Increase In Flexural Strength Research Articles

The Effect of Carbon Nanotubes and Carbon Microfibers on the Piezoresistive and Mechanical Properties of Mortar

Sustainability, safety and service life expansion in the construction sector have gained a lot of scientific and technological interest during the last few decades. In this direction, the synthesis and characterization of smart cementitious composites with tailored properties combining mechanical integrity and self-sensing capabilities have been in the spotlight for quite some time now. The key property for the determination of self-sensing behavior is the electrical resistivity and, more specifically, the determination of reversible changes in the electrical resistivity with applied stress, which is known as piezoresistivity. In this study, the mechanical and piezoresistive properties of mortars reinforced with carbon nanotubes (CNTs) and carbon micro-fibers (CMFs) are determined. Silica fume and a polymer with polyalkylene glycol graft chains were used as dispersant agents for the incorporation of the CNTs and CMFs into the cement paste. The mechanical properties of the mortar composites were investigated with respect to their flexural and compressive strength. A four-probe method was used for the estimation of their piezoresistive response. The test outcomes revealed that the combination of the dispersant agents along with a low content of CNTs and CMFs by weight of cement (bwoc) results in the production of a stronger mortar with enhanced mechanical performance and durability. More specifically, there was an increase in flexural and compressive strength of up to 38% and 88%, respectively. Moreover, mortar composites loaded with 0.4% CMF bwoc and 0.05% CNTs bwoc revealed a smooth and reversible change in electrical resistivity vs. compression loading—with unloading comprising a strong indication of self-sensing behavior. This work aims to accelerate progress in the field of material development with structural sensing and electrical actuation via providing a deeper insight into the correlation among cementitious composite preparation, admixture dispersion quality, cementitious composite microstructure and mechanical and self-sensing properties.

Investigation of The Use of Nano Powder On Roller Compressible Fibrous Concrete Roads

Despite the fact that our country's road network is inferior to that of industrialized countries, the volume of motor traffic is increasing. Thus, optimal solutions are imperative during both project and construction phases of highway investments. Concrete superstructures offer an alternative to flexible superstructures in various regions globally, including airport runways, warehouses, urban roads, streets, highways and industrial buildings. The objective of this study was to enhance the compressive and flexural strength of concrete and provide resistance against abrasion. To achieve this, a roller compressible concrete (RCC) mixture design was developed by incorporating basalt fiber, nano TiO2, and nano Fe2O3 additives. The experimental results were subjected to statistical analysis via the technique of analysis of variance (ANOVA). The findings of the study indicated that the strength performance of the optimal RCC mixture design reinforced with nano powder and fibers was superior to that of conventional concrete. Upon examination on a material basis, it was determined that the compressive strength exhibited an increase when the water/binder ratio was utilised within the range of 0.38–0.4. As the utilisation of nano-Fe2O3 and basalt fiber materials increased, their compressive strength exhibited a corresponding enhancement. The incorporation of basalt fiber into the composite material resulted in an increase in flexural strength at all ratios where it was utilised. It can be concluded that basalt fiber has the greatest potential for enhancing flexural strength. The optimal water-to-binder ratio for flexural properties is between 0.34 and 0.38. While nano powders can have a positive impact, they cannot achieve the maximum level of strength. For improving abrasion resistance, it was established that reducing the water/cement ratio, using fly ash, basalt fiber, and nano Fe2O3 in the mixture decreased abrasion. However, the usage of nano TiO2 did not have a significant positive effect. The material with the least effect on compressive, flexural and abrasion resistance was identified as nano TiO2. When materials other than nano TiO2 are utilised in accordance with the established optimal mixture calculation, the durability of the resulting RCC road will reach the requisite standard.

Study on early hydration and pore structure evolution of cement paste containing graphene oxide

Graphene oxide (GO) significantly enhances cement hydration. This study investigates the effects of GO on the early hydration and pore structure evolution of cement paste by examining its impact on the setting time and mechanical properties of cement-based materials. In situ monitoring of the hydration process and microstructural changes was conducted using low-field nuclear magnetic resonance technology. The findings reveal that GO's nucleation effect accelerates cement hydration, reducing the setting time and increasing both the hydration rate and degree. Moreover, hydration products utilize GO as a template, leading to adjusted morphologies and enhanced interlinking of C–S–H gels. This results in a marked reduction in porosity and a denser microstructure within the cement paste. Consequently, the early mechanical properties of the cement paste are improved, with a significant increase in flexural strength observed at 72 hours. These results suggest that GO, which is cost-effective, size-controllable and suitable for mass production, holds great potential for applications in cement-based materials.

