John O. Akindoyo

Polyurethane types, synthesis and applications – a review

Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.

Preparation and Characterization of Poly(lactic acid)-Based Composites Reinforced with Poly Dimethyl Siloxane/Ultrasound-Treated Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunch fiber and polylactic acid were used to produce composites by melting cast method. Fiber loading was considered up to 40 wt%. Oil palm empty fruit bunch fibers were treated using ultrasound and polydimethylsiloxane to improve the interfacial adhesion. The structure and surface properties of the fibers were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and contact angle measurement. Moreover, Fourier transform infrared spectroscopy, tensile, flexural, X-ray diffraction, contact angle, differential scanning calorimetry, and thermogravimetric analysis were used to investigate composites’ properties. The analysis revealed that polydimethylsiloxane treatment composites show reduced wettability with increased crystallinity. GRAPHICAL ABSTRACT

The effects of wettability, shear strength, and Weibull characteristics of fiber-reinforced poly(lactic acid) composites

Abstract The wettability, interfacial shear strength (IFSS), and Weibull characteristics of oil palm empty fruit bunch (EFB) fibers were studied to evaluate the mechanical properties of EFB- and poly(lactic acid) (PLA)-based composites. The fiber surface was modified through ultrasound and poly(dimethyl siloxane) treatment. The effects of treatment on the morphology, wettability, and structure of fibers were examined by scanning electron microscopy, contact angle, and Fourier transform infrared spectroscopy analysis, respectively. In addition, the Weibull characteristic was used to find the variability in strength of the fibers with respect to surface treatment. Furthermore, the IFSS of EFB fiber-PLA sandwich was investigated through single-fiber pull-out test, using a less strenuous technique. The mechanical properties (tensile strength, tensile modulus, flexural strength, and flexural modulus) of the composites were determined through mechanical testing. A comparison was drawn among the properties of PLA, raw EFB fiber-based composites, and treated EFB fiber-based composites. Additionally, the inter- and intra-relationship of fiber treatment, wettability, and IFSS with the mechanical properties of the PLA/EFB composites were also accounted.

Synthesis of Hydroxyapatite through Ultrasound and Calcination Techniques

There is a growing demand for hydroxyapatite (HA) especially in medical applications, production of HA which is totally green is however a challenge. In this research, HA was produced from biowaste through ultrasound followed by calcination techniques. Pre-treatment of the biowaste was effectively achieved through the help of ultrasound. After calcination at 950°C, the obtained HA was characterized through Thermogravimetric (TGA) analysis, X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR). Spectrum of the produced HA was compared with standard HA index. The spectrum is in agreement with the standard HA as confirmed through FTIR, XRD and TGA result. Furthermore, morphological study of the HA through Field emission scanning electron microscope (FESEM) shows almost uniform spherical shape for the HA as expected. Based on the results obtained herein, combining ultrasound with calcination can help to produce pure HA with potential medical applications without the use of any organic solvent.