Light Resin Transfer Molding

Posted on June 16th, 2014 by admin

Sintex – Wausaukee has been providing innovative solutions with light resin transfer molded components for more than 30 years. Today, SWC continues to lead the FRP component market space providing custom molded products to Original Equipment Manufacturers worldwide.

The LRTM process is based on a minimal tooling structure as compared to the traditional RTM or other closed molding process such as SMC or BMC. LRTM tooling costs are a fraction of the price of equivalent RTM molds. The typical LRTM mold has one rigid half for the “A surface” of the mold with then a light weight “see through” semi flexible upper mold half. Each mold half is made from a thermoset polyester or vinyl ester tool with a gel-coat surface. Tools generally have a fiberglass reinforced thermoset polymer laminate backing that is supported by steel tubing or frame to retain the tooling shape and provide an ergonomic orientation.

SWC’s industry leading expertise in Light Resin Transfer Molding (LTRM) produces innovative and cost-effective solutions for our OEM customers. SWC specializes in LTRM parts for:

Mass transit products including Docket 90 interiors parts (close outs, seating, boxes) and external parts (window assemblies, fairings)
Agricultural equipment such as wheel covers, fenders, hoods, trunk covers and engine covers
Construction equipment such as fenders, hoods, engine covers and cab roofs
Architectural and industrial site furnishings like planters, sitting arrangements and receptacles
Recreational products including trike bodies, wheel covers and fenders

Advantages of LRTM Glass Reinforced Composites


Structures made of composites have a long life and need little maintenance. Composites are corrosion resistant with matrices and binders that prevent environmental attack on fibers and increase resistance to corrosive environments.

High Strength to Weight Ratio

Strength-to-weight ratio is a material’s strength in relation to how much it weighs. Composites have the highest strength-to-weight ratios in structures today. Composites can be made to resist bending in multiple directions or a single direction as needed.


Composites combine high strength and low weight, are non-corrosive and have thermal and electrical insulation properties. Composites can be machined like wood using diamond-tool equipment.

Custom Engineered & Tailored

Composites can be custom tailored for very specific purposes – a particular load, strength in one direction or greater strength to weight ratio. Composites can be designed and optimized to further reduce weight and improve properties by tailoring the binders, fiber type and fiber orientation.

Design Flexibility

Composites can be molded into complex parts that would require sub-assemblies if done in metal. Components can be designed with rigid, semi-rigid, or foam materials. Components can be made fire retardant, or include EMI/RFI shielding.

Hardware & Fixture Integration

Molded composite components can be designed and manufactured to integrate hardware and fixtures into the completed part reducing component assembly and installation costs.

Excellent Cosmetic Finish

Composites can be designed with a high level of surface detail. Parts can be offered in various thickness either coated with high gloss gel coats or with a paintable surface.


General Design Guidelines

Minimum Radius6 mm (0.236 in)
Minimum Draft2 degrees
Minimum Thickness3 mm (0.118 in)
Maximum Thickness12.7 mm (0.500 in)
Typical Reinforcement Loading30 – 40 %
Density (GP resin)1578 kg/m3 (0.057 lb/in3)
Die Lock (Reverse Draft)No

Selection Guidelines

Moderate production rates (100 – 7,000 parts/year)
Consistent dimensional tolerances
Consistent resin/glass ratio
Higher strength parts
Two sided finish
Cost effective tooling
Sintex - Wausaukee Composites

Our Products