CM8001

Styrofoam consists of a lot of gas because of the foaming agent. When styrofoam added to acetone, the gas will be released making the styrofoam more solid because of the escaping gas.

a) LDPE is not rigid. It is very soft and flexible whereas HDPE is rigid and not flexible.
b) For linear HDPE, the molecular structure makes the polymer rigid, higher strength than branching LDPE which is soft and have lower strength.

In plastic, the polymer chains are aligned in the same direction and the weak dispersion forces between them allows them to slip pass one another hence when subjected to pulling, it stretches. On the other hand, paper in the molecular level does not have such properties and it is similar to cross-linked polymers where the structure is rigid. Therefore, when paper is pulled, the same thing does not happen.

a. The polymers used for human body should not react in human body, should be non-toxic, light-weight and durable.

b. Poly(methylmethacrylate), PMMA, is used in contact lenses. They are transparent, light-weight, durable and not reactive when placed in human eye. Other than PMMA, polyacrylamide is also used.
c. “Hard” lenses are made from PMMA and “soft” lenses are made from polyacrylamide. The difference is that polyacrylamide contains nitrogen atoms while PMMA does not. This allows polyacrylamide lenses to be gas-permeable and allow oxygen to reach the eye hence being more comfortable for the user. “Hard” lenses are less comfortable and more difficult to place on the eye. The “softer” lenses are soft and flexible which is easier to fit on the eye.