Search Results (41)

Resin-based binders are one of the main materials used in foundry molding and core sands. Self-curing sand with furfuryl resin is one of the most popular technologies in the production of molds and cores for complex, critical castings made of iron and non-ferrous alloys. It has dominated small-batch production and the production of large-sized castings. This work is part of the research on new molding sands for mold additive manufacturing (3D printing). Three-dimensional printing technology in the production of sand-casting molds and cores is finding increasing industrial application in the production of castings from non-ferrous metal alloys. The aim of the research presented in this paper was to determine the influence of furfuryl resin type (classical and designed for 3D printing of sand molds) on cast iron casting properties. The pouring parameters were elaborated on the basis of the MAGMA software. Microscopic observations of castings, produced in classical and 3D-printed molds, were conducted, as well as an assessment of the roughness of the samples. The gas emissions from molding sands with both types of furfuryl resin were tested and analyzed in the context of the roughness of the castings obtained. It was proven that molding sand with furfuryl resin designed for 3D printing was characterized by lower gas emissions, which, in the case of molding sands with organic binders, is beneficial from an environmental point of view. Full article

Self-healing coatings can replace conventional coatings and are capable of self-healing and continuing to protect the substrate after coating damage. In this study, two types of self-healing resins were synthesized as coatings: Type-A via Diels–Alder crosslinking of furfuryl-modified diglycidyl ether bisphenol A with bismaleimide, and Type-B through epoxy blending/curing to form a semi-interpenetrating network. FTIR and Raman spectroscopy confirmed the formation of Diels–Alder (DA) bonds, while GPC tests indicated incomplete monomer conversion. Both resins were applied to glass and wood substrates, with performance evaluated through TGA, colorimetry (ΔE), gloss analysis, and scratch-healing tests (120 °C/30 min). The results showed that Type-A resins had a higher healing efficiency (about 80% on glass substrates and 60% on wood substrates), while Type-B resins had a lower healing rate (about 65% on glass substrates and 55% on wood substrates). However, Type-B is more heat-resistant, has a slower decomposition rate between 300 and 400 °C, higher gloss retention, and less color difference (ΔE) between wood and glass substrates. The visible light transmission of Type-B (74.14%) is also significantly higher. Full article

Improving the durability of short-rotation wood can be achieved through chemical and thermal modification. Chemical and thermal modification can have an impact on the physicochemical properties of wood, which can affect wood’s surface characteristics and its resistance to weathering. The purpose of this study was to investigate the surface characteristics and artificial weathering resistance of chemically and thermally modified short-rotation teak wood coated with linseed oil (LO)-, tung oil (TO)-, and commercial oil-based coatings consisting of a mixture of linseed oil and tung oil (LT) and commercial oil-based polyurethane resin (LB) coatings. The short-rotation teak woods were prepared in untreated and treated with furfuryl alcohol (FA), thermal treatment (HT) at 150 and 220 °C, and combination of glycerol–maleic anhydride (GMA) impregnation with thermal treatment at 150 and 220 °C. The surface characteristics measured were surface free energy, wettability, Persoz hardness, bonding quality, and color changes before and after artificial weathering exposure. The results showed that chemical and thermal modifications treatment tended to reduce total surface free energy (SFE), hardness, wettability, and bonding quality. FA and GMA at 220 °C treatments provided homogenization effect on surface characteristics, especially in total SFE and wettability. The total SFE of untreated wood ranged from 45.00 to 51.13 mN/m, and treated wood ranged from 40.58 to 50.79 mN/m. The wettability of oil-based coating according to K-value ranged from 0.20 to 0.54. TO presented better photostability than LO. Short-rotation teak wood coated with oil-based commercial coatings presented better weathering resistance compared to pure natural drying oil. Commercial oil-based coatings provided better weathering protection for the chemically and thermally modified teak wood. The application of oil-based coatings on chemically and thermally modified short-rotation teak is being considered for the development of a better wood-protection system. Full article

