The process involves the fusion and blending of various plastic varieties with additional raw materials, utilizing a series of fundamental procedures. This results in the formation of plastic granules or powder, which can be molded and formed according to specific requirements. The ultimate objective is to create new products of superior quality, which may significantly differ from their predecessors.
Plastic items like bags and shopping bags can be recycled into carpets and panels, while plastic beverage bottles can be transformed into wool jackets. Conversely, the same type of used product can undergo closed-loop recycling, like bottle recycling, to create new bottles.
1- Over the past years, there has been a noticeable increase in the production and utilization of plastic worldwide. This can be attributed to its numerous advantages, including its durability, lightweight nature, and ease of molding and shaping. Moreover, its affordability has made it a popular choice in various industries and for a wide range of products used in different applications. However, the extensive use of plastic has given rise to several environmental issues, necessitating the need to find a solution for disposing of old and used plastic. Additionally, there are several factors that contribute to plastic being a finite resource, with approximately 3%-4% of energy and non-renewable sources, such as oil and gas, being consumed in its production. Furthermore, plastic waste tends to accumulate in landfills or natural areas, posing further challenges. Certain types of plastic polymers require specific conditions and a considerable amount of time to decompose.
2- The process of recycling plastic is widely recognized as a crucial procedure in tackling the issues arising from plastic usage, as well as the extensive dependence on it for manufacturing plastic products. Moreover, the effectiveness of plastic recycling heavily relies on the precise selection of components and materials, as well as the accurate adherence to the instructions and steps involved in the recycling process. Despite its apparent simplicity, this process demands expertise, knowledge, and skill from individuals working in this industry.
The inception of plastic recycling dates back to the 1970s when the first dedicated plastic recycling factory was established in Pennsylvania in 1972. This pioneering facility marked the beginning of a new era, as numerous efforts were made to initiate and embrace the recycling process. Consequently, the scope of packaging, be it packaging materials or other forms, expanded significantly on a larger scale than ever before.
1- Consideration is given to the difference in plastic type and shape during the recycling process, as these factors significantly impact the molding and formation of the plastic.
2- It is important to note that recycling plastic involves more steps compared to other materials like glass and metals, as it requires the addition of various dyes, chemicals, and glues.
3- The plastic recycling process involves several general steps and is influenced by multiple factors. These include treating each type of plastic separately, following recycling guidelines throughout the process, and raising awareness among individuals to facilitate the successful disposal of waste and completion of the recycling process.
4. The recycling process involves multiple stages once the materials are transported to recycling centers and facilities.
5. Sorting: Plastic materials are categorized based on their types, either through manual sorting or by utilizing sophisticated sorting machines equipped with advanced sensors that can distinguish the polymer type using infrared or X-rays. Additionally, these machines have the capability to sort plastic materials based on their colors by detecting the color of the material through sensors, enabling them to handle large quantities of plastic materials efficiently.
The significance of this phase lies in the presence of plastic varieties that are not suitable for recycling, hence they are eliminated. Resizing: During this step, plastic materials are resized and altered in dimensions using specialized machines designed for shredding these materials. These machines are equipped with industrial blades that cut the materials as they rotate, after which the cut materials pass through a screen. This stage is crucial for preparing the plastic materials for further processing to facilitate their handling. It is important to mention that some recycling companies conclude the recycling process at this stage, as the materials are provided to other industries. Wet separation: Plastic fragments undergo washing and cleaning through wet separation to eliminate dirt and various contaminants like paper, sand, silt, and gravel by washing them with water. The washing process for plastic materials involves the use of floating surface tanks and basins based on density. Water, tanks, and washing machines are utilized to spray hot water continuously to remove dirt from the surfaces of plastic materials. Additionally, disinfectants, detergents, and chemicals are employed to enhance the cleaning process.
In the dry separation phase, plastic materials are sorted through various methods: pneumatic classification based on shape, size, or density; classification by melting point when exposed to heat; color classification using fluorescent or ultraviolet light; and classification based on light absorption ability.
During compounding, plastic materials are transformed into granules for reshaping, often enhancing quality by combining with other elements. Converting plastic into spherical granules aids in distribution and remanufacturing, achieved through machines like assembly lines or plastic extrusion machines.
Manufacturing occurs through one of two methods:
1- The injection-molding process involves injecting granules into a mold that mirrors the shape of the material being formed, such as molds for toothbrushes, car parts, and more. Plastic is molded or formed in a mold and then heated to melt and expand it into the desired shape using high-pressure air. Additionally, the blow molding method can be utilized to produce bottles. Commonly recycled plastic materials like HDPE, PVC, PP, and PET are frequently recycled, with some companies specializing in recycling specific types of plastic products.
2- Challenges in plastic recycling include the risk of contaminating entire batches of recycled materials due to pollution from certain dyes used in the plastic industry. Furthermore, there is a low percentage of plastic materials being recycled, as only 10% of purchased plastic is recycled, mainly due to people’s lack of awareness or refusal to participate in the recycling process. The mixing of plastic materials also makes it difficult to separate dirt and debris during the recycling process.