Lamination with the RTM injection method

The ESFOM Company supplies polyethylene foam suited to the products manufactured in the RTM (Resin Transfer Moulding) technology. Laminates are made in closed forms; RTM involves forcing the catalyzed resin into a tightly closed mould previously dry filled with the reinforcing fibre and/or spacer material. The counter-mould is made with steel stiffeners and reinforcements, in a way similar to the mould and that allows for the use of higher injection pressure while the closing is performed in a mechanical way.

RTM lamination relates to the production of polyester laminate elements with the use of closed forms. Laminate products are made in accordance with the files provided by the customer.

Main features of the RTM method:

• high quality and uniform/repeatable structure of laminates
• low emission of volatile substances into the environment
• very good mechanical properties that allow for additional reduction of the wall thickness of the product,
• high glass content and the highest product strength when compared to other methods,
• aesthetic and smooth surface on both sides (even without the application of gel coat), high process efficiency,
• wall thickness tolerance of up to 0.25 mm,
• low waste and low material consumption,
• low unit manufacturing cost of an element – at a relatively high cost of the tooling.

The manufacture of products in closed forms.

At first, gel coat is applied (product manufacture without the application of gel coat is also possible). In the next phase, the supporting layers (glass, synthetic and sandwich type mats, coremat, roving, etc.), as well as possible reinforcements and adaptations are placed on the mould. The use of compressed air, special clamps, actuators or presses ensures adequately tight closure of the mould parts. These parts need to have proper strength due to the high closing forces and pressure related to the resin injection, when this method is applied. Special pastes, composite materials, as well as metal frame structures and reinforcements are used for the above purpose. After the mould has been closed, the resin is injected through special opening or openings.