Synthetic plastics have made tremendous contributions to the promotion of industrial development and the improvement of people's living standards. In the early stages of the plastic industry, the chemical stability of synthetic materials was one of the major concerns and research focuses. Decades have passed, and its stability issues have been adequately resolved. Interestingly, today, its stability has become a significant factor hindering further development. "Agricultural film" serves as a prime example. Due to its non-biodegradable nature, it is a one-time use product, and the simplest disposal method is to burn it. This practice not only wastes resources but also causes air pollution.
The recycling and utilization of discarded plastic products have become a global issue. Traditional methods of landfilling and incineration are being gradually replaced by processes of reuse, degradation, or decomposition. The recycling of discarded plastic products not only protects the environment and conserves energy but also offers excellent economic benefits.
Option One: Sound Insulation Materials
Shredded foam plastic, after being heated to reduce its volume to less than 1/20 by infrared radiation, is then mixed with a special cement to create building materials resembling popcorn. These materials offer an average noise reduction of 60%, with noise suppression exceeding 90% for certain frequencies. Currently, this material is being used for the soundproofing walls and ceilings in power plant facilities.
Option Two: Manufacturing lightweight roof insulation materials
Shred waste expanded polystyrene foam, mix it with expanded perlite, cement, and mortar, ensuring a uniform blend. Cure the mixture on the roof surface for 3 days, allowing for natural drying. Then, level it with cement mortar to form a lightweight concrete insulating layer. Materials produced using this method have low production costs, excellent insulation properties, and provide a cozy indoor environment in winter and summer.
The manufacturing process involves cleaning waste expanded polystyrene, crushing it to a particle size of 0.1cm to 0.5cm, mixing with 32.5-grade silicate cement in a volume ratio of 2:1 to 3:1, adding an early-strength agent (inorganic alkali) at a mass ratio of 1% to 3%, blending it into a paste with water, then adding rosin soap as a foaming agent and blending again. The mixture is then molded, demolded after one hour, cured for 7 days to form 10cm thick boards. These boards have good thermal conductivity and compressive strength, achieving insulation performance equivalent to that of a clay brick wall 95cm thick. For roof application, apply a layer of cement mortar on the board, water-cure it, and then use asphalt felt as a waterproofing layer.
Option 3: Produce Waterproof Rolled Materials
Clean and dry waste polystyrene foam, dissolve it in inexpensive phenol or chlorohydrocarbon waste liquid, add toughening agents and film-forming waterproof and wear-resistant agents to mix into a sticky consistency. After blowing or applying onto the glass fabric surface, it can dry into waterproof membranes for roofs or pipeline applications. The solvent can be cooled and recycled for reuse.
Prospects Bright, Sorting Technology Must Keep Pace
It's noteworthy that both chemical and physical methods of conversion and utilization face a major challenge: the mixed variety of recycled plastics is difficult to identify and classify. Additionally, they are particularly unclean, making cleaning a daunting task with high operational costs, thus reducing manufacturers' enthusiasm.
Current solutions mainly include two approaches: limiting the production of multi-component plastic products and improving the level of sorting and collection. In the past, to protect beverages like juice from UV radiation inside bottles, manufacturers would use blue and green plastic bottles. It is now considered that a reasonable solution to UV radiation is to cover all clear bottles with labels, leaving small holes like sewing machine needles to easily peel off the labels.
Furthermore, sorting is a crucial factor in determining the economic viability of material reuse. Currently, overseas sorting technology is advancing rapidly, with many automated sorting lines already in use, capable of accurately sorting and processing different types of materials.
With the widespread use of recycled plastics, since the 21st century, China's plastic recycling industry has gradually flourished, with small and medium-sized enterprises popping up like springs. Investment is active, shifting from the previous family workshop-style plastic recycling model to a pure business model driven by market demand. It is now developing into an environmentally friendly industrial economy characterized by clustered recycling and processing, intensive market transactions, and being fully driven by market demand and price. The prospects for recycled plastics are promising.