Following the vision of the European Commission, organisations and workers establishing Industry 5.0 approaches aspire to more future-proof, resilient, sustainable, and human-centred European industries. In this contribution, we explore how technological innovations that contribute to a “win–win” interaction with involved stakeholders may be advanced in a human-centred and transparent proceeding supported by impartial expert translators who provide information or knowledge-based guidance for decision-makers, initiators and implementers in manufacturing innovation driven by sustainability. We elaborate a stepwise procedure for agreeing on milestones and conjointly treading the path towards solving innovation challenges during a translation process. We exemplify the technological aspects of such a process using an innovation case aiming at identifying parameters for enhancements in a vacuum-bagging process applied to the manufacturing of composite parts from prepregs based on condensation-curing matrix resins made from renewable resources. In detail, we present a straightforward design of an experimental approach varying the dwelling temperature and the temperature ramps during the curing of stacked prepregs. In this way, we demonstrate that for cured composites comprising a poly(furfuryl alcohol)-based matrix, the porosity and connected mechanical properties achieved with autoclave-free curing processes sensitively depend on these process parameters. Applying the resulting data-based model is shown to support decision-making for sustainable composite manufacture. Full article

The nanocomposites with reversible cross-linking covalent bonds were prepared by reacting furfurylamine (FA)-modified diglycidyl ether of bisphenol A (DGEBA) and furfuryl-functionalized aniline trimer-modified graphene (TFAT-G) with bismaleimide (BMI) via the Diels-Alder (DA) reaction. The successful synthesis of the TFAT modifier is confirmed by nuclear magnetic resonance (NMR) hydrogen spectroscopy and IR spectroscopy tests. The structure and properties of TFAT-G epoxy nanocomposites are characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), tensile, and resistivity. The results show that TFAT-G was uniformly dispersed in the resin, and 1 wt% TFAT-G composites increased to 233% for tensile strength, 63% for elongation at break, 66% for modulus, and 7.8 °C for Tg. In addition, the addition of unmodified graphene degrades the mechanical properties of the composite. Overall, the graphene/self-healing resin nanocomposites have both good self-healing function and electrical conductivity by adding 1 wt% modified graphene; this allows for the maintenance of the original 83% strength and 89% electrical conductivity after one cycle of heating repair. Full article

The present study explores the processability and properties of poly(furfuryl alcohol) (PFA)-based composites and draws comparisons with the industry-standard epoxy resin matrices used in printed circuit board applications. A poly(furfuryl alcohol)-based fiberglass prepreg was used to manufacture composite cores laminated with copper foil, which were then integrated in situ into printed circuit board prototypes through industry-typical manufacturing and assembly processes. Both copper cores and printed boards were tested to characterize the electrical properties and overall quality of the prototypes. The fabrication of the copper cores and manufacturing methods of the printed boards are described, alongside the results from the characterization of the cores and the testing of the printed boards. The inherent advantages and disadvantages of the material are highlighted, and areas of improvement for the processability of the material and reliability of the technology are discussed. Full article

The catalytic transformation of furfural to cyclopentanone has been investigated using two different liquid phases as solvent: water and 30 wt.% tert–butanol in water. When using neat water at 160 °C, 40 bar of H₂, and after 2 h of reaction time, furfural polymerizes, and the yield of cyclopentanone is just 42% with a low carbon balance, indicating that furfural is transformed to non-detected by-products, likely heavy resins. When using 30 wt.% tert–butanol in water, the yield of cyclopentanone is ca. 20%, and the major product is furfuryl alcohol with a 47% yield. We have studied the catalytic transformation of the most relevant reaction intermediates in the overall conversion of furfural to cyclopentanone. In the presence of tert–butanol, two steps are inhibited in the overall pathway: (i) the Piancatelli rearrangement of furfuryl alcohol and (ii) the transformation of cyclopentenone. This inhibition is attributed to the neutralization of protons from water dissociation by surface sites on the catalyst, preventing their participation in the overall reaction. To counteract these inhibitions when tert–butanol is present, higher H₂ pressure (60 bar) and temperatures (200 °C) are required. We have been able to obtain productivities per gram of catalyst and mols of Cu basis of 411 g_prod·h⁻¹·g_cat⁻¹ and 14 g_prod·s⁻¹·mol_Cu⁻¹, respectively, which is substantially above that found for other copper-based catalysts. Full article

