What Is Resin Transfer Moulding?
Resin Transfer Moulding, more often known as RTM, is a process which uses low pressure closed moulding to create a dimensionally accurate, high quality surface finish. It is a form of composite moulding, which uses liquid thermoset polymers which are reinforced with numerous forms of fibres; usually fibreglass is used, although there are a wide variety of options for more robust industrial applications; often a combination of several reinforcements is used. Polymers are often Polyester, Phenolic, Epoxy, Methyl Methacrylate or Vinyl Ester.
The selection of different polymers and reinforcements; called the matrix selection when numerous choices are made in a combination; is what dictates the cost of the moulding materials, as well as mechanical and finished surface performance. Other minerals are often added to reduce cost and increase fire retardancy among other things.
Fibres that constitute the reinforcements are introduced to the mould in dry form in either random continuous strand mat, binder bound chopped mat or woven cloth format. Often the fibre is preformed to the specific shape of the mould to ensure a good fit and smooth finish, alternatively it can be hand tailored to the shape of the mould during the moulding process. The surface of the mould is often gel coated by spraying the mould surface before the fibre is situated. Upon installing the fibre into the mould, a premixed resin and catalyst are injected into the aforementioned closed mould cavity, which encases the fibres.
The advantages of Resin Transfer Moulding are mainly the comparatively low pressure that is required in production; it almost never exceeds 100 psi of pressure; and the high quality finished product. Other advantages include the cleaner and healthier process which improves conditions for the machine’s operators; the option of extremely thin products which in some cases can be less than 0.1 mm thick; and the low volatility of emissions.
Although RTM shares some common aspects with Compression Moulding, it differs in that in transfer moulding, the resin is inserted into the mould which contains the fibres, layered or otherwise, whereas in compression moulding, the components for moulding are already in the mould when heat and pressure are applied. The lack of pressure applied in Resin Transfer Moulding means that it is often considerably cheaper than its compression counterpart.
In summary, in the current economic down turn, it is important to choose a method of moulding that is cost effective and extremely efficient when you are intending to mould plastics, as it can save your company a great deal of money and ensure a high quality finish every time.
Resin transfer moulding, like its counterparts compression moulding and injection moulding, can be relatively cheap when used for the correct applications. RTM can create a high quality finish on plastic products of almost any size.
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