Study on the Reinforced Properties of Geopolymer Fibers with a Sustainable Development Role

Geopolymers are of great significance in reducing the consumption of mineral resources, saving energy, protecting the environment, and realizing sustainable economic and social development. This experiment investigated geopolymer mortar with fly ash and metakaolin as the primary binders, assessing the impact of different fiber types and volume fractions on the mortar’s flexural and compressive strength. The results indicated that optimal mechanical properties could be achieved with a fly ash-to-metakaolin ratio of 35:65. The mechanical performance is the best, with a compressive strength of 54 MPa, a flexural strength of 3.4 MPa, and a split tensile strength of 1.9 MPa at 28 days. Different fibers influenced the splitting tensile strength to varying degrees; with a 1.5% volume fraction of steel fibers, geopolymer mortar exhibited the best reinforcement effect, showing a 70% increase in flexural strength and a 142% increase in tensile strength. Mechanistic analysis revealed that the reinforcement from refined various fibers could refine the structure and further enhance the strength. Of steel geopolymer fibers’ The reinforcing effect of steel fibers is the best among them, and the internal structure is the most compact. The geopolymer mortar hydration products of geopolymer mortar reinforced with PP fibers, PVA fibers, steel fibers, and carbon fibers were amorphous network-structured zeolites (Na2[Al2Si3O10]·2H2O). The limitations of geopolymers can be effectively addressed through the aforementioned research, which can effectively reduce the use of cement and achieve the goal of sustainable development.

Coconut fiber and fly ash polymer hybrid composite treated silane coupling agent: Study on morphology, physical, mechanical, and thermal properties

Composite materials made from natural ingredients are currently being developed by researchers as materials that are more environmentally friendly. Hybridization techniques used in making composite materials continue to progress, involving the combination of several raw materials with similar or different properties, such as organic/organic, organic/inorganic, and inorganic/inorganic. In this research, coconut fiber which is an organic material is combined with fly ash which is an inorganic material. The contrasting properties of these two raw materials prompted the evaluation of their combination by including a silane coupling agent, which facilitates the bonding of organic and inorganic components. The essence of this research is to test the effect of adding silane coupling material on several parameters, namely physical properties (density, water absorption, and thickness swelling), mechanical properties (tensile strength, tensile modulus, elongation, and flexural strength), and thermal properties. To prepare coconut fiber, alkaline treatment is used to remove hemicellulose and lignin. Then, the coconut fiber was soaked in a 5 % vinyltrimethoxysilane (TVS) solution by weight. The addition of silane coupling material affects the physical properties of the composite resulting in a decrease in water absorption by 33 % and a decrease in thickness swelling by 0.3 %. The inclusion of silane coupling agent led to an increase in tensile strength, tensile modulus, and flexural strength, while elongation decreased by 20 %. Thermal properties analysis showed that the silane treatment affected the decomposition of the composite material, reducing it by 2 % from 90 % without the coupling agent to 88 % with the coupling agent.

Investigation on the influence of waste-based fillers on the mechanical and thermal characteristics of rigid polyurethane foams

An investigation was conducted to analyze the impact of incorporating coal powder particles at different weight ratios (5, 10, 15, 25, and 35) on the mechanical properties and thermal conductivity coefficient of the polyurethane polymer. The thermal conductivity coefficient of the samples was calculated using Holmarc's Lee's Disc apparatus device. The mechanical properties like compressive, tensile, and bending strengths were measured using a universal machine. The results indicated that increasing the coal powder ratio leads to an improvement in the thermal insulation ability due to a decrease in the value of thermal conductivity. Also, the addition of these percentages led to a rise in the values of the mechanical qualities represented by the compressive strength, especially at the ratio of 25 wt. %, with a value equal to 2.79 MPa (MPa). The flexural resistance and tensile strength increase at a ratio of 35 wt. %, with values equal to 20.4 MPa and 2.86 MPa respectively. The results indicate that the addition of coal powder enhances the ability of thermal conductivity at the ratios (5 %, 10) wt. %, with values equal to 0.119 W/m ºC and 0.114 W/m ºC, respectively, by increasing the thermal conductivities of the samples. The aim of this study is, investigate the effect of filler used coal powder waste on the mechanical and thermal properties of PU. The filler materials show the advantages of recycling waste. Filler influences the morphology and strengthens the brittleness. Additionally, the technology of polyurethane materials conforms to the use of coal powder. The overall amount of energy used to produce PU composites is decreased when waste of filler is used to partially replace petrochemical components

Exploring Damage Patterns in CFRP Reinforcements: Insights from Simulation and Experimentation.

