A Research to Distinguish Various Polymers and Their Properties

Abstract

A polymer is any number of natural or synthetic compounds which can contain thousands of atoms held together by covalent bonds. This is made up of a chain of monomers linked together. There are two different types of polymers, cross linking and linear. Linear polymers the individual strands are not connected. Therefore, they can slide past each other easily. The more a linear polymer is stretched causes the loss of shape or even breakage. cross linked polymers are connected. This makes the polymer harder to stretch but will eventually turn back to the original shape. Nylon, snake and puff, green slime, polyester and gloop are all forms of polymers made in this experiment.

Purpose

Distinguish various polymers and their properties. Determine which polymers are cross-linked and linear. Compare and contrast polymers using functional groups.

Results

Nylon-66 is an example of a condensation polymer. One component is dissolved in an aqueous layer and a second is dissolved in a dense organic layer. This reaction occurs where the two layers meet and a linear polymer forms. Throughout this reaction, sodium hydroxide is often added in small amounts. The reason for this is to remove the HCl molecule in order to drive the reaction. This polymer is stringy, strong, flexible so it will match up with A and D from figure 1. This fits with the polymer because the reactions are both linear.

In the Snake and Puff demonstration a small amount of p-nitroaniline is mixed with concentrated sulfuric acid to form a paste. The paste is heated until the reaction produces long, plastic like polymer snakes and puffs of smoke. p-nitroaniline has two different functional groups. The puzzle piece from figure 1 that fits this is c because it has two different symbols for the functional group. In this reaction the sulfuric acid dehydrates the p-nitroaniline. This means during dehydration, water is removed from the reaction and is replaced with sulfuric acid.

In part B, the alcohol that is given is ethylene glycol and one is glycerol. In this experiment a person is to determine which is which by making two polymers and comparing their properties. In order to complete this task obtain two test tubes and label them A and B. Clamp each on a ring stand in the hood. Add approximately 2.5 grams of phthalic anhydride and 0.2 grams of sodium acetate. Add 2.0 mL of alcohol to each tube. Then heat the tubes gently. Continue heating gently to effect a degree of polymerization where the properties of the two polymers can be compared. One polymer will be reddish purple.

The other appears a light brown. Once this has been done pour out the contents of the test tubes on two separate pieces of aluminum foil. Let the polymers cool and then examine the results. Based on the results the polymer in test tube A is a cross linked polymer. The texture is rigid and resembles rungs on a ladder. Test tube B is a linear polymer, this is stringy and flexible. Patterns A and D from figure 1 fit test tube B which is linear. Patterns F and D are the best model for test tube A because it is cross linked. The proper name for the alcohol in test tube B is ethylene glycol. Test tube A, is named glycerol.

The next experiment is green slime. This is when borax is added to the linear polymer, a new polymer like slime is formed. To make this happen, place 20 mL of poly(vinyl alcohol) solution in a zip-lock bag. Add 3 mL of sodium borate solution along with a few drops of food coloring. Gently knead the bag with your hands to mix around the solution. When a solid gel has formed, remove it and investigate the characteristics. The polymer that is formed is a slimly substance.

It does not flow when placed on a countertop. When the polymer is held it slowly slides and stretches down. It does not show any signs of breaking or cracking. It can be flattened when pressed against a countertop. When the polymer is rolled into a ball it is able to bounce. In handling the polymer it mainly stays at room temperature. Based off of figure 2 from the lab manual, model B describes the formation of the poly(vinyl alcohol)/borate polymer. This is best, because the model shows two chains fit together and it gives a spot for alcohol to attach to it.

In making silly putty or gloop, measure out 15 mL of white glue and 7.5 mL of laundry starch. Place in a plastic bag and add a couple drops of food coloring. Mix with popsicle stick then take the polymer out and knead it with your hands. In comparison to the slime, the gloop does not flow and it does not crack. The gloop cannot be flattened without breaking. While the slime could bounce, the gloop does not have this characteristic. The gloop can be separated with more work and effort unlike the slime. The gloop is more of a cross linked polymer while the slime is more of a linear polymer based on the observations.

Conclusion

Polymers are not hard to make. They are tricky to identify their physical properties and then classifying them. Based on the results from the reactions it can be determined that Nylon-66 and slime are linear polymers. This means snake and puff and gloop are cross linked polymers based on the characteristics observed. In the polyester procedure, test tube B, was figured to be ethylene glycol while test tube A was glycerol. Ethylene glycol is a linear polymer and glycerol is a branched polymer.