Injection moulding composites

Injection moulding compositions have a number of requirements with regard to granule flow and cure characteristics not always met by conventional formulations. For example, granules should be free-flowing (i.e. of a narrow particle size distribution and not too irregular in shape). There are also certain requirements in terms of viscosity. 

In marked contrast to conventional injection moulding, where orientation effects normally depress conductivity, in this investigation the injection-moulded composite material yielded not only a lower percolation threshold than compression moulded samples, but in the injection direction, also gave conductivity values two to three orders of magnitude higher than the latter. 

The selective hydrogenation of an olefinic bond in crotonaldehyde gives n-butyraldehyde in presence of a suitable catalyst n-butyraldehyde reacts with poly (vinyl alcohol) to form poly (vinyl butyral) which is used as an interlayer for safety glass as well as for coating fabrics and for injection-moulding compositions. Butyraldehyde also finds use in making oil-soluble and alcohol-soluble resins. Butyraldehyde is a raw material for the manufacture of butyric acid and butyric anhydride... 

S ToU, PO Anderson. Microstructural characterization of injection-moulded composites using image analysis. Composites 22 298-306, 1991. 

G. Phiri, M. C. Khoathane, and E. R. Sadiku, Effect of fibre loading on mechanical and thermal properties of sisal and kenaf fibre-reinforced injection moulded composites. J. of Reinforced Plastics and Composites 33 (3), 283-93 (2014). 

Both thermoplastics and thermosets can be formed by compression moulding (Fig. 24.5). The polymer, or mixture of resin and hardener, is heated and compressed between dies. The method is well suited to the forming of thermosets (casings for appliances, for instance) and of composites with a thermosetting matrix (car bumpers, for example). Since a thermoset can be removed while it is still hot, the cycle time is as short as 10 seconds for small components, 10 minutes for large tliick-walled mouldings. Pressures are lower than for injection mouldings, so the capital cost of the equipment is much less. 

Injection moulding - Elastomers Compression moulding - Composites Hand/spray lay-up - Composites... 

The injection moulding of melamine-formaldehyde moulding powders is now carried out on a small scale. Temperatures are somewhat higher than for U-F (e.g. barrel temperatures 100-115°C mould temperatures 163-177°C). Otherwise the considerations are the same as for the urea-formaldehyde compositions. 

One limitation of epoxide moulding compositions is their short shelf life (typically 1-3 months), which necessitates strict stock control. The compounds may be compression, transfer or injection moulded, although compression moulding is preferred for long-fibre grades. 

As a result, the merits of fiber fillers for the manufacture of conducting composite materials by extrusion and injection moulding methods can be realized sufficiently. 

In some compositions the PIB is plasticized with ethyl oleate to improve low temp properties. .. Since the propint is a stiff paste it can be inserted into a rocket motor by a type of injection moulding process (Refs 3 5)... 

The hydrophilic/hydrophobic SIN composition of PDMS with poly(HEMA) and poly(AAC) were proposed as a potential apphcation for high-permeability soft contact lenses. Other sUicone-containing IPNs for contact lenses include polymerization of MMA in the presence of polymerized methacryloxypropyl trimethoxysilane, the cross-linking of a polymeric hydrogel of a copolymer of NVP during the final compression or injection-moulding process. 

Chen, F. and Jones, F. R Injection moulding of glass fibre reinforced phenolic composites 1. Study of the critical fibre length and the interfacial shear strength, Plast.. Rubber Composites Proc. Appl., 23, 241 (1995). 

Fig. 30. Design principles of direct compounding injection moulding machine for processing highly filled polymer compositions...

With mixed aramid fibre/particulate flake compositions in polycarbonate, however, the previously mentioned processing operations significantly reduced the levels of fibre and flake orientation relative to corresponding observations with single particle compounds [167]. For example, in sheet extrusion and injection moulding, the flakes oriented perpendicular to the fibres losing their biaxial orientation parallel to the surrounding machine surfaces. 

In addition to the nature of particulate platelet orientation induced during injection moulding, the associated consequences on molecular orientation and crystalline order of the host thermoplastic matrix have also been reported with particular regard to various flake-filled polypropylenes [174], together with an attempt to interrelate these higher order structural parameters with physical properties of the composites [175]. 

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