Toughening mechanisms in poly(lactic) acid reinforced with TEMPO-oxidized cellulose

Abstract

The mechanical properties of poly(lactic) acid (PLA) were modified by the addition of small amounts of cellulose, prepared from the mechanical disintegration of birch Kraft pulp following oxidation of the primary alcohol groups mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The TEMPO-fibrillated cellulose (TOFC) was subsequently acetylated in acetic anhydride to degrees of substitution (DS) of 0.4 and 0.6 to enhance the compatibility between the polar cellulose and the non-polar polymer. The fracture behaviour of tensile specimens prepared from PLA film containing weight fractions of 1, 2 and 5 % of TOFC was considerably altered. The strain-to-failure of PLA modified by the incorporation of 1 wt% TOFC acetylated to a DS of 0.6 increased approximately 25-fold and the work of fracture by order of magnitude. The increase in the fracture properties were, nevertheless, accompanied by a reduction in Young's modulus of around 60 % at both DS levels. At the higher TOFC addition levels, no toughening was observed, with the strains-to-failure and works of fracture both decreasing compared to pure PLA film. On the other hand, the Young's modulus and tensile strength of films prepared from PLA incorporating TOFC esterified to a DS of 0.6 was found to be greater than that of pure PLA film.Possible mechanisms explaining the increase in toughness at 1 wt% are postulated.

Enhanced ductility and tensile properties of hybrid montmorillonite/cellulose nanowhiskers reinforced polylactic acid nanocomposites

“…Thus, the existence of a proportional content of hydrophilic groups may contribute to plasticization leading to enhanced deformability. It may also be the case that the addition of CNW leads to nucleation of crazes in the amorphous fraction of the PLA resin, as has been previously observed for a different system [28]. In addition, Fig.…”

“…According to Bulota and Hughes [28], the high strain-to-failure arising from craze nucleation is indicated by a whitening of the polymer matrix due to air scattering. As can be clearly observed from This result suggests that CNW might nucleate crazes, possibly due to their high surface to volume ratio.…”

Rubber‐toughened PLA blends with low thermal expansion

“…Blending is probably the most extensively used methodology to improve PLA mechanical properties. In literature, PLA has been blended with different plasticizers and polymers (biodegradable or non‐biodegradable) to achieve desired mechanical properties, such as PEGs,2 LDPE,3 PVAC,4 PMMA,5 poly(ethylene‐ co ‐octene) (EOR),6 poly (ethylene‐glycidyl methacrylate) (EGMA),7 PCL,8 PBAT,9 natural rubber,10 isocyanate‐terminated prepolymer of polybutadiene,11 and cellulose 12. These PLA blends universally display a significant increase in elongation compared to neat PLA.…”

Functionalized Polymers from Lignocellulosic Biomass: State of the Art

“…Although the vast majority of reports are focused on MFC's ability to reinforce [79][80][81][82][83][84][85][86][87] and toughen [85][86][87][88][89][90][91] polymer matrices, there is an increasing number of publications dedicated to the superior barrier properties of MFC for packaging materials [76,84,[92][93][94][95][96][97][98][99]. The recent reviews of Siró et al [97], Lavoine et al [98] and Johansson et al [99] give an overview of these competitive nanomaterials.…”