Formulation and Characterization of Bio-Enhanced Thermoset Resin Composites for Additive Manufacturing
Abstract
The transition to sustainable construction materials is essential to reducing the environmental footprint of the building industry. This research project aims to develop, characterize, and optimize thermoset bio composite materials for use in additive manufacturing—specifically, 3D printing of structural housing components. By integrating renewable fillers and partially bio-based resin matrices, the project proposes novel composite formulations that meet the dual demand for high performance and environmental responsibility. The research was structured in three complementary studies. The first focused on enhancing epoxy resin with cellulose nanofibers (CNFs) derived from both bleached and lignin-containing pulp, to assess how residual lignin influences reinforcement efficiency. It was found that 0.75 wt% bleached CNF significantly improved composite toughness (41%) and stiffness (79%), while lignin-containing CNFs, although mechanically less effective, contributed to thermal stability through their antioxidant nature. The second study addressed the processability of bio-filled epoxy composites by optimizing extrusion parameters for wood flour–epoxy systems. Using a factorial design, the effects of particle size, wood content, and extrusion rate were evaluated. A 55:45 epoxy-to-wood ratio was identified as optimal, yielding composites with superior mechanical performance, dimensional stability, and fire resistance—confirming their suitability for extrusion-based 3D printing applications. To further enhance the sustainability of the matrix itself, the third study investigated the partial replacement of petroleum-derived phenol in phenol-resorcinol-formaldehyde (PRF) resins with bio-oil obtained from the pyrolysis of waste wood. Substitution levels of up to 50% were tested, with 30% bio-oil replacement maintaining satisfactory flexural properties and curing behavior. Although 50% substitution led to a decrease in strength and stiffness, it introduced ductility and flexibility into the material. Thermal and curing behavior were shown to be tunable by adjusting the formulation and curing temperature. Together, these studies provide a holistic approach to the design of bio-based thermoset composites—from reinforcement and process optimization to resin sustainability. The findings demonstrate the feasibility of creating high-performance, 3D-printable construction materials that align with the goals of carbon reduction, circular resource use, and sustainable development in the construction sector.