Samy Yousef

Characterization of waste printed circuit boards recycled using a dissolution approach and ultrasonic treatment at low temperatures

Recently, the separation of waste printed circuit boards (WPCBs) using organic solvents has become more prevalent because it is an environmentally friendly and efficient technique. However, the relatively high temperatures (∼135 °C) used during the separation process lead to higher energy consumption, faster solvent degradation, and possibly higher emissions of toxic fumes. This work aims to develop a new approach to separate all layers of WPCBs at lower temperatures to avoid the above-mentioned drawbacks. Di-methyl formamide (DMF) was used in the present technique as an organic solvent, while ultrasonic treatment was applied in order to accelerate the breakage of the internal van der Waals bonds of brominated epoxy resin (BER), thus decreasing the separation time. The experiments were conducted on five WPCB samples with the same surface area of 100 mm2, cut from five different WPCB models. The experiments were carried out at 25 °C (used as a reference), 50 °C, and 75 °C to study the effect of heating rate on the separation time and on the concentration of the BER dissolved in DMF. Ultraviolet-visible spectroscopy, metallographic microscope, and SEM-EDS were used to examine the recovered BER and fiberglass structure as well as the main metal compositions of each sample, respectively. The results showed that separation time and concentration of BER strongly depended on the WPCB models. In addition, the dissolution process at 50 °C resulted in the concentration of BER close to 25 °C for most of the models, while the concentration was lowest at 75 °C. At the same time, the trend in separation time was exactly opposite, with 75 °C resulting in the fastest separation time and 25 °C in the slowest. This facile approach appears promising for its potential applications in WPCB recycling and could be applied on an industrial scale.

Sustainable approach to recycling of multilayer flexible packaging using switchable hydrophilicity solvents

Multilayer Flexible Packaging Waste (MFPW) represents the largest fraction of packaging waste and is mainly composed of multiple plastic films laminated with Al foil. In the EU, mechanical and chemical recycling technologies are usually used to separate polymeric fractions from Al; however, these recycling practices have inherent crucial restrictions related to the recycling rate ( 99% while making the reprocessing of extracted polymers much simpler. Dissolved plastic materials could easily be recovered in the form of solid residues without heating through saturation of an adhesive polymer/SHS solution by CO2 under cooling, thus changing the hydrophilicity of the solvent and converting it into a polar water-miscible form. Although the experiments were conducted on the lab-scale on six different types of MFPW, selected depending on the most active packaging technologies in the EU (as used for potato chips, chocolate, bakery goods, ground coffee, ice cream, and biscuits), the authors took into account the possibility of technology implementation at the industrial scale through designing a technology layout for the developed approach (based on the sequence of treatment processes and the obtained results). Metallographic microscopy, SEM-EDS, FTIR, and TGA were used to examine the materials recovered from each MFPW type as well as the changes in the SHS solvent. Lastly, the CO2-equivalent emissions and economic performance of the developed technology were evaluated.

Influence of Pelvis Width and Leg Length on the Wear Behavior of UHMWPE Hip Cup

Total hip joint replacement considered one of the success sections of the modern medicine, but still the wear of total hip prostheses is a significant clinical problem and this problem might be increasingly complex with adding the influence of pelvis width and leg length during the preclinical testing. This study aims to analyze the effect of the leg length (femur and tibia) and the pelvis width on the wear behavior of ultra-high molecular weight polyethylene (UHMWPE) hip cup. The experiments have been carried out on a total leg joint’s simulator (TLJS), which was particularly designed for this purpose according to ISO 14242-1 standard. The TLJS consists of three units: leg components (femur, tibia, and foot), quick-return mechanism, and cam mechanism were used to reproduce the flexion–extension and external–internal movement, respectively, and upper body was used to stimulate the pelvis construction and applied load. The wear behavior of the tested cups (in weight loss form) was evaluated under dry lubricating conditions, and then the wear mechanism of worm cups was examined by using scanning electron microscopy. The results showed that the length of the femur, tibia, and pelvis width have a positive effect on the wear rate of the tested cups due to flexion and pelvic moment which is resulted by the ground reaction force and pelvic rotation force.

Synthesis and characterization of CNTs/POM nanocomposite acetabular hip cup

ABSTRACT Polyoxymethylene (POM) considered as the most appropriate alternative for ultra-high molecular weight polyethylene (UHMWPE) in the hip joint replacement application due to their biocompatibility, high mechanical properties, and cheapness. The wear is the main cause of the failure in the hip joint and the wear resistance of UHMWPE is still better than the wear resistance of POM. This research aims to improve the wear behavior of POM by blending it with 0.02 wt% of functionalized carbon nanotubes (CNTs) and using paraffin oil dispersion technique to obtain a uniform dispersion. The injection molding and machining process were used to produce the new (CNTs/POM) nanocomposite acetabular hip cup which has a high wear performance. The wear rate of the CNTs/POM cups was evaluated using a total leg joint’s simulator at 1,000 N for 3 million cycles under serum-based lubricated conditions. Moreover, the wear mechanism of cups was examined by scanning electron microscopy as well as the dispersion of CNTs inside the cup matrix. The results show that the wear resistance of POM cup has been improved by adding functionalized CNTs ∼402% and ∼221%, when compared with a virgin POM and UHMWPE, respectively, because of increasing the melting temperature and crystallinity degree. GRAPHICAL ABSTRACT