Commercial Composites Research Articles

Scalable production of robust and creep resistant ultra-high filled wood-plastic composites

With the widespread use of wood-based materials in human life, the availability of wood resources has gradually decreased. The use of low-value wood that does not require chemical adhesives can address the depletion of wood resources used to prepare wood-based composites. However, the development of high-strength, low-cost, scalable wood-based composites from low-value wood is challenging. In this study, high-performance ultra-high filled wood-plastic composites (UFWPC) composed of up to 95 wt% wood flour were prepared through cell wall densification and the construction of multiple cross-linked networks via deep cross-fusion. The UFWPC exhibited excellent mechanical properties, with a flexural strength that was 5.9 times higher than that of commercial particleboard, 2.1 times higher than commercial fiberboard, and 2.6 times higher than commercial wood-plastic composites. UFWPC also demonstrated excellent creep resistance, with a creep strain 76.79 % lower than that of commercial wood-plastic composites. Finally, a customizable large-scale commercial continuous flat-pressing system was established to produce UFWPC. The highly efficient preparation of UFWPC makes it an excellent alternative to commercial wood-plastic composites, particleboard, and fiberboard. This approach provides a promising valorization and sustainability method for recycling plastics and low-value wood.

Efficient photocatalytic degradation of methylene blue via synergistic dual co-catalyst on SrTiO3@Al under visible light: Experimental and DFT study

BackgroundPhotocatalytic oxidation is a green method for water purification. However, the operation of traditional photocatalysts depends on exposure to UV radiation, which only forms a small portion of the spectrum comprising sunlight. The expansion of photocatalyst absorption to the visible range of light could greatly improve the efficiency and economic viability of the process. MethodsThe photocatalyst was prepared by first synthesising SrTiO3 nanoparticles by chemical precipitation followed by calcination. Then, SrTiO3 was doped with aluminium using a flux method with Al2O3 and SrCl2 at 1150 °C. Finally, the dual co-catalysts, Rh/Cr2O3 and CoOOH, were photodeposited onto SrTiO3@Al via sequential irradiation. Significant findingsThe Rh/Cr2O3/SrTiO3@Al/CoOOH nanocomposite degraded 87% of methylene blue (MB) (10 mg/L) under visible light in 1 h, a 3.3-fold improvement over pure SrTiO3 and 2.1-fold over a similar commercial composite. This enhancement is due to efficient charge separation resulting from Al doping and improved carrier transport as a result of the anisotropic deposition of the co-catalysts. Optimisation showed that 20 mg of photocatalyst in 50 mL of MB solution (5 mg/L) degraded 100% thereof within 45 min. DFT calculations showed uneven electron distribution in SrTiO3′s conduction band and structural changes with Al doping, further enhancing photocatalytic activity.

On the suitability of photocuring-assisted DIW for manufacturing complex prosthesis from commercial dental composites

A 3-D printing method to produce dental prostheses of complex shapes from a commercial, photocurable resin-ceramic slurry is developed and optimized. The microstructure, mechanical properties and wear behavior of the resulting material are evaluated and compared with a conventional/control sample and other ceramic-polymer dental composites. Commercial resin-ceramic dental slurries can be successfully extruded and appropriately photocured in a low cost 3-D printing system to produce cost-efficient complex dental parts that could be used in indirect restorations. The printing process does not appreciably introduce defects in the material and the 3-D printed composites exhibit mechanical properties (hardness, elastic modulus) and wear resistance comparable to the control material and analogous, conventional dental composites. The main wear mechanisms under sliding contact against a hard antagonist are plastic deformation at the asperity level and ceramic particle pull-out due to filler/matrix interfacial weakness.Graphical 3-D printing commercial resin-filler slurries creates cost-efficient tooth prostheses with properties akin to conventional dental composites