Furfurylation can effectively improve the quality of fast-growing wood, but its leachability is unclear. In this study, fast-growing poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were impregnated with low concentrations of 5%–20% furfuryl alcohol (FA), and the chemical and microscopic changes during leaching tests were analyzed by UV spectra and confocal laser scanning microscopy (CLSM). The results show that FA impregnation can regulate the weight percentage gain, but its effectiveness in regulating the cell wall bulking coefficient decreased as the impregnation concentration was increased. Impregnation with 15% and 20% FA showed no significant difference in the effect on volume swelling efficiency. The inverse relationship between the concentration of FA and the leaching rate was demonstrated by leaching tests, UV spectra, and CLSM. Notably, the leaching rate of poplar and Chinese fir wood was more than 30% when impregnated with 5% FA. Although the entirety of the furfuryl alcohol was deposited in the cell wall when impregnated with low concentrations of FA, the binding was not stable. The weight percentage gain of furfurylated Chinese fir was greater than that of poplar, but its leaching rate was lower, indicating that the cured furfuryl alcohol resin in poplar was not as stable as that in Chinese fir. Therefore, differences in tree species should be considered in low-concentration FA impregnation, as the improvement effect of concentrations below 10% on the properties of fast-growing wood is weak and the leaching rate of FA is significant. Full article

The exploitation of bio-based foams implies an increase in the use of renewable biological resources to reduce the rapid consumption of petroleum-derived resources. Both tannins and furfuryl alcohol are derived from forestry resources and are, therefore, considered attractive precursors for the preparation of tannin–furanic foams. In addition, toughening modification of tannin–furanic foams using polyvinyl alcohol (PVOH) results in a more flexible network-like structure, which imparts excellent flexibility to the foams, whose relative properties are even close to those of polyurethane foams, which are the most used for fabrication of insoles for athletes. In addition, the addition of PVOH does not affect the thermal insulation properties of the foams by testing the thermal conductivity, resilience, and elongation at break, while reducing the brittleness of the samples and improving the mechanical properties. Also, the observation of the morphology of the foam shows that the compatibility between PVOH and tannin–furanic resin is good, and the cured foam does not show fragmentation and collapse, while the bubble pore structure is uniform. The developed flexible foam derived from biomass resources endows the foam with good thermal insulation properties and high mechanical properties, and the samples exhibit suitable physical parameters to be used as flexible insoles for athletes. Full article

Two reversible furan–maleimide resins, in which there are rigid -Ph-CH₂-Ph- structures and flexible -(CH₂)₆- structures in bismaleimides, were synthesized from furfuryl glycidyl ethers (FGE), 4,4′-diaminodiphenyl ether (ODA), N,N’-4,4′-diphenylmethane-bismaleimide (DBMI), and N,N′-hexamethylene-bismaleimide (HBMI). The structures of the resins were confirmed using Fourier transform infrared analysis, and the thermoreversibility was evidenced using differential scanning calorimetry (DSC) analysis, as well as the sol-gel transformation process. Mechanical properties and recyclability of the resins were preliminarily evaluated using the flexural test. The results show the Diels–Alder (DA) reaction occurs at about 90 °C and the reversible DA reaction occurs at 130–140 °C for the furan–maleimide resin. Thermally reversible furan–maleimide resins have high mechanical properties. The flexural strength of cured FGE-ODA-HBMI resin arrives at 141 MPa. The resins have a repair efficiency of over 75%. After being hot-pressed three times, two resins display flexural strength higher than 80 MPa. Full article

