Mechanical PVC recycling is a circular process that converts waste plastics into reproducible products through physical processing steps such as separation and sorting, cleaning, crushing, and compound granulation. Recent systematic reviews have evaluated advancements in machinery-driven solutions including high-efficiency shredders, granulators, extrusion moulders, and advanced sorting systems employing hyperspectral imaging and robotics. These engineering innovations are critical for improving the efficiency and quality of recycled plastic materials, enabling higher material recovery rates while reducing energy consumption and environmental impact.

The integration of Industry 4.0 technologies, notably digital twins and artificial intelligence, has emerged as a transformative force in PVC recycling. These technologies enable predictive maintenance, real-time quality assurance, and process optimisation, addressing critical engineering constraints including thermal degradation, additive leaching, and feedstock heterogeneity. Emerging innovations like additive manufacturing and microwave-assisted depolymerisation offer scalable, low-emission solutions that could revolutionize PVC reprocessing.

Mechanical PVC recycling faces significant challenges due to PVC's complex composition and the high levels of hazardous additives added to achieve desired material quality. The high chlorine content in raw PVC, approximately 56% of the polymer's weight, requires separation from other plastics before mechanical recycling. Because mechanical recycling involves no chemical reaction, the recyclate retains its original composition, which poses challenges when PVC products contain different additives depending on their application—rigid PVC is unplasticized while flexible PVC contains plasticizers.

The quality of recycled plastic materials depends heavily on the purity and uniformity of the input waste stream. When different kinds of PVC waste are fed to a mechanical recycler, the resulting product's composition is difficult to predict, which is problematic because most PVC products require a specific PVC content. Post-industrial waste, which is relatively pure and comes from PVC production and installation, is easily recycled and can be collected directly from processors or even recycled by producers themselves as raw material. Post-consumer waste, containing mixed materials from various applications, requires further sorting and cleaning, adding cost to the recycling process and typically producing lower-quality recyclate.

Recycled plastic materials derived from PVC can be used in various applications including flooring, roofing, and piping, but the economic viability of mechanical recycling remains challenging. The journey of recycled plastic begins with collection of discarded plastic items, followed by sorting at recycling centers where plastics are separated based on resin codes. This separation is crucial because different types of plastics have different properties and recycling requirements. Once sorted, plastics are cleaned to remove contaminants, then shredded into small pieces called flakes, which are melted and reformed into new plastic pellets.

Looking forward, regulatory instruments such as REACH and Extended Producer Responsibility (EPR) are influencing machinery compliance and design standards. Sustainable manufacturing frameworks promoting energy efficiency, eco-designs, and modular integration in recycling systems are driving the development of digitally optimized, machinery-integrated recycling models aligned with circular economy principles. Mechanical PVC recycling will remain a critical component of sustainable polymer recovery strategies, providing the foundation for a more circular plastics economy as the demand for recycled plastic materials continues to grow across global markets.