Carbon Fiber Reinforced Polymers (CFRP) have become increasingly significant in real-world applications due to their superior strength-to-weight ratio, corrosion resistance, and high stiffness. These properties make CFRP an ideal material for reinforcing concrete structures, particularly in scenarios where weight reduction is crucial, such as in bridges and high-rise buildings. The transformative potential of CFRP lies in its ability to enhance the durability and load-bearing capacity of concrete structures while minimizing maintenance costs and extending the lifespan of the infrastructure. This research explores the impact of reinforcing structural elements with advanced composite materials on the strength and durability of concrete and reinforced concrete structures. By integrating Carbon Fiber Reinforced Polymer (CFRP) reinforcements, we subjected both rectangular and T-section concrete beams to comprehensive three-point bending tests, revealing a substantial increase in flexural strength by 45% and crack resistance due to CFRP reinforcement. The study revealed that CFRP reinforcement increased the flexural strength of concrete beams by 45% and improved crack resistance significantly. Additionally, the load-bearing capacity of the beams was enhanced by 40% compared to unreinforced specimens. These improvements were validated through finite element simulations, which showed a close alignment with the experimental data. Furthermore, an innovative simulation study was conducted using a finely tuned finite element numerical model within the Abaqus calculation code. This model accurately replicated the laboratory specimens in terms of shape, dimensions, and loading conditions. The simulation results not only validated the experimental observations but also provided deeper insights into the stress distribution and failure mechanisms of the reinforced beams. Novel aspects of this study include the identification of specific failure patterns unique to CFRP-reinforced beams and the introduction of an enhanced interaction model that more accurately reflects the composite behavior under load. In CFRP-reinforced beams, specific failure patterns were identified, including flexural cracks in the tension zone and debonding of the CFRP sheets. These patterns indicate the points of maximum stress concentration and potential weaknesses in the reinforcement strategy. The study revealed that while CFRP significantly improves the overall strength and stiffness, careful attention must be given to the bonding process and the quality of the adhesive used to ensure optimal performance. These findings contribute significantly to the understanding of material interactions and structural performance, offering new pathways for the design and optimization of composite-reinforced concrete structures. This research underscores the transformative potential of composite materials in elevating the structural integrity and longevity of concrete infrastructures.

Mechanical properties and repairing mechanism of recycled cement stabilized macadam for road base based on microbial induced carbonate precipitation technology

The utilization of recycled coarse aggregate derived from construction and demolition waste (CDW) in the construction of road cement stabilized macadam base could effectively alleviate the shortage of natural sand and aggregate resources. To explore the repairing effect of microbial induced carbonate precipitation (MICP) on recycled cement stabilized macadam (RCSM), the physical, mechanical, and microscopic properties of recycled concrete aggregate under different precipitation precursor concentrations were researched in this paper. The mechanical properties of RCSM with varying contents of recycled concrete aggregate were analyzed before and after repairing. Based on scanning electron microscopy (SEM) and mercury intrusion porosimeter (MIP) tests, the microstructure and pore structure parameters of recycled concrete aggregate were explored, and the repair mechanism of MICP on RCSM was revealed via the performance analysis of recycled concrete aggregate and RCSM. The results show that MICP could effectively reduce the water absorption of recycled concrete aggregates, while simultaneously enhancing its apparent density and crushing resistance. In a certain range, the higher the concentration of the precipitation precursor, the better the repairing effect on the performances of recycled concrete aggregates. However, while the concentration of urea or calcium source concentration exceeding 1.0 mol/L, the activity of urease would start to be inhibited. The unconfined compressive strength of RCSM after MICP repairing could be increased by 22.7 % with a maximum extent compared with that before repair, while the maximum increase of indirect tension strength and flexural tensile strength was 15 % and 8.2 %, respectively. The biological CaCO3 generated by MICP reaction could fill the micro-cracks and pores of the recycled concrete aggregate efficaciously. Besides, it could also optimize the pore parameters and pore size distribution parameters, and enhance the adhesive strength of interfacial transition zone (ITZ) between cement and recycled concrete aggregates, which could improve the mechanical properties of RCSM.

