CM8001

Styrofoam is a foaming agent and when acetone dissolves the polymer, gas is allowed to escape causing the polymer to collapse on itself thus becoming denser.

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

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

When the piece of plastic is stretched, the strip narrows and “necks down”. The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the 3-D structure is not reversible, and if the pulling continues, the plastic breaks.
When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. This is because the cellulose molecules in paper are held for more rigidly in place, and are not free to become aligned.

a) Durable. Good inductors. Low cost. Contains the same elements found in the human body (safe). Lack of reactivity with body fluids. Non-toxic.

b) Hard lenses are made up of PMMA. It is durable and chemically inert. On the other hand, soft lenses are made up of silicone acrylate. It is inexpensive, it has higher oxygen permeability, has good lens moisture and is comfortable to wear.

c) For hard lenses, it is able tor retain its shape easily. It requires no water to maintain their shape, thus it will not pull moisture away from the eyes leaving the eyes more moist. It is also durable as it does not tear easily.
For soft lenses, it is easily distorted when blinking as suction is removed to a certain extent. Soft lenses draw water away from eyes leading to dry eyes. It is also fragile and it tears easily because it is made of thin gel-like plastic.