Week 9
In the class last week, we had Adele from Precious Plastics Shanghai to lead us through the process of plastic transformation and recreate the stool. After a brief explanation, Adele showed us how to classify, chop and heat the plastic. Many novel tools and instruments have been used. After that, we will finalize it. This step caused some failures in the finished product due to our negligence and unskillful. What impressed me in this process was the step of heating the melted plastic. This step reminded me of the actual plastic heating scene. According to common sense, I learned that dioxin is produced when plastic is burned, which is a persistent organic pollutant (POP) and can seriously harm the atmosphere as well as cause great harm to human health.
After class, I learned more about the environmental impact of plastics and the main treatments in the engineering practice, and I have thought about it.
Generally speaking, as one of the three major synthetic materials, plastics have brought many benefits to the development of production technology and the improvement of people’s quality of life. But the disposal of plastic waste is a more difficult problem. Due to the large amount of plastics collected and classified, the plastics are often difficult to decompose in the natural environment for a long time, especially the plastic bags and agricultural mulch films that are discarded after use. Plastics scattered in urban areas, scenic tourist areas, water forests, roads and railways, causing serious white pollution to the natural environment and urban landscape, have caused widespread concern and anxiety.
For waste plastics, there are usually four methods from an engineering perspective:
- Direct regeneration of waste plastics (similar to the crafts in our class)
Direct recycling refers to the method of directly plasticizing waste plastics, plasticizing after crushing, plasticizing after corresponding pretreatment, and then forming and processing the recycled plastic products. Direct recycling also includes the addition of appropriate auxiliaries (such as anti-aging agents, colorants, stabilizers, etc.).
- Waste plastics production of building materials products using waste plastics to produce building materials is waste plastic flooring and packaging materials are as follows:
2.1 Production of soft assembled floor: using waste plastic as the main raw material, and then pulverizing, cleaning and other processes to produce plastic granules and then adding an appropriate amount of plasticizers, stabilizers, lubricants, pigments, and other admixtures, through cutting and mixing, injection molding and molding process.
2.2 Production of floorboard: using waste agricultural film and calcium carbonate as the main raw materials, after mixing raw materials, mixing, granulating, squeezing, cooling and punching.
2.3 Production of the artificial board: using grass residue, sunflower seed skin, and waste plastic as the main raw materials, plus several auxiliary chemical raw materials, which are mixed and hot pressed.
- Waste plastic pyrolysis oil
A large number of discarded plastics can be chemically recycled, that is, by heating or adding a certain catalytic plastics to make macromolecules, the polymer chains are broken and petroleum products are produced. The pyrolysis oil production technology is complicated in process, requires high cracking raw materials, cracking catalysts and cracking conditions, and has a large investment, so the method is still being explored and promoted.
- Waste plastics incineration to recover heat
Waste plastics are used as raw materials to recover energy from combustion. The calorific value of waste plastics is as high as 33492~37565kJ/kg, which is higher than coal and slightly lower than the specific gravity, which has a good effect.
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