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Industrial Chemistry
March 12, 2025 | UR Gate

Preparation of Clay Slime with Experimental Procedure



Objective:

The aim of this experiment is to observe changes in the physical properties of the polymer due to crosslinking with a crosslinking agent.


Theoretical Principle:

The polymer used in this experiment is poly(vinyl alcohol) (PVA), and the crosslinking agent is borax, which is sodium borate (Na₃BO₃). Borax dissolves in water to form boric acid (H₃BO₃). Boric acid accepts hydroxide (-OH) from water, as shown in the following equation:



The hydrolyzed molecule then reacts with PVA as illustrated below:



In the above equation, two PVA chains are crosslinked by borax, resulting in the production of four water molecules. The water content gives the polymer its flexibility and makes it sticky. However, when the polymer dries, it returns to a nearly solid and transparent state.


Materials and Equipment:

  1. 100 mL of 4% PVA solution
  2. 10 mL of 4% sodium borate (borax) solution
  3. Glass beaker
  4. Glass stirring rod or wooden stirring stick
  5. Rubber (surgical) gloves


General Safety Guidelines:

Wear gloves and laboratory goggles during this experiment, as with all lab procedures.
Both borax and PVA can irritate the eyes. Hands should be washed thoroughly after the experiment.


Procedure:

Note:
  • PVA does not dissolve easily in water, so prepare the PVA solution at least one day in advance.
  • The PVA and borax should be mixed in approximately a 10:1 ratio.

  1. Pour 100 mL of 4% PVA solution into the glass beaker.
  2. Food coloring can be added to the PVA solution to create different colors. Simple food dyes are recommended. This coloring should be added before introducing the borax solution, or it can be added directly to the borax solution.
  3. Add 10 mL of 4% borax solution to the beaker and immediately start stirring the mixture using a glass or wooden stirring rod.
  4. Take some of the slime in your hand and stretch it slowly.
  5. The slime is non-toxic and safe to handle. It can be stored in a plastic bag or container.
  6. Record your observations during the reaction.
  7. Follow good laboratory practices and wash your hands with soap and water after the experiment.


Data and Analysis:

Record your observations in your notebook:
  • Before adding borax to the PVA solution, what do you observe?
  • After adding borax to the PVA solution, what do you observe?
  • What happens when you stretch the crosslinked PVA slowly?
  • What happens when you stretch the crosslinked PVA quickly?


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