No abstract

Recent research has proven that starch offers a wide range of industrial, commercial, and utility applications if they are optimally processed and refined. In this study, the effect of hydrogen peroxide (HP), sodium persulfite, peracetic acid (PAA), and sodium perborate (SPB) bleaching agents on the physiochemical, surface, mechanical, and flow properties were investigated. The various bleached starch bioplastics were characterized using Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. Hydroxyl and carbonyl (C=O) stretching were seen for HP- and PAA-bleached starch bioplastics at 3285 and 1736 and 3265 and 1698 cm−1, respectively. The C=O band was absent for SPB-treated starch, whereas the C=S band was seen on sodium hyposulfite (SHS)-treated starch. The morphologies of starch were retained with little agglomerations, except for HP-treated starch bioplastics with a morphology change. HP-treated starch had the highest percentage crystallinity (66%) and the highest thermal stability (74% weight loss), whereas PAA-treated starch had the lowest percentage crystallinity (34%) and the lowest thermal stability (88% weight loss). HP- and SHS-bleached starch bioplastics had the best surface, mechanical, and expansion properties.

Despite the abundance of gypsum and other materials needed for the production of plaster of Paris (POP) in the country, Nigeria relies heavily on the importation of orthopaedic POP bandage. Therefore, the present study aimed at producing POP bandage (LPOP) from locally sourced pure gypsum and cassava starch. Physico-chemical parameters, such as amylose content, amylopectin content, water absorption capacity (WAC), swelling capacity (SC) and browning-charring temperature (BCT) were obtained for the starch binder. A slurry of pure gypsum powder and 2% gelatinized starch binder was impregnated on cotton gauze and cured in an oven at 180 • C for an hour to produce the LPOP. A comparative mechanical test was carried out on the LPOP and a POP bandage (CPOP) acquired from the market using a universal testing machine. The results showed that starch contains 9.06 mg per 100 g amylose and 24.1 mg per 100 g amylopectin which implied that it has a good binding property. The SC, WAC and BCT were evaluated to be 69.79, 81.94 and 190 • C, respectively. The yielding tensile force for LPOP and CPOP are 148 and 460 N, respectively. The horizontal compressive strength of the LPOP and CPOP are 1712 and 1595 N while the vertical compressive strengths are 1070 and 623 N, respectively. These results show that the LPOP produced from locally sourced materials compete favourably in terms of mechanical properties with POP bandage in the market. Thus, based on its strength, it is recommended for orthopaedic casting.