Mechanical and Thermal Properties of Toughened Poly(L-lactic) Acid and Lignin Blends

Abstract

Fully degradable poly(L-lactic) acid (PLLA) and lignin blends were prepared using the melt blending method. The impact strength of PLLA was dramatically improved by 52.4% and 36.6% with the addition of 5 wt% and 10 wt% of lignin, respectively. Meanwhile, the Young's modulus was maintained. Polarized optical microscopy (POM) results indicated that lignin served as a nucleating agent for the heterogeneous crystallization of PLLA in blends, which was responsible for the improvement in the impact strength. The introduced lignin also promoted the cold-crystallization of PLLA, which was demonstrated by differential scanning calorimetry (DSC). The blends of PLLA with lignin are considered to be a promising material because of the improved toughness, the full degradability, and the lower price compared with pure PLLA.

Effect of processing conditions and lignin content on thermal, mechanical and degradative behavior of lignin nanoparticles/polylactic (acid) bionanocomposites prepared by melt extrusion and solvent casting

“…This behavior was explained considering that the decrease in the mechanical properties was due to the existence of lignin particles which prevented the formation of a long range continuous phase of PLA [38]. Indeed, it has been already observed [34] that enhanced elongation at break of neat PLA in presence of lignin particles can be attributed to the flexibility of the lignin structure (benzene rings are linked with ether linkages that act as internal plasticizers [39,40]). These previous studies were related to the use of lignin microparticles in PLA and it supposed that the mechanism is still valid even in the presence of nanosized lignin.…”

“…When increased amount of lignin was added to PLA, the cold crystallization temperature shifted to lower temperatures in the case of extruded material (from the original 101.7°C to 100.8°C and 96.1°C for E-PLA/1LNP and E-PLA/3LNP, respectively). In the case of cast samples, the segmental motion of PLA molecular chains (T cc = 94.2°C) may have been affected by presence of lignin, leading to a shift in the T cc to higher temperatures (mean values of 94.9°C and 95.5°C for C-PLA/1LNP and C-PLA/3LNP, respectively) [32].…”

Nucleation, Crystallization, and Thermal Fractionation of Poly (ε-Caprolactone)-Grafted-Lignin: Effects of Grafted Chains Length and Lignin Content

“…The effect of lignin content on the isothermal and nonisothermal crystallization kinetics of different polymeric materials has been reported, but none of them deals with PCL. Additionally, a considerable amount of articles study properties of polymer/lignin blends, but crystallization kinetics are not considered.…”

Physical and Mechanical Properties of Recycled Polypropylene Composites Reinforced with Rice Straw Lignin

“…In addition, the emerging utilization of biomass for bio-energy liberates a large amount of lignin. Even though considered as a waste and the major application of lignin is burned to produce energy (Mu et al 2014;Su and Fang 2014), lignin has potential as a reinforcer or filler for polymer composites due to the compatibility property with chemicals, and it possesses the reactive functional groups .…”

“…In addition, lignin was blended with polyvinyl chloride and resulted in renewable and biodegradable materials with increased surface reflectance characteristics as the amount of lignin increases (Mishra et al 2007). When lignin was blended with poly(L-lactic) acid, the impact strength of poly(L-lactic) acid was improved appreciably, as well as its toughness; the resulting composite was less expensive compared to neat poly(L-lactic) acid plastic (Mu et al 2014). The impact strength and structural properties were also improved when lignin was added to a hemp/epoxy resin composite matrix (Wood et al 2011).…”