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.

High density polyethylene (HDPE) composites reinforced with short bamboo fibre (BF) were fabricated by compression moulding technique. BF were extracted from bamboo culm and treated with 0.5 M NaOH. The composites were developed by melt-compounding various weight fractions (2, 4, 6, 8 and 10 wt.%) of the treated BF with HDPE with the aid of single screw laboratory extruder at a temperature of 180-220 °C. The extrudates were thereafter moulded into various test specimens with the aid of carver laboratory press at a temperature of 230 °C and applied pressure of 0.2 kPa for 10 min. Effect of the treated BF on the mechanical properties and water uptake behaviour of the composites were studied. The results revealed that there was enhancement in the mechanical properties from 2 - 4 wt.% of BF while the water absorption rate increased with increase in the fibre weight fraction. The morphology of the composites showed that there was a homogenous dispersion of BF at lower weight fraction, although fibre agglomeration was noticed at higher weight fraction. The results of this study revealed that treated bamboo fibres are suitable for reinforcing HDPE.

The increase in demand for thermoplastics as a light-weight material for automobile application and other commercial purposes prompts more research into the available polymer resources. In this research, the possibility of enhancing the performance of recycled waste plastics (RWP) as polymer-based composites was examined. Particulate snail shell was obtained by grounding and sieving snail shells to obtain 53–63 μm passing which was used as reinforcement in the recycled waste plastics. The composites were developed by adding varying proportions of the snail shell particulate (SSP) to RWP using a randomly dispersed process in a hot compression moulding machine maintained at 190°C for 7 min. Selected properties of SSP-reinforced RWP composites were examined. The results showed an appreciable enhancement in the properties of composites developed compared to an unreinforced RWP matrix that serves as control. The ultimate tensile strength was enhanced by about 64%, while Young’s Modulus and impact strength were enhanced by 37% and 29%, respectively. Wear and water repellant potentials were highly enhanced with the addition of 15 wt% of SSP with values of about 52% and 91%, respectively. This revealed that high content of the SSP contributes to the improvement of the strain-hardening potentials of the developed composites. The results showed that this composite material can be suitably adapted for use in the interior of automobiles as door sills or the floor panel.

The mechanical properties of coconut shell ash (CSA) reinforced polyester composite have been optimized. Various test specimens were developed by dispersing 10, 20, 30 and 40 wt.%, of CSA in unsaturated polyester resin in decreasing particle sizes of 40, 30, and 20 µm in an open mould using hand lay-up technique. Tensile, flexural, and impact strengths, as well as tensile and flexural moduli and Shore D hardness of all test samples were determined. The results showed that 10–20 wt.% CSA increased tensile, flexural, impact strengths and flexural modulus for all particle sizes, but 30–40 wt. % CSA engendered depreciation in corresponding performance. For all particle sizes, 10–40 wt. percent CSA resulted in an increase in tensile strength, whereas 10–40 wt. percent resulted into a linear increase in Shore D hardness. Further observation portrayed that in each case, the finest CSA (20 µm) have the optimum result. Statistical analysis carried out on experimental outcomes confirmed the experimental variables (particle proportion and sizes) to be significant. From the surface plot, the strength responses revealed more dependence on the individual variables than their interactions. Regression models developed for individual responses are termed statistically fit in representing the experimental data.