Mechanical Properties of Silicon Carbide Composites Reinforced with Reduced Graphene Oxide.

This article presents research on the influence of reduced graphene oxide on the mechanical properties of silicon carbide matrix composites sintered with the use of the Spark Plasma Sintering method. The produced sinters were subjected to a three-point bending test. An increase in flexural strength was observed, which reaches a maximum value of 503.8 MPa for SiC-2 wt.% rGO composite in comparison to 323 MPa for the reference SiC sample. The hardness of composites decreases with the increase in rGO content down to 1475 HV10, which is correlated with density results. Measured fracture toughness values are burdened with a high standard deviation due to the presence of rGO agglomerates. The KIC reaches values in the range of 3.22-3.82 MPa*m1/2. Three main mechanisms responsible for the increase in the fracture toughness of composites were identified: bridging, deflecting, and branching of cracks. Obtained results show that reduced graphene oxide can be used as a reinforcing phase to the SiC matrix, with an especially visible impact on flexural strength.

Sustainable basalt fiber reinforced polyamide 6,6 composites: Effects of fiber length and fiber content on mechanical performance

The aim of this study is to explore the use of sustainable basalt fiber (BF) as compared to glass fiber and talc in injection molded engineering polyamide 6,6 (PA 6,6) plastic composite. Basalt fibers having lengths of 3 mm and 12 mm were added to PA 6,6 at 23 and 30 wt.% to fabricate the composites. The addition of basalt fiber restricts the mobility of the polymer chain in the composites, leading to its increased viscosity. Rheological results showed that the out-of-phase response to the applied stress indicated that the 3 mm basalt fiber composite could dissipate more energy, and the elastic behaviour of the composite under deformation increased with increasing basalt fiber wt.%. The fiber length had a larger effect on the mechanical properties of the composites as compared to the fiber load. The 12 mm basalt fiber composites at 23 wt.% and 30 wt.% produced higher tensile strength and modulus than the 3 mm basalt fiber composites while the 3 mm basalt fiber composite at 30 wt.% resulted in a 25 % increase in flexural strength. The experimental and the theoretical modulus predicted by the rule of mixtures showed an interaction between the matrix and the basalt fiber. Morphological analysis shows more agglomeration in composites with 3 mm fiber than the 12 mm. Glass fiber-reinforced PA 6,6 showed slightly higher performance than basalt fiber-reinforced PA 6,6. However, the basalt fiber-reinforced composites demonstrated better performance in tensile strength, flexural modulus, flexural strength, and heat deflection temperature than talc-reinforced composites.

Poly(butylene succinate) reinforced by small amount of grafted nanofibrillated bacterial cellulose: Toughness variability based on nanocomposites preparation method

Polybutylene succinate (PBS) is a promising biodegradable polymer; however, its low mechanical performance limits its application. To address this issue, long fiber length nanofibrillated bacterial cellulose (HP-NFBC), produced by a bottom-up process using cellulose-producing bacterium and hydroxypropyl cellulose (HPC) as a dispersing agent was used as reinforcement agent. Hydrophobic moieties were grafted on HP-NFBC surface to increase surface compatibility. Nanocomposites prepared by both solvent casting and melt-kneading were evaluated. By solvent casting, the addition of 0.25 wt% of grafted HP-NFBC increased the toughness by 212 %. Melt-kneading revealed an increase in flexural strength and young’s modulus. More evident improvement was observed when the nanocomposites were annealed, and the ultimate strength increased by 113 % at 2 wt% of grafted HP-NFBC incorporation. Great increased in toughness were achieved only by small incorporation of grafted HP-NFBC. Additionally, compost biodegradation tests were conducted to confirm that the nanocomposites had biodegradability similar to that of PBS.

