Making nylon

Nylon is a condensation polymer formed by combining a diamine with a dicarboxylic acid or diacyl chloride. We shall react diaminohexane, H 2 N–(CH 2 ) 6 –NH 2 with sebacoyl chloride, ClCO–(CH 2 ) 8 –COCl. Since our starting ingredients have 6 and 10 carbons, the nylon formed is called nylon 6, 10.

This acyl chloride has a relatively high molar mass, so is not very volatile and does not fume when the bottle is opened.

Make a solution of sebacoyl chloride by dissolving 1.5 mL in 25 mL of tetrachloroethylene (an organic solvent). Why don’t we dissolve it in water? Because acyl chlorides decompose in water.

The diamine is a solid.

Dissolve 2 g of the diamine in 25 mL of water.

Add 5 g of hydrated sodium carbonate.

The reaction between the diamine and the acyl chloride is a condensation reaction which releases HCl. By making the solution alkaline, we will neutralise the HCl as it forms. Mix to dissolve.

Prepare a clean beaker by greasing the sides with paraffin oil. This prevents the nylon from sticking to the glass.

Click on the movie to see what happens when the two solutions are mixed. (You may have to wait for it to finish loading.) Audio: To prepare nylon the sebacoyl chloride solution in the organic solvent is placed into the beaker which has previously been treated with paraffin oil, and the diamine in water is then poured carefully on top of that solution. We finish up with a two-phase system where the amine and the sebacoyl chloride interact with each other and it is possible now with tweezers to pick up at the interface and to actually pull the nylon out of that interface. Now we can actually continue pull that almost indefinitely to produce a huge long continuous fibre of the nylon material.

By supporting the thread on test tubes, a very long thread can be pulled out of the beaker…

…a very long thread!