Stephen C. Agwuncha

Kinetic release studies of nitrogen-containing bisphosphonate from gum acacia crosslinked hydrogels

Natural polymer hydrogels are useful for controlling release of drugs. In this study, hydrogels containing gum acacia were synthesized by free-radical polymerization of acrylamide with gum acacia. The effect of gum acacia in the hydrogels on the release mechanism of nitrogen-containing bisphosphonate (BP) was studied at pH 1.2 and 7.4. The hydrogels exhibited high swelling ratios at pH 7.4 and low swelling ratios at pH 1.2. The release study was performed using UV-Visible spectroscopy via complex formation with Fe(III) ions. At pH 1.2, the release profile was found to be anomalous while at pH 7.4, the release kinetic of BP was a perfect zero-order release mechanism. The hydrogels were found to be pH-sensitive and the release profiles of the BP were found to be influenced by the degree of crosslinking of the hydrogel network with gum acacia. The preliminary results suggest that these hydrogels are promising devices for controlled delivery of bisphosphonate to the gastrointestinal region.

Mechanical properties of sisal fibre-reinforced polymer composites: a review

Abstract There has been a growing interest in the utilization of sisal fibres as reinforcement in the production of polymeric composite materials. Natural fibres have gained recognition as reinforcements in fibre polymer–matrix composites because of their mechanical properties and environmental friendliness. The mechanical properties of sisal fibre-reinforced polymer composites have been studied by many researchers and a few of them are discussed in this article. Various fibre treatments, which are carried out in order to improve adhesion, leading to improved mechanical properties, are also discussed in this review paper. This review also focuses on the influence of fibre content and fabrication methods, which can significantly affect the mechanical properties of sisal fibre-reinforced polymer composites.

The use of polypropylene in bamboo fibre composites and their mechanical properties – A review

Bamboo fibre has gained significant interest as a sustainable reinforcement fibre in natural fibre/polymer composites, which is as a result of specific mechanical properties and being a biodegradable material compared to glass fibres. The article also gives a summary of how to improve the mechanical properties of bamboo fibre reinforced polypropylene (BFRP) composites as presented in various researches and the methodology of attaining these ultimate properties of bamboo fibres with polymeric matrices leading to improved BFRP. Mechanical properties of BFRP composites are improved by introducing coupling agent. Fibre treatment and nanoclay addition, in the right proportion, as reported have improved mechanical properties of BFRP composite.

Thermal, structural and morphological properties of High Density Polyethylene matrix composites reinforced with submicron agro silica particles and Titania particles

Abstract HDPE—based composites samples filled with 2, 4, 6, 8 and 10 wt.% submicron agro-waste silica particles extracted from rice husk ash (RHA) at constant 0.3 wt.% Titania loading were prepared using rapra single screw extruder at temperature of 200–230 °C. The extrudates were compressed with a laboratory carver press at a temperature of 230 °C for 10 min under applied pressure of 0.2 kPa and water cooled at 20 °C min−1. Thermal, structural and morphological properties of the composites were studied. The results of the thermogravimetric analysis (TGA) revealed that the composites with 10 wt.% SiO2 have the best maximum thermal degradation temperature of 438.73 °C. The crystal structure of neat HDPE, and the siliceous composites developed revealed two obvious diffractive peaks of about 21.3° and 23.7° corresponding to typical crystal plane (1 1 0) and (2 0 0) of orthorhombic phase respectively. The diffractive peaks do not shift with the addition of silica particles; this clearly indicates that the addition of silica particles did not exert much effect on the crystalline structure of HDPE. There is no much difference in the interplanar distance (d-value). Lamellar thickness (L) of HDPE increases with the addition of silica particles, which implies that silica particles aid the formation of more perfect crystals. Scanning electron microscopy studies indicated that there were chains inter diffusion and entanglement between HDPE matrix and the silica particles at lower weight fraction (2–4 wt.%) of submicron silica particles which resulted into homogeneous dispersion of the particles within the matrix.

