Sustainable and high‐performance composites based on glycidyl methacrylate‐grafted poly(lactic acid) and cellulose nanofibrils

Abstract

We investigate the microstructure, thermal stability, melt‐rheological behavior, and mechanical properties of sustainable composites based on a modified poly(lactic acid) (PLA) matrix and cellulose nanofibril (CNF) fillers. For this purpose, glycidyl methacrylate (GMA)‐grafted PLA (PLA‐g‐GMA) was fabricated via reactive melt‐mixing of neat PLA with GMA and it was melt‐compounded with different CNF filler loadings (0.5–10.0 wt%). The NMR and FT‐IR spectroscopic analyses of PLA‐g‐GMA/CNF composites confirmed that GMA was successfully grafted on the PLA backbone and that there are intermolecular chemical reactions and specific interactions between the GMA group of the PLA‐g‐GMA matrix and the hydroxyl group of the CNF filler in the composites. As the result, the glass transition and cold‐crystallization temperatures of the PLA‐g‐GMA matrix in the composites were measured to increase with the increase of CNF loading. In addition, the thermal decomposition temperature of the PLA‐g‐GMA matrix as well as the residue at 500°C of the composites increased with the CNF loading, resulting from the barrier and flame retardation roles of CNFs to the PLA‐g‐GMA matrix. The elastic storage moduli, impact strength, and complex viscosity were found to be higher for the composites with higher CNF loadings, which is due to the good interfacial adhesion between the PLA‐g‐GMA matrix and the CNF filler in the composites at glassy, rubbery, and melt states.

Crystallinity-Independent Toughness in Renewable Poly(l-lactide) Triblock Plastics

“…Efforts to simultaneously upgrade PLLA’s thermal and mechanical properties have spawned a rich subfield. Melt-blending with rubbery polymers is the most well-explored approach, owing to the low cost of bulk rubber, translatability to existing melt-processing capabilities, and property tunability under a wide parameter space. , In blends, the most significant mechanical property enhancements most often require reactive − or nonreactive compatibilization. − In other approaches without adding rubber, polymer-grafted cellulose nanocrystals have garnered attention as crystal nucleators , and tougheners. − Amphiphilic non-PLA diblock polymers have also conferred toughness and aging resistance to atactic PLA, − as well as toughness and accelerated crystallization to semicrystalline PLLA. , Finally, thermomechanical preconditioning of PLLA − and its composites can produce highly oriented matrices with improved strength, ductility, and thermal resistance.…”