This article presents the findings of a study focusing on the gas generation of 3D-printed cores fabricated using binder-jetting technology with furfuryl resin. The research aimed to compare gas emission levels, where the volume generated during the thermal degradation of the binder significantly impacts the propensity for gaseous defects in foundries. The study also investigated the influence of the binder type (conventional vs. 3D-printed dedicated binder) and core construction (shell core) on the quantity of gaseous products from the BTEX group formed during the pouring of liquid foundry metal into the cores. The results revealed that the emitted gas volume during the thermal decomposition of the organic binder depended on the core sand components and binder type. Cores produced using conventional methods emitted the least gases due to lower binder content. Increasing Kaltharz U404 resin to 1.5 parts by weight resulted in a 37% rise in gas volume and 27% higher benzene emission. Adopting shell cores reduced gas volume by over 20% (retaining sand with hardener) and 30% (removing sand with hardener), presenting an eco-friendly solution with reduced benzene emissions and core production costs. Shell cores facilitated the quicker removal of gaseous binder decomposition products, reducing the likelihood of casting defects. The disparity in benzene emissions between 3D-printed and vibratory-mixed solid cores is attributed to the sample preparation process, wherein 3D printing ensured greater uniformity. Full article

Furfurylation is an effective and green method for wood or bamboo modification that can significantly improve its physical and mechanical properties and the resistance against biological deterioration and the attack of subterranean termites. To elucidate the effect of furfurylation on the physical and multiscale mechanical properties of bamboo, the conditions of the furfurylation process were modified to cause an independent variation of the physical and multiscale mechanical properties in differently-treated bamboo samples. This was achieved by impregnating bamboo samples with solutions containing 15%, 30%, 50%, or 70% furfuryl alcohol (FA) by either of the two impregnation processes, vacuum pressure (V-P) and soaking (S) impregnation, while applying different curing conditions (wet- or dry-curing). The physical properties we measured included the absorption rate, weight percent gain (WPG), swelling efficiency (SE), and anti-swelling efficiency (ASE); the macro-mechanical properties involved the modulus of rupture (MOR), the modulus of elasticity (MOE), parallel-to-grain compressive strength (CS), and tensile strength (TS); the micro-mechanical properties included the tensile strength of bamboo’s vascular bundle and hardness and the indentation modulus of bamboo’s fiber cell walls. Finally, the correlation between the different physical and mechanical properties of the modified bamboo samples was analyzed. The results indicate that V-P impregnation made bamboo more permissible for the penetration of FA, while wet-curing was more conducive to ensuring a high curing rate. The dimensional stability of the bamboo samples treated with a high FA concentration through V-P impregnation and of those furfurylated by the S-Wet process using either medium or high FA concentrations was significantly increased. However, the dimensional stability of the bamboo samples modified with either low or medium FA concentrations decreased in both dry and wet curing. In terms of mechanical strength, furfurylation had little effect on the macro- and micro-mechanical properties of bamboo and was slightly improved in comparison to untreated samples. The results also showed a positive correlation between the macro- and micro-mechanical strength of the modified bamboo samples and a significant negative correlation between the mechanical strength and ASE. In soaking impregnation, the WPG and ASE were positively correlated, while the WPG and CS were negatively correlated. Interestingly, the correlation between the mechanical properties and ASE was not significant. Finally, both V-P-Wet and S-Wet approaches can be recommended for bamboo furfurylation, the former being time-saving and having a high curing rate in FA resin while significantly improving the moisture absorption and mechanical strength of bamboo. The advantage of the latter process is simplicity, a high utilization rate of FA, and a significant improvement in the dimensional stability of bamboo. Full article

