Volume 20 Issue 2

The thermal properties of starch/PVOH formulations gelatinized with glycerol, cross-linked with boric acid, incorporated with clay and loaded with 2 wt%, 4 wt%, and 7 wt% sayote fibers were investigated. The FTIR spectra, SEM micrographs, DSC, and TGA results revealed a successful blending in starch/PVOH (50/50) and starch/PVOH (65/35) fomulations with glycerol as plasticizer and boric acid as cross-linking agent. Plasticized and cross-linked starch/PVOH reinforced with clay and varying amounts of sayote fiber suggest more inter- and intra- molecular hydrogen bonding interactions, making the composite more crystalline and thermally stable. The SEM micrographs showed a smoother surface with the addition of boric acid and a more orderly woven surface with 2 wt% sayote fiber loading. DSC thermograms reveal that the formulations were compatible and had good blending interactions, since the experimental enthalpies of melting were higher than their theoretical values. The addition of sayote fiber increased the thermal stability of starch/PVOH composite blends and prevented the re-crystallization of starch. TGA curves showed that the addition of sayote fibers formed stronger blends that delayed the degradation of the composite. The starch/PVOH (50/50) and starch/PVOH (65/35) composite blends were more crystalline and thermally stable at 2 wt% to 4 wt% sayote fiber loading.

The objective of this study was to determine both the physical and mechanical properties of experimental panels made from recycled corrugated cardboard. Two types of composite samples, derived from two different raw materials — namely, unprinted and printed cardboard — were manufactured. The physical characteristics of the specimens, including density, water absorption, dimensional stability, thermal conductivity, and sound absorption, were tested. Additionally, the mechanical properties, such as the modulus of elasticity, modulus of rupture, and internal bond strength, were evaluated. Based on the findings of this research, the samples made from unprinted cardboard exhibited higher density, lower thickness swelling, and slightly better thermal insulation properties than those made from printed raw material. In contrast, the samples containing printed material demonstrated superior mechanical properties, suggesting they may be more suitable to be used where structural properties are desired. Overall, the properties of both types of samples indicate that such panels have an important potential to be used as sustainable products, serving as a green alternative material for indoor applications.

Impact-resistant automotive components were studied by evaluating the effects of single-screw and twin-screw extrusion on the mechanical properties of composites made from fluorene-modified nanocellulose (FCF) or bamboo fibers (30 wt%) combined with various polymers. Natural fiber composites were injection molded, and their mechanical properties were evaluated. Results showed that fluorene-modified nanocellulose exhibited improved dispersion when kneaded with polycarbonate and polyamide 6 using twin-screw extrusion, resulting in increases of over 5000 MPa in flexural modulus and over 40 MPa in maximum flexural stress compared to the base polymer. However, composites made with polyamide 66 and bamboo fibers required high injection molding temperatures exceeding 260 °C, which led to thermal degradation and reduced the fiber reinforcement effect on mechanical properties. The polypropylene showed weak interfacial compatibility with bamboo fibers, resulting in limited reinforcement effects in both single and twin-screw extrusion. The brittleness of the fibers did not significantly influence the elongation of the PP composite. Nonetheless, it exhibited less reduction in elongation compared to composites where bamboo or FCF was added to other polymers. Building on these results, flexural tests were conducted on composites combining high-impact polypropylene with natural fibers, demonstrating the potential for high-impact-resistant composite materials suitable for automotive applications.

Biochars, produced via pyrolysis, are gaining attention in applications ranging from soil amendments to energy storage and environmental remediation. While lignocellulosic biochars from woody biomass are well studied, algal biochars remain comparatively overlooked despite offering diverse organic and inorganic content that may broaden their applications. This study investigates how pyrolysis temperature and oxidative pretreatment affect the structure and properties of biochars derived from two macroalgae, Ulva expansa and Sargassum sp., under various pyrolysis conditions (500 to 900 °C). Using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and nanoindentation, it was found that the C-O and C-N surface functional groups decreased in Ulva but the C=O and C-O-C groups increased in Sargassum upon pyrolysis. The reduced modulus ranged between 2.6 to 7.9 GPa and was governed by pyrolytic carbon content and inorganic composition. Of these two factors, the amount and type of pyrolytic carbon were determined by the heating conditions, with oxidation at 200 °C generally preserving more carbon than oxidation at 300 °C. Meanwhile, the final pyrolysis temperature dictated residual carbon content, salt formation, and carbonation. These findings highlight the potential for tailored pyrolysis to produce algal biochars with customizable structures and properties, enabling environmental and industrial applications such as carbon sequestration, filtration, and energy storage.