The effects of cellulosic fillers on the mechanical, morphological, thermal, viscoelastic, and rheological properties of polyhydroxybutyrate biopolymers

The aim of this study was to determine the effects of cellulosic fillers on the conventional and dynamic mechanical, thermal, morphological, and rheological properties of polyhydroxybutyrate (PHB) biopolymers. Polyhydroxybutyrate as a biopolymer matrix and cellulosic fillers including wood flour, microcrystalline cellulose, and cellulose nanofibrils (0.5 and 5 wt%) as reinforcing agents were used to produce the composite. According to the results obtained, the addition of 0.5 wt% cellulose nanofibrils improved both the flexural and tensile moduli of elasticity but other fillers and filler loading levels generally decreased the mechanical properties attributable to aggregations of fillers in the matrix. Thermal analysis results showed that the addition of cellulosic fillers did not influence the glass transition and crystallization temperature of the PHB whereas the crystallinity and melting temperature generally increased with the addition of the cellulosic fillers. Thermal stability of the composites generally improved with addition of the cellulosic fillers. The dynamic mechanical analysis results showed that both storage and loss moduli of all the samples generally decreased with increasing temperature. Elastic and viscous moduli of all the samples initially decreased with frequency but then generally increased according to the rheological analysis.