RTM - Resin Transfer Molding

RTM is of major interest for various molding applications as it promises performance improvements and cost savings over traditional methods. It is a strong, lightweight alternative to die-cast, stamped or other formed metal parts.  Some of the major applications; of the RTM process include:

  • Class A outer body panels and assemblies
  • Aerospace and automobile parts
  • Truck panels
  • Oil Industry
  • Military
  • Boat hulls
  • Agriculture industry
  • Water industry
  • Medical composites



The key benefits of resin transfer molding include the following:

  • Good surface quality
  • Physical properties close to SMC
  • Wide range of reinforcements
  • Large, complex shapes
  • Weight Reduction
  • Dimensional tolerances
  • Low capital investment
  • Corrosion Resistance
  • Fire Retardant
  • Heat Resistance
  • Chemical Resistance
  • Weather Resistance
  • Less material wastage
  • Tooling flexibility
  • Strength
  • Low environmental impact
  • Labor savings
  • Zero air entrapment within the product
  • Low Cost Epoxy Tooling
  • Large Panel Capabilities Class (A) Surface
  • Dimensionally Stable Tailored to Meet Specific Physical Properties
  • Meets Low Production Needs



RTM Process:

In Resin Transfer Molding (RTM), dry fiberglass reinforcement is first loaded into a closed mold. Resin is net or near-net shape, RTM offers superior surface finishes, close control of tolerances and less material waste.

RTM is a closed-mold, vacuum-assisted process that employs a flexible solid counter tool used for the B-side surface compression. This process yields excellent strength-to-weight characteristics, high glass-to-resin ratios and increased laminate compression. In this process, fiber preform or dry fiber reinforcement is packed into a mold cavity that has the shape of the desired part. The mold is then closed and clamped.  Catalyzed, low viscosity resin is then pumped into the mold under pressure, displacing the air at the edges, until the mold is filled. After the fill cycle, the cure cycle starts during which the mold is heated, and the resin polymerizes to become rigid plastic. Gel coats may be used to provide a high-quality, durable finished product.

The light RTM (LRTM) process, on the other hand, is similar to that of RTM, but differs in the method of closing the mold. The closure of the mold is done mechanically or by applying vacuum between two seals in the mold peripheral flange.

Final RTM products will be light in weight and high in strength. However, RTM uses heavy structured tooling to withstand the hydraulic pressure.