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<p>The world is today faced with the problem of plastic waste pollution more than ever before. Global plastic production continues to accelerate, despite the fact that recycling rates are comparatively low, with only about 15% of the 400 million tonnes of plastic currently produced annually being recycled. Although recycling rates have been steadily growing over the last 30 years, the rate of global plastic production far outweighs this, meaning that more and more plastic is ending up in dump sites, landfills and finally into the environment, where it damages the ecosystem. Better end-of-life options for plastic waste are needed to help support current recycling efforts and turn the tide on plastic waste. A promising emerging technology is plastic pyrolysis; a chemical process that breaks plastics down into their raw materials. Key products are liquid resembling crude oil, which can be burned as fuel and other feedstock which can be used for so many new chemical processes, enabling a closed-loop process. The experimental results on the pyrolysis of thermoplastic polymers are discussed in this review with emphasis on single and mixed waste plastics pyrolysis liquid fuel.</p>
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This work investigates some mechanical properties and microstructures of PPS-AlMMC and compares the properties of the composites and those of the aluminium 6063 (AA6063) alloy. Periwinkle shells were milled to particle sizes of 75µm and 150µm and used to produce PPS-AlMMC at 1,5,10 and 15wt% filler loadings using two-step casting technique. The mechanical properties and microstructures of the composite materials were compared with those of the AA6063 alloy. It was observed that the filler distributes uniformly in the matrix due to the two-step casting technique. Improved strength, ductility, hardness and modulus were obtained when the filler was used to reinforce the alloy. However, using a filler of bigger particle size resulted to reduced tensile strength, ductility and toughness of composites.
Natural fibres such as coir, jute, flax, and hemp have been considered for technical applications. These fibres, though with some desirable qualities such as low density and environmental compatibility, possess the common property of non-uniformity along their length and, as a result, variable diameter and variable cross-sectional area. Several other factors, such as gauge length, fibre species and origin, strain rate, method of extraction of the fibres, porosity and pore size distribution, have been identified to influence the tensile strength of natural fibres and limit their applications in composites. Besides, several authors have used different diameters for the same type of natural fibre, such as coir, resulting in significant inconsistency in the tensile properties. For the same type of coir fibre, and from tensile strength reports from ten authors, an average tensile strength of 120.97 ± 42.30 MPa was obtained. The average number of fibres used in most cases for the tensile test was less than the requirement for natural fibres. All these factors were addressed with the aim of improving the overall properties of natural fibres and their composites.
The effect of using mixtures of palm kernel shell and coconut shell as carburizers for low carbon steel at 950oC on the tensile properties and case hardness was studied. The carburizers were washed, dried, milled and sieved to 150µm particle size. They were mixed in various compositions to serve as carburizers. In each composition, 20wt% of calcium carbonate (CaCO3) was added as energizer. Tensile and hardness specimens were machined from low carbon steel. Seven tensile and seven hardness specimens were subjected to pack carburization process with different compositions of the carburizers, and thereafter quenched and tempered at 450oC for forty five minutes in a heat treatment furnace. The tensile and hardness properties show that better properties were obtained with mixtures of the carburizers compared to the use of single carburizing agent.
Nano-CaCO3 (NCC) obtained from Achatina achatina shells were used as single filler and as partial replacement of carbon black (CB) to produce vulcanized natural rubber (NR) filled at 5, 10, 15, 20, 25 and 30 pphr. The SEM micrographs showed that the dispersion of the fillers in the hybrid composites up to 15wt% replacement of CB was very good. Higher strengths were obtained up to 25 pphr for composites that contained 95wt%CB/5wt%NCC and 90wt%CB/10wt%NCC, while the composites that contained 85wt%CB/15wt%NCC showed higher strength up to 20 pphr compared to the CB filled samples. The NR filled with hybrid CB/NCC up to 15wt% replacement of CB offered comparative hardness and abrasion resistance; while 95wt%CB/5wt% NCC filled sample showed lower compression set over CB reinforced samples up to 30 pphr and comparative tensile strength, hardness, elastic modulus and abrasion resistance. As single filler, the synthesized nanoparticles imparted significant improvement in the mechanical properties of vulcanized NR; however, the properties were inferior to the CB reinforced sample due to poor dispersion of the NCC in vulcanized NR. The thermal and oxidative stability of the hybrid composites up to 15wt% replacement of CB were better than those of the CB filled samples.
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