Right from the early days, polymer materials have been discovered as being beneficial for various applications but a poor understanding of these materials greatly handicapped their usage. However, with a change in this trend, polymer materials have gradually displaced other materials in most applications. In recent times, due to improved research and knowledge, polymer-based materials are the first choice materials for several applications and are now replacing other materials rapidly. More advanced materials from polymers are being developed daily as a substitute for other materials even in areas where polymers are considered not to be suitable in the time past. More recently, polymers have replaced metals and ceramics in applications like constructions, aerospace, automobiles, and medical. It is no doubt that this trend will continue due to the inherent properties of polymers and sustainability potential. Today, most of the limitations of polymers are being taken care of in the formulation of composite materials. Besides, the adaptation to positive environmental influence is being handled by scientists and researchers. Hence, this review reveals core areas of application of polymer-based composites and the significance of these materials to the advancement of humanity.

Hard tissue regeneration and regrowth have continued to be a challenge in the field of conventional medicine in this 21^st century. Over the years, the regrowth of broken bones and diseased hard tissue has remained a major concern in medical research. Since the discovery of hydroxyapatite (HA), a bioceramic compound that possesses the ability to activate bone regrowth and bond directly with regenerated bone, it has subsequently become an indispensable biomaterial. Currently, it is being used across the medical fields due to its exceptional biocompatibility. This became plausible because the main mineral phase of mammalian bones is HA. It has found application in various medical fields like medical instruments, drug delivery, bone and tooth fillers, prosthetics, orthotics, and in-vitro implants. As the importance of HA geometrically increases, it is necessary to critically evaluate and propose the most economic process of synthesizing and manufacturing this important bioceramic material. This review, therefore, highlights the different sources of HA and the synthesis/production methods for each source with a strong emphasis on the environment. Thus, the appraisal was carried out based on the properties of the derived HA. Such properties include but are not limited to geometry, particle size, morphology, thermal stability, and stoichiometry to suggest the most economic and environmentally sustainable sources and processing routes.

Thermoplastics and thermosetting plastics are two major classes of polymers in that have recently become materials that are indispensable for humankind. Regarding the three basic needs of human beings—food, shelter, and clothing—polymers and polymer-based materials have gained pre-eminence. Polymers are used in food production, beginning with farming applications, and in the health sector for the development of various biomaterials, as well as in shelter and clothing for a variety of applications. Polymers are the material of choice for all modern-day applications (transportation, sporting, military/defence, electronics, packaging, and many more). Their widespread applications have created many negative challenges, mainly in the area of environmental pollution. While thermoplastics can be easily reprocessed to obtain new products, thermosetting plastics cannot; thus, this review focuses more on the use of waste from thermoplastics with less emphasis on thermosetting plastics. Hence, the review presents a concise summary of the availability of waste thermoplastics as raw materials for product development and the anticipated benefits. The prospects for waste thermoplastics and thermosetting plastics, the possibility of cleaning the environment, and the uncovering of opportunities for further research and development are presented. The limitations of the current methods of waste polymer recycling are highlighted with possible future prospects from newly introduced methods. With zero tolerance for polymer waste in our environments, potential uses for recycled thermosetting plastics are described. Waste polymers should be seen as potential raw materials for research and development as well as major materials for new products. Recycled polymers are expected to be processed for use in advanced materials applications in the future due to their availability. This review shows that the major source of environmental pollution from polymers is the packaging, hence the need to modify products for these applications by ensuring that most of them are biodegradable.

This work was on the comparative evaluation of the property effects obtainable when acetylation is applied to parts of selected agro fibers that are obtainable within common localities. The fibers were subjected to different concentrations of acetylation treatment at ambient temperature for 3 h. The physico-chemical, morphological, and tensile properties of the fibers were examined after the treatment. It was discovered from the results that the procedures variedly influenced the constituents of the fibers, their resulting tensile properties as well as their post-acetylation treatment surface morphology. The proportion of crystalline cellulose in the starting fibers greatly influenced their post treatment composition, behaviour and properties. The results show that plantain fibers had the highest aspect ratios, followed by banana fibers with values of about 1000 and 417, respectively. These fibers exhibited the least density and are thus potential plant fibers for composite development. Banana fiber had the least density of about 1.38 g/cm³ while that of DombeyaBuettneri fiber possessed the highest value of 1.5 g/cm³. There was significant enhancement in the hemicellulose content of Combretum Racemosum, while the lignin content of the plantain fibers was highly reduced. The treatment favoured the enhancement of the tensile properties in Combretum Racemosum fibers, which had enhanced tensile strength and strain at all compositions of the treatment. Optimum tensile strength and strain values of 155 MPa and 0.046, respectively, are achieved at 4% composition. Dombeya Buettneri fibers showed the highest ultimate tensile strength among the plant fibers in the untreated condition, which was gradually decreased as the concentration of the reagents was increased. Overall, 4% acetylation treatment is optimum for tensile properties’ enhancement for most of the natural fibers evaluated.

This study investigates the effects of calcined and uncalcined eggshell particles (ESP) and sisal fiber (SF) on the mechanical and wear properties of eggshell particles/sisal fiber reinforced epoxy composites. Egg shell was processed to obtain calcined and uncalcined egg shell particulate of −43 μm and sisal fibers was extracted by soil retting and treated with NaOH. The composite was developed using the hand lay-up method by blending the selected materials in predetermined proportions. SEM/EDS and XRD of the egg shell particles were carried out while mechanical and wear properties of the developed composites were evaluated. SEM images of the fracture surfaces were also examined. The results showed that eggshell particles contain CaCO₃ and the uncalcined ESP/SF reinforced epoxy composite showed improved properties than the calcined ESP/SF composites in most of the tests performed. Also, it was observed that most of the tests gave the best results at different weight fractions. However, 3 wt. % emerged as the weight fraction with optimum values.