Impact of Surface Modification and Nanoparticle on Sisal Fiber Reinforced Polypropylene Nanocomposites

The use of plant fibers, polymer, and nanoparticles for composite has gained global attention, especially in the packaging, automobile, aviation, building, and construction industries. Nanocomposites materials are currently in use as a replacement for traditional materials due to their superior properties, such as high strength-to-weight ratio, cost effectiveness, and environmental friendliness. Sisal fiber (SF) was treated with 5% NaOH for 2 hours at 70°C. A mixed blend of sisal fiber and recycled polypropylene (rPP) was produced at four different fiber loadings: 10, 20, 30, and 40 wt.%, while nanoclay was added at 1, 3, and 5 wt.%. Maleic anhydride grafted polypropylene (MAPP) was used as the compatibilizer for all composites prepared except the untreated sisal fibers. The characterization results showed that the fiber treatment, addition of MAPP, and nanoclay improved the mechanical properties and thermal stability and reduced water absorption of the SF/rPP nanocomposites. The tensile strength, tensile modulus, and impact strength increased by 32.80, 37.62, and 5.48%, respectively, when compared to the untreated SF/rPP composites. Water absorption was reduced due to the treatment of fiber and the incorporation of MAPP and nanoclay.

Immiscible Polymer Blends Stabilized with Nanophase

The importance of phase morphology in immiscible blend makes the issue of stability also very important. In this chapter, we try to explain the role of nanoparticles in the stabilization of dispersed phases from the experimental and theoretical point. As inorganic particles, it might seem impossible from the classical chemistry point of view. However, their sizes and shapes have them some very important advantages, such that interactions that may not have been possible with microsize particles now are with nanoscale particles. However, it is not as straightforward as it sounds. Therefore, factors that are necessary for these particles to act as compatibilizers and those required of the polymer blends are discussed here so that first timers in material science of polymer blends can follow through.

Crystallization and Morphological Changes in Nanostructured Polymer Blends

Abstract The crystallization processes in polymer blends and the subsequent morphology and crystal structures formed are of great interest because of their significance, especially in the determination of their performance properties. Therefore, in this chapter, the fundamentals of crystallization in polymers were discussed first and then related to the real situation in polymer blends with nanoparticles. Fractionated crystallization phenomenon was thoroughly looked into as it relates to dispersed phase and confined domain. Nanostructured polymer blends present a not too different scenario when compared to the neat polymers, but still, their crystallization processes offer something to talk about. In addition, the polymorphic development in immiscible blends was also a subtopic that was discussed. In all, an adequate amount of literature was referred to.

17 – Biomedical applications of polyolefins

In this chapter we discuss the use of polyolefins (POs) in the biomedical fields; POs being the largest volume polymers in the plastic industry today. The main focus will be on the two main types of POs, viz: polyethylene (PE) and polypropylene (PP), which have substantial biomedical applications in addition to their other uses. Hence, an overview of PE, PP, other higher POs, and their properties are reviewed to map out the technical characteristics that are advantageous for biomedical applications. POs are easy to fabricate into useful products and have increasing design capability. They also have the potential for use in many applications because of their excellent cost/performance values such as low density, easy recyclability, and diverse processability. Biomedical applications of these POs in medical implants, medical devices, and in the production of pharmaceutical consumables in the form of packaging materials; vials, bottles, and syringes will be highlighted with numerable references made.

Improving the thermal and flame resistance properties of polyolefins

Abstract The thermal properties of polymers play a significant role in determining the environment where they can be applied. Most polyolefins have poor thermal properties such as low melting temperature, poor specific heat capacity, and conductivity just like most polymers. Also, as a matter of requirement by law, most polymers including polyolefins are required to have low flammability properties which is achieved by the addition of flame retardants (FRs) to the polyolefins during compounding. Improving on these aforementioned properties will go a long way to widen the present areas of application. Therefore there is the need to constantly review the processes and measures put in place to improve these important properties of polyolefins. The chapter takes a critical look at the current efforts by scientists in improving the thermal and FR properties of polyolefins. However, most works showed that blending of the polyolefins with other polyolefins or polymers, compounding with nanoparticles or treated fibres are some of the common ways this improvement can be achieved.