STRENGTH IMPROVEMENT OF HYDROXYPROPYL METHYLCELLULOSE/ STARCH FILMS USING CELLULOSE NANOCRYSTALS

Abstract

Interest in cellulose nanocrystals obtained from natural resources has grown mainly because of features that such materials provide when inserted into polymeric matrices. The present study aimed to evaluate the effect of cellulose nanocrystals addition on the mechanical and barrier properties of biofilms made from hypromellose (or hydroxypropyl methylcellulose - HPMC) and cassava starch blends (CS). The cellulose nanocrystals were produced by acid hydrolysis and characterized by optical microscopy (OM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Films were made with pure CS, pure hypromellose and also with blends of CS and hypromellose by casting and were mechanically tested. Then cellulose nanocrystals were added to the blends in the concentrations of 1, 3 and 10% (m/m). The films were evaluated about mechanical performance and surface of fracture by scanning electron microscopy (SEM). New tests were conducted and it was observed that the reinforcement with nanocrystals improved the mechanical properties. In the regions of fracture of the tested films, the cellulose nanocrystals also promoted an improvement in the cohesion of the hypromellose and starch molecules in the blend and created a more homogeneous surface.