Problem 93 - Chemistry The Central Science

Question

If you want to make a polymer for plastic wrap, should you strive to make a polymer that has a high or low degree of crystallinity?

Step-by-Step Solution

Answer

To create a suitable polymer for plastic wrap, you should strive for a lower degree of crystallinity. This results in a more flexible, transparent material with sufficient barrier properties for food packaging and storage, allowing the plastic wrap to effectively adhere and conform to different food items and containers.

Step 1: Understanding polymer crystallinity

Crystallinity refers to the degree of structural order in a solid material. In the context of polymers, crystallinity affects properties such as stiffness, density, transparency, and barrier properties. A high degree of crystallinity results in a stiffer, denser, and less transparent material, while a low degree of crystallinity leads to a more flexible, less dense, and more transparent material.

Step 2: Considering the desired properties of plastic wrap

Plastic wrap is used primarily for food packaging and storage. For this purpose, some essential properties of the material include flexibility, transparency, and barrier properties against moisture, air, and odors.

Step 3: Assessing the role of crystallinity in plastic wrap material properties

When it comes to producing a suitable material for plastic wrap, a lower degree of crystallinity is favored due to the following reasons: 1. Flexibility: A lower crystallinity allows the polymer chains to move more freely, giving the material higher flexibility, which is crucial for plastic wrap to adhere and conform to different food items and containers. 2. Transparency: A more amorphous structure (lower crystallinity) results in a higher degree of transparency, making it easier to see the food items being wrapped, which is a valuable property for food packaging. 3. Barrier properties: Although a high crystallinity might provide better barrier properties against gases and moisture, this difference can be compensated by using multiple layers or adding other barrier materials in the production of plastic wrap.

Step 4: Choosing the appropriate degree of crystallinity

To produce a polymer with properties suitable for plastic wrap, a producer should strive to create a polymer with a low degree of crystallinity. This will result in a material that is flexible, transparent, and has sufficient barrier properties for food packaging and storage.