Preparation And Properties Of Kenaf Bast Fiber Filled (Plasticized) Pol Y(Lactic Acid) Composites

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Date
2008-06
Authors
Ramarad, Suganti
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Abstract
Kenaf bast fiber (KBF) filled plasticized poly(lactic acid) (p-PLA) composites was prepared and examined stage by stage in this study. Firstly, poly(lactic acid) (PLA) was plasticized with 5 up to 20 wt% poly(ethylene glycol) (PEG) via internal mixer. Blend with 10 wt% PEG was chosen as matrix for composite as it showed the best impact strength and elongation at break. Secondly, maleic anhydride grafted PLA (MAPLA) was successfully produced with 0.22% grafting using reactive grafting method, and used as a compatibilizer for the composite system. p-PLAlKBF composite was compounded via internal mixer and compression molded into test specimens. KBF loading was varied from 10 to 40 wt%. Characterization was done by means of tensile and impact testing, dynamic mechanical analysis, water absorption, soil burial and natural weathering. At 40 wt% KBF loading, tensile strength and modulus improved by 120% and 213% respectively, while strain at break and impact strength dropped by 99% and 52% respectively compared to neat p-PLA. Improvement in properties suggests effective stress transfer between fiber and matrix. Morphological studies leads to assumption that PEG interrupts the interaction between KBF and PLA, forming undesirable interphase. Tensile strength and modulus dropped while strain at break improved when 5 wt% MAPLA was added to the composite systems. MAPLA is believed to interact with PEG instead of KBF, enhancing the 'plasticization effect instead of performing as a compatibiIizer for the composite system. Tensile strength and modulus improved only when 10 wt% MAPLA was added to 40 wt% KBF composite, suggesting saturation of MAPLA-PEG interaction, allowing remaining MAPLA to interact with KBF. PLA/KBF and PPIKBF composites were also prepared at 40 wt% KBF loading for comparison with p-PLA/KBF composite. pPLA composite had lower tensile strength (-38%) and modulus (-26%) but higher impact strength (+20%) than that of PLA composite. However, p-PLAIKBF had comparable tensile strength, higher modulus (+31%) and lower strain at break (-38%) and impact strength (-61%) compared to PPIKBF composite. Storage and loss modulus of p-PLA composites increased with increasing KBF loading. This is due to stiffness of KBF fiber that restricts the mobility of polymer chains. Tan delta decreased with increasing KBF loading. All composites did not reach saturation at the end of test. This was due to leach out of water soluble PEG and formation of micro cracks due to fiber swelling that permit continuous penetration of water molecules into the composite. Soil burial and natural weathering showed higher weight loss with increasing KBF loading in both p-PLA and PP composites, suggesting enhanced degradation with the presence of KBF. However, p-PLA composites showed higher weight loss than PP composites.
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Engineering , Material and Mineral Resources
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