• To prepare four polymer elastomers in the laboratory
• To examine physical properties of the elastomers
• To describe the role of bonding and crosslinking in organic molecules
• To compare addition and condensation polymerization.

Applicable Science Concepts:

• Definition of a polymer
• Definition of an elastomer
• Definition of crosslinking
• Explanation of polymerization with structural formulas:
  Addition Polymerization
  Condensation Polymerization
  
• National Standards for 9-12

Materials:

• Elmer's® White Glue-All
    (30 mL per ball)
• Elmer's® Blue Glue Gel
    (30 mL per ball)
• Borax powder (solid sodium tetraborate decahydrate), Na₂B₄O₇•10H₂O(s)
    (1 g per ball)
• Liquid latex rubber, from local craft or hobby store
    (15 mL per ball)
• 5% acetic acid solution, CH₃COOH(aq), (household vinegar)
    (15 mL per ball)

• Saturated sodium silicate solution, Na₂SiO₃(aq)
    (12 mL per ball)
• 50% ethanol solution, C₂H₅OH(aq)
    (3 mL per ball)
• Small disposable plastic cups
• Plastic stirring rod or wooden stick
• Tap water
• Small sealable plastic bags

Equipment:

• Balance
• Weighing boats or weighing paper
• Meterstick and/or metric ruler
• Small length of string
• Graduated cylinder

Safety:

• Safety goggles and lab aprons should be worn to protect eyes and clothing. This is especially important when working with the latex and sodium silicate polymer experiments.
• If a chemical gets into eyes, immediately flush eyes with water.
• Elmer's® White Glue-All and Blue Glue Gel are nontoxic, but should not be ingested.
• Borax is sodium tetraborate decahydrate. It is an eye irritant.
• Liquid Latex is preserved in ammonia and has a very strong odor. Do not inhale. It may also irritate skin, so handle with gloves. If it comes in contact with skin, wash thoroughly with soap and water.
• 5% acetic acid solution is the same as household vinegar.
• Sodium silicate solution is irritating to skin. Handle with gloves.
• Ethanol is flammable. Keep away from flames.
• For Material Safety Data Sheets (MSDS) on these chemicals, click here.

Experiment:

• Preparation:

Polymer Balls
Ball #1 Elmer's® White Glue-All and Borax Powder	Ball #2 Elmer's® Blue Glue Gel and Borax Solution	Ball #3 Liquid Latex and Acetic Acid Solution	Ball #4 Sodium Silicate Solution and Ethanol Solution
Procedure for Ball #1	Procedure for Ball #2	Procedure for Ball #3	Procedure for Ball #4

• Investigations:  Compare properties of the polymer balls .


Physical Appearance:  Describe the texture, color, and other observable characteristics.
Density:  Find the density of each polymer ball. Determine volume without using water displacement method.  (Water will break down some of the polymers.)
Bounce Height:  Drop each ball from the same height and record how high it bounces.  Repeat the procedure until you have consistent data.
Temperature Changes: Describe the changes in properties after the polymer balls have been heated and cooled.
Exposure to Air:  Use two sets of balls. Store one set in sealed plastic bags; leave second set exposed to air. After 24 hours, repeat first days investigations and compare data.

• Photo Documentation:  Click here for photographs from this experiment.