Unfilled Samples Research Articles

Mechanical and ballistic performance of individual and synergistic filler reinforced glass fiber epoxy composites

AbstractThis study examines the influence of individual (Graphene) and synergistic fillers (Graphene + Boron Carbide (B4C)) on the mechanical and ballistic performance of glass fiber epoxy‐reinforced composites (GFERCs). The different filler‐reinforced GFERCs were processed using the compression molding technique and cut as per testing standards. The results showed that the sample GF3 which had both the graphene and B4C filler together had significantly enhanced the tensile, flexural, hardness, and impact properties. The properties showed an improvement of 23.3%, 34%, 7%, and 13%, respectively when compared with the unfilled GF1 sample. The ballistic test results also revealed this synergistically filled GF3 sample had the least back‐face signature (BFS) value of 23.5 mm after impact. Fractographic studies showed that the synergistic effect of graphene and B4C also improved the bonding between the epoxy resin and glass fiber. The high toughness required for energy absorption is provided by matrix hardening, strong interfacial bonding, and fiber pullouts. Mainly the hard strike face created by the B4C particles and the energy transfer provided by the graphene particles proved pivotal in ensuring energy dissipation in the composite. Finally, it was observed that the synergistic fillers played the most important role in improving the performance of GFERCs by enhancing the energy dissipation mechanisms.Highlights Multiple fillers (Graphene+B4C) enhanced the mechanical and ballistic properties. Synergistic toughening provided by the B4C and graphene particles. Hybrid fillers exhibited strong interfacial bonding.

Dynamic mechanical analysis of alginate/gellan hydrogels under controlled conditions relevant to environmentally sensitive applications.

Hydrogels are natural/synthetic polymer-based materials with a large percentage of water content, usually above 80%, and are suitable for many application fields such as wearable sensors, biomedicine, cosmetics, agriculture, etc. However, their performance is susceptible to environmental changes in temperature, relative humidity, and mechanical deformation due to their aqueous and soft nature. We investigate the mechanical response of both filled and unfilled alginate/gellan hydrogels using a combined axial-torsional rheometric approach with cylindrical samples of large length/diameter ratio under controlled temperature and relative humidity. Dynamic Mechanical Analysis (DMA) is performed on the same specimen in both torsion and extension under identical experimental conditions. This rheometric approach ensures consistent initial and boundary conditions, which are essential for a reliable estimation of viscoelastic moduli G* and E*, and their dependence on temperature, frequency, and relative humidity. Our findings indicate that humidity critically affects the mechanical response of the material due to sample volume shrinkage, necessitating corrections to the viscoelastic moduli. We also find temperature plays a role only at low/medium relative humidity values. The inclusion of fillers leads to a modest increase in the elasticity of the hydrogel, probably due to restricted water diffusion out of the sample. In connection with the latest, unfilled samples in breaking tests present only slippage due to twist-induced surface water excess, opposite to breakage events shown by filled samples, probably linked to restricted water diffusion.

Effect of Butadiene Rubber Crystallization on Low-Temperature Properties of Butadiene/Silicone Rubber Blends with Potential for Mars Applications

This study explores the impact of butadiene rubber (BR) crystallization on the low-temperature properties of butadiene/silicone (VMQ) rubber blends (BR/VMQ) designed for Martian applications. Two types of BR, semi-crystalline high-cis Buna CB24 and amorphous Buna CB550, were blended with VMQ, and their mechanical and thermal properties were evaluated. Kinetics of vulcanization, static mechanical properties, dynamical mechanical analysis, thermal shrinkage, and differential scanning calorimetry were utilized. The research demonstrates that the semi-crystalline BR improves mechanical properties but induces greater shrinkage at low temperatures. Conversely, using amorphous BR provided more consistent mechanical properties across the Martian temperature range and reduced material shrink by 6.71% for samples with carbon black, by 8.36% for samples with silica, and by 11.63% for unfilled samples. Future research will be required to evaluate the impact of volume change on the sealing properties of the BR/VMQ blends.

Improving the acoustic performance of flexible polyurethane foam using biochar modified by (3-aminopropyl)trimethoxysilane coupling agent.

This study aims to investigate the potential of integrating natural biochar (BC) derived from eggshell waste into flexible polyurethane (FPU) foam to enhance its mechanical and acoustic performance. The study explores the impact of incorporating BC at various weight ratios (0.1, 0.3, 0.5, and 0.7wt. %) on the properties of the FPU foam. Additionally, the effects of modifying the BC with (3-aminopropyl)trimethoxysilane (APTMS) at different ratios (10, 20, and 30wt. %) and the influence of diverse particle sizes of BC on the thermal, mechanical, and acoustic characteristics of the FPU composite are investigated. The functional groups, morphology, and elemental composition of the developed FPU composites are analyzed using Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) techniques. Characteristics such as density, gel fraction, and porosity were also assessed. The results reveal that the density of FPU foam increased by 4.32% and 7.83% while the porosity decreased to 50.22% and 47.05% with the addition of 0.1 wt. % of unmodified BC and modified BC with 20wt. % APTMS, respectively, compared to unfilled FPU. Additionally, the gel fraction of the FPU matrix increases by 1.91% and 3.55% with the inclusion of 0.1 wt. % unmodified BC and modified BC with 20 wt. % APTMS, respectively. Furthermore, TGA analysis revealed that all FPU composites demonstrate improved thermal stability compared to unfilled FPU, reaching a peak value of 312.17°C for the FPU sample incorporating BC modified with 20 wt. % APTMS. Compression strength increased with 0.1wt. % untreated BC but decreased at higher concentrations. Modifying BC with 20% APTMS resulted in an 8.23% increase in compressive strength compared to unfilled FPU. Acoustic analysis showed that the addition of BC improved absorption, and modified BC enhanced absorption characteristics of FPU, reaching Class D with a 20 mm thickness. BC modified with APTMS further improved acoustic properties compared to the unfilled FPU sample (Class E), with 20% modification showing the best results. These composites present promising materials for sound absorption applications and address environmental issues related to eggshell waste.

