- Styrofoam contains mostly air hence when it is released by dissolving it in acetone, it looks like the huge quantity of solid is dissolved into a smaller quantity of liquid and is more dense.
2a. LDPE is soft, stretchy and flexible. It will not be resistant to cuts.
2b. It is successful in this application as a thin layer of HDPE was used. This allows the gloves to be less rigid and more flexible. At the same time, HDPE is also orderly arranged, hence maintaining the strength and resistance to being cut.
3. This does not happen in paper. When the plastic is stretched, the 3D structure is altered whereby the molecules become aligned and move in the direction of the pull. This is because there are weak dispersion forces between the HDPE molecules and are easier to break.
On the contrary, paper tears when it is pulled. This is due to the cellulose molecules having stronger intermolecular forces of attraction between the molecules hence it is difficult for molecule to slip pass one another.
3a. It should be safe, biocompatible, cost effective and long lasting.
3b. Polymers such as polymethyl methacrylate (PMMA) are used. More commonly now is the use of Silicone-acrylate materials under trade names such as Kolfocon. Lenses that are comfortable, safe, inexpensive and permeable to oxygen are a few desirable properties.
3c. The difference is that in hard contact lenses, PMMA is used. It is a rigid non permeable plastic. In soft contact lenses, silicone is used. Silicone is more flexible and comfortable to the user during long hours of wear. Silicone also allows oxygen to reach the eye hence it is healthier and safer compared to PMMA.