ABSTRACT

The aim of this research is to develop a value-added product from a renewable resource, investigate the effect of its loadings on the mechanical and thermal properties of PS, as well as, to investigate the interaction between PS and plasticiser (ENO). Neem oil has high contents of unsaturated fatty acids which can be converted to epoxy fatty acids. The vegetable oil-based epoxy materials are sustainable, renewable and biodegradable materials replacing petrochemical-based epoxy materials in some applications. Neem oil was epoxidised at 600C and one atmospheric pressure for 5 hours. Fourier transform infrared (FTIR) spectroscopy was used to identify the unsaturation and epoxy group in the neem oil (NO) and epoxidised neem oil (ENO). Disappearance of the absorption band around 3011.7 cm-1 shows that the C=C has been used up and the appearance of a band around 943 cm-1 which is not seen in the spectrum of the raw neem oil confirm the success of epoxidation. ENO was used as a green plasticiser and added to PS. ENO was added to PS at different contents using solution casting method. Different compositions of PS/ENO blends; (95/5, 85/15, 75/25, 65/35, 45/55, and 35/65) were tested for mechanical performance, thermal behaviour, morphological arrangement and miscibility. Comparison of mechanical properties such as elongation at break, tensile strength and tensile modulus revealed apparent compatibility domain for 95/5 PS/ENO (8.70±0.08, 24.40±0.02 and 37.0±1.0). The miscibility of the two components (PS/ENO) in solution phase was investigated by reduced as well as relative viscosities. The viscosity measurements revealed that miscibility occurs between the compositions 95/5, 85/15, 45/55 and 35/65 wt% PS/ENO while phase inversion and phase separation occur at compositions 65/35 and 75/25 wt% showing immiscibility and incompatibility. Morphological arrangements of the blends were examined by scanning electron microscopy (SEM). The SEM micrographs of the blends showed a two-phase system appearing bright (epoxy phase) and the other appearing black (PS phase) in virtually all the micrographs, even though the heterogeneity due to phase inversions (phase changes) was relevant for some compositions. For other compositions, a domain distribution showed considerable miscibility within the range of compositions. But blends composition of 95/5, 85/15. 65/35 wt% show better morphology. However, blend composition of 35/65 forms another region within the morphology leading to phase separation. The thermal study reported that plasticisation of the PS with ENO at certain compositions lowers the glass-transition temperature (Tg), crystallisation temperature (Tc) as well as melting temperature (T