Qn 1. Acetone dissolves the polymer, allowing the gas of the foaming agent to escape. The polymer collapses on itself and is more dense because the gas has been removed.


Qn 2a. LDPE cannot be used in this application because it does not have the required strength.

Qn 2b. The molecules of HDPE must line up in a way that produces the required strength. Using a thin liner of HDPE allows sufficient flexibility.


Qn 3. No,  as the chains that make up a polymer can be stretched, using them to flow past each other. Paper, on the other hand will break when pulled.


4a) bio compatible, light weight, flexible, low cost.

4b) hard contact lenses are made from PMMA. soft lenses are made from polyacrylamide. desirable properties – transport, flexible low density, tough, easy to mould, nonreactive to chemicals on eye surface, easy to manufacture, refractive index, hydrophilic permeable by oxygen.

4c) polyacrylamide has nitrogen atoms in its structure, making it hydrophilic, keeping lens soft and flexible but educes clarity of vision.