Advancing reinforcement of sustainable gypsum composites: High-performance design by reusing waste materials

This study tends to optimize and develop an innovative gypsum material by incorporating hybrid waste compounds. Using a Doehlert design, this work explores the effects of introducing paper (X1), polystyrene (X2), and polyester fibers (X3), as well as their interactions, on gypsum's thermophysical and mechanical behavior. Bulk density, thermal conductivity, flexural strength, compressive strength, and the fire resistance test were performed on the developed formulations. Statistical analysis emphasizes the significant influence of all process variables on gypsum properties. Polyester fibers notably enhance flexural strength when combined with the cooperative effect of paper and polystyrene wastes, which strike a balance between physical and mechanical characteristics. The optimum formulation parameters lead to a significant 33% decrease in bulk density, a 43% reduction in thermal conductivity, a notable 42% increase in flexural strength, and a significant reduction in compressive strength of around 50%, but still meet the 2 MPa standard. The new samples show ductile behavior, highlighting gypsum's potential as a load-bearing material with excellent thermal insulation properties and impressive fire resistance. This research significantly improves our understanding of the effectiveness of a gypsum compound incorporating waste in a hybrid manner, bringing this approach into line with sustainable development objectives.

Effect of mullite fiber on the properties of glass composite sealing materials

Glass-based sealing materials exhibit significant potential for utilization in solid oxide fuel cells (SOFCs). We conducted a study on the impact of mullite fibers with varying particle sizes on glass composite sealing materials. We evaluated and discussed properties such as coefficient of thermal expansion (CTE), softening temperature (Ts), gastightness, interfacial compatibility, and flexural strength of the sealing materials with different ranges of fiber particle sizes. Our findings indicate that the three different particle sizes of mullite fiber-glass composite sealing materials met the required coefficients of thermal expansion, displayed good interfacial compatibility, and exhibited gastightness lower than 0.0016 sccm cm−1. Notably, the mullite fiber-reinforced sealing material that underwent ball-milling for 1 h outperformed the other two variants. It demonstrated fewer defects, a 57.1 % increase in flexural strength, and a 117.4 % higher maximum strain value.

Development and mechanical characterization of horse hair with titanium dioxide nanoparticles reinforced polyester composite

This study aims to examine the effects of waste material more especially horse hair as fiber on mechanical and physical properties. Tensile, flexural, impact, and hardness properties of horse hair fiber and titanium dioxide nanoparticles (TiO2 NPs) polyester composite were investigated to determine whether the latter might be used as a new material in various engineering applications for a longer life. To improve the impact resistance of the composite, horse hair fiber is mixed in different ratios with titanium dioxide and polyester as filler. Tensile, flexural, and impact mechanical properties were assessed using the Universal Testing Machine, the Rockwell Hardness Testing Machine, and the Izod Impact Test. Specimens were hand-put up using various fiber weight ratios. The results of this study showed that Specimen 5 showed a tremendous increase in flexural strength (98.87 MPa), tensile strength (91.46 MPa), hardness (115 HV), impact strength (15.98 J m−1), and water uptake (10.18%) as compared to the neat and also with the other Specimens. Scanning electron microscopy (SEM) was used to investigate the fracture surface in more detail in order to search for failure mechanisms and the dispersion of nanoparticles. SEM micrographs verified the uniform dispersion of the nanoparticles. Results suggest that these composites can be used as a material for a variety of applications, including biological claims that they are a practical, durable, and environmentally friendly choice.

ZrO2 reinforced porous Si3N4-based ceramics with improved mechanical properties fabricated via vat photopolymerization (VPP)

Porous Si3N4 ceramics are widely applied in many fields owing to their excellent properties such as high electromagnetic wave permeability, oxidation resistance, and wear resistance. Besides, the vat photopolymerization (VPP) technique can fabricate porous Si3N4-based ceramics with complex shapes and high precision. Nevertheless, The high absorptivity and refractive index of Si3N4 to ultraviolet light make it difficult to form porous Si3N4-based ceramics with the VPP technique. In this work, the addition of ZrO2 simultaneously improved the printability of Si3N4 slurries and the performance of Si3N4 ceramics via VPP technology. Rheological behavior and curing properties of the slurries were investigated, and the influence of ZrO2 content on the mechanical properties of printed Si3N4-based ceramics was investigated systematically. The addition of ZrO2 decreased the UV absorptivity of composite powder, thus improving the curing depth from 25.2 ± 2.6 μm to 64.8 ± 3.7 μm. XRD analysis revealed that ZrO2 in the composite ceramics mainly exists as the phase of yttria-stabilized tetragonal zirconia (Zr0.92Y0.08O1.96), which could ensure the effect of phase transformation toughening. With the increase of ZrO2 content, flexural strength and fracture toughness of porous Si3N4-based ceramics exhibited a trend of increase first and then decrease. As ZrO2 content increased to 10 wt%, the flexural strength and fracture toughness of porous Si3N4-based ceramics were improved from 214.7 MPa and 4.23 MPa·m1/2 to 345.0 MPa and 5.69 MPa·m1/2, respectively. Therefore, this work provided an important reference for the fabrication of high-performance porous Si3N4-based ceramic components with complex structures.

