Materials: Wear Safety Goggles

Polymer Lab

Objective: To understand how a polymer is linked using monomers; and to compare the properties of some polymers produced using the same crosslink monomer.

Materials: Wear Safety Goggles.  Small disposable cups or plastic tray  Polymers: (labeled A-D or as provided)  Crosslinker—4% Sodium Borate solution  Toothpicks and/or small stirring sticks  Timer  Measuring tape

Procedure: 1. Put on safety goggles and other safety equipment required by your instructor. 2. Obtain the polymer solutions in dropper bottles and record the names of each in the chart. 3. For each solution tested, add 30 drops of polymer solution to one small cup. Record its properties in the chart. 4. Add 15 drops of the crosslinker solution (Sodium Borate) to the cup. Start the timer and begin to stir the solution. 5. Stop the timer when you think the entire solution has reacted and formed the polymer. Be sure to stir consistently for each reaction. 6. Record the reaction time to become a polymer in the chart. 7. To determine the thickness, place a small stick in the center of each polymer and time how long it takes to fall over when inserted into the polymer. This procedure should be conducted consistently, so determine when you will stop the timer based on the position of the falling toothpick. Record this time in the chart below as the thickness time. 8. To determine length stretched, use the entire amount of polymer formed, then slowly stretch it across the table. When any part of it breaks, stop and measure the length that it will go without breaking. Record this in the chart. 9. To determine flow time, place entire polymer on a 45 degree angle piece of card and measure the time it takes it to flow to the 5 cm. mark. Record this in the table. 10. Repeat this procedure for each polymer. 11. CLEAN up the polymers and dispose of them as indicated by your instructor. The Reaction: Sodium borax acts to link together chains of the polymers. Data: Polymer Name Time to Thickness— Maximum Flow Rate— and Properties: change into time for stick length time to flow Solution: polymer: to fall (sec.) stretched 5 cm at 45° (sec) (cm) angle (sec.)

Analysis/Conclusion:

1. Which polymer had the strongest initial crosslinks using this monomer? Provide evidence for your conclusion.

2. Make a graph of ONE of the measurements to compare the polymers. Summarize the pattern that this graph shows about the polymers.

Phase 2 and 3 only:  How thorough were the reactions of the polymers with the crosslinker? Was there any “leftover” solution? Explain why the amounts of this leftover solution may vary.

 Give at least one suggestion of how to improve the procedure for this lab activity to provide more accurate or precise data.

Phase 3 only:  How might impurities in the polymer or borate solution possibly affect the results? Give one example. How could you test the solutions for this?