Morphology and mechanical properties of poly(ethylene brassylate)/cellulose nanocrystal composites

Poly(ethylene brassylate), a novel inexpensive biodegradable polyester, has been reinforced with cellulose nanocrystals (CNCs) with the aim of improving its thermal stability and mechanical properties. The composites have been characterized through calorimetry, tensile tests, thermogravimetry and electron microscopy. The addition of small amounts of CNCs improves both the stiffness and the ductility of the composites, suggesting the existence of some compatibilizing effect. Adding large CNC amounts increases the Young modulus (e.g., 150% for 50 wt% CNCs), but now the material shows brittle behavior. Degradation of the CNCs starts at lower temperature suggesting mutual reactivity. The SEM analysis of the composites with ductile behavior reveals the formation of a percolating network crossing through the interconnected domains that conform a PEB-rich continuous phase. Processing consisting on reinforcement dispersion by sonication followed by melt processing results in composites in which the improvement of mechanical properties does not involve any trade-off.