Physico-mechanical properties of bio-composites fabricated from polylactic acid and rice husk treated with alkali and ionic liquid

Abstract

In the present work, chemically treated rice husk (TRH) and untreated rice husk (UTRH) reinforced polylactic acid (PLA) bio-composites were produced using Haake rheomixer and compression moulding processes. Alkali (NaOH) and ionic liquid (IL: 1-ethyl-3-methylimidazolium acetate) treated rice husk samples are TRHN4 and TRHILN4 respectively. Using UTRH, TRHN4 and TRHILN4 the fabricated bio-composites are UTRH-PLA, TRHN4-PLA and TRHILN4-PLA respectively. The tensile strength (TS), tensile modulus (TM), impact strength (IS) and hardness values of TRHN4-PLA and TRHILN4-PLA were found to be much higher than the corresponding values of the UTRH-PLA bio-composites.  The tensile fracture surface morphological features of TRHN4-PLA and TRHILN4-PLA composites, observed by scanning electron microscopy (SEM), revealed less micro voids and fibre agglomerates, which indicates that better filler-matrix interfacial adhesion occurred in the case of chemical treated RH compared to UTRH when blended with PLA. However, composites TRHN4-PLA and TRHILN4-PLA showed lower water uptake capacity compared to UTRH-PLA.  From the FTIR spectra of UTRH, TRHN4 and TRHILN4 together with water absorption behaviour of the composite specimens, it appeared that chemical modifications significantly reduced the hydrophilic nature of RH, resulting in improved fibre-matrix interfacial adhesion. The overall physico-mechanical properties of fabricated bio-composites were found to follow this order: TRHILN4-PLA>TRHN4-PLA>UTRH-PLA.