Mechanical Properties Improvement
Mechanical Properties Improvement
The deterioration of mechanical properties in recycled plastic products is a problem that needs to be addressed in many industries because it directly affects product safety and quality. Accordingly, multiple methods for mitigating this deterioration are being investigated. The following section introduces case studies showcasing multifaceted evaluations of improvements and changes in physical properties of resins molded with a molding technique (advanced recycling process) utilizing a molten resin reservoir.
Advanced Recycling Process (Molding Using a Molten Resin Reservoir) This advanced recycling process is the result of research conducted at Fukuoka University that focused on improving the mechanical properties of recycled plastics.
This treatment is performed during the melt kneading and molding processes, which are part of the material recycling of waste plastics.
Fig. 1 Material Recycling Process1)
After secondary sorting, the waste plastic is fed into an extruder, where it is melted, extruded, and cut at the die exit to form pellets. A molten resin reservoir is provided as the final stage.
In a chemically degraded plastic, scission of the polymer main-chain occurs, so it cannot be rejuvenated. In contrast, physical degradation only involves changes in, the molecular aggregation. This treatment method directs, the material through a molten resin reservoir to restore molecular aggregation (entanglement).
Fig. 2 Image of Aggregation State of Polymers2)
Fig. 2 shows a schematic of the state of molecular aggregation. Without the advanced recycling process, there is presumably little entanglement between the molecules. With the advanced recycling process, molecular relaxation progresses within the molten resin reservoir, and entanglement likely expands. When there are many entanglements, and after the material cools, the intermediate layers containing tie molecules between the crystals expand, likely restoring the mechanical properties.