DISP - Spectacle Frame Materials - Week 2 Flashcards
What consititues a plastic frame?
A shell frame made of plastic
What constitutes a metal spectacle frame?
A frame made entirely of metal parts
What constitutes a metal / nylon cord (semi-rimless supra / string mount / rimlon) frame?
A nylon cord that holds the lens in place
What constitutes a composite/combination spectacle frame?
Consists of both metal and plastic materials
What are half eye frames used for?
For near (lookovers)
Describe a rimless mounted frame?
Spectacles in which the nose bridge and temple arms are directly screwed into the lens, and thus there is no need for a frame around the lenses.
Describe a semi-rimless mounted lens.
Lenses are held/mounted only at the top.
Describe a numount mounting.
When there is only one attachment to the lens (such as the nasal edge). The entire nose bridge and both temple arms are one continuous piece.
Name and describe the two broad categories of plastic materials.
Thermoplastic - capable of being reformed under heat.
Thermosetting - set or hardened in the final stages of adjustment. Will not soften on reheating.
What are the two main methods of manufacturing a spectacle frame?
Injection moulding
Machining
Can also be made from moulding, followed by machining
Name three ways joints are placed into plastic frames.
Heat inserted into a mould
Rivetted into the front and side through the reinforcing wire
Soldered into the reinforcing wire
Name some popular plastics used in frame manufacture.
Cellulose acetate Cellulose acetate Polyamides Co-polyamides Epoxyresin Polycarbonate Rubber
Describe cellulose acetate. What kind of plastic is it, and what happens to it when in contact with bodily fluids like sweat?
It is a clear thermoplastic. It tends to whiten with continued exposure to sweat.
Name 4 advantages and 4 disadvantages of cellulose acetate.
Advantages
- easily polished
- colour-fast
- easily repaired (softens at 57C)
- low allergy risk
Disadvantages
- blisters if overheated
- leaching of plasticisers causes frames to be brittle
- frames return to their flat state if overheated
- frames may be damaged by solvents like acetone
Which is cheaper to produce, cellulose proprionate or acetate?
Proprionate
Name 5 advantages and 4 disadvantages of cellulose proprionate.
Advantages
- slightly lighter than cellulose acetate
- can be made thinner than cellulose acetate
- cheaper to produce than cellulose acetate
- hypoallergenic
- easily polished
Disadvantages
- blisters if overheated
- leaching of plasticisers causes frames to be brittle
- less colour stable
- frames may be damaged by solvents like acetone
Describe two properties of nylons.
Highly flexible and very tough
What kind of frames is nylon typically used for (2)?
Sportswear and sunglasses
How are nylon frames made?
Moulding
Is nylon easily fitted to lenses?
No, its difficult, and should be cold fitted.
Name 3 advantages and 4 disadvantages of nylon.
Advantages
- lightweight
- strong and flexible
- not affected by temperature
Disadvantages
- poor surface quality
- very difficult to adjust
What kind on materials are polyamides and co-polyamides based on?
Nylon
Name 4 advantages and 3 disadvantages of polyamides and co-polyamides.
Advantages
- lighter than acetate
- hypoallergenic
- very hard and durable
- thinner than other frames
Disadvantages
- will shrink if overheated
- difficult to adjust or repair
- cold glzing
Name 4 advantages and 2 disadvantages of epoxy resin.
Advantages
- lighter than acetate
- hypoallergenic
- very hard and durable
- will not age (no plasticisers)
Disadvantages
- will return to its original shape if overheated
- Cannot be easily repaired
