CM8001

Structural rearrangement: From expanded, when you add acetone IMF is removed. Therefore, molecules exist singularly. Then after acetone is evaporated, new molecules form a IMF therefore leading to a new structure.

a. It is not very strong – easy to tear
Crystalline structure of LDPE is amorphous. That makes the mechanical strength of the LDPE lower than HDPE which has a uniformly crystalline domain.

b. uniformly crystalline domain allows HDPE to be much stronger. Thus, much harder to tear.

Plastic is a LDPE which is a thermoplastic material. This means it allows molecules to slip past one another allowing the plastic to stretch and cause necking.
Paper is a form from cellulose that contains a hydroxyl group. It allows formation of hydrogen bonds with oxygen on the neighbouring chain. It holds the chain firmly which causes stiffness to increase.

a. high transparency
high chemical resistance
high resistance to lipids
very good stress-cracking resistance

b. PMMA (poly methyl methylcrylate) – Hard
PHEMA (poly hydroxylethylmothacrylate) – Soft
c. Soft contact lens are gel-like plastic made of PS. Hard contact lens are PMMA lens, these are firm and durable plastic. Soft contact lens are softer and much more moist. Thus it is easier to wear and much more comfortable.