General Safety Guidelines

Polymers are used for lots of things. Three of the most important are rubber, plastics, and fibers. We're going to take a look at how rubber, plastics, and fibers are different from each other, using some things you have seen before: rubber bands, garbage bags, and nylon fishing line. The rubber band is, of course, made of rubber, while the garbage bag is made of a plastic, and the nylon fishing line is made of a fiber.

Your challenge is very simple. You are going to have to answer two simple questions. Here they are:

1. Which material will stretch the furthest without permanently deforming? That is to say, which one will stretch the furthest and still bounce back to its original shape?

2. Which material will stretch the furthest before it breaks?

Of course, there are some rules. Rule #1: Your teacher is going to want numbers. You can't just say which one stretches the furthest. You going to have to be able to say exactly how far each will stretch.

Rule #2: It's not enough just to know how far they will stretch. Yow have to be able to say how far each sample will stretch compared with its original length. This ratio is called the percent elongation, and here's the formula to calculate it:

Materials

Your teacher is going to provide the following materials so you can carry out this investigation:

Goggles or safety glasses
Nylon fishing line
Strips cut from a plastic garbage bag
Rubber bands
Yardsticks
2 pairs of needle-nosed pliers

Pre-Lab

Using the materials listed, develop a plan to test each polymer sample. Remember that during the test, the stress must be placed on the sample. This plan should include all testing methods, criteria, and types of data you intend to collect. This plan must be approved by your teacher prior to proceeding with the lab.

Post-Lab

Create a table that describes the data collected during the experiment. This table must be easy to read and easy to follow. On the same sheet as your pre-lab plan, write a report of your findings.

Application

Congratulations! You've just landed a sales job at a company that makes all different kinds of polymers. You were hired because of your experience testing polymers and their physical properties. You have to help your customers find the right polymer for their needs. Below are descriptions of some customers, and your job is to pick whether their needs call for rubber, plastic, or fiber. Use what you learned in the lab exercise to decide which is right for each customer. Your teacher may ask you to give specific examples of polymers that might work for each customer as well.

1. A cowpoke who needs rope for rounding up cattle

2. A carpenter who wants to build a house with shatterproof windows

3. A bungee jumper who needs a new bungee cord

4. A knitter who needs yarn for making socks

5. A guitar player who needs new strings

6. A veterinarian who needs surgical gloves

7. Now that you've made your sales recommendations, it's time for your annual performance review. To keep from being downsized, match each type of polymer in the left column with the correct behavior characteristics in the right column. Base your answers on your observations in the experiments you just carried out.

   A. rubber B. plastic C. fiber

   easy to stretch, easy to permanently deform easy to stretch, hard to permanently deform hard to stretch, easy to permanently deform hard to stretch, hard to permanently deform