The goal of this research was improving the mechanical and physical properties of poly lactic acid (PLA) using cellulose nanofiber (CNF) as reinforcing and maleated PLA (PLA-g-MA) as a compatibilizer. PLA/nanocellulose composites were prepared through melt mixing with maleated PLA (5 wt%) and two levels of cellulose nanofibers (CNFs) (3 and 5 wt%) using twin screw extrusion. Nanocomposites fracture morphology, thermal properties, crystallization behavior, and mechanical behavior were determined as a function of cellulose nanofibers and PLA grafted on maleic anhydride content using scanning electron microscopy (SEM), atomic force microscopy, heat distortion temperature (HDT), impact, and tensile testing. The SEM micrographs confirmed the uniform dispersion of CNF within PLA matrix in the presence of maleated PLA. Among nanocellulose and compatibilizer, the latter one has better role in enhancement of nanocomposites HDT. Compatibilized nanocomposites (PLA/CNF5/PLAgMA5) exhibited maximum impact strength which was 131% higher than that of neat PLA. Compared to pure PLA, 138 and 40% improvements for the tensile strength and Young’s modulus can be obtained for the resulting nanocomposite with PLA/CNF5/PLAgMA5, respectively.
AbstractIn this research, maleated poly(lactic acid) (PLA-g-MA) was manufactured by different levels of maleic anhydride (MAH). Also PLA-g-MA effects as a compatibilizer were investigated on PLA/cellulose nanofiber (CNF) composites. The grafting reaction was performed in the presence of dicumyl peroxide (DCP) as an initiator at constant level (0.2 phr) via reactive extrusion. Furthermore, the effects of four different levels of MAH (1–4 phr) were studied on the physical properties of PLA grafted films. We used the Fourier transform infrared (FTIR) and titration methods for confirmation of the grafting process. Based on the titration method, the greatest amount of yield was gained by 4 phr of MAH in grafting. Contact angle analysis shows that increasing the amount of MAH led to a decrease in the contact angle of films. Moreover, the glass transition temperature (Tg) and % crystallinity were decreased by increasing MAH content. PLA-g-MA was added to the composites in two levels of 3% and 5% in total. CNF was used at a constant level of 5%. The thermal, morphological and mechanical properties of nanocomposites were determined as a function of PLA-g-MA content using thermogravimetric analysis, heat distortion temperature (HDT) and tensile testing. All the prepared nanocomposite materials showed improvement in the mechanical and thermal properties compared to neat PLA.
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