DISP - Spectacle Frame Materials - Week 2

Question 1

What consititues a plastic frame?

Answer 1

A shell frame made of plastic

Question 2

What constitutes a metal spectacle frame?

Answer 2

A frame made entirely of metal parts

Question 3

What constitutes a metal / nylon cord (semi-rimless supra / string mount / rimlon) frame?

Answer 3

A nylon cord that holds the lens in place

Question 4

What constitutes a composite/combination spectacle frame?

Answer 4

Consists of both metal and plastic materials

Question 5

What are half eye frames used for?

Answer 5

For near (lookovers)

Question 6

Describe a rimless mounted frame?

Answer 6

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.

Question 7

Describe a semi-rimless mounted lens.

Answer 7

Lenses are held/mounted only at the top.

Question 8

Describe a numount mounting.

Answer 8

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.

Question 9

Name and describe the two broad categories of plastic materials.

Answer 9

Thermoplastic - capable of being reformed under heat.

Thermosetting - set or hardened in the final stages of adjustment. Will not soften on reheating.

Question 10

What are the two main methods of manufacturing a spectacle frame?

Answer 10

Injection moulding
Machining
Can also be made from moulding, followed by machining

Question 11

Name three ways joints are placed into plastic frames.

Answer 11

Heat inserted into a mould
Rivetted into the front and side through the reinforcing wire
Soldered into the reinforcing wire

Question 12

Name some popular plastics used in frame manufacture.

Answer 12

Cellulose acetate
Cellulose acetate
Polyamides
Co-polyamides
Epoxyresin
Polycarbonate
Rubber

Question 13

Describe cellulose acetate. What kind of plastic is it, and what happens to it when in contact with bodily fluids like sweat?

Answer 13

It is a clear thermoplastic. It tends to whiten with continued exposure to sweat.

Question 14

Name 4 advantages and 4 disadvantages of cellulose acetate.

Answer 14

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

Question 15

Which is cheaper to produce, cellulose proprionate or acetate?

Answer 15

Proprionate

Question 16

Name 5 advantages and 4 disadvantages of cellulose proprionate.

Answer 16

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

Question 17

Describe two properties of nylons.

Answer 17

Highly flexible and very tough

Question 18

What kind of frames is nylon typically used for (2)?

Answer 18

Sportswear and sunglasses

Question 19

How are nylon frames made?

Answer 19

Moulding

Question 20

Is nylon easily fitted to lenses?

Answer 20

No, its difficult, and should be cold fitted.

Question 21

Name 3 advantages and 4 disadvantages of nylon.

Answer 21

Advantages

• lightweight
• strong and flexible
• not affected by temperature

Disadvantages

• poor surface quality
• very difficult to adjust

Question 22

What kind on materials are polyamides and co-polyamides based on?

Answer 22

Nylon

Question 23

Name 4 advantages and 3 disadvantages of polyamides and co-polyamides.

Answer 23

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

Question 24

Name 4 advantages and 2 disadvantages of epoxy resin.

Answer 24

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

Question 25

What is the most common material in composite frames?

Answer 25

Carbon fibre set in nylon

Question 26

Name 4 advantages and 5 disadvantages of composite materials.

Answer 26

Advantages

• carbon fibre is 60% lighter than acetate
• good shape retention
• very strong
• can be made considerably thinner

Disadvantages

• cannot be easily repaired
• better to cold glaze
• difficult to adjust
• not available in transparent colours
• brittle when dropped

Question 27

What kind of lenses is polycarbonate usually associated with?

Answer 27

Ophthalmic lenses

Question 28

What is an advantage and disadvantage of using pure nickel as a metal frame?

Answer 28

Advantage - very malleable, and easily adjusted

Disadvantage - causes allergies in ~10% of the population

Question 29

Name 8 advantages and 2 disadvantages of titanium metal frames.

Answer 29

Advantages

• extremely lightweight
• very strong
• high corrosion reistance
• hypoallergenic
• flexible
• low electrical/thermal conductivity
• holds adjustments well
• excellent surface hardness/abrasion resistant

Disadvantages

• very expensive
• welding more difficult

Question 30

Name 5 advantages and 1 disadvantage of aluminium metal frames.

Answer 30

Advantages

• lightweight
• hypoallergenic
• stain/tarnish/corrosion resistant
• solf and cold to the touch
• holds its adjustment well

Disadvantages

• thick frames due to its softness
• causes autism

Question 31

Give three examples of natural materials for frames.

Answer 31

Wood
Tortoise shell
Buffalo horn

Question 32

How can allergic reactions to frames be reduced?

Answer 32

Using a plastic coat