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Polymers - Coggle Diagram
Polymers
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Composites
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can dramatically reduce fuel usage due to lighter materials. More expensive when producing but cheaper to run
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glass fibres so incredible strong (defects only found on micrometer scale) so need to exert large amounts of force to break
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High performance
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for large complex shapes, fibres and matrix usually come in precombined sheet form known as prepreg
for continuous profiles and symmetric shapes, reinforcement may be processed as bare fibres impregnated with resin during the process itself and wound over/pulled through formers to provide shape
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Moulding processes
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Injection moulding
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Scrim when multiple injection barrels on a single tool. Once the injection cycle completed, pressure is oscillated before met freezing. occurs in controlled orientation reducing voids but is expensive and can potentially damage the mould
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fibres suffer attrition during transport along screw of injection moulder and during passage through runners and die
probability of fibre alignment due to flow geometry may result in unfavourably oriented weaker sections
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Blow moulding
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the parison (material) supplied in hot tubular form enclosed in spirit mould, air forces it to adopt the shape
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Blow Film
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tube blown up with air which is drawn up in a continuous process. contained in a bubble by collapsing rolls on top
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forms sheets and bags (bags require heat sealing at regular intervals and regular perforations to permit tear off or cutting)
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Filament winding
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fibre orientation controlled by relative speed of rotation of the mandrel and speed of transverse along mandrel by feed eye
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Hot press moulding
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cure and forming techniques require high temperatures, reducing resin viscosity and forming pressure
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Thermosetting polymers
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epoxy resin, unsaturated polyester
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Thermoplastic
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comparatively poor thermal properties, not useful for high temp applications
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nylons, polyethylene, ABS, PET and polypropylene
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