Resin transfer moulding technique

For some years there has been concern at the amount of styrene vapour in workshops preparing reinforced polyester laminates. More recently this has increased interest in polyester-polyurethane hybrids and in the further development of closed moulding and resin transfer moulding techniques as well as greater use of lower styrene levels. 

Flow diagram of the resin transfer moulding technique. 

The term frequently applied to the total thickness of a thermoset composites moulding, particularly when fabricated by hand-lay, spray/projection, cold-press or resin injection (resin transfer) moulding techniques. However more correctly it should only refer to the fibre-reinforced portion of that total thickness and strictly speaking therefore, should not include the gelcoat, or when applicable, either the flowcoat or any other part or feature of the overall moulded component and its construction. 

Bickerton S, Kelly P. Compression resin transfer moulding (CRTM) in polymer matrix composites. In Advani S, Hsiao K-T, editors. Manufacturing techniques for polymer matrix composites (PMCs). Cambridge (UK) Woodhead Publishing Limited 2012. 

Manufacturing methods for composites vary from manual to fully automated processes, whereby the latter have better quality control than the former. Wet layup, pultrusion, and filament winding are all discussed in some detail, while other techniques such as pull-winding, resin transfer moulding, vacuum bag moulding, and injection moulding are left to specialized composite materials texts. 

Why is resin transfer moulding the preferred technique for liquid composite moulding systems ... 

The work briefly described above was specifically concerned with transfer moulding resins for monolithic packaging but we have since shown that the technique of inhibitor addition is also applicable to other encapsulation methods and materials e.g. powder coating. Work is continuing in this area. 

Sreekumar PA, Joseph K, Unnikrishnan K et al (2007) A comparative study on mechanical properties of sisal-leaf liber-reinforced polyester composites prepared by resin transfer and compression moulding techniques. Compos Sci Technol 67 453 61... 

However, silicone transfer moulding compounds have only been used to a limited extent for packaging integrated circuits. This is due to the less effective lead seal of the silicone resins compared with epoxies, a factor which is more important for a multi-lead IC than for a discrete device. This lead-seal deficiency can be overcome by a technique... 

Transfer molding is used for the manufacture of small components and is particularly useful with multi-cavity tools and where small inserts are to be moulded in. Materials used are polyester and epoxide dough moulding compounds, although a new liquid resin injection technique is reported. 

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