefits can be obtained, which is very suitable for the production level of my country's glass fiber reinforced plastic industry.