Question of the Week: Prospects, Technologies, and Approaches for Plastic Recycling
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With the development of material civilization and the rapid progress of science and technology, plastic materials are being used in an increasingly wide range of applications. However, as their use expands, the amount of waste plastic also increases inevitably. How to make the most of this waste plastic in order to reduce environmental pollution and maximize its value has become a topic of discussion. Due to the cost of used plastics and their recyclability, they represent an effective way to reduce costs and enhance competitiveness in the market; as a result, they have become a target pursued by many companies. However, due to the great diversity of used plastics and the wide range of modification methods available, this has also become a challenge for many companies. Those who are interested are invited to share their thoughts on how to make the most of the value of recycled plastics and maximize their utility – topics such as the uses of recycled plastics, methods for modifying them, future prospects for their application, and related technologies. Please have cuiwhu post under this topic to claim the prize
:Several teachers at our school are working on modifying PP with recycled rubber powder… I wonder if there’s any progress so far! Last year, I also worked as a volunteer for my teacher during the summer vacation... All I did was work with glue powder and PP every day...
Prospects, technologies, and approaches for plastic recycling: 1) Prospects: Coal and oil, the two main raw materials for plastics, are both non-renewable resources. From both the perspective of resource utilization and environmental protection, it is inevitable to recycle plastics. Its share in the plastics industry is bound to increase. 2) Plastic recycling technology: Basically the same as that for non-recyclable plastics. 3) Sources: From waste, recyclable components, daily consumables, etc. 4) Defects: a) Currently, recycled plastics are mainly used for lower-grade applications, that is, in uses of a lower quality than that of the raw materials, such as being used indoors instead of outdoors. b) After being used as raw material, it gradually ages over time; its weathering and light resistance decline significantly, and its processing properties such as heat resistance also change. c) A considerable portion of the recycled plastics has lost their color, resulting in a reduced ability to adjust their color when used ； d) The pigments, additives, and other substances used in the recycled material are not standardized, and their composition is complex, which affects the use of this recycled material in food and hygiene-related applications.
Recycling uses (as I know and have come across): 1. Wood-plastic composite materials: These are made by combining recycled plastic with wood, thereby producing a material similar to wood. This type of material is very popular abroad, but it has not yet been widely adopted in China. – Wood-plastic composite materials are new types of materials that are environmentally friendly, energy-efficient, and possess excellent heat resistance and chemical resistance. 2. They can be reused as scrap material: mainly for injection molding, and can be used to produce products with relatively low technical requirements; there are only these two applications
The recycling of waste plastics is an inevitable trend; as crude oil becomes increasingly scarce, this task becomes all the more urgent； Furthermore, traditional methods of landfilling or incineration cause secondary pollution to the environment, and regulations on these practices will surely become increasingly strict. Personally, I think the current several technical directions are as follows: 1. Separation and screening of mixtures. Due to the difficulty in collecting and sorting used plastics, separating the mixtures is crucial for their further utilization when it is not possible to achieve complete sorting of the recycled materials. 2. Recycling of returned materials. It mainly involves remelting and reprocessing some waste materials from plastic factories for reuse. However, due to degradation to varying degrees during re-injection or use, the molecular weight decreases, which results in lower performance compared to new material; therefore, the proportion of such recycled material that can be used cannot be very high. 3. Pyrolysis to convert into chemical raw materials or fuels. Waste plastics are converted into other chemical raw materials or fuel using high-temperature or catalytic cracking methods. 4. Mix recycled plastics with other materials to use as building materials.
Let’s talk about the PVC waste from our company: after being crushed, it is mixed into asphalt to be used in road construction
I support the depolymerization of used plastics followed by re-polymerization; this results in resin slices of better quality and higher profit margins, and the solid impurities within can also be filtered out cost-effectively. It seems that such technology exists abroad.
