PMMA (polymethyl methacrylate), commonly known as acrylic or plexiglass, is a high-performance thermoplastic. This high-value material has the following core advantages.
- Excellent optical performance: The light transmittance is as high as 92%, second only to glass, but the light is soft and glare-free, and it is called “artificial crystal”.
- Lightweight and high-strength: The density is only 1.15-1.19 g/cm³ (about half of ordinary glass), the impact strength is more than 16 times that of glass, it is resistant to falling and has blunt-angle particles after breaking, and it is highly safe.
- Excellent weather resistance: It is resistant to acid and alkali corrosion, UV aging, suitable for complex indoor and outdoor environments, and has a long service life.
- Widely used in display windows, skylights, light boxes, signboards, display stand decorations, storage boxes, etc.
When PMMA has completed its mission and entered the recycling system, it faces new challenges. During the recycling process, it is often mixed with other materials, hidden in the salt water base material, and difficult to distinguish. For high-value PMMA recycled materials, how to purify them from complex mixtures has always been a problem that has plagued the field of renewable resources.
Current status and challenges of PMMA recycling
PMMA (commonly known as acrylic or plexiglass) is a high-value engineering plastic, and its recycling has significant economic and environmental benefits. However, the traditional recycling process faces many challenges:
- Difficult sorting: PMMA is often mixed with other transparent plastics such as PC, PS, etc., and traditional optical methods are difficult to distinguish
- Sensitive to pollution: PMMA is extremely sensitive to impurities, and trace pollutants can affect the performance of recycled materials
- Thermosensitive properties: PMMA has poor thermal stability and improper treatment can easily lead to degradation
These factors cause recycled PMMA to often only be used at a downgraded level, which is difficult to meet high-end application requirements
The infrared optical sorting system achieves efficient identification of PMMA through the following core technologies:
- Feature spectrum identification: PMMA has a unique absorption characteristic peak in the near-infrared band (especially 1,650-1,750nm)
- High-resolution detector: Using InGaAs array detector, the spectral resolution can reach 6nm
- Intelligent algorithm system: A pattern recognition algorithm based on deep learning can distinguish PMMA from similar materials such as PC and PS
- High-speed air jet sorting: After identification, the material is separated by a precisely controlled compressed air nozzle.
Modern advanced equipment such as the GOLDERNSORTER GIPLUS series can achieve a detection speed of more than 4,500 times per second and an identification accuracy of more than 99%.
