What are the methods for handling used plastic products?

In order to meet the needs of protecting the global environment, the world's plastics processing industry has developed many new environmental technologies. In terms of resource conservation, it mainly improves the product's ageing performance, prolongs life, multi-functionality, and appropriate product design. In terms of resource recycling, it mainly studies high-efficiency sorting of plastic waste, separation technology, high-efficiency melt recycling technology, Chemical recycling technology, fully biodegradable materials, water-soluble materials, edible films; in the reduction technology, mainly research on waste plastic compression and volume reduction technology, film bag container technology, under the premise of ensuring application performance, try to Thinning technology; in the development of CFC substitutes, mainly research on carbon dioxide foaming technology; in the research of alternatives, mainly to develop PVC and PVDC substitutes.

In the treatment of urban plastic solid waste, three methods of landfill, incineration and recycling are currently used. Due to different national conditions, countries vary. The United States is mainly landfill, and Europe and Japan are mainly based on incineration. Due to the landfill treatment, the plastic products are generally light and not easy to rot, which will result in the landfill becoming a soft foundation and will be difficult to use in the future. Incineration treatment, because the plastic generates a large amount of heat, it is easy to damage the furnace, and the gas generated after incineration will promote the warming of the earth. Some plastics will release harmful gases and pollute the atmosphere when incinerated. Adopting the method of recycling and reuse, due to labor consumption, high recycling cost, and lack of corresponding recycling channels, the world recycling and recycling only accounts for about 15% of the total plastic consumption. However, due to the limited world oil resources, from the perspective of saving the earth's resources, the recycling of plastics is of great significance. To this end, all countries in the world have invested a lot of manpower and material resources to develop various key technologies for the recycling of waste plastics, and are working to reduce the cost of recycling and recycling plastics.

I. Recycling heat method

Most of the plastics are made from petroleum. The main component is hydrocarbons, which can be burned. For example, polystyrene burns more heat than dye oil. Some experts believe that the plastic waste can be sent to the incinerator for combustion, which can provide heat for heating or power generation. Because 86% of the petroleum dyes are directly burned, only 4% of them are made of plastic products. When the plastics are used up, they are sent to the heat. It is normal to burn off. The use of heat is one of the last methods of plastic recycling. It should not be underestimated. But many environmental groups are opposed to burning plastics. They believe that the incineration method will burn all the messy chemicals and produce toxic gases. For example, half of the PVC component is chlorine, and the chlorine gas emitted during combustion has a strong erosion and destructive power, and is the culprit causing evil.

At present, there are 200,000 tons of PVC waste in Germany every year, 30% of which are burned in the incinerator, which is very popular and the law has to formulate countermeasures. The German Federal Environment Agency has stipulated that all incinerators must meet the limit of less than 0.1 ng per nanometer of exhaust gas. Although the air pollution standards of incinerators in Germany are already recognized as high standards in the world, they still do not dare to say that the combustion method will not release harmful substances due to mechanical failures. Therefore, it is foreseeable that environmental groups in various countries will vigorously oppose the incineration method to recover heat.

2. Classification and recycling method

As a plastic recycling, the most important thing is to classify. Common plastics are polystyrene, polypropylene, low density polyethylene, high density polyethylene, polycarbonate, polyvinyl chloride, polyamide, polyurethane, etc. The difference between these plastics is difficult to distinguish. Most of the current plastic classification work is done manually. Recently, there has been a new research progress in machine classification. A German chemical technology association invented the use of infrared rays to identify categories, which are both fast and accurate, but with high sorting costs.

Chemical reduction method

Researchers began to try to extract the chemical components of the plastic for reuse. The process used is to cut off the long chain of the polymer and restore its original properties. The cracked material can be used to make new plastics. Some methods involve the chemical cracking of the combined carbon atoms by the addition of chemical elements, or the addition of energy to cause their thermal cracking.

Bayer AG has developed a hydrolyzed chemical reduction method to crack PUC sponge mats. Tests have shown that chemical reduction is technically feasible, but it can only be used to treat clean plastics, such as corner powders and other plastic waste produced during manufacturing. Plastics contaminated with other contaminants used in the home are difficult to treat by chemical decomposition. The application of this reduction method will not use the hydrolysis method to treat waste in the 21st century. Some new chemical decomposition methods are still in the process of research, and Ford Motor Company of the United States is currently applying ester hydrolysis to the treatment of automotive waste plastic parts.

The US-based Rendezvous Institute of Technology has developed a solution that decomposes plastic waste, heating this patent-pending solution with six different types of plastics that are mixed together. Six different polymers can be extracted separately at different temperatures. In the experiment, the polystyrene plastic chips and related solutions were mixed into a dissolved state at room temperature, sent to a sealed container for heating, and then sent to a lower pressure "flash chamber", and the solution evaporates quickly ( Recycling is done again, and the rest is pure polystyrene that can be reused.

It is everyone's responsibility to protect the environment and reduce the environmental pollution caused by waste plastic products. Only by working together with the goal of environmental protection can we make our living environment better.