Developing an eco-friendly cementitious grout using paper sludge ash and steel fiber recovered from waste tires

Cement is the most important component in cementitious grout production,andtt accounts for 7% of global greenhouse gas emissions. Reducing the amount of cement used in infrastructure and buildings is a desirable way to lower the total carbon footprint associated with grout production. relatedly, developments in manufacturing and transportation lead to the production of cars in large numbers, which in turn leads to an increase in the production of byproduct waste like waste tires, which are thrown away directly without recycling. Thus, this study aims to develop a novel sustainable grout by recycling paper sludge ash waste (PSA) and waste steel fiber (WSF) as partial cement replacements. This will help reduce grout production costs, minimize environmental pollution during cement production, and enhance landfill and waste management. The Grout mixtures used in this paper were prepared using ordinary Portland cement (OPC), WSF extracted from vehicle tires, PSA, and water. Different proportions of WSF(0, 1, 2, 3%) and PSA(5, 10%) were used in the weight of cement in designing sustainable grout. The mechanical properties of the sustainable grout were evaluated by examining extensive tests including flow tables, compressive strength, and flexural strength. The results showed that partially replacing the cement with 3% WSF and 1% WSP with 5% PSA resulted in a significant improvement in workability ,as well as a clear increase in compressive and flexural strength at an early age compared to the reference mixture.

Effect of moisture content on the mechanical performance of 3D printed continuous reinforced two-matrix composite

Additive manufacturing, particularly Fused Filament Fabrication, has gained significant attraction in recent years. In order to increase the mechanical performances of several components, continuous reinforcements, such as carbon fibers, can be coextruded with a polymeric matrix.The present study relies on a specific 3D printing process, called towpreg coextrusion, which exploits continuous carbon fibers covered with an epoxy resin and polyamide (PA) as the thermoplastic matrix, thus obtaining a 3D printed two-matrix composite. Since polyamide is a highly hygroscopic material, the impact of moisture content on the mechanical properties of 3D-printed continuous composites was investigated. Tensile and flexural specimens were manufactured and tested under both undried and dried conditions. Drying treatment was carried out at a temperature of 70 °C for 2 h in oven, with weight measurements before and after for quantifying weight loss and then the moisture removal. Additionally, through thermogravimetric analysis, the thermal stability of the material was assessed. It was observed that the drying process allows for a reduction of up to 0.56% by weight of moisture in the specimens. Thus, the drying process led to an improvement in the mechanical properties of the material. Specifically, the tests reveal a 15% increase in tensile strength and an 11.5% increase in flexural strength following the drying process, reaching values of 392.78 MPa and 151.06 MPa, respectively. Similarly, an increase in the tensile and flexural moduli was noted in the treated specimens. Finally, fractured samples underwent optical and scanning electron microscopy analysis, through which different fracture mechanisms of the material and the presence of macrovoids and microvoids attributable to the 3D printing process were observed. Knowledge of deposition defects represents an important starting point for the improvement of the process and the mechanical properties obtained to date. This research provides valuable insights into optimizing 3D-printed continuous composites, emphasizing the importance of moisture control for superior mechanical performance in industrial applications.

Evaluation of Treatment Performance of Different Methods on Wheat Straw Composites

The objective of this research is to evaluate the impact of both traditional and innovative techniques on the qualities of wheat straw, as well as the mechanical performance of epoxy composites which use wheat straw as a reinforcing material. Two different methods were used for treatment: Alkali treatment (AlT) was carried out using NaOH at concentration of 5% w/v for 1 hour at 25°C, Microwave irradiation (MwT) aws performed at 300 W for 20 minutes. It was found that Alkali and microwave treatment both changed the surface morphology of wheat straw. Microwave treatment provided further improvement in the mechanical properties of the composite materials, enabling a 37% increase in tensile strength and 62% increase in flexural strength. Microwave reclamation, which is cleaner and performs better than chemical reclamation, shows promising performance for more sensitive material application areas.

