PRESS MOULDING

Press moulding is used to cover a range of processes in which a mould is filled with material comprising fibre/resin/filler. The mould is then closed and pressure (and usually temperature) is used to cure the mixture thereby moulding the component. 

The moulding compounds separate into those using thermosetting resins (SMC, BMC, DMC) and thermoplastics (TSC, GMT) and are used with specific processes (Table 11.9). These can contain either random, chopped or orientated glass fibres (Table 2.7). As compounds are developed for specific properties and applications, both the process route and property level are known and will be reproducible. 

The principal data from other chapters are listed in Table 11.10 for reference. 

Some typical data are given in Table 11.11 for two compounds and processes. 

A higher fibre volume fraction can be obtained with SMC than BMC compounds, which is reflected in the higher value of properties for the former than the latter. However the compounds come in different forms (sheet and dough for SMC and BMC, respectively) and this dictates the shape and geometry of the mould. 

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The cross-linking reaction is carried out after the resin has been applied to the glass fibre. In practice the curing is carried out either at elevated temperatures of about 100°C where press mouldings are being produced, or at room temperature in the case of large hand lay-up structures. 

In the industrial world bricks are mostly made in an automated production process. After the raw materials have obtained the correct composition and plasticity, the forming process follows. In The Netherlands hand moulding, press moulding and extrusion moulding are applied in coarse ceramics. Occasionally the stamping press is still used, mainly in the manufacture of roof tiles. 

Fig.11.2.2 Press moulding, (source Koninklijk Verbond van Nederlandse Baksteenfabrikanten [Eng. Royal Association of Dutch Brick Manufacturers])...

Details are given of the use of three different types of aminosilanes for crosslinking plasticised PVC. Data are given for milling, followed by press moulding and... 

The press-mould has to be filled with enough material to exceed by 2 g the amount necessary for pressing the test core, and the time elapsing from the moment... 

Yang et al used a low viscosity resin solution which was allowed to infiltrate the buckypapers to impregnate the SWNT rope networks. A hot-press moulding process was used for moulding and euring to produce the final composites. Nanocomposites with preformed tube networks and high SWNT... 

Compression moulding (hot press moulding) Moulding compounds (often complex mixtures, e.g. dough or bulk moulding compounds) prepared in Z-blade mixer and heated under pressure in closed mould Small to medium articles, especially electrical mouldings large capital outlay... 

Compression moulding or hot press moulding is one of the oldest processes, dating from the early history of the rubber industry, before plastics were developed. In recent years, much of the innovation has been stimulated by the use of new materials. 

Cold Press Moulding—A low pressure, low temperature process in which fibres are impregnated with a cold cure resin and then pressed between matched dies. 

Dough Moulding Compound (DMC)—A mixture of chopped fibres, fillers and thermosetting resin, used in hot press moulding and injection moulding. 

Hot Press Moulding—Heated matched dies are loaded with thermosetting compound and pressed together until cured. 

Autoclave/vacuum bag No Compression moulding Hot press moulding No... 

Hot press moulding is a mass production method for the manufacture of composite components. A hydraulic press is used capable of applying a pressure of about 100 tonnes/m of platen area. A matched metal tool is located between the platens, the cavity between the tool halves having been machined to produce the shape required. The tool is heated to about 130-170°C either from the heated platens or directly (by cartridge heaters, etc.). 

Hot press moulding can be carried out either using dry reinforcement to which a resin mix is added when in the tool or by the use of a previously produced compound of resin... 

Products for outdoor use such as wall cladding, can be press moulded in many variants from SMC or BMC. Pultruded profiles can also achieve B1 fire status if a resin such as DCPD or unsaturated polyester/MMA is used with up to 250 phr of ATH as part of the additive package. The classification of flame resistant GRP systems in the SBI test will be a great boost for the materials enabling them to satisfy the fire protection rules of the future. 

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