PVA Based Composite Films with Cellulose Fibers Prepared by Acid Hydrolysis

Two types of cellulose fibers were obtained from microcrystalline cellulose (MCC) by acid hydrolysis and ultrasound treatment using different concentrations of sulphuric acid. The effect of acid concentration on cellulose fibers characteristics was studied by scanning electronic microscopy (SEM), dynamic light scattering (DLS), and X-ray diffraction analysis (XRD), pointing out interesting features from the standpoint of different end-use properties. An important increase of MCC crystallinity, from 51.4% to 74.3%, was observed by XRD analysis after the treatment with 60% sulphuric acid. The cellulose fibers were used as reinforcements in a polyvinyl alcohol (PVA) matrix and the crystallinity, transparency and mechanical properties of the resulted composites being investigated. The incorporation of the two types of cellulose fibers into PVA led to transparent composites films with improved mechanical properties. A steady improvement of the tensile modulus of PVA composites was observed with the increasing amount of fibers, an increase of 83.3 % being obtained with cellulose fibers resulted from MCC treatment with higher acid concentration (60%).