Sodium Iodide as a Contrast Agent for X-ray Micro-CT of a Wood Plastic Composite

The properties of wood plastic composites (WPCs) depend on their microstructure, particularly the level and geometry of wood reinforcement in the composite. We hypothesize that impregnating a WPC with a radiocontrast agent will increase the contrast between wood and plastic, allowing better visualization of its microstructure and numerical analysis of the geometry of its wood reinforcement. A commercial WPC was scanned using X-ray micro-CT, impregnated with aqueous sodium iodide, and then rescanned. CT data from both scans were visualized, and we analyzed the geometry of wood reinforcement and levels of wood, plastic, zinc borate (ZB), and voids in the WPC. ZB occurred mainly as discrete particles between wood flakes, and interfacial voids formed a network of cracks within the WPC. Sodium iodide labeling made it possible to clearly visualize wood and plastic in the WPC and quantify levels of different phases and the geometry of wood particles. However, sodium iodide was not an ideal contrast agent because it swelled wood particles, closed interfacial voids, and partially dissolved ZB particles. We suggest methods of overcoming these limitations and conclude that advances in labeling are necessary to improve our understanding of the relationship between the microstructure of WPCs and their properties.

Recycling of Waste Fiber-Reinforced Plastic Composites: A Patent-Based Analysis

Fiber-reinforced plastic composite materials are increasingly used in many industrial applications, leading to an increase in the amount of waste that must be treated to avoid environmental problems. Currently, the scientific literature classifies existing recycling technologies into three macro-categories: mechanical, thermal, and chemical; however, none are identified as superior to the others. Therefore, scholars and companies struggle to understand where to focus their efforts. Patent analysis, by relying on quantitative data as a precursor to new technological developments, can contribute to fully grasping current applications of each recycling technology and provide insights about their future development perspectives. Based on these premises, this paper performs a patent technology roadmap to enhance knowledge about prior, current, and future use of the main recycling technologies. The results show that recycling macro-categories have different technology maturity levels and growth potentials. Specifically, mechanical recycling is the most mature, with the lowest growth potential, while thermal and chemical recycling are in their growth stage and present remarkable future opportunities. Moreover, the analysis depicts several perspectives for future development on recycling technologies applications within different industries and underline inter- and intra-category dependencies, thus providing valuable information for practitioners and both academic and non-academic backgrounds researchers interested in the topic.