Characterisation and development of new bio-filler using mimusops elengi seed shell powder for polypropylene composites

Tan, Wuan Chien (2020) Characterisation and development of new bio-filler using mimusops elengi seed shell powder for polypropylene composites. Master dissertation/thesis, UTAR.

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Abstract

In recent year, high dependency on petroleum based plastics, deterioration of the environment due to the pollution caused by the unmanageable plastics waste disposal has emerged the interest in sustainable development of biocomposites. Plant fibers are abundantly available, biodegradable, light weight with high specific properties. The present research study is an effort to combine the advantages offered by the renewable resources for the production of the biocomposites. The greatest challenges is the weak compatibility between the natural fiber and matrix resulted in the weak mechanical properties of the composites. Alkaline treatment is one of the wellknown approach to overcome this problem. Biocomposites were prepared from Mimusop elengi seed shell powder (MESSP) and polypropylene (PP) blend by using Brabender internal mixer at 180 °C and rotor speed of 60 rpm for a mixing time of 8 minutes. The MESSP loading was varied from 0 - 40 wt. % and it was found that the saturation point was achieved at 20 wt. % MESSP. Composite development is not feasible above 20 wt.% MESSP due to poor wetting by PP. Characterisation of MESSP were conducted to study the potential of MESSP as the filler for PP composites. Physico-mechanical properties, processing-ability, thermal stability, biodegradability and water absorption properties of PP/MESSP composites were studied. Processing-ability and thermal stability of the composites were comparable to the neat PP showing insignificant effect on the composites up to 20 wt. % MESSP. Tensile modulus and impact strength were enhanced with increasing MESSP loading. However, reduction of tensile strength and elongation at break was obtained with increasing MESSP loading attributed to the poor interfacial adhesion between PP and MESSP as confirmed by the scanning electron microscopic (SEM) morphological analysis. Positive results were observed with the increased weight loss in the soil burial test indicating significant extend of bio-degradability of the composites with increasing MESSP loading. Chemical modification of MESSP with alkali treatment was performed to improve the polymer-matrix compatibility. Fourier transform infrared (FTIR) and SEM analysis proved that treatment with 5 w/v % sodium hydroxide (NaOH) solution produced a better modification on the chemical compositions and structural characteristics of MESSP as compared to 6 w/v %, 7 w/v % and 8 w/v % of NaOH solution. Treated MESSP filled PP (PP/TMESSP) composites had an affirmative effect on the mechanical properties and water absorption resistance. It was found that an increase of 30 % in tensile strength and 28% in impact strength at the optimum 15 wt. % of PP/TMESSP composites as compared to that of untreated MESSP filled PP (PP/MESSP) composites. Water absorption resistance and the crystallinity of PP/TMESSP composites were also improved. Better interfacial adhesion between PP and TMESSP were observed as compared to PP and MESSP through SEM images. However, thermogravimetric analysis showed that the maximum decomposition temperature of PP/TMESSP composites was lower as compared to PP/MESSP composites due to removal of thermally stable lignin layers of MESSP upon alkali treatment.

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