Search

This study focuses on treating Guadua angustifolia bamboo fibers to enhance their properties for reinforcement applications in composite materials. Chemical (alkali) and physical (dry etching plasma) treatments were used separately to augment compatibility of Guadua angustifolia fibers with various composite matrices. The influence of these treatments on the fibers' performance, chemical composition, and surface morphology were analyzed. Statistical analysis indicated that alkali treatments reduced the tensile modulus of elasticity and strength of fibers by up to 40% and 20%, respectively, whereas plasma treatments maintain the fibers' mechanical performance. FTIR spectroscopy revealed significant alterations in chemical composition due to alkali treatments, while plasma-treated fibers showed minimal changes. Surface examination through Scanning Electron Microscopy (SEM) revealed post-treatment modifications in both cases; alkali treatments served as a cleanser, eliminating lignin and hemicellulose from the fiber surface, whereas plasma treatments also produce rough surfaces. These results validate the impact of the treatments on the fiber mechanical performance, which opens up possibilities for using Guadua angustifolia fibers as an alternative reinforcement in composite manufacturing. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the effect of propylamine addition to urea-formaldehyde resin on the properties of resultant plywood. The research consisted in investigating the properties of both liquid and cured resins, as well as the produced plywood. Studies have shown that the incorporation of propylamine adversely affected reactivity of the adhesive mixtures by increasing their pH. The evaluation of adhesive chemical structure with FTIR spectroscopy showed some slight changes indicating the reaction of formaldehyde with introduced modifier. The addition of propylamine contributed to the considerable reduction of free formaldehyde contained in the cured adhesive. Furthermore, the propylamine was also found to work effectively as a formaldehyde scavenger by significantly reducing the hazardous emission from plywood. However, based on the results of bonding quality, delamination, bending strength and modulus of elasticity it was found that application of propylamine resulted in a noticeable deterioration of plywood properties. Therefore, the amount of introduced modifier should not exceed 1% of solid UF resin. [ABSTRACT FROM AUTHOR]

Partial liquefaction of residual biomass shows good potential for developing new materials suitable for making bio-based composites. Three-layer particleboards were produced by replacing virgin wood particles with partially liquefied bark (PLB) in the core or surface layers. PLB was prepared by the acid-catalyzed liquefaction of industrial bark residues in polyhydric alcohol. The chemical and microscopic structure of bark and residues after liquefaction were evaluated by means of Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), while the particleboards were tested for their mechanical and water-related properties, as well as their emission profiles. Through a partial liquefaction process, some FTIR absorption peaks of the bark residues were lower than those of raw bark, indicating hydrolysis of chemical compounds. The surface morphology of bark did not change considerably after partial liquefaction. Particleboards with PLB in the core layers showed overall lower densities and mechanical properties (modulus of elasticity, modulus of rupture, and internal bond strength), and were less water-resistant as compared to the ones with PLB used in the surface layers. Formaldehyde emissions from the particleboards were 0.284–0.382 mg/m2·h, and thus, below the E1 class limit required by European Standard EN 13986:2004. The major emissions of volatile organic compounds (VOCs) were carboxylic acids as oxidization and degradation products from hemicelluloses and lignin. The application of PLB in three-layer particleboards is more challenging than in single-layer boards as PLB has different effects on the core and surface layers. [ABSTRACT FROM AUTHOR]

Most composites produced come from fossil fuel sources. Renewable strategies are needed for the production of composites. Charcoal fines are considered waste and an alternative for the production of biocomposites. The charcoal fines resulting from the pyrolysis of any biomass are an efficient alternative for the production of green composites. Studies to understand how the pyrolysis parameters influence the properties of this material for the production of biocomposites are necessary. Charcoal has a high carbon content and surface area, depending on final production temperatures. This study aims to evaluate charcoal fines as potential reinforcing agents in biocomposites. This study investigated for the first time charcoal fines from three pyrolysis temperatures (400, 600, and 800 °C) to identify the most suitable charcoal for use as a raw material in the production of carbon biocomposites with 30% by weight incorporated into a polyester matrix composite. Apparent density, porosity, morphology, and immediate chemical composition and Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) of charcoal fines were evaluated. The charcoal fines produced at 800 °C showed interesting potential as polymeric matrix fillers due to their higher porosity (81.08%), fixed carbon content (96.77%), and hydrophobicity. The biocomposites were analyzed for flexural and tensile strength and scanning electron microscopy. The results revealed an improvement in resistance at elevated temperatures, especially at 800 °C, with higher breaking strength (84.11 MPa), modulus of elasticity (4064.70 MPa), and traction (23.53 MPa). Scanning electron microscopy revealed an improvement in morphology, with a decrease in roughness at 800 °C, which caused greater adhesion to the polyester matrix. These results revealed a promising new biocomposite compared to other natural lignocellulosic polymeric composites (NLFs) in engineering applications. [ABSTRACT FROM AUTHOR]

The new segmented poly(thiourethane-urethane)s (PTURs) based on 1,1′-methanediylbis(4-isocyanatocyclohexane) (HMDI, Desmodur W®), polycarbonate diol (PCD, Desmophen C2200) and (methanediyldibenzene-4,1-diyl)dimethanethiol were synthesized by one-step melt polyaddition method. The obtained PTURs, with a content of 30–60 wt% of the hard segments (HS), were tested in which the influence of changes in the HS content on their properties was determined. The polymers were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), thermal analysis (DSC, TGA) and thermomechanical analysis (DMTA). Additionally, tensile strength, optical (refractive index, UV-VIS and color) and surface properties of the obtained polymers (contact angle and surface free energy) and adhesion to copper were examined. FTIR analysis verified the supposed structure of the polymers obtained and showed a complete conversion of the isocyanate groups. TGA analysis confirmed the relatively good thermal stability of the polymers. On the other hand, after performing the DSC analysis, it was possible to state that the obtained materials were partially or completely amorphous, and the microphase separation decreased with increasing HS content in the polymer. Similar observations were made from the DMTA data. In addition, the hardness, tensile strength, modulus of elasticity, storage modulus, adhesion to copper, refractive index and total free surface energy increased with increasing HS content in the polymer. [ABSTRACT FROM AUTHOR]