Plastic experiment ② Recycling by thermal decomposition of PS solvent and PE
Addressing environmental issues with plastics has become a problem. Originally, it is durable and long-lasting due to the nature of plastic, so it is not easily decomposed in nature. Biodegradable plastics are expensive, but they are starting to be used little by little. This time we will deal with recycling.
Experiment 1: Recycling of PS (polystyrene) with solvent
you need : Acetone, beaker, styrofoam stick
Styrofoam made of PS polystyrene dissolves surprisingly well in organic solvents such as acetone. If you hide it with a paper cup, it's a magic show. Styrofoam dissolves in acetone while generating a gas. This is because butane is added to increase the volume when manufacturing.
Take the melted Styrofoam with disposable chopsticks and soak it in hot water, and the acetone inside will fire. It cannot be used if it is foamed with acetone, but it can be recycled in this way.
Experiment 2: Oilification by thermal decomposition of PE(polyethylene)
you need : Polyethylene (PET bottle cap)), heat equipment that can be tightly sealed, glass tube, beaker
The principle is very simple, when PE is heated to about 400 ° C, it will be squeezed. It becomes octane, which is the main component of paraffin and light oil.
We have all the tools. Use a can of curry powder that can be sealed and is resistant to heat. Chop the lid of the PET bottle, put it in a can, and heat it. The joint between the glass tube and the can was made of plaster.
Return the gas with a beaker that stores water. Since the paraffin component is also extracted, it becomes a lump. If you want to collect only light oil components, put zeolite (stone in the aquarium) in the can and it will absorb paraffin.
The problem here is still the cost. Since the plastic is purposely overheated and returned to light oil, it is a negative energy source. However, we are taking into consideration the processing of plastics and receiving subsidies from the government.
The reason why it is so easily pyrolyzed is to look at the structural formula on the left. Both are hydrocarbon compounds and have similar structures. If the polyetile cuts at an appropriate place, it becomes an octane.
Current status of recycling
Styrofoam is consumed in large quantities. The volume is reduced by heat without using chemicals as in this experiment. The photo shows the processing in the market. A company called Pana Chemical Co., Ltd. processes 7,000 tons a month.
A PE oiling experiment was underway in Palau. The cost was subsidized by JICA and was carried out by Brest Co., Ltd. Profitability is a bottleneck.
The current state of plastic recycling in Japan is 86%. I think it's something really good, but most of the plastic we actually collect is burned. And because it uses heat, it is included in thermal recycling. Therefore, the true recycling is less than 20%. We also export a lot of waste plastics to Southeast Asia. Details are written in the PDF below.