Non-metals Flashcards
What is polyethylene made of?
Polymer of ethylene with covalent bonds
What 2 processes are used to synthesise polyethylene?
- Condensation polymerization
2. Addition polymerisation
UHMWPE and PMMA are formed by?
Addition polymerisation
What is ram extrusion?
Pre compressed powder is heated and pressurised into a rod
What is sheet compression moulding?
Heated powder with applied pressure for a longer period (24hours) to increase homogenicity
(Then undergoes milling to achieve desired shape)
What is direct compression moulding?
Resin pressurised and heated in a single mould
better = smoother surface
What is hot isostatic compression moulding?
Cold pressing the resin into a bar then heating it under pressure in an inert atmosphere
What does gamma irradiation of the poly do? 2
Sterilized
Improves cross linking
Why is poly packaged in an inert gas?
To prevent oxidation and degredation
Advantages of UHMWPE? 4
Tough
Ductile
Resilient
Resistant to wear
PMMA function?
Fixation and load distribution in orthopaedic implants
Components of the powder of PMMA? 4
- Polymer
- Benzoyl peroxide (Initiator)
- Barium sulfate (Radio opacifier)
- Coloring agent
Components of the liquid of PMMA? 3
- Monomer
- DMPT (accelerator) - Dimethyl para toluidine
- Hydroquinone (stabiliser)
Features of PMMA? 3
- Youngs Mod btw cortical and cancellous bone
- Strongest in compression
- Poor tensile and shear strength
What are ceramics composed of?
Inorganic metal and non-metal compounds