Polyhydroxy-3-Butyrate (PHB)-Based Composite Materials Reinforced with Cellulosic Fibers, Obtained from Barley Waste Straw, to Produce Pieces for Agriculture Applications: Production, Characterization and Scale-Up Analysis

Abstract

Cellulosic fibers obtained from Barley straw were utilized to reinforce PHB. Four different processed fibers were employed as reinforcing material: sawdust (SW), defibered (DFBF), delignified (DBF), and bleached (BBF) fibers. The composite was processed from two different perspectives: a discontinuous (bach) and an intensification process (extrusion). Once processed and transformed into final shape specimens, the materials were characterized by mechanical testing (tensile mode), scanning electron microscopy, and theoretical simulations by finite elements analysis (FEA). In terms of mechanical properties, only the elastic moduli (Et) exhibited results ranging from 37% to 170%, depending on the reinforcement composition. Conversely, strengths at break, under both tensile and bending tests, tended to decrease, indicating poor affinity between the components. Due to the mechanical treatment applied on the fiber, DFBF emerged as the most promising filler, with mechanical properties closest to those of neat PHB. DFBF-based composites were subsequently produced through process intensification using a twin-screw extruder, and molded into flowerpots. Mechanical results showed almost identical properties between the discontinuous and intensification processes. The suitability of the material for agriculture flowerpots was demonstrated through finite analysis simulation (FEA), which revealed that the maximum von Mises stresses (5.38 × 105 N/m2) and deformations (0.048 mm) were well below the limits of the composite materials.