DEVELOPMENT AND CHARACTERIZATION OF BIOCOMPOSITES FROM POLYLACTIC ACID AND GROUNDNUT SHELL ASH NANOPARTICLES

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Department of Engineering

ABSTRACT
Polylactide (PLA) is an emerging material mainly because it can be synthesized from renewable resources and is thus environmentally and ecologically safe. It found application in packaging and biomedical. In terms of cost, however, PLA cannot rival the traditional packaging materials. Creative solutions are therefore needed to make PLA a more financially viable packaging alternative. This study was carried out in order to improve the properties and reduce the cost of PLA. Composites of Polylactic Acid (PLA) and Groundnut Shell Ash nanoparticles (GSAnp) were produced using injection moulding method. The GSAnp were produced by grinding groundnut shell ashin a ball mill and the optimal ball milling time of 10 hours with average nanoparticle size of 20nm was achieved. After the production, the GSAnpwas characterized using Energy Dispersive Spectrum (EDS), X-ray Fluorescence (XRF), X-ray Diffractometer (XRD) and Brunauer-Emmett Teller (BET) analysis to determine the chemical composition, phase composition and specific surface area. Taguchi method was used to determine the combination of process parameters that gave the composite best combination of properties.Various process parameters varied were Wt% GSAnp, polyethene glycol(PEG) %, annealing temperature (oC) and time(hrs). The optimal combination of process parameters was obtained at 20wt% GSAnp, 4wt% PEG, annealing temperature of 100oC and time of 6 hours. This combination was found to produce a good interfacial bonding between the reinforcement and the matrix. The XRD spectrum of the PLA revealed two peaks located at 2theta= 18.45° and 45.6° while the compositeexhibits major broad diffraction peak at 2theta = 36, 45, 65 and 78.5º with the presence of silica and alumina phases.Mechanical testing of the composite gave better tensile modulus, flexural strength and hardness values in comparison with the PLA used. After the mechanical test, SEM morphological study showed that the GSAnp at 20nm as a reinforcement has smooth spherical surface. The GSAnpwas fairly dispersed in the polymer matrix. The maximum endothermic peaks shifted to higher temperature with GSAnp addition and improved the thermal stability of the produced composite.The storage modulus of the PLA decreases from 3100 to 500MPa, while that of the composite from to 4250 to 700MPa at 30 and 90oC respectively, showing that the composite has better storage modulus.The weight loss as a result of biodegradation ranges from 2.5 to 20.5% after 20 daysfor PLA and 3.4 to 21.5% after 100days for the composite. Hence, the mechanical, thermal and biodegradable properties ofthe developed nanocomposite material can be employed for use in food packaging and other disposable products as well as infire-retardant materials.