Plastic is a material that is used to great extent. Most plastics that are commercially used today are petroleum based, meaning that they can take more than a century to degrade. Nothing in our natural environment is capable of easily breaking them down since polyurethane and polyethylene are manmade polymers that microorganisms don’t recognize as food. When burned, plastics release cancer causing carcinogenic chemicals that are equally harmful to people and the environment. The world is drowning in excess environmentally harmful plastic which is made from oil- a nonrenewable resource.
One environmentally friendly alternative to the current commercial plastic is Bioplastics. Bioplastics are biodegradable plastics that have components derived directly from renewable raw plant materials. Their polymers are made from plant materials and they decay into natural materials that blend harmlessly with soil. Some bioplastics can break down in a matter of weeks.
In this project, Corn starch, Agar and Gelatin were used as biopolymers and Glycerol and Sorbitol as plasticizers. Seven types of Bioplastics were made using various combinations of these raw materials and plasticizers. Then their tensile strengths, biodegradability, thermal properties, and water degradation properties were compared. Their tensile strength testing and thermal analysis (differential scanning calorimetry/ Thermogravimetric analysis) were performed in the polymer synthesis lab at UALR using their testing apparatus’s. For Tensile Strength, the average maximum load, load at break, stress, strain and time to break were calculated for each Bioplastic sample and various other commercial plastics using the three strips. For the thermal analysis, the samples TGA and DSC were measured.
To test the biodegradability, compost was prepared using soil, green scraps, wood chippings, dry leaves, and newspaper. Then each of the samples was buried in separate compost bins for four weeks. After four weeks, the samples were taken out, dried, and measured for their final weight.
To test the water degradation, eight containers were filled with 50 ml of water and the samples, along with the Wal-Mart bag (used as a control) were dropped into the containers. They were observed initially at the five minute mark, ten minute mark, and thirty minute make for signs of degradation, and after that they were observed at one hour intervals. This process was continued for a two day time period.
The results suggest that Corn Starch Bioplastic has most tensile strength with considerable biodegradation and minimal water degradation. They also suggest that the gelatin + glycerol sample was the most thermally stable.