SYNTHESIS AND CHARACTERIZATIONS OF NOVEL MISWAK POWDER-BASED DENTAL COMPOSITES

This study aimed to synthesize a novel miswak based dental composite by incorporating miswak powder, chlorhexidine (CHX), and silica fillers in different proportions into a resinous mixture and assess the influence of these fillers on the physical, mechanical, and biological properties of newly developed composites. The stock monomer solution was synthesized using urethane dimethacrylate, triethylene glycol dimethacrylate, and hydroxyethyl methacrylate. Four experimental groups (A, B, C, D) were prepared using 30% stock monomer with 70% filler formulations, while two commercial composites were used as control groups (E, F). The highest value of degree of conversion was shown by Group D, whereas the lowest – by Group A. Compressive strength evaluation showed Group E had the highest value, while the lowest value was recorded for Group B. Furthermore, cytotoxicity assessment showed that all the groups of composites had a biocompatible nature, except Groups A and B, having slight cytotoxicity. Thus, the experimental groups can be used as restorative materials as they exhibited optimum properties.

Bacterial adhesion and surface roughness of particulate-filled and short fiber-reinforced composites.

The objective of the study was to assess the initial adhesion of Streptococcus mutans (S. mutans) and surface roughness of different particulate-filled (PFC) and short fiber-reinforced (SFRC) composites. Five PFC composites (CeramX Universal, Filtek Universal, Omnichroma, Tetric Prime and Venus Diamond) and four SFRC composites (everX Posterior, everX Flow Bulk, everX Flow Dentin and experimental packable SFRC) were tested in this study. A non-contact 3D profilometer was employed to assess the surface roughness (Ra) of the polished specimens (using 4000-grit abrasive paper). For the bacterial adhesion test, the specimens (n = 5/group) were immersed in a solution of S. mutans to facilitate initial adhesion. To determine the number of cells on the surfaces of the discs as colony-forming units (CFU), the vials holding the microbial samples were highly agitated using a vortex machine. Subsequently, the samples were diluted multiple times and anaerobically incubated for 48h at 37°C on Mitis Salivarius Agar plates (Difco) supplemented with bacitracin. Bacterial adherence assessment was performed using SEM. The data were analyzed using ANOVA. All tested PFC and SFRC composites showed similar adhesion of S. mutan. The lowest Ra values (0.26µm) (p < 0.05) were found in the flowable SFRCs (everX Flow Bulk & Dentin), while the highest values (p < 0.05) were observed in CeramX and everX Posterior (0.42µm). Experimental SFRC had comparable Ra value (0.38µm) than other commercial composites. The presence of short microfibers in the composite appeared to have no adverse effects on the initial adhesion of bacteria or the surface roughness.

Sustainable engineering polymer composites fabricated using delignified bamboo fiber as reinforcement and walnut shell powder as filler

Developing sustainable engineering materials using renewable resources and agro-wastes represents an effective method for reducing carbon emissions and environmental pollution. In this study, a novel approach to fabricating high-performance biomass-based polymer composites was presented. Specifically, partially delignified bamboo fiber (DBF) and walnut shell powder (WSP) were incorporated into the matrix, namely melamine-hexamethylenediamine-urea (MHU) resin which was previously known for its excellent interfacial compatibility. Mechanical property investigations show that the DBF, acting as the reinforcement, provided the hybrid composites with high flexural and tensile strength up to 220 and 120 MPa, respectively, greatly surpassing those of commercial wood-plastic composites, wood-based composites, and natural wood, making them promising structural materials. As the filler, walnut shell powder endowed the composites with high hardness (Shore D > 90) and an appealing mirror-like surface gloss. Owing to the protection provided by the MHU matrix, the composite containing 38 % MHU exhibited outstanding flame retardancy (UL 94-V0 grade), which was further supported by cone calorimeter test (CCT) results. An unexpected and intriguing finding is that the composites exhibited fluorescence under UV irradiation. The rare silvery-grey fluorescence color imparted self-anticounterfeiting property to the composites. This study demonstrated the significant potential of bamboo fiber and walnut shell in the development of sustainable engineering materials.

