Poly(lactic acid) (PLA) is a viable biopolymer replacement for non-sustainable plastics, sourced form biomass such as corn and sugarcane. Widespread use of PLA throughout industry is limited because of its poor mechanical properties such as brittleness. While the integration of plasticizers into polymer matrices has been shown to improve the toughness of brittle polymers, it often comes at the cost of mechanical strength. The addition of nanoparticles offers the benefit of both mechanical strength retention and increased toughness. Cellulose nanocrystals (CNCs) are, from a green perspective, a logical component to employ for improving mechanical properties of sustainable polymers. Derived from the most abundant polymer on Earth, cellulose, CNCs can be produced on a large scale and tailored for dispersion in various polymers through surface modification and functionalization.<br/><br/>This research investigates the functionalization of CNCs with an inner, rubbery poly(butyl acrylate) (PBA) block to act as cushion, improving toughness, and an outer poly(ethylene glycol) (PEG) block for compatibility with the PLA matrix. Through a combination of solvent casting and melt pressing, nanocomposites of nonfunctionalized CNCs and PEG functionalized CNCs were made at 0.5, 1, 2, and 5 wt%. Blends of PLA, PEG, and nonfunctionalized CNCs were also cast to assure the necessity of functionalization. PEG of molecular weights 550, 2000, and 5000 were grafted to the CNC surface via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) coupling. Thermogravimetric analysis (TGA) and Kaiser tests confirmed successful grafting. All functionalized CNC composites displayed equivalent thermal stability to neat PLA by TGA, and PEG grafted CNCs of molecular weight 2000 and 5000 exhibited dramatic improvements in ductility. Optimization of CNC dispersion methods and implementation of an inner PBA block are being investigated to further improve nanocomposite mechanical properties.

Cellulose nanocrystals as reinforcement filler in poly(lactic acid) matrices

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.