Assessment of physical properties of self-bonded composites made of cellulose nanofibrils and poly(lactic acid) microfibrils

Cellulose nanofibrils and poly(lactic acid) microfibrils, two bio-based polymers were used to elaborate composite films, and their properties were evaluated. Cellulose nanofibrils were obtained from organic pulping with total chlorine-free bleaching and were manufactured using high-pressure homogenization; while poly(lactic acid) microfibrils were obtained from a commercial partner. Morphological aspects of cellulose nanofibrils were assessed by atomic force microscopy showing traditional morphology for the elaborated nanofibrils, as well as the effects of sonication on the poly(lactic acid) microfibrils. Self-bonded composite films with different compositions were fabricated by hot pressing following methodologies previously reported. Uniaxial tensile stress was measured with a universal testing machine showing a decrease in most mechanical properties because of the low interactions between cellulose nanofibrils and polylactide microfibrils. Water vapor permeability was evaluated with a thermohygrometer and surface energy with the sessile-drop contact angle method these results showed good values for printing and gluing, with surface free energies ranging between 27 and 60 m Nm⁻¹. Furthermore, industrial standards for paper-like materials and thermal properties of the composites were also analyzed of which it is to highlight the good bending strength as well as the concurrence of the results of Parker Print Surface tests with those of water contact angle.