Effects of neat and silver coated fly ash cenospheres on the properties of styrene-butadiene-styrene block copolymer composites obtained by a solution mixing method

Utilization of industrial by-products to develop novel value-added materials while mitigating their environmental impact is a crucial issue. Fly ash (FA) microparticles are a common component of power plant waste. This work aims to investigate the impact of varying concentrations of neat/silver-coated FA on the morphology and thermal properties of styrene-butadiene-styrene/FA composites. Composite materials based on styrene-butadiene styrene triblock copolymer (SBS) with various volume fractions of as-received and silver-coated FA were prepared using a solution mixing method. Silver-coated cenosphere particles were prepared using an electroless plating method. Scanning electron microscopy and optical microscopy showed that the solution mixing method obtains composite materials characterized by uniform dispersion of filler without large particle aggregates and predominantly unbroken cenospheres. The tensile strength of the composite with 10% of both as-received and silver-coated fly ash remains at the level of the unfilled SBS sample. However, at higher filler concentrations (20% and 30%), a decrease in strength by 27% and 42% respectively is observed, possibly due to the agglomeration of FA, which leads to a poorer interface and dispersion at higher filler weights. Additionally, thermal analysis in an oxygen atmosphere showed that the introduction of both as-received and metallized cenospheres in the same quantity increased the thermal stability of the tested composition. The temperatures at 5% mass loss of SBS/FA composites were on average 70°C higher than those of the original SBS.

3D-printed nanocomposites filled with untreated and surface-modified PTFE powders treated by a Na-naphthalene-system

This study focuses on the mechanical properties of DLP/LCD-type 3D-printed nanocomposites comprised of polyester acrylate resin with DPGDA reactive diluent filled with untreated PTFE and surface-modified PTFE powders by the Na-Naphtalenide system. To obtain the nanocomposites, untreated and surface-modified PTFE powders were incorporated into the resin systems at loading ratios ranging from 1% to 6%. The X-ray photoelectron spectroscopy (XPS) data following the Na-naphthalene system treatment demonstrated the existence of functional groups such as OH, carbonyl, and C=C unsaturation groups on the surface of the untreated PTFE powders. The study showed improvements for the nanocomposites obtained through a DLP/LCD type 3D printer up to a certain ratio in terms of tensile strength, Young's modulus, Izod impact resistance, and Shore D hardness values. Evaluating the promising samples, the nanocomposites with surface-modified PTFE powders of 2% and 1% showed increases of 5.1% and 7.6% in ultimate tensile strength and Izod impact resistance compared to the unfilled polyester acrylate sample. On the other hand, the nanocomposite with untreated PTFE powders of 1% only showed increases of 2.4% and 3.2% in ultimate tensile strength and Izod impact resistance. Moreover, Young’s modulus showed less decrease for surface-modified PTFE-filled nanocomposites.

Optimization Course of Titanium Nitride Nanofiller Loading in High-Density Polyethylene: Interpretation of Reinforcement Effects and Performance in Material Extrusion 3D Printing.

In this study, titanium nitride (TiN) was selected as an additive to a high-density polyethylene (HDPE) matrix material, and four different nanocomposites were created with TiN loadings of 2.0-8.0 wt. % and a 2 wt. % increase step between them. The mixtures were made, followed by the fabrication of the respective filaments (through a thermomechanical extrusion process) and 3D-printed specimens (using the material extrusion (MEX) technique). The manufactured specimens were subjected to mechanical, thermal, rheological, structural, and morphological testing. Their results were compared with those obtained after conducting the same assessments on unfilled HDPE samples, which were used as the control samples. The mechanical response of the samples improved when correlated with that of the unfilled HDPE. The tensile strength improved by 24.3%, and the flexural strength improved by 26.5% (composite with 6.0 wt. % TiN content). The dimensional deviation and porosity of the samples were assessed with micro-computed tomography and indicated great results for porosity improvement, achieved with 6.0 wt. % TiN content in the composite. TiN has proven to be an effective filler for HDPE polymers, enabling the manufacture of parts with improved mechanical properties and quality.

Effect of multi-walled carbon nanotubes reinforcement on self-healing performance of natural rubber

Abstract This work is motivated by the desire to restore the quality of rubber-based product properties with the intention of prolonging the service life period, thus helping create a sustainable environment by proposing effective rubber waste management. This study experimentally investigated an intrinsically self-healing zinc thiolate grafted natural rubber (NRZT) compound filled with multi-walled carbon nanotