Resin Transfer Moulding (RTM)
Resin Transfer Moulding is a resin injection process. Rotec is using vinylester and epoxy resins with fiberglass reinforcement in various forms such as veil, continuous mat and various combinations of mat and fabric. By RTM technology Rotec manufactures high quality products with high strength-to-weight ratios, optimal dimensional precision and guaranteed reproduction.
Five phases
The RTM process consists of five phases; placement of reinforcement, mould closure, resin injection, resin curing, and finally; demoulding. Rotec is using mostly steel and aluminium moulds for manufacturing.
When starting the moulding process, the (dry) layers of pre-cut fiberglass reinforcement are placed in the open mould. The size, shape and weight of the glass reinforcement is predetermined for each product. When the full set of glass reinforcement is placed, the mould is closed and, by a hydraulic press, a clamping force is applied . During the third stage of the process, the matrix material (resin) is being injected by high pressure injection. Once the injection phase is completed, the product is cured in the mould by the application of heat (80°C). During the final phase, the flange is removed from the mould and trimmed to remove excess resin.
Advantages
The process is automated to a maximum extent and therefore has significant advantages over alternative production methods such as hand lay-up or spray-up. These advantages include:
- Strong products with a high strength-to-weight ratio;
- Very accurate dimensions;
- Constant quality;
- Pre-defined glass content;
- Precise fiber orientation;
- A short manufacturing cycle;
- Low styrene emission
- Machining is limited to trimming product ends or edges
RTM requires extensive investments in moulds, injection equipment and hydraulic presses, especially in the case of high-pressure injection. Next to this, designing and controlling the process from design through all stages of production, requires know-how and experience.
The RTM process is still gaining importance in the manufacturing sector. It is replacing contact moulding and spray up technologies in situations where high surface qualities need to be obtained or when optimal mechanical properties are of utmost importance.
High Quality
Rotec is specialized in high pressure resin injection to meet the demand of it’s customers for high quality products. With high pressure injection a very high fiber content can be achieved, with 60% - 75% fiber to resin ratio by weight. A high fiber content, precise fiber orientation and the properties of the resin system are the determining factors in obtaining high quality products.
Rotec has developed the RTM technology even further and has built up proprietary technology. The glass fiber material is cut with an advanced CNC cutting machine and is positioned into the open mould as a ready made preform.
Resins
Vinylester or Epoxy resins are being injected into the closed mould containing the reinforcement material. The core material may include materials such as polymer concrete. The precise dimensions and composition of the products are based on calculations performed by Finite Element Analysis. The initial data have been refined over time and updated based upon product testing and long term behavior in the field.
In addition to Flanges, Rotec also produces Manhole Covers, panels and custom designed flanges with RTM technology.
