CNC dispersion in PLA and PBAT using two solvents: morphological and rheological properties

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ORIGINAL RESEARCH

CNC dispersion in PLA and PBAT using two solvents: morphological and rheological properties Mojtaba Mohammadi . Charles Bruel . Marie-Claude Heuzey . Pierre J. Carreau

Received: 21 May 2020 / Accepted: 12 September 2020  Springer Nature B.V. 2020

Abstract Cellulose nanocrystals (CNCs) were dispersed via solution casting in amorphous (A) and semi-crystalline (SC) poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT). The protocol, optimized following the Hansen solubility parameter theory, relies on binary mixtures of tetrahydrofuran and dimethyl sulfoxide for the polymers and CNCs, respectively. First highlighted through atomic force microscopy, good filler dispersion and distribution were confirmed by a decrease of the linear viscoelastic region and significant increases of the complex viscosity, storage modulus, and apparent yield stress of the nanocomposites with CNC content, specifically at low frequencies. CNC percolation thresholds of 1, 0.3, and 0.3 wt% were determined in A-PLA, SC-PLA, and PBAT, respectively. These are the lowest to be reported in the literature until now. While PLA retained solvent traces, leading to a significant plasticizing effect, solvent removal was complete in PBAT. It was attributed to the crystallization of PBAT at the drying temperature (70 C).

M. Mohammadi  C. Bruel  M.-C. Heuzey  P. J. Carreau (&) Center for High Performance Polymer and Composite Systems (CREPEC), Department of Chemical Engineering, E´cole Polytechnique de Montre´al, Montreal, QC H3T 1J4, Canada e-mail: [email protected]

Keywords Nanocomposites  Cellulose nanocrystals (CNCs)  PLA  PBAT  Solvent selection  HSP theory

Introduction Polymeric materials have advantageously replaced their metallic counterparts in industries as diverse as aerospace, aeronautics, automotive, medical, sensors, or agriculture (Andrady and Neal 2009). This is notably due to their lightness, low cost, durability, and water resistance (Andrady and Neal 2009). Nonbiodegradable fossil-based polymers, such as polyethylene, polypropylene, polystyrene, and poly (vinyl chloride), are the most employed and contribute disproportionally to the wastes released to the environment (Tokiwa et al. 2009). This issue could, in part, be addressed by using biodegradable plastics produced from bio/fossil-based resources (Rujnic´-Sokele and Pilipovic´ 2017). Poly (lactic acid) (PLA) and poly (butylene adipate-co- terephthalate) (PBAT) have recently received significant attention. Their properties such as biodegradability and biocompatibility make them suitable for automobile products, textiles and fibers, films and packaging, and biomedical applications (drug delivery, blood vessels, tissue engineering, and scaffolding) (Nofar et al. 2018; Ferreira et al. 2019a).

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Cellulose

In addition to its eco-friendly advantages (Tokiwa and Calabia 2006), PLA has interesting mechanical and physical properties, among which high modulus (2–16 GPa), high tensi