Currently, there are mainly 9 ways to comprehensively utilize waste plastics at home and abroad: 1. Producing fuel. Last June, a new practical technology – the technology and equipment for recycling waste plastics into fuel – was successfully developed in Chengdu. These waste plastic recycling plants use waste plastics such as food bags, used woven bags, beverage bottles, plastic shoe soles, insulation material from wires and cables, foam lunch boxes, and plastic toys to produce high-quality 90# fuel. This fuel has been tested by the Sichuan Provincial Technical Supervision Bureau and found to be high-quality fuel free of lead. The strength of these companies lies in their use of this type of fuel, and approximately half a ton of fuel can be produced from 1 ton of waste plastic. Experts say that there is no technical issue with breaking down discarded plastic to produce fuel, but in terms of actual production, there are no reports or records available from countries such as Europe, the United States, and Japan. In China, research in this area is possible in laboratories, but in practice it is difficult to achieve economic viability due to high production costs, which prevents large-scale production. Thus, this technological achievement developed in Chengdu provides an effective and practical new technique for China to address \"white pollution\". 2. Produce waterproof and freeze-resistant adhesive. Using foam plastic waste as the raw material to produce a variety of water-resistant adhesive products for indoor and outdoor building decoration under special formulation and processing conditions is an ideal project that requires little investment, yields quick results, is competitive, and helps to eliminate plastic pollution. Several tons of finished rubber can be produced from each ton of waste material. Assuming a minimum packaging volume of 5 kg per ton of rubber, which corresponds to 200 barrels, the overall production cost is around 3,000 yuan, with the selling price being approximately 6,000 yuan. 3. Production of aromatic compounds. Japan is carrying out research and development to put into practical use new technologies for producing chemical raw materials from waste plastics. The method involves heating waste plastics such as PE and PP to 300°C to decompose them into carbohydrates, after which a catalyst is added to synthesize aromatic compounds such as benzene, toluene, and xylene. When the reaction is carried out at 525°C, 70% of the waste plastic can be converted into useful aromatic substances, which can be used as raw materials for chemicals and pharmaceuticals, as well as as additives to improve the quality of gasoline, offering a wide range of applications. The remaining components can be converted into hydrogen and propane. 4. Prepare a multifunctional resin adhesive. This product features good adhesion, high gloss, strong impact resistance, and acid-alkali resistance. It can be produced at a rate of 1 ton per day; the cost per ton is 2,300 yuan, while the market price is 5,000 yuan. It is used in industry to produce various fiberglass products, which helps to **reduce production costs. Additionally, it can be used to manufacture waterproof coatings, anti-rust paints, and furniture putty adhesives; it can serve as a substitute for various types of silicone adhesives, wood adhesives, and printing adhesives. 5. Automatic aluminum-plastic separator. Aluminum-plastic composite packaging is widely used in packaging for food, pharmaceuticals, and other industries. With societal progress, waste is increasing year by year. Since aluminum and plastic are combined together, it is not possible to granulate them, and recycling them is not pursued; thus, they can only be burned, which pollutes the environment and wastes resources. By using an automatic aluminum-plastic separator, the waste aluminum-plastic packaging is placed in a container along with water and the separator; within about 20 minutes, the aluminum and plastic are completely separated. From each ton of waste aluminum-plastic packaging, 0.85 tons of recycled plastic and 0.1 ton of waste aluminum can be obtained. 1 ton of waste aluminum-plastic composite materials is recycled and processed daily, generating a profit of 1,000–2,000 yuan. 6. Fire-resistant decorative panels. It is widely used in interior decoration, ceiling construction, furniture manufacturing, etc. This product not only has a vibrant and colorful appearance, but also features fire resistance, water resistance, corrosion resistance, insulation, no deformation, no aging, and the ability to be curled in any shape. 7. Recycled particles. By using specialized granulation equipment, plastic waste such as polyethylene and polypropylene can be processed through a series of steps including crushing, cleaning, heating and plasticizing, and extrusion molding, to produce recycled pellets that are in high demand in the market. A profit of 300–500 yuan can be earned per ton produced. 8. Produce Ke Lou Wang. It is an upgraded version of traditional waterproof materials; when applied to the surface of buildings, it acts like a layer of sodium silicate. It seals surfaces quickly and has very low permeability. It dries fast, sets quickly, has good leveling properties, strong adhesion, and resistance to acids and alkalis. Its service life can exceed 20 years. Moreover, it is easy to apply – construction can be carried out throughout the year without the need for heating, and it’s ready once applied. Low cost and high profit: the cost per ton is 2,000–3,000 yuan, while the market price is 5,000 yuan. 9. Produce plastic woven bags. Sangcai Town, Shanting District, Zaozhuang City, Shandong Province, uses discarded white plastic products to manufacture plastic woven bags, which not only helps to address environmental pollution issues but also increases farmers’ incomes. At present, the town has 201 plastic pellet processing plants and 23 plastic woven bag factories, which produce 500 million woven bags per day. A complete chain for the acquisition, transportation, processing, and printing of recycled plastics has been established, with annual sales reaching 350 million yuan. This industry employs over 6,000 people from rural areas, serving as a key sector that helps farmers improve their economic conditions.