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•A short-time impregnation process (70 min) achieves high weight percentage gain and uniform impregnation effect.•The modification can simultaneously enhance and toughen wood with ...improved effects of more than 100%.•The modified wood exhibited recyclability and retained satisfactory strength after reprocessing.
It is indeed challenging to simultaneously strengthen and toughen woody material while maintaining its recyclability using existing modification technology. In this study, we have successfully fabricated high-performance and re-processable basswood with outstanding dimensional stability through reactive waterborne acrylic resin impregnation. The pathways of resin movement within the basswood’s multi-scale structure were discussed in detail. In comparison with unmodified wood, the compressive strength parallel/perpendicular to the grain, hardness, and modulus of rupture (MOR) were increased by 73.8 %, 179.4 %, 406.1 %, and 113.6 %, respectively. The compressive strength reached the standard of C70 degree for concrete, and MOR complied with the highest standard (TB20) of hardwood used as a building material. Moreover, the impact bending strength was enhanced by 113.1 % compared with the unmodified wood. Additionally, the water uptake of modified wood was 85.4 % lower than the unmodified wood, and the anti-swelling effect reached up to 42.8 %. Furthermore, the modified wood demonstrated recyclability and retained satisfactory strength after reprocessing, with the tensile strength of the first recovery reaching 22.5 MPa and the flexural strength reaching 31.5 MPa. This study thus provided a novel strategy for creating high-performance and recyclable wood, which holds significant promise for expanding the application area of woody materials, especially as a replacement for non-renewable materials such as concrete in the construction field.
The market for new durable products of modified wood has increased substantially during the last few years, especially in Europe. This increased interest depends partly on the restricted use of toxic ...preservatives due to increased environmental concern, as well as the need for reduced maintenance for wood products that are mainly for exterior use. Furthermore, as sustainability becomes a greater concern, the environmental impact of construction and interior materials should be included in planning by considering the entire life cycle and embodied energy of the materials used. As a result, wood modification has been implemented to improve the intrinsic properties of wood, widen the range of sawn timber applications, and acquire the form and functionality desired by engineers, without bringing environmental friendliness into question. The different wood modification processes are at various stages of development, and the challenges that must be overcome to expand to industrial applications differ amongst them. In this paper, three groups of wood modification processes are discussed and exemplified with modified wood products that have been newly introduced to the market: (i) chemical processing (acetylation, furfurylation, resin impregnation etc.); (ii) thermo-hydro processing (thermal treatment); and (iii) thermo-hydro-mechanical processing (surface densification). Building on these examples, the paper will discuss the environmental impact assessment of modification processes and further development needs.
This study aimed to investigate the relationship between the properties of pore size distribution and water sorption in melamine-urea-formaldehyde (MUF) resin-impregnated wood by scanning electron ...microscopy (SEM), nitrogen adsorption (NAD) measurement, mercury intrusion porosimetry (MIP), water-soaking, and moisture adsorption over saturated salt solutions. The results showed that MUF resin not only filled the macropores and mesopores of the wood, such as those of vessels and wood fibers, but also penetrated the cell walls and replaced some hygroscopic groups of cell wall polymers, thus significantly reducing the water sorption. The porosity and cumulative pore volume of the RI140 and RII140 samples (impregnated with 10% and 20% MUF resin solution, respectively, with each dried at 140 ℃) were 19.25% and 1.20 mL·g−1, and 9.85% and 0.89 mL·g−1, respectively, which were lower than those obtained for the control group (CK). The specific surface area of RII140 was lower than that of CK. The pore size range of the CK and RII140 samples was 3.1–22.9 nm and 2.5–5.1 nm, respectively. The water absorption rate and equilibrium moisture content values for MUF resin-impregnated wood were inversely proportional to the drying temperatures and weight percent gain (WPG). The MUF resin leaching efficiency was inversely proportional to the drying temperature but proportional to the WPG.
•The relationship between pore size distribution and water sorption behavior of MUF resin-impregnated wood (RIW) was studied.•The lower drying temperatures benefited the resin diffused into the wood cell wall micropores and made it over-bulking.•As drying temperature and WPG increased, more wood macropores were blocked and significantly decreased the water absorption.
•The plantation wood was modified by combined of resin and densification.•The strength class of treated wood by compound modification was increased greatly.•The fire resistance by compound ...modification was improved significantly.•The relationship between selected properties and microscopic images was built.
The abundant fast-growing Chinese fir is a low-grade building material due to its low mechanical strength and poor combustion performance. The impregnation with boric phenol formaldehyde resin (BPF) improve the mechanical properties and combustion performance in laboratory. Chinese fir wood was thermos-mechanically densified in laboratory scale with varying compression ratios after wood was impregnated with BPF resin with a concentration of 30%. The effects of the combination of BPF resin impregnation and compression ratio on mechanical properties and combustion performance were discussed. The test results have showed that the mechanical properties at high temperature and combustion performance were improved significantly. The higher the compression ratio, the better the mechanical properties and combustion performance of the BPF-densified-specimen.
To improve the undesirable intrinsic properties of plantation wood, this study presents the development of unilaterally surface-densified wood with high dimensional stability, surface hardness, and ...bending property for value-added applications. Poplar wood (Populus euramevicana cv. ’I-214′) was surface impregnated with a reactive waterborne acrylic resin followed by unilateral surface densification and equilibration. The influence of resin weight percent gain (WPG) and compression temperature on the physical and mechanical properties were investigated. Results indicated that the waterborne acrylic resin permeated into cell lumens and cured to form a rigid three-dimensional, water-resistant network. Set-recovery (SR) of the surface densified layers decreased dramatically when the deformation was fixed by the cured resin. A higher resin WPG resulted in a lower SR. Densified layers with WPG lower than 4.7% yielded SR values lower than 2.0%. Surface properties of the surface densified wood were dependent on resin WPG and compression temperature. Surface hardness increased significantly with increasing resin WPG. Samples with WPG higher than 3.4% had a static hardness of 5.9 kN, which is more than double that of the un-densified control. Thickness of the effective dense layer and total dense layer increased with increasing WPG and compression temperature. The modulus of rupture (MOR) and modulus of elasticity (MOE) of the only surface densified (OSD) wood increased 28.2% and 37.6%, respectively, compared with the un-densified control. Samples with low WPG had comparable MOR and MOE to the OSD wood. The resin-impregnated and surface densified wood with excellent performance is suitable for flooring, desktop, tabletop, bathroom cabinet applications.
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•An environmentally-friendly process was developed to make surface-densified wood.•The effect of resin WPG and compression temperature on wood properties was studied.•The densified wood showed low set-recovery, high hardness and bending property.•The densified wood demonstrated excellent performance for flooring and tabletops.
Resin transfer molding (RTM) has been attracting much attention to produce FRP products due to lower manufacturing cost than an autoclave molding method and unnecessity of human skills unlike a hand ...lay-up method. The quality of RTM products is highly dependent on the state of resin impregnation into fiber preform during the mold-filling stage, and it is required to avoid creation of molding defects such as dry spots and voids. Ultrasonic testing can be applied to monitor impregnation and cure of resin in RTM. In this study, an experimental setup was designed to achieve unidirectional resin flow, and ultrasonic monitoring system was proposed. By analyzing the reflected waves from the upper and lower surfaces of the FRP layer in the mold, it was found that our method could evaluate not only residual air voids and resin impregnation into fiber bundles, but also cure degree of resin. Therefore, it was proven that the system could monitor entire RTM molding process.
•Continuous external Rogowski (CER) diagnostics have been successfully installed and resin encapsulated to ITER's superconducting toroidal field Coils, meeting the desired dimensional accuracy and ...electrical performance.•Thorough pre-qualification tests had demonstrated the key operations involved in the process of CER integration, and validated the hydraulic and vacuum tightness of the manufactured connection assemblies.•The established integration and resin encapsulation procedure has been validated for high vacuum compatibility and outstanding reproducibility.•Noises are expected to be substantially suppressed for the CER diagnostics integrated to TF Coils, thanks to the low thermonuclear load and favourable service conditions inside superconducting magnets.•As a pioneering attempt of plasma diagnostics integration to reactor-scale superconducting magnets, the success of this venture has significantly implications to the development of cryogenic-based diagnostics for DEMO and future reactors.
Continuous External Rogowski (CER) are the primary plasma current diagnostics for the ITER tokamak, as well as the only diagnostics built into the ITER Toroidal Field Coils (TF coils). The integration of CER diagnostics to the TF coils faced numerous technical challenges, such as: the integrated components have to withstand the maximum pressure foreseen during ITER TF coil resin impregnation (350 kPa), comply with the high vacuum requirements that the helium leak rate shall be <2.7 × 10−9 Pa-m3/s, and survive at cryogenic temperature. The CER diagnostics integration campaign turned out to be a marked success, thanks to a comprehensive pre-qualification program and well-coordinated collaborations among the participating parties. All four sets of CER diagnostics have so far been integrated to the respective TF coils. As a pioneering attempt of building plasma diagnostics into reactor-scale superconducting magnets, the potential implications of this venture to the diagnostics development for DEMO and future fusion reactors are discussed. The gained experiences and lessons learned from this venture are summarized at last.
Abstract A major remaining challenge for Nb 3 Sn high field magnets is their training due to random temperature variations in the coils. The main objective of our research is to reduce or eliminate ...it by finding novel impregnation materials in replacement of the epoxies currently used. An organic olefin-based thermosetting dicyclopentadiene resin, C 10 H 12 , commercially available in Japan as TELENE ® by RIMTEC, was used to impregnate a short Nb 3 Sn undulator coil developed by ANL and FNAL. This magnet reached short sample limit after only two quenches, compared with ∼100 when CTD-101K ® was used. Ductility, i.e. the ability to accept large strains, and toughness were identified as key properties to achieve these results. In addition, we have been investigating whether mixing TELENE with high heat capacity ceramic powders such as Gd 2 O 3 , Gd 2 O 2 S, and HoCu 2 , increases the specific heat ( C p ) of impregnated Nb 3 Sn superconducting magnets. The viscosity, heat capacity, thermal conductivity, and other physical properties of TELENE with high- C p powder fillers were measured in this study as a function of temperature and magnetic field. The TELENE-87 wt%Gd 2 O 2 S had a peak in C p between 4.3 K and 5.3 K at fields between 0 and 8 T. We have also investigated the effect on the mechanical properties of pure and mixed TELENE under 10 MGy of gamma ray irradiation at the Takasaki Advanced Radiation Research Institute in Takasaki, Japan. TELENE-87 wt%Gd 2 O 2 S exhibited exceptional radiation resistance. Impregnating an undulator coil with TELENE mixed with Gd 2 O 2 S powder will verify whether the coils’ thermal stability further improves, or whether its low diffusivity will require engineering the material with high-thermal conductivity components. Short magnet training will lead to better magnet reliability, lower magnet margins, lower risk and substantial saving in accelerators’ commissioning costs. Part of this study is supported by the U.S.-Japan Science and Technology Cooperation Program in high energy physics operated by MEXT in Japan and DOE in the U.S.
The demand for products made of fiber‐reinforced polymer composites (FRPC) is constantly growing. These lightweight products are characterized by high stiffness, high tensile strength, and high ...service life. FRPC processes that employ thermoset‐impregnated continuous rovings are easily automated and provide the products with the highest unidirectional tensile strength. A critical disadvantage of continuous fiber‐reinforced polymers is caused by relatively high production costs. Among others, three main factors contribute to these production costs: (1) material costs, especially when carbon fibers are used, (2) costs for manufacturing semi‐finished products, such as textiles or preimpregnated fabrics, and (3) costs for waste occurring along the entire chain of process steps. In this context, one group of processes shows outstanding characteristics: processes in which rovings are in situ impregnated with a thermoset resin and then directly processed. Wet filament winding and pultrusion are the most popular but not the only representatives of this group. For all these processes, in situ impregnation is the key element, and various technologies have been developed for this purpose, each with its own unique fluid‐mechanical effects on rovings. A fundamental understanding of these effects is crucial to achieve products of the utmost quality. The paper at hand provides an overview of manufacturing processes that employ in situ impregnation of continuous rovings, specifically focusing on impregnation technologies. On this basis, phenomenological models describing the effects on the rovings during processing (impregnation, tension, and spreading) are reviewed.
Review on the state of the art of processing continuous filament bundles impregnated with thermoset resins
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