Strong and tough graphene/PVC composites with well dispersed graphene via dropwise coagulation and melt blending methods

Toward strong and tough reduced graphene oxide (rGO)/poly(vinyl chloride) (PVC) composites, GO/PVC particles with well dispersed GO are prepared via dropwise coagulation using homogenous GO/PVC dispersion. Then, rGO/PVC composite materials are obtained by reducing GO with VC and melt blending. With low GO content by weight (GO:PVC = 0.2:100), the rGO/PVC composite's tensile strength, elongation at break, Young's modulus and toughness are increased by 100.1 %, 102.4 %, 179.1 % and 432.3 %, respectively. Further, the rGO/PVC particles with high GO content (GO:PVC = 1:100) are applied as functional masterbatch for commercial PVC-based wood plastic composite (WPC). With only 0.07 wt% GO (relative to WPC), the tensile strength, elongation at break, Young's modulus and toughness of WPC are enhanced by 62.4 %, 75.4 %, 57.2 % and 236.3 %, respectively. This study provides a simple approach to obtain strong and tough graphene/PVC composites toward industrial application.

Relationship between microstructure and dielectric/thermal management properties of biomass ramie fiber and its applications in recyclable wave-transparent composites

Industrial fiber crops are increasingly utilized in functional composites as substitutes for conventional fibers, aiming to address the limited microwave transmittance (MWT) and thermal conductivity (λ) of commercial glass fiber-reinforced composites (D-GFRC), which significantly reduce the service life of communication equipment shells and result in substantial waste pollution. Ramie fiber-reinforced composite (RFRC) possesses good dielectric/thermal management properties attributed to distinctive microstructure. However, the uncontrollable microstructure and unclear structure-property relationship of ramie fiber hinder its application in communication composites. Herein, the microstructures of ramie fiber, including aggregation and micro/nanopores structures, were successfully manipulated by coupling physical fields (temperature and force fields) with the guidance of molecular simulation. Subsequently, a clear relationship between microstructure and dielectric/thermal management properties was established. Moreover, leveraging this relationship, the performance of RFRC was optimized through coupled physical fields. Specifically, the MWT of RFRC reaches an impressive 95.9 %, and the λ is enhanced by 140 % compared to that of D-GFRC. Importantly, RFRC waste can be completely transformed into functional particles, thereby achieving a closed-loop utilization. This research strategy offers valuable insights into the regulation of microstructures and the development of recyclable wave-transparent composites derived from industrial crops.

Protein Immobilization on Bacterial Cellulose for Biomedical Application.

New carriers for protein immobilization are objects of interest in various fields of biomedicine. Immobilization is a technique used to stabilize and provide physical support for biological micro- and macromolecules and whole cells. Special efforts have been made to develop new materials for protein immobilization that are non-toxic to both the body and the environment, inexpensive, readily available, and easy to modify. Currently, biodegradable and non-toxic polymers, including cellulose, are widely used for protein immobilization. Bacterial cellulose (BC) is a natural polymer with excellent biocompatibility, purity, high porosity, high water uptake capacity, non-immunogenicity, and ease of production and modification. BC is composed of glucose units and does not contain lignin or hemicellulose, which is an advantage allowing the avoidance of the chemical purification step before use. Recently, BC-protein composites have been developed as wound dressings, tissue engineering scaffolds, three-dimensional (3D) cell culture systems, drug delivery systems, and enzyme immobilization matrices. Proteins or peptides are often added to polymeric scaffolds to improve their biocompatibility and biological, physical-chemical, and mechanical properties. To broaden BC applications, various ex situ and in situ modifications of native BC are used to improve its properties for a specific application. In vivo studies showed that several BC-protein composites exhibited excellent biocompatibility, demonstrated prolonged treatment time, and increased the survival of animals. Today, there are several patents and commercial BC-based composites for wounds and vascular grafts. Therefore, further research on BC-protein composites has great prospects. This review focuses on the major advances in protein immobilization on BC for biomedical applications.

Dodging reality, striking the virtual: An undulating strategy for effectively enhancing CF/PEEK interfacial adhesion!

The design of carbon fiber (CF)-reinforced polyetheretherketone (PEEK) composite materials with suitable interfaces has consistently been challenging. In this study, we sulfonated poly (phthalazinone ether sulfone ketone) (PPESK) and PEEK to prepare water-soluble SPPESK and SPEEK. Subsequently, we prepared a water-soluble sizing agent (SPPESK/SPEEK) via a straightforward blending process. This sizing agent tended to accumulate randomly on the surfaces of CFs, forming a thin film with a heterogeneous structure in the nanoscale. At the molding temperature of the composite material, the two components on the fiber surface exhibited different rheological behaviors, with PEEK preferentially infiltrating the SPEEK region, forming strong molecular entanglements. Meanwhile, the SPPESK region provided a rigid supportive structure, offering the potential for the mechanical interlocking of PEEK in the interface layer. The performance of the prepared composite materials was significantly enhanced, with their interlaminar shear strength and flexural strength reaching 87.1 MPa and 975.8 MPa, respectively. With respect to those of commercial fiber-reinforced PEEK composites, an 89.8 % increase in interlaminar shear strength and a 79.39 % increase in flexural strength were observed. This interface reinforcement mechanism presents a universally applicable strategy for the future development of fiber-reinforced composite materials.

Release of contraction stress of dental resin composites by water sorption

Polymerization shrinkage of bonded resin composite restorations will result in the development of curing contraction stresses during setting and can cause debonding of the restoration or failure of the surrounding tooth structure. However, the hygroscopic expansion that occurs after exposure of the restorative to the wet oral environment can compensate for this shrinkage. ObjectivesThe purpose of this study was to determine the hygroscopic expansion of six commercial resin composites and relate it to their composition, mechanical properties, shrinkage, and contraction stress development. MethodsShort-term volumetric shrinkage and contraction stress of the different composites were measured by mercury dilatometry and a universal testing machine. The long-term contraction stress was measured by the deflection of a bilayer strip of metal and a resin composite, which were stored dry as well as wet to determine the effect of hygroscopic expansion. The curvature of the strip was measured by profilometry over a period of 3 months. ResultsThe curvature of the strip correlated well (r2 =0.74) with the initial contraction stress, showing that the contraction stress is an important factor in initial deformation. The water sorption in all specimens showed that the initial deformation, within 2–4 weeks after curing, was completely counteracted. A high correlation (r2 =0.90) between deflection and relative water sorption was found, where the relative water sorption is defined as the absolute water sorption corrected for the inorganic filler volume of the composite. SignificanceWithin a period of 2–4 weeks after curing most of the curing contraction stresses of resin composite restoratives will be released by hygroscopic expansion.

Ionic Liquid-Based Silane for SiO2 Nanoparticles: A Versatile Coupling Agent for Dental Resins.

The current longevity of dental resins intraorally is limited by susceptibility to acidic attacks from bacterial metabolic byproducts and vulnerability to enzymatic or hydrolytic degradation. Here, we demonstrate synthesizing an ionic liquid-based antibiofilm silane effective against Streptococcus mutans, a major caries pathogen. Furthermore, we incorporate this silane into dental resins, creating antibiofilm- and degradation-resistant materials applicable across resin types. FTIR, UV-vis, and NMR spectroscopy confirmed the synthesis of the expected ionic liquid-based silane. The characterization of SiO2 after the silanization indicated the presence of the silane and how it interacted with the oxide. All groups achieved a degree of conversion similar to that found for commercial resin composites immediately and after two months of storage in water. The minimum of 2.5 wt % of silane led to lower softening in solvent than the control group (GCTRL) (p < 0.05). While the flexural strength indicated a lower value from 1 wt % of silane compared to GCTRL (p < 0.05), the ultimate tensile strength did not indicate differences among groups (p > 0.05). There was no difference within groups between the immediate and long-term tests of flexural strength (p > 0.05) or ultimate tensile strength (p > 0.05). The addition of at least 5 wt % of silane reduced the viability of S. mutans compared to GCTRL (p < 0.05). The fluorescence microscopy analysis suggested that the higher the silane concentration, the higher the amount of bacteria with membrane defects. There was no difference among groups in the cytotoxicity test (p > 0.05). Therefore, the developed dental resins displayed biocompatibility, proper degree of conversion, improved resistance against softening in solvent, and stability after 6 months of storage in water. This material could be further developed to produce polymeric antimicrobial layers for different surfaces, supporting various potential avenues in developing novel biomaterials with enhanced therapeutic characteristics using ionic liquid-based materials.

