CM8001

Acetone dissolves polymers, allowing the gas of the foaming agents to escape. The polymer collapses on itself and becomes denser as the gas has been removed.

a. LDPE cannot be used here as it lacks the required tensile strength.

b. The molecules of HDPE must line up in a formation that gives sufficient strength. Using a thin HDPE liner gives sufficient flexibility to the gloves.

Stretching the piece of plastic causes the polymer strands to take up a parallel conformation in the direction of the stretch. The irreversible structural change will at a certain magnitude of force cause the plastic to break.

Paper on the other hand, will not stretch significantly as it is made of bleached cellulose, which is more rigid in conformation. This is why they are prone to breakage instead of realignment.

a. It should be firstly chemically durable and stable, so that it will not break down in the body for a long time. Secondly it should be non-toxic, so that it will not trigger an immunological response. Thirdly it should be insoluble, so that it will not dissolve in fluid constituents. And lastly it should be unreactive, so that it will not cause blood agglutination.

b. There are many different polymers used should as polymethyl methacrylate, polymacron, 2-hydroxyethyl methacrylate. These polymers are used as they are non-toxic, permeable to oxygen and comfortable when in contact with the eye. The materials must also be easy to clean and able to conform to various eye shapes.

c. Hard lenses are usually made of polymethyl methacrylate, which is not gas permeable. Soft lenses on the other hand are usually made of silicone polymers which allows them to be more flexible and allows oxygen to come into contact with the eye. This causes soft lenses to be generally more comfortable to wear.