Mechanical properties of carbon nanotube (CNT) reinforced polymers using electron‐deficient aromatics as additives

AbstractIn initial experiments the effects of aromatic model substances on carbon nanotube (CNT) dispersions in dimethylformamide (DMF) were investigated. Electron‐deficient aromatics interact strongly with CNTs, causing increased agglomeration and sedimentation. Conversely, electron‐donating aromatics stabilize CNT dispersions in DMF. Polymers with electron‐deficient aromatics, such as polydinitrostyrene (PDNS), exhibit a concentration‐dependent effect: low concentrations lead to stabilization of dispersions, while higher concentrations lead to sedimentation. This suggests that such polymers can enhance attraction between the matrix of CNT‐reinforced polymers as well as stabilize the dispersed CNTs. Polycarbonate, modified with polydinitrocarbonate (PDNC) and reinforced with CNTs showed improved mechanical properties. The addition of 6 wt.% CNTs and 6 wt.% PDNC resulted in a notable improvement with a 22% increase in tensile strength, a 29% increase in flexural strength, a 39% increase in Young's modulus and a 47% increase in flexural modulus. This enhancement resulted in an overall mechanical performance comparable to the high‐performance polymer polyetherimide. However, there must be noted, that the addition of PDNC increases the CNT particle size, which can negatively affect mechanical properties. The results highlight the additive's dual role in enhancing adhesive interactions while potentially increasing CNT agglomerate sizes.Highlights Interactions of CNTs dispersed in DMF and various aromatics were investigated. Polydinitrocarbonate (PDNC) was synthesized as a new additive for CNT‐composites. Polycarbonate/CNT‐composites were obtained using extrusion. Test specimens with CNT contents up to 6 wt.% were obtained. Mechanical properties of polycarbonate reached the level of polyetherimide.

Comparative Evaluation of the Flexural Strength of Heat-Activated Polymethyl Methacrylate Denture Base Resin With and Without 0.2% by the Weight of Silver Nanoparticles Cured by Conventional and Autoclave Methods: An In Vitro Study.

Heat-activated polymethyl methacrylate (PMMA) is the most common and widely accepted denture base material. Two important drawbacks are the development of denture stomatitis and the high incidence of fracture of denture bases. The present study investigated the effect of adding 0.2% by weight of silver nanoparticles (AgNps) and using the autoclave method of terminal boiling on the flexural strength of heat-activated PMMA denture base resin. A total of 40 samples of heat-activated PMMA blocks were divided into four groups, with 10 samples (n = 10) in each group. Group 1 consisted of unmodified heat-activated PMMA resin (PMMA-1) polymerized by the conventional method of terminal boiling (conventional curing); Group 2 consisted of 0.2% by weight AgNPs added to heat-activated PMMA resin (PMMA-2) polymerized by conventional curing; Group 3 consisted of PMMA-1 polymerized by the autoclave method of terminal boiling (autoclave curing); and Group 4 consisted of PMMA-2 polymerized by autoclave curing. The flexural strength was tested using a universal testing machine. Descriptive statistics were expressed as mean ± SD and median flexural strength. Kruskal-Wallis ANOVA with Mann-Whitney U post hoc test was applied to test for statistical significance between the groups. The level of significance was set at p<0.05. The results showed a statistically significant reduction in flexural strength in Group 2 compared to Group 1. The samples from Group 4 showed a statistically significant increase in flexural strength compared to Group 2. The Group 4 denture base had the highest flexural strength (115.72 ± 7.27 MPa) among the four groups, followed by Group 3 (104.16 ± 4.85 MPa). The Group 1 samples gave a flexural strength of 101.45 ± 3.13 MPa, and Group 2 gave the lowest flexural strength (85.98 ± 3.49 MPa) among the four groups tested. The reduction in flexural strength of the heat-activated PMMA denture base after adding 0.2% by weight of AgNP as an antifungal agent was a major concern among manufacturers of commercially available denture base materials. It was proved in the present study that employing the autoclave curing method of terminal boiling for the polymerization of 0.2% by weight of AgNp-added heat-activated PMMA denture base resulted in a significantly higher flexural strength compared to the conventional curing method of terminal boiling for polymerization. Unmodified heat-activated PMMA gave higher flexural strength values when polymerized by autoclave curing compared to the conventional curing method of terminal boiling.