topic 3.1 Flashcards
(28 cards)
What are thermoplastics?
Plastics that soften when heated and can be reshaped multiple times
Examples include acrylic, polyethylene, polypropylene, and polystyrene.
What are thermosetting plastics?
Plastics that set permanently after heating and cannot be reshaped
Examples include epoxy resin, melamine formaldehyde, and urea formaldehyde.
How does injection moulding work?
Polymer granules are heated until molten, injected under high pressure into a closed mould cavity, and cooled to solidify
Suitable mainly for thermoplastics, with some thermosets.
What are the advantages of injection moulding?
High production speed and volume, high precision and complex shapes possible, low wastage
Excess material can often be recycled.
What are the limitations of injection moulding?
High initial tooling cost, not cost-effective for small batches
How does blow moulding work?
A tube of molten polymer is inflated inside a mould using compressed air to form hollow parts
What are common uses of blow moulding?
Plastic bottles, containers, fuel tanks
What are the advantages of blow moulding?
Efficient for hollow products, good surface finish, uniform wall thickness
What are the limitations of blow moulding?
Limited to hollow shapes, less precise than injection moulding
How does compression moulding work?
Preheated polymer is placed into an open mould, closed, and compressed under heat and pressure to shape and cure
What types of plastics is compression moulding suitable for?
Thermosetting plastics like melamine and phenolic
What are the advantages of compression moulding?
Good for large, strong parts, lower tooling costs than injection moulding
What are the limitations of compression moulding?
Longer cycle times, less detailed surface finish
How does rotational moulding work?
Polymer powder is placed in a hollow mould, heated, and rotated on two axes to melt and coat the mould evenly
What are suitable thermoplastics for rotational moulding?
Polyethylene
What are common uses of rotational moulding?
Large hollow items like kayaks, tanks, playground equipment
What are the advantages of rotational moulding?
Uniform wall thickness, cost-effective for large, hollow parts without seams
What are the limitations of rotational moulding?
Slow process, limited to hollow parts
List some properties and uses of polypropylene (PP)
- Lightweight, chemical resistant
- Food containers, automotive parts
List some properties and uses of polyethylene (PE)
- Tough, flexible, waterproof
- Bottles, toys, containers
List some properties and uses of polystyrene (PS)
- Rigid, easy to mould
- Packaging, disposable cutlery, CD cases
List some properties and uses of acrylic (PMMA)
- Transparent, scratch-resistant
- Lenses, display cases, lighting covers
List some properties and uses of melamine formaldehyde
- Hard, heat resistant, electrical insulator
- Kitchenware, electrical fittings
List some properties and uses of epoxy resin
- Strong, heat and chemical resistant
- Adhesives, coatings, electronic components
