Principle Overview
The core principle of the Resin Transfer Molding (RTM) process involves placing a preform—composed of reinforcing materials designed according to specific performance and structural requirements—into a mold cavity that has been pre-fabricated to precise dimensions. Within a controlled pressure range, a specialized resin system is injected into the closed mold cavity using an injection system. The resin impregnates the reinforcement and cures to form the final composite component.
The mold is equipped with peripheral sealing and clamping systems, as well as injection and venting systems, to ensure smooth resin flow, complete evacuation of air from the cavity, and thorough wetting of the fibers. Additionally, the mold includes a heating system that enables the resin to cure and form the composite part. RTM is a molding method that does not require the use of prepregs or autoclaves.
Resin Requirements
RTM-specific resins should exist as liquids or solids at room temperature and remain chemically and physically stable during storage, without undergoing changes in composition or properties.
The resin system must have an appropriate viscosity at the processing temperature (typically within the range of 0.2–0.8 Pa·s). Excessively high viscosity can hinder resin flow and fiber wetting, while excessively low viscosity may cause unstable resin flow and diffusion, leading to void formation.
The resin must have a sufficiently long gel time to ensure complete mold filling and fiber impregnation. Additionally, it should maintain a low-viscosity window of at least 40 minutes to meet the processing requirements of RTM.
The resin should not produce volatile by-products during injection and curing. It must also exhibit good wetting and adhesion properties with the reinforcing materials.
Typical Advantages
Compared with traditional molding techniques, the greatest advantage of the RTM process is its one-step resin impregnation, which replaces the multi-step impregnation procedures of conventional methods. This eliminates the need for prepreg manufacturing, lay-up, vacuum bagging, and autoclave curing, thereby significantly reducing both processing time and production costs.
Plant No.4, Area E, Nanju Industrial Park,Hangbu Town, Shucheng County, Anhui, China 