Research on the green evaluation system of the hot

Research on the green evaluation system of polymer materials (Part I)

with the continuous increase of modern polymer products, polymer waste has also become an important source of environmental pollution. The EU environmental protection directive RoHS will be implemented soon, and China's corresponding management measures will also be introduced soon. For polymer processing industry, how to deal with export trade barriers and meet environmental protection requirements has become one of the top priorities. This requires that when evaluating and using polymer materials, not only performance, cost and other indicators, but also environmental factors should be considered

with the increase of production, polymers have become one of the main waste sources, which has a great impact on the environment. At present, many countries have successively formulated environmental directives and regulations for products, requiring producers to be responsible for the 3R (reuse, recycle and reduce) treatment of waste products, in which polymers account for a considerable proportion. Japan implemented the household appliance recycling law (harl) in 2001, the European Union implemented the WEEE Directive in April 2005, and will implement the RoHS directive in July 2006. Similar directives in China are also being formulated and are expected to be implemented soon

all these directives and regulations require producers to achieve a high recycling rate of products and reduce the final waste of products. Figure 1 shows the recycling ratio of different materials achieved by common electrical products in Europe. It is obvious from this that the recycling of polymer materials has become a bottleneck restricting the matching degree of the overall environmental directives of products. This requires that in the process of polymer development and production, in addition to considering the performance and cost of the material itself, we should also fully consider the recyclability of the material and environmental impact. In this paper, the recyclability of materials and environmental impact are collectively referred to as green degree, but in many cases, the recyclability of materials and environmental impact are not completely consistent, especially in metal materials. Metal materials have good recyclability, but they will produce great environmental pollution in the process of processing and recycling

Figure 1 recycling status of different materials in European electrical products

due to the important impact of polymer materials on the environment, the green evaluation system of polymer materials has also become one of the focuses of product life cycle research in recent years. K. G. Snowdon has established a life cycle assessment system for aluminum containing panel products based on polycarbonate/abs with environmental impact of polycarbonate materials. H. Terho made LCA (life cycle assessment) analysis of Nokia cable made of pbt/ldpe materials, and compared the different effects of LDPE, LLDPE and HDPE materials on the environment. G. Lewis et al. Analyzed and simulated the life cycle of photoelectric induction components in upm-880 products of United Solar Systems Corporation, in which the main materials are tefzel (a polytetrafluoroethylene resin) and EVA. D. Pollock et al. Conducted LCA research on Pe1 in inkjet printing cartridge products, which together with film anti adhesion function 1 as the quantitative evaluation target of plastic film opening, PP, polyester and other materials. H. Tomita et al. Conducted LCA research on the material recovery and recycling of compact tapes and compact disks (mainly PS, polycarbonate and PC). J. A. Stuart analyzed and summarized the material selection model in product life cycle design. Lkarni established an environmental impact assessment system for electronic components based on Environmental Assessment (EIA) software system. These studies are aimed at a specific class of products and polymer materials. China mainly analyzes the environmental impact of materials in products. After the implementation of the environmental directive of products, it is necessary to take the polymer itself as the object of research and analysis. Through the life cycle analysis of polymer materials, predict and simulate the 3R status of polymer materials, and establish a green evaluation system that reflects the characteristics of polymers

3R based polymer life cycle

3r is expressed as increasing the proportion of reuse (reus will be through fully packaged subscription based service e) and recycling, and reducing the final waste. For products, reuse means that product components are directly put into the production of new products or the maintenance of old products; Recycling refers to the recycling of materials; Waste means some materials that cannot be produced in the next stage. From the perspective of polymer materials, this concept needs to be reset: reuse means that materials can be directly put into the next stage of production without adding other components; Recycling refers to adding other components to the material for modification and putting it into the next stage of production; Waste means that the properties of recycled polymers can no longer meet the needs of reproduction. At this stage, how to reduce the final solid waste is the key to reduce. The life cycle process of polymer is shown in Figure 2 (a), and Figure 2 (b) shows the performance changes of polymer during the life cycle. Where time point TM represents the time when the polymer enters the recycling stage, and time point TN represents the time when the polymer enters the waste stage

Figure 2 life cycle process of polymer

from the perspective of enhancing the environmental friendliness of polymer, on the one hand, it is to prolong TM and TN as much as possible and prolong the time before the material enters the waste stage. On the other hand, it is to minimize the amount of waste materials and the impact of waste on the environment. According to ASTM (American Society for testing material) d standard, the final treatment of polymers can be divided into: degradation, biodegradation, oxidative degradation, photodegradation, incineration and other methods. In the final treatment of materials, it is a better way to reduce the adverse impact on the environment to avoid landfill treatment and implement renewable energy

key indicators of polymer green degree evaluation

the green degree evaluation of polymer includes the following key indicators. These indicators are not isolated from each other, but linked and influenced by each other. Based on the analysis of these indicators, a framework system can be established for the quantitative evaluation of the green degree of polymer materials

the material itself contains additional dangerous substances

in order to enhance the application performance of polymers and develop new materials, it is usually necessary to add material modification to polymers. However, the implementation of RoHS and similar laws has put forward restrictions on the additive materials of polymers. Producers are required to limit the use of harmful substances such as lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers in the development and production of polymer materials. Even if harmful substances remain due to raw materials or production process, the content should be strictly controlled within the specified percentage. From the perspective of increasing the recyclability of materials, it is necessary to consider not only the current content of dangerous substances in materials, but also the content of dangerous substances in materials during recycling and reuse, so as to ensure that materials can meet the requirements of laws and regulations and be put into reproduction

Table 1 performance comparison of recycled PET, PVC and HCM materials with new materials

Table 2 performance changes caused by the recycling of residual additives recycled from pet and PE

the performance of recycled polymer materials will inevitably change, and controlling this change in a small range is an effective means to prolong the cycle of material recycling. This is not only related to the material itself, but also has an important relationship with processing methods, use environment and recycling methods. Table 1 shows the performance comparison of three polymer recycling materials and new materials. In terms of the evaluation system requiring low rotating speed of the rotary table, the smaller the change of the performance of a material after recycling compared with the new material, the greater the possibility of recycling this material, so the better the green degree