Plastic from potatoes? So went up the cry at the start of a Year 9 chemistry lesson. Our topic was polymers; the joining together of small monomer molecules to form longer chain polymers. Polymers may be synthetic (man made), or naturally occurring, eg. starch. In starch, the monomer is glucose and is the reason why many starchy foods taste sweet on eating – try chewing a piece of bread for 3-5 minutes, the enzyme amylase, in your saliva, starts to break down the starch to simpler sugars such as maltose and glucose, and the bread starts to taste sweet.
Back to our investigation!
If we can alter the chemical structure of the polymer chains, then we can develop a material that has similar properties to a synthetic plastic, but has the added advantage of being biodegradable. Firstly, we extract the starch from the potato – this involved much squashing of grated potato, hands included, filtering, more squashing and decanting, until we were left with a white solid (our starch polymer). The procedure continued with the addition of glycerol, boiling, changing the solution pH, more boiling and finally food colouring. We have now set the plastic aside to dry and soon look forward to testing the properties of our new material.