RTM (resin transfer moulding)

RTM family is a group of technologies allowing for the production of laminates such as: LRTM (Light Resin Transfer moulding), VARTM (Vacuum Resin Transfer moulding) and the classic heavy RTM.

RTM

This is a technology based on injection techniques allowing to produce big laminates. Characteristic to RTM technology are solid and massive moulds, thanks to which we may inject material with big pressure (2-10 bars).

The production of RTM laminations consists of the following stages:

Firstly, a mould should be prepared to the production: it is cleaned and degreased. Secondly, it is covered with several layers of a separator (wax) and then, polished to be smooth. The prepared this way moulds (the upper and the bottom mould half) are covered with gelcoat, which is supposed to look good and protect them. Moulds can be covered both manually and by injection. Then, the reinforcement form which the laminate will be made has to be fitted. In the serial production, a moulder fits a core made of reinforcing material. The reinforcing material (made of glass, carbon or aramid fibers) has to have structure allowing for the easy flow of the resin, thanks to which its full impregnation in a short time is possible.

After that, the moulds are closed and an adhesive is pumped into them. Polyester, vinylestes, epoxy, methacrylic and many others resins serve as the adhesive. The choice of a resin depends on required qualities of a laminate. The adhesive is injected up till the time it drains from control orifices on the edges of the mould, which would mean that the reinforcement is fully impregnated.

Finally the product is ready, so the mould can be prepared to the production of another laminate. The advantages of the application of the RTM technology are: the possibility of acquiring products that are smooth on both sides and the relatively short time of the production (in comparison to the hand lay-up method). Moreover, thanks to the RTM method the reduction of evaporating styrene is possible and it is what significantly improves the quality of work.

LRTM (Light Resin Transfer Moulding)

VARTM (Vacuum Assisted Resin Transfer Moulding)

The LRTM and VARTM technologies are the improved versions of RTM to which vacuum has been added. Thanks to this kind of combination one can reduce the costs of production because the application of the lower pressure (0,4-1 Bar) allows for making less massive moulds. The VARTM method uses a vacuum bag as an upper mould half, while in LRTM both halves are made of composites.

The LRTM and VARTM production of the laminates consists of the following stages:

Firstly, a mould should be prepared to the production: it is cleaned and degreased. Secondly, it is covered with several layers of a separator (wax) and then, polished to be smooth. The moulds prepared this way (in case of LRTM these are two moulds) are covered with gelcoat which is supposed to look good and protect them. Moulds can be covered both manually and by injection. Then, the reinforcement, form which the laminate will be made, has to be fitted. In the serial production a moulder fits a core made of reinforcing material. The reinforcing material (made of glass, carbon or aramid fibers) has to have a structure allowing for the easy flow of the resin thanks to which its full impregnation in a short time is possible.

After that, the moulds are closed and an adhesive is pumped into them. It can be processed in two ways: (1) an adhesive is injected in the central part on the mould, while a vacuum is applied on its circumference; (2) an adhesive is pumped to the tubule on the circumference of the mould, while a vacuum is applied to its central part.

Polyester, vinylestes, epoxy, methacrylic and many others resins serve as the adhesive. The choice of resin depends on required qualities of a laminate.

Finally the product is ready, so the mould can be prepared to the production of another laminate. The LRTM technology is the most frequently applied in the production of boats and water equipment, but its possibilities are infinite i.e.: elements of car body, trailers, aircrafts etc.

The VARTM technology is being used in composite production in which only one part of the laminate is visible i.e.: parts of cars’ mirrors, bumpers, hoods etc.