Renewable lignocellulosic materials are promising green plastic alternatives to fossil fuel-based plastics. However, the hydrophilic nature and poor water resistance of lignocellulosic materials have hindered their practical applications. This study reports a facile metal-ion-modification (MIM) route, swelling with aqueous metal ion solutions, and drying to convert conventional hydrophilic paper and wood pulp into biodegradable hydrophobic paper and tableware without the addition of hydrophobic sizing chemicals/materials. Metal ions such as Fe3+ and Zr4+ can coordinate with pulp fibers’ polar groups (i.e., O.H., C=O, and COOH) that induce self-assembly of their surface fibrillated “hairy” cellulose nanofibrils to form a more compact structure with fewer available O.H. groups for water sorption. The formation of coordination bonds with polar groups (i.e., O.H., C=O, and COOH) decreases the surface energy of pulp fibers and increases their hydrophobicity and water resistance. Only ~3 mg of metal ions is needed to induce the wettability transition in 1 g of kraft pulp, resulting in hydrophobic paper and tableware with water contact angles (WCAs) of 120-140° and displayed wet tensile strengths of up to 9.5 MPa, and low water absorbency, which were comparable to synthetic polymer films. This MIM technique can be integrated into the existing paper-making process for the scalable production of hydrophobic papers and tableware, providing an alternative route for developing sustainable and biodegradable plastic counterparts. The MIM-induced lignocellulose hydrophobization mechanisms were elucidated using X-ray photoelectron spectroscopy (XPS), Fourier transforms infrared spectroscopy (FT-IR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and density functional theory (DFT). Furthermore, this MIM technique was also evaluated for its applicability in wood treatment. The treatment effectively tunes the wood surface from hydrophilic to hydrophobic, enhancing its water resistance. The MIM treatment significantly improved the dimensional stability of SYP, red oak, and poplar. For example, the Fe3+ treatment reduced the tangential swelling of SYP, poplar, and red oak by 57%, 50%, and 40%, respectively. Overall, this eco-friendly and facile MIM method holds promise for developing sustainable and biodegradable alternatives to conventional plastics, contributing to a more environmentally friendly future.

[pt] Os compósitos de matriz polimérica reforçados com fibras se destacam em diversas aplicações industriais, devido as suas características, como baixo custo, baixa densidade e boa resistência mecânica. Porém, o ambiente ao qual o compósito será exposto e a variação de temperatura a qual o compósito é submetido, irão exercer influência no comportamento do material. Estudos sobre as características microestruturais e o comportamento mecânico de compósitos poliméricos com fibras de luffa (Luffa cylindrica) e híbridos (fibra de vidro/luffa) em ambientes úmidos são recentes e, para os compósitos de luffae, principalmente, para os híbridos poucas pesquisas foram realizadas. Assim, com a finalidade de obter materiais com diferentes propriedades e comportamentos, foram fabricados e estudados compósitos com matriz epóxi reforçada com fibras de vidro, fibra de luffae híbridos vidro-luffa. O ensaio de envelhecimento foi realizado em amostras submersas em água destilada em duas temperaturas de envelhecimento (25°C e 60°C). O tempo total de envelhecimento foi de 4 meses (120 dias). Para a avaliação da degradação mecânica foram realizados ensaios não-destrutivos (termografia e ensaio sonoro) e ensaios destrutivos (impacto). O processo de absorção de água nos compósitos também foi avaliado. O presente estudo tem como relevância o preenchimento de lacunas de conhecimento do comportamento de híbridos vidro/luffa, notadamente em ambiente úmido com variação de temperatura. Como resultado, observou-se que o ensaio de envelhecimento indicou que os valores de absorção máxima dos compósitos de fibra de vidro, luffa e híbrido, assim como, seus respectivos coeficientes de difusão mostraram-se condizentes com os valores encontrados na literatura. Os compósitos de fibra de luffa foram os que apresentaram maior valor de absorção. Já os resultados do ensaio de impacto, permitiram identificar os modos de falha e avaliar o efeito entre as temperaturas de envelhecimento. Os compósitos de fibra de vidro tiveram pouca variação da resistência ao impacto antes e após o envelhecimento a 25ºC e a 60ºC. Já os compósitos de fibra de luffa e híbrido apresentaram uma variação considerável antes e após o envelhecimento a 25ºC e 60ºC. O ensaio sonoro permitiu avaliar o efeito do envelhecimento sobre o módulo de elasticidade e o fator de perda. O resultado do ensaio sonoro dos compósitos híbridos mostrou que o módulo de elasticidade e o fator de perda não tiveram diferenças significativas entre os tempos de envelhecimento indicando que a hibridização atuou de modo eficiente para proteger as fibras de luffa. O ensaio de termografia foi usado como uma nova abordagem para avaliar a condutividade térmica dos compósitos. Por fim, conclui-se que a hibridização foi eficiente, pois os compósitos híbridos apresentaram características em relação a absorção, resistência ao impacto e condutividade térmica, intermediárias aos compósitos de fibra de vidro e fibra de luffa e, principalmente a hibridização reduziu de modo significativo a degradação do compósito de luffa quando exposto a ambiente úmidos, além de proporcionar uma alternativa de projeto mais ambientalmente amigável. / [en] Polymer matrix composites reinforced with fibers stand out in various industrial applications due to their characteristics such as low cost, low density, and good mechanical strength. However, the environment to which the composite will be exposed and the temperature variation to which the composite is subjected will influence the material s behavior. Studies on the microstructural characteristics and mechanical behavior of polymer composites with Luffa cylindrica fibers and hybrid fibers (glass/luffa) in humid environments are recent, and few studies have been carried out for the Luffa and, especially, the hybrid composites. Thus, in order to obtain materials with different properties and behaviors, composites were fabricated and studied with an epoxy matrix reinforced with glass fibers, Luffa fibers, and glass-Luffa hybrids. The aging test was carried out on samples submerged in distilled water at two aging temperatures (25°C and 60°C). The total aging time was 4 months (120 days). Non-destructive tests (thermography and sound test) and destructive tests (impact) were performed to evaluate mechanical degradation. The water absorption process in the composites was also evaluated. The present study is relevant to filling knowledge gaps in the behavior of glass/luffa hybrids, especially in a humid environment with temperature variation. As a result, it was observed that the aging test indicated that the maximum absorption values of the glass, Luffa, and hybrid fiber composites, as well as their respective diffusion coefficients, were consistent with the values found in the literature. The Luffa fiber composites had the highest absorption value. The results of the impact test allowed for the identification of failure modes and the evaluation of the effect between aging temperatures. The glass fiber composites had little variation in impact strength before and after aging at 25°C and 60°C. The Luffa and hybrid fiber composites showed considerable variation before and after aging at 25°C and 60°C. The sound test allowed for the evaluation of the aging effect on the modulus of elasticity and loss factor. The sound test results for the hybrid composites showed that the modulus of elasticity and loss factor had no significant differences between aging times, indicating that hybridization efficiently protected the luffafibers. The thermography test was used as a new approach to evaluate the thermal conductivity of the composites. Finally, it is concluded that hybridization was efficient because the hybrid composites had characteristics regarding absorption, impact resistance, and thermal conductivity that were intermediate between glass and Luffa fiber composites, and mainly hybridization significantly reduced the degradation of the Luffa composite when exposed to humid environments, as well as providing a more environmentally friendly design alternative.