Casting cores produced in additive manufacturing are more often used in industrial practice, in particular in the case of the production of unit castings and castings with very complex geometry. The growing interest in the technology of 3D printing of cores and molds also brings emerging doubts related to their mechanical and technological properties. This article presents a comparison of the properties of cores made of sand with acid-curing furfuryl resin, made with 3D printing technology; the cores were prepared in a conventional way (mixing and compaction). The main purpose of this research was to determine the possibility of using shell cores as a substitute for solid cores, aimed at reducing the amount of binder in the core. The influence of the type of the binder and the size of the grain matrix fraction on the obtained mechanical and technological properties of the cores, with particular emphasis on abrasion and thermal deformation, as well as on the kinetics of their hardening, was demonstrated. Full article

The use of isosorbide-derived polymers has garnered significant attention in recent decades as a high-performance, renewable material sourced from biomass. Of particular interest is isosorbide methacrylate, which possesses low viscosity (<500 cps), high thermal properties (T_g ≈ 220 °C), and high modulus (>4 GPa). These characteristics present a promising opportunity to replace BPA-derived methacrylate compounds in various applications. This investigation aims to synthesize and characterize isosorbide-based low-viscosity resin systems for 3D printing. The resin blends are composed of isosorbide methacrylate and two bio-renewable methacrylates, furfuryl methacrylate (FM) and bis-hydroxymethyl-furan methacrylate (BHMF-M), polymerized through a digital light processing (DLP) technique. The addition of the bio-based co-monomers serves to enhance the fracture toughness of the brittle isosorbide methacrylate crosslinked homopolymer (G_Ic = 37 J/m²). The resulting polymers exhibit T_g values greater than 200 °C and G_Ic around 100 J/m². These resin systems hold potential for imparting high bio-based content to polymers used in additive manufacturing for high-performance applications. Full article

Bamboo is a material with excellent development prospects. It is increasingly used in furniture, decoration, building, and bridge construction. In this study, Furfurylated bamboo bundles and phenol-formaldehyde resin were used to make bamboo-scrimber composites (BSCs) via molding-recombination and hot-pressing processes. The effects of the impregnation mode, furfuryl-alcohol concentration, and curing temperature on the various physical–mechanical properties and durability of the composites were evaluated. Scanning-electron microscopy (SEM) was used to observe the microstructural differences. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to investigate changes in the chemical constituents. The heat resistance was also investigated using thermogravimetric analysis. The results showed that the density of the furfurylated BSC increased by up to 22% compared with that of the BSC-C with the same paving mode. The furfurylated BSCs had lower moisture contents: the average moisture content of the furfurylated BSCs was 25~50% lower than that of the BSC-C. In addition, the furfurylated BSCs showed better dimensional stability and durability, since the decay-resistance grade of the BSCs was raised from decay resistance (class II) to strong decay resistance (class I). In terms of the mechanical properties, the furfurylation had a slight negative effect on the mechanical strength of the BSCs, and the modulus of rupture (MOR) and horizontal shear strength (HSS) of the BSCs were increased to a certain extent under most of the treatment conditions. In particular, the highest HSS for indoor use and MOR of the furfurylated BSCs increased by 21% and 9% compared with those of the untreated BSCs, respectively. The SEM results indicated that the FA resin effectively filled in the bamboo-cell cavities and vessels, and the modified bamboo-parenchyma cells were compressed more tightly and evenly. The FTIR and XPS spectroscopy showed that the hydroxyl group of carboxylic acid of the bamboo-cell-wall component reacted with that of the furan ring, and the cellulose and hemicellulose underwent acid hydrolysis to a certain extent after the furfurylation. Overall, the present study highlights the potential of furfurylation as a modification method to enhance BSC products. Further research should focus on improving the ability of furfurylated BSCs to prevent the growth of Botryodiplodia theobromae. Additionally, the influence of furfuryl-alcohol resin on the bonding strengths of PF adhesives should be further clarified. Full article