Search Results (2)

Lignin-based polyurethanes represent a promising strategy for developing more sustainable wood coatings by partially replacing fossil-derived polyols with renewable aromatic biopolymers. In this study, a polyurethane formulated with organosolv lignin (LPU) was synthesized and applied on two non-durable European wood species, Fagus sylvatica L. and Picea abies L., and compared with a commercial fossil-based polyurethane (CPU). Coated samples were evaluated for color stability, gloss evolution, wettability, adhesion, impact and scratch resistance, and biological durability. Accelerated ageing was performed under xenon-light irradiation, while decay resistance was assessed against Gloeophyllum trabeum and Trametes versicolor. Additional tests examined susceptibility to blue-stain fungi and surface morphology via SEM. LPU produced a matte film with intrinsically darker coloration but excellent chromatic stability and minimal gloss variation during ageing. Its initial hydrophobicity was higher on beech and comparable to CPU on spruce. Although CPU exhibited superior adhesion and slightly better mechanical resistance, LPU provided enhanced protection against blue-stain fungi—particularly on spruce—and a more uniform response to decay fungi across wood species. Overall, despite its darker appearance, the lignin-based formulation offered functional protection comparable to the commercial coating, confirming its potential as a viable bio-based alternative for above-ground wood applications. Full article

Wood plastic composite (WPC) usage and demand have increased because of its interesting chemical and mechanical properties compared to other plastic materials. However, there is a possibility of structural and mechanical changes to the material when exposed to the external environment; most research on wood plastic is performed on the material with elevated fiber content (40–70%). Therefore, more research needs to be performed regarding these issues, especially when the fiber content of the WPC is low. In this study, composite materials composed of high-density polyethylene (HDPE) reinforced with yellow birch fibers (20 and 30%) were made by injection molding. The fibers were treated with dissolved zinc oxide (ZnO) powder in sodium oxide (NaOH) solution, and the fabricated material was exposed to fungal rot. ZnO treatment in this case is different from most studies because ZnO nanoparticles are usually employed. The main reason was to obtain better fixation of ZnO on the fibers. The mechanical properties of the composites were assessed by the tensile and Izod impact tests. The impact energies of the samples fabricated with ZnO-treated fibers and exposed to Gloephyllum trabeum and Trametes versicolor decreased, when compared to samples fabricated with ZnO-nontreated fibers. The mechanical properties of the samples composed of ZnO-treated fibers and exposed to rot decreased, which were reported by a decreased Young’s modulus and impact energies. The usage of ZnO treatment prevented mycelium proliferation, which was nonexistent on the samples. It has been noted that the decrease in mechanical properties of the treated samples was because of the action of NaOH used to dissolve the ZnO powder. Full article