Evaluation of the Mechanical, Thermal and Rheological Properties of Hop, Hemp and Wood Fiber Plastic Composites

Abstract

The aim of this study was to evaluate the use of waste natural fibers from milled hop bines and hemp stalks, without chemical treatment, and compare them to a commercial wood fiber for use in wood–plastic composite (WPC) materials. The fibers were characterized (density, fiber size and chemical composition). WPCs were produced by the extrusion of a blend of fibers (50%), high-density polyethylene (HDPE) and coupling agent (2%). The WPCs were characterized for their mechanical, rheological, thermal, viscoelastic and water resistance properties. Pine fiber was about half the size of hemp and hop fibers and thus had a higher surface area. The pine WPC melts had a higher viscosity than the other two WPCs. Additionally, the tensile and flexural strengths of the pine WPC were higher than those of hop and hemp WPCs. The pine WPC was also shown to have the least water absorption followed by hop and hemp WPCs. This study highlights that different lignocellulosic fibers influence their WPC properties. The properties of the hop- and hemp-based WPCs were comparable to commercial WPCs and can be improved by further milling/screening the fibers to a smaller particle size (volumetric mean of ~88 μm) to increase their surface area, fiber–matrix interactions and improve stress-transfer.

Characterization of Thermo-Mechanical and Chemical Properties of Polypropylene/Hemp Fiber Biocomposites: Impact of Maleic Anhydride Compatibilizer and Fiber Content

“…After homogenization and heating inside the extruder, the composites emerged in the form of filaments, which were cooled in a water tank at room temperature and then cut into pellets using a knife mill. Such a procedure for producing thermoplastic composites using natural fibers is reported in the literature, where polypropylene is processed with various fibers, such as hemp [ 51 ], kenaf [ 52 ], jute and short pine needles [ 53 ], and catole coconut [ 54 ].…”

Effective Lignin-Based Binders for Particle Boards

“…The shorter fibers of pine led to composites of better tensile and flexural strengths and lower water absorption. 22 Other promising candidates for the preparation of bio-based materials are vegetable oils. The high abundance and low cost of these raw materials enable the production of different kinds of polymers, which can be used as coatings, adhesives, insulators, binders, medicinal structures, and matrices for the synthesis of composites.…”

“…Additionally, natural fibers have lower production cost and energy consumption compared to traditional reinforcements, such as glass and carbon fibers. , Recently, high-density polyethylene was reinforced with different fibers, such as hop, hemp, and pine wood. The shorter fibers of pine led to composites of better tensile and flexural strengths and lower water absorption …”

The effect of vermiculite on flame retardancy, physical and mechanical properties of wood plastic composites

“…Polypropylene, polyethylene, and polyvinyl chloride are generally employed as thermoplastic polymers for producing WPCs. At the same time, wood flour is the favored lignocellulosic material (Rowell 2007), while other natural fibers are also being evaluated (Talcott et al 2023). Meanwhile, thermoplastic polymers are considered harmful to the environment, whereas wood rises as one of the world's most sustainable, abundant, and green raw materials.…”