Bio-plastics are a great alternative to traditional plastics, which are often composed of petroleum products. As years pass, we have less and less petroleum available to us, so it is important to find a suitable alternative. You can't beat the light-weight, low-cost applications of plastic products, so many companies are experimenting with making a similar product out of a more renewable product. Starch plastics are a good alternative, because corn is readily available, and when the plastic is done being used, it can be broken down rather than sent to a landfill.
This is a simple recipe that can be made in any kitchen, with common items often found in the average pantry. It can be a fun experiment for the classroom, as well as at home. The main purpose of this is to garner interest in the subject, so that future scientists will be able to develop more sustainable ways to make plastic products.
This experiment is quick, simple, and won't make a big mess!
Step 1: Step 1: Supplies
1. 1 tbl cornstarch
2. 1 tsp vinegar
3. 1 tsp glycerin
4. 4 tbl water
2. Small pot
3. Cookie sheet
4. Aluminum foil (optional)
5. Measuring cups
6. Stove top (or hot plate)
These are all ingredients that can be found in most kitchens, aside from the glycerin. Glycerin is used as a plasticizer in this application, but is often an important additive in lotions and other skin care products because of it's hydrating properties.
Different ingredients will affect the final outcome in different ways. For instance, glycerin will make the plastic more flexible. The acetic acid in vinegar helps the starch to dissolve easily, because it adds ions to the mixture. Vinegar is a much more readily available ingredient than ammonium acetate, which would be used in a larger scale commercial bio-plastics operation. Water is used as a solvent, also to denature the starch. That way, a thin film can be created as a final product.
Step 2: Step 2: Add All Ingredients to Pot
The order does not matter. Simply measure all ingredients (this is not rocket science, so it doesn't need to be exact) and mix them together in the pot. Stir until combined, then turn on stove to low/medium heat.
Step 3: Step 3: Heat Up the Mixture
After the heat is turned on, the mixture should be stirred regularly to avoid clumping. It will be a milky color at first, but will soon get thicker and turn slightly translucent. It is important to keep the heat low so that the heat is equally distributed throughout. This process happens fairly quickly (the pictures above were taken ~30 seconds apart), so keep stirring until the mixture thickens!
Step 4: Step 4: Turn Off the Heat!
Once the mixture is easily scoopable, turn off the heat! Stir a few more times, then pour/scoop the mixture onto an aluminum foil lined cookie sheet. The foil is optional, but it will be easier to remove later when the plastic is dry.
Step 5: Step 5: Form the Plastic
The mixture will feel similar to hair gel when it is first on the pan, and will need to cool a bit before it can be formed. Let it sit for a minute or so, then spread with a spatula on the foil. Over the next 15 minutes, the plastic will begin to harden and not stick to fingers when touched, but it will still be soft. The plastic should be left alone for several hours, until completely set.
If you wish to form the plastic into a small bowl or other simple shape, it can be left on the foil for about an hour, then formed almost like playdoh. After forming, set it back on the foil and allow to dry for several hours or overnight. Resist the urge to touch the finished product throughout the drying process, as it will still be soft.
Step 6: Bio-plastics Experiment
The great thing about this particular project is that it will dissolve in hot water and is made from materials that will not harm the environment further. If a small child or pet were to chew on your home made bio-plastic, they would not be harmed in any way (aside from it being a possible choking hazard). This is because all of the ingredients are completely safe for consumption. There are a great deal of positive aspects to these environmentally friendly plastics, and I encourage you to continue researching or trying other plastic recipes.
Thanks for reading!