RTM process
This article briefly introduces the RTM process, advantages, common materials and typical applications to help companies better understand and apply this advanced technology.
1. What is the RTM process?
RTM (Resin Transfer Molding) is a closed-mold, low-pressure injection molding technology for composite materials. Dry reinforcement materials (such as glass fiber and carbon fiber) are pre-placed in a mold, thermosetting resin is injected, and the resulting part is cured. RTM is a process between traditional hand lay-up and high-pressure compression molding, balancing production efficiency, product quality, and cost control. It is widely used in industries such as automotive, wind energy, rail transportation, and architectural decoration.
2. RTM Process
Mold Preparation (usually metal or composite)
Reinforcement Laying
Mold Closing and Sealing
Resin Injection (commonly polyester, epoxy, or vinyl)
Curing (heated or room temperature)
Mold Demolding and Trimming
3. Advantages of RTM
Excellent Surface Quality: Controlled mold surfaces ensure a smooth and consistent surface.
Stable Structural Performance: High fiber volume content and excellent reinforcement.
High Level of Automation: Suitable for medium to large-scale production.
Environmentally Friendly and Clean: Closed-loop process with virtually no styrene emissions.
Flexible Design: A variety of sandwich structures or functional layers can be integrated.
4. Commonly Used Materials for RTM
Types | Common Materials |
Reinforcement Materials | Glass fiber stitch mat, chopped strand mat, fabric, etc. |
Resin | Unsaturated polyester, vinyl ester, epoxy resin, etc. |
Release Agent | Wax-based or silicone-based release agent |
Mold Material | Aluminum mold, stainless steel mold, high-strength composite mold |
5. Application Scenarios of RTM Products
Automotive Parts: Bumpers, Doors, Hoods, Instrument Panel Frames
Wind Turbine Blade Structures: Reinforcement Beams, Shells, etc.
Rail Transit Interior Parts, Seat Shells
Architectural Curtain Wall Panels, Composite Facade Decorative Panels
Marine Structures, Doors, Seats
6. FAQ
What is the difference between RTM and hand lay-up?
RTM uses a closed mold to inject resin, resulting in a better surface finish, higher efficiency, and less pollution; hand lay-up is an open process with more manual labor.
Does RTM require fiber preforms?
Yes. We recommend using materials with stable structures and controllable thickness, such as stitch mats and woven glass fiber fabric.
Is RTM suitable for mass production?
Yes, RTM enables automated, continuous production, particularly in the automotive and wind power industries.
Does using RTM reduce waste?
Yes, closed injection molding increases resin utilization, reducing residue and pollution.
7. Summary
RTM is becoming a mainstream mid- to high-end molding method in the composites industry. It offers excellent production consistency, environmental friendliness, controllability, and high strength. For applications requiring high quality and stable batch sizes, such as automotive, rail transportation, and architectural decoration, RTM is undoubtedly a worthwhile molding solution.