DEVELOPMENT AND CHARACTERIZATION OF SISAL FIBRE REINFORCED THEVETIA PERUVIANA OIL BASED BIO-COMPOSITES FOR INDUSTRIAL APPLICATION

Abstract

The increased global environmental consciousness and dwindling fossil resources have led to a growing interest in bio-composites derived from renewable resources. Among the possible technical approaches, using natural fibres to reinforce plant-based polymer resins seems to be the most promising solutions. In this research, sisal fibre was extracted from sisal plant (Agave sisallana) by water retting method; the fibre was treated with 1M KOH solution; which enhanced the fibre ultimate tensile strength from 0.52 MPa to 0.96 MPa for neat and treated fibres respectively. The effect of the alkaline treatment on the surface morphology of the fibres was studied using scanning electron microscope that showed that alkaline treatment enhanced the fibre surface by removing wax, pectin, lignin and other impurities. Thevetia peruviana oil (TPO) was extracted by soxhlet method and was subjected to structural elucidation and characterization using Proton NMR spectrophotometer, Fourier transform infrared (FTIR) Photospectrometry and Gas chromatography mass spectrometer to determine the oil fatty acid content and its triglyceride structure. The oil carbon – carbon double bonds was calculated to be 3.27. A range of new bio-polymers ranging from soft to hard thermosets were prepared by cationic polymerization of Thevetia peruviana oil with styrene and divinylbenzene and catalyzed by modified boron trifluoride etherate. The fully cured thermosets were found to contain between 74.7 to 85.6% cross linked materials with crosslink densities between 1.34 x 103 to 1.83 x 103mol/m3. The ultimate tensile strength of the materials ranged from 0.5 to 0.56 MPa, the young moduli varied from 3.83 to 5.38 MPa, the elongation at break varied between 56 to 63 %, the density of the polymers varied between 0.849 to 0.865 gcm-3, impact strength varied from 2.30 to 2.80 J and hardness varied between 3.50 to 3.80 BHN. Three sets of novel bio-composites were developed using different weight fractions of sisal fibres of 5 mm length to reinforce Thevetia peruviana oil (TPO) resins. The new bio-composites density varied between 0.821 to 0.876 gcm-3 depending on the fibre volume fraction. The dependence of morphology and physical properties of the composites on the content of sisal fibres was investigated by scanning electron microscopy and tensile testing. Investigation showed that sisal fibre loading and polymer resin composition play an important role in improving the mechanical properties of the resulting composites; as the sisal fibre content increases from 0 to 15 wt%, the TPO-based composites young modulus varied between 5.25 to 7.84 MPa, ultimate tensile strength varied between 1.40 to 2.00 MPa, the elongation varied between 56 to 64 %, Furthermore, the composites exhibit resistance to acids, alkalis and various solvents and also possessed lower water absorption. SEM images of the composites show that considerable improvements in the TPO-based bio composites properties should be possible by optimization of the resin structure and fibre. The sisal fibre reinforced TPO composites have properties that make it relevant for industrial application.