Nowadays the use of natural fiber composites has gained significant interest due to their low density, high availability, and low cost. The present study explores the development of sustainable 3D printing filaments based on rice husk (RH), an agricultural residue, and recycled polypropylene (rPP) and the influence of fiber weight ratio on physical, thermal, mechanical, and morphological properties of 3D printing parts. Thermogravimetric analysis revealed that the composite’s degradation process started earlier than for the neat rPP due to the lignocellulosic fiber components. Mechanical tests showed that tensile strength increased when using a raster angle of 0° than specimens printed at 90°, due to the weaker inter-layer bonding compared to in-layer. Furthermore, inter layer bonding tensile strength was similar for all tested materials. Scanning electron microscope (SEM) images revealed the limited interaction between the untreated fiber and matrix, which led to reduced tensile properties. However, during the printing process, composites presented lower warping than printed neat rPP. Thus, 3D printable ecofriendly natural fiber composite filaments with low density and low cost can be developed and used for 3D printing applications, contributing to reduce the impact of plastic and agricultural waste.

Catechol-containing polymers inspired by marine mussels have gained significant interest in recent years, leading to applications in several fields. Among these polymer systems, poly(vinylcatechol-styrene) (PVCS) has become a popular option due to its exceptional underwater adhesion strength, with readily available monomers and diverse synthetic routes being available. However, the translation of any novel adhesive chemistry from academic research to real-world applications can be challenging. Acrylates, epoxies, and urethanes were introduced to markets over half a century ago and remain dominant. However, bonding in wet environments remains lacking. The work presented here addresses this gap by focusing on the formulation of PVCS-based adhesives for conditions outside of the research lab. An emphasis was placed on handling properties when working underwater. A collection of different substrates were bonded together and several commercial glues provided benchmarks. Environmental conditions were studied to broaden the potential applications of PVCS adhesives in underwater settings. By optimizing formulations, we present an adhesive system that retains the superior underwater bonding of PVCS while also offering enhanced workability. This approach may help open the door to utilization of a new adhesive chemistry for underwater applications.