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Kraft lignin (KL) or plasticized KL (PKL)/poly(lactic acid) (PLA) composites, containing different lignin contents and with and without the coupling agent, were prepared in this study using twin-screw extrusion at 180 • C. Furthermore, ε-caprolactone and polymeric diphenylmethane diisocyanate (pMDI) were used as a plasticizer of KL and a coupling agent to improve interfacial adhesion, respectively. It was found that lignin plasticization improved lignin dispersibility in the PLA matrix and increased the melt flow index due to decrease in melt viscosity. The tensile strength of KL or PKL/PLA composites was found to decrease as the content of KL and PKL increased in the absence of pMDI, and increased due to pMDI addition. The existence of KL and PKL in the composites decreased the thermal degradation rate against the temperature and increased char residue. Furthermore, the diffusion coefficient of water in the composites was also found to decrease due to KL or PKL addition.PLA is considered one of the most promising biopolymers due to its excellent properties, which include biodegradability, biocompatibility, and renewability, as well as good mechanical properties [10][11][12]. PLA is derived from agricultural products (e.g., corn and potato) and is usually produced by ring-opening polymerization of lactide and condensation of lactic acid without polluting the environment during the production process [6,10,13]. However, despite its properties, the application of PLA has been limited because of its higher price and lower resistance to heat and water [11,13]. It has been proposed that compounding PLA with filler can improve its properties and remove some of its drawbacks [5,[11][12][13][14][15]. Recently, some studies have introduced lignin to improve the performance of PLA and reduce the cost [10,13,14].Lignin is one of the most abundant biopolymers, accounting for nearly 25% of lignocellulosic biomass [16][17][18][19]. It is usually easily obtained as a byproduct of the pulping industry and has some positive properties, including being biodegradable, non-toxic, and low-cost and having low density and excellent thermal and moisture resistance [20][21][22][23]. Due to these properties, research on lignin application for bioplastics has increased. Lignin has been known to have positive effects on composite properties. Some studies have observed that lignin addition enhances resistance for heat and moisture [14,15,24]. Furthermore, lignin has also been utilized as a stabilizer to prevent oxidation on plastic composites [25]. However, some studies have reported that the presence of lignin can deteriorate the mechanical properties of lignin-based composites. Lignin has been found to be incompatible with most aliphatic polyesters, including PLA, PBS, and PCL, thus deteriorating the mechanical properties of the composites [26][27][28]. However, it has been found that this strength deterioration, which is caused by lignin addition, can be overcome by adding coupling agents [26,[29][30][31]. Isocyanate coupling agents, such...

Journal of Wood Chemistry and TechnologyPublication details, including instructions for authors and subscription information:Graft copolymerization of styrene onto kraft lignin (KL) was achieved by atom transfer radical polymerization (ATRP) using a fully substituted lignin-based macroinitiator (KLM). The number average of molecular mass (M n ) of polystyrene copolymer graft side-chains was achieved by varying the ratio of the DMF: water solvent system from 5:0 to 1:4. A M n of up to ∼206,000 was obtained using a DMF/water ratio of 3:2 (v/v). However, as the M n increased, the overall ATRP became less controlled. In addition, the thermal properties of the lignin-g-polystyrene copolymers improved significantly with increasing M n of polystyrene copolymer side-chains.

Lignin-based electrospun nanofibers (eNFs) were prepared and thermally stabilized at 250°C and subsequently carbonized at 1400°C. The starting blend was prepared in dimethyl formamide (DMF) solution with lignin and polyacrylonitrile (PAN), while a lignin-grafted-PAN (L-g-PAN) copolymer served as compatibilizer. The viscosity was highest of the DMF solution with PAN, and decreased for the lignin/PAN blends and additionally in presence of L-g-PAN. The uniform eNFs with clean surfaces dispose of diameters between 400 nm and 1 μm. The average diameter of eNFs decreased by the thermal treatment and at higher lignin contents in the blends. Remarkable shrinkage by carbonization was observed in all nanofibers. The successful carbonization of all electrospun carbon nanofibers (eCNFs) was confirmed by Fourier transform-infrared (FT-IR) spectroscopy. The specific tensile strength and elastic modulus of the eCNF mats from lignin/PAN blends were improved by the addition of L-g-PAN, and it can be safely concluded that it acts as a compatibilizer between lignin and PAN.