The effect of surface modifications with corona discharge in pinus and eucalyptus nanofibril films

Abstract

The corona treatment is promising for the improvement of the quality of fabrics and composites, but there are only a few studies on its effectiveness for surface modification of nanofibril films for printing and packaging purposes. This investigation aimed to evaluate the effect of the evolution of corona discharge exposition on the superficial, physical and mechanical properties of eucalyptus and pinus nanofibril films. Cellulose nanofibrils were produced from commercial bleached cellulose pulps after 30 passages in a SuperMasscolloider Grinder. Films were formed by a casting method. The corona discharge treatment was applied for 10, 30, 60, and 300 s at a distance of 3 cm. Furthermore, the duration of the surface modification was evaluated after 6, 24, 48, 72, and 96 h. The corona discharge promoted the formation of hydroxyl, carbonyl, and other functional groups by breaking C–C bonds and their subsequent reaction with oxygen. The best corona treatment time was 30 s, for which maximum water vapor permeability of 13.1 and 14.2 g mm/KPa day m2 was found for the eucalyptus and pinus films, respectively. In addition, maximum water absorption (of around 35%) was observed for films of both genera treated for 30 s. The tensile strength increased in response to increasing corona treatment exposition. Pinus nanofibril films showed better performance than eucalyptus nanofibril films due to their higher crystalline index and nanofibril dimensions. Through the analysis of contact angle and surface energy, it was verified that printing of corona treated nanofibril films should be carried out for up to 24 h when the films still exhibit the treatment effect.