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

ObjectivesThe purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites. MethodsThe Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter. ResultsDirect contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range. SignificanceThe addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

Preparation of Al-doped mesoporous silica spheres (Al-MSSs) for the improvement of mechanical properties and aging resistance of dental resin composites

ObjectiveThe purpose of this study was to synthesize Al-doped mesoporous silica spheres (Al-MSSs) and evaluate the effect of them as functional fillers on the mechanical properties and aging resistance of dental resin composites. MethodsAl-MSSs were prepared by a two-step method. The effect of Al-MSSs on the performance of the composites was evaluated using neat resin matrix, commercial composites 3M Z350XT and samples containing mesoporous silica spheres (MSSs) and nonporous silica spheres (NSSs) as control. The neat resin matrix consisted of resin monomer (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 49.5/49.5, wt%) and photoinitiator (camphor quinone/Ethyl-4-dimethylaminobenzoate, 0.2/0.8, wt%). The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of them were evaluated by a universal testing machine and microhardness tester. The mechanical stabilities of the prepared composites in wet environment were evaluated by immersing them in deionized water at 37 °C. In addition, we evaluated the effect of Al-MSSs on other properties of the dental resin composites such as polymerization shrinkage, degree of conversion, curing depth, contact angle, water sorption and solubility according to ISO 4049: 2019. ResultsThe synthesized Al-MSSs possessed good dispersibility with an average particle size of about 505 ± 16 nm. The mechanical properties of resin composites gradually increased with the increase of the loading amounts of inorganic fillers. The reinforcing effect of Al-MSSs was similar to that of MSSs and better than that of the NSSs groups at the same filler loading. After aging in deionized water at 37 °C for 30 days, the mechanical properties of all resin composites decreased. However, the decrease percentage of the composites filled with Al-MSSs was significantly lower than the other groups, indicating that the stability of the dental composites in wet environments was significantly improved by the Al-MSSs fillers. Furthermore, Al-MSSs had no obvious influence on the biocompatibility and other properties of dental resins. SignificanceThe prepared Al-MSSs could effectively improve the mechanical properties and aging resistance without sacrificing other physic-chemical properties of dental resin composites.

The effect of dental material type and masticatory forces on periodontitis-derived subgingival microbiomes

Restorative dental materials can frequently extend below the gingival margin, serving as a potential haven for microbial colonization, and altering the local oral microbiome to ignite infection. However, the contribution of dental materials on driving changes of the composition of the subgingival microbiome is under-investigated. This study evaluated the microbiome-modulating properties of three biomaterials, namely resin dental composites (COM), antimicrobial piezoelectric composites (BTO), and hydroxyapatite (HA), using an optimized in vitro subgingival microbiome model derived from patients with periodontal disease. Dental materials were subjected to static or cyclic loading (mastication forces) during biofilm growth. Microbiome composition was assessed by 16S rRNA gene sequencing. Dysbiosis was measured in terms of subgingival microbial dysbiosis index (SMDI). Biomaterials subjected to cyclic masticatory loads were associated with enhanced biofilm viability except on the antibacterial composite. Biomaterials held static were associated with increased biofilm biomass, especially on HA surfaces. Overall, the microbiome richness (Chao index) was similar for all the biomaterials and loading conditions. However, the microbiome diversity (Shannon index) for the HA beams was significantly different than both composites. In addition, beta diversity analysis revealed significant differences between composites and HA biomaterials, and between both loading conditions (static and cyclic). Under static conditions, microbiomes formed over HA surfaces resulted in increased dysbiosis compared to composites through the enrichment of periopathogens, including Porphyromonas gingivalis, Porphyromonas endodontalis, and Fretibacterium spp., and depletion of commensals such as Granulicatella and Streptococcus spp. Interestingly, cyclic loading reversed the dysbiosis of microbiomes formed over HA (depletion of periopathogenes) but increased the dysbiosis of microbiomes formed over composites (enrichment of Porphyromonas gingivalis and Fusobacterim nucleatum). Comparison of species formed on both composites (control and antibacterial) showed some differences. Commercial composites enriched Selenomonas spp. and depleted Campylobacter concisus. Piezoelectric composites effectively controlled the microbiome viability without significantly impacting the species abundance. Findings of this work open new understandings of the effects of different biomaterials on the modulation of oral biofilms and the relationship with oral subgingival infections.

Thermal Oxidative Aging and Service Life Prediction of Commercial Ethylene-Propylene-Diene Monomer Spacer Damping Composites for High-Voltage Transmission Lines.

The aging behavior and life prediction of rubber composites are crucial for ensuring high-voltage transmission line safety. In this study, commercially available ethylene-propylene-diene monomer (EPDM) spacer composites were chosen and investigated to elucidate the structure and performance changes under various aging conditions. The results showed an increased C=O peak intensity with increasing aging time, suggesting intensified oxidation of ethylene and propylene units. Furthermore, the surface morphology of commercial EPDM composites displayed increased roughness and aggregation after aging. Furthermore, hardness, modulus at 100% elongation, and tensile strength of commercial EPDM composites exhibited a general increase, while elongation at break decreased. Additionally, the damping performance decreased significantly after aging, with a 20.6% reduction in loss factor (20 °C) after aging at 100 °C for 672 h. With increasing aging time and temperature, the compression set gradually rose due to the irreversible movement of the rubber chains under stress. A life prediction model was developed based on a compression set to estimate the lifetime of rubber composites for spacer bars. The results showed that the product's life was 8.4 years at 20 °C. Therefore, the establishment of a life prediction model for rubber composites can provide valuable technical support for spacer product services.

Poly (aniline-co-aniline-2,5-disulfonic acid) / L-ascorbic acid / Ag@SiO2 / polysafranin nanocomposite: synthesis, characterization and anomalous electrical behaviour.

We report the synthesis of sulfonated copolyaniline/polysafranin/L-ascorbic acid/Ag@SiO2 fine powdered nanocomposites and investigate the influence of incorporating the dye on their conductivity. The composite was characterized via IR, UV, cyclic voltammetry (CV), electric, dielectric, SEM, TEM, TGA and DSC measurements. Microscopy images revealed intensified spherical particles that were dispersed across the entire surface, and the SiO2/Ag particles were distributed on the surface. The XRD results exhibited peaks at many 2q values, and their interatomic spacing (d) and crystallite (grain) sizes were calculated. The thermal degradation curves exhibited an interesting model of stability. The cyclic voltammogram exhibited redox peaks identical to those of the reported analogues. The d.c. conductivity of the oligomer varied from 0.06 - 0.016 (s/cm), and that of the composite varied from 0.008 to 0.016 (s/cm). The material changed from a semiconductor to a metallic material. The observed conductivity is mainly attributed to self-doping between the sulfonate groups and the charged nitrogen atoms in the polymer chains. The frequency dependence of the permittivity, ε', showed a marked effect on the frequency window under consideration. The permittivity, ε', is independent of the increase in the frequency of the oligomer and the composite. This behavior supports the non-Debye dependency by confirming the occurrence of electrode polarization and space charge effects. In conclusion, the incorporation of safranin dye with a thermally stable, highly sulfonated polyaniline derivative/Ag@SO2 nanocomposite achieved improved conductivity after heating. The d.c. conductivities are comparable to those of many commercial inorganic or organic composites, and because of their attractive electrical properties, we suggest that these materials are promising for electronic field applications.

Constructing a Novel Moderately Modulus "Rigid-Flexible" Structure with Synergistic Reinforcement on the Carbon Fiber Surface to Enhance the Mechanical Properties of Carbon Fiber/Epoxy Composites at Elevated Temperatures.

To improve the mechanical performance of carbon fiber (CF)/epoxy composites in high-temperature environments, a moderately modulus gradient modulus interlayer was constructed at the interface phase region of composites. This involved the design of a "rigid-flexible" synergistic reinforcement structure, incorporating rigid nanoparticle GO@CNTs and a flexible polymer polynaphthyl ether nitrile ketone onto the CF surface. Notably, at 180 °C, compared to commercial CF composites, the CF-GO@CNTs-PPENK composites displayed a remarkable improvement in their mechanical characteristics (interfacial shear, interlaminar shear, flexural strength, and modulus), achieving enhancements of 173.0, 91.5, 225.7, and 376.4%, respectively. The principal reason for this the moderately modulus interface phase composed of GO@CNTs-PPENK (where GO and CNTs predominantly consist of carbon atoms with sp2-hybridized orbitals, forming highly stable C-C structures, while PPENK possesses a "twisted non-coplanar" structure), which exhibited resistance to deformation at high temperatures. Moreover, it greatly improved the mechanical interlocking, wettability, and chemical compatibility between CF and the epoxy. It also played a crucial role in balancing and buffering the modulus disparity. The interface failure behavior and reinforcement mechanisms of the CF composites were analyzed. Furthermore, validation of the presence of a moderately modulus gradient interlayer at the interface phase region of CF-GO@CNTs-PPENK composites was performed by using atomic force microscopy. This study has established a theoretical foundation for the development of high-performance CF composites for use in high-temperature fields.

Durability ratings of post-treated wood-based composites after 14 years of field exposure

Several commercial wood-based composites (softwood plywood [SWP], hardwood plywood [HWP], medium-density fiberboard [MDF], oriented strand board [OSB], and particleboard) [PB]) were post-treated with alkaline copper quat and copper azole at two different retention levels. The treated specimens were installed on concrete blocks covered with 5-sided PVC boxes simulating the crawl space conditions (protected above-ground) in Japanese houses in Southern Japan where decay and termite activity are high. The experimental variables are a comparison of treated versus untreated, preservative type and retention levels. During 14 years of exposure, the specimens were biannually visually rated. In general, termite damage became visible earlier and the harshness of attack was higher when compared to decay damage. The untreated and treated MDFs were the most resistant under the protected above ground conditions at the end of 14 years exposure. Particleboard durability performance followed the MDF rating during the same period. The untreated OSB, HWP, and SWP were the least resistant composite types. The treatments substantially increased the durability of the mentioned composite types by 317.6%, 80.5%, and 133% higher termite grading when correlated to their untreated controls, respectfully, yet they failed to maintain full protection. Based on statistical analysis, preservative types and retention levels did not significantly affect decay and termite ratings.

Near–infrared light–cured dental restoration materials with upconversion nanoparticles

Development of light–cured dental restoration materials with superior tissue penetration and mechanical properties is of paramount significance for treating oral diseases such as dental caries, which are among the most prevalent diseases globally. Herein, we report near–infrared (NIR) light–cured dental restoration materials with judiciously designed upconversion nanoparticles (UCNPs) as NIR-to-UV/Vis light nanotransducers. 808 nm NIR light-driven photopolymerization of methacrylate-thiol-ene resin materials is demonstrated, a photocuring depth of more than 11 cm is obtained for the resulting resin, and a NIR photocuring depth of more than 5 mm can be still achieved in the resin composite materials with 40 wt% SiO2 nanofillers. Importantly, the as-proposed dental restoration materials are found to exhibit superior mechanical properties, which can be comparable with commercial dental resin composites that are photocured by blue light. The in vitro and in vivo biocompatibility of the resulting materials was evaluated, and NIR light-driven restoration of the extracted teeth from periodontal or third molar-extracted patients was performed. This research can pave an avenue for NIR dental restoration chemistry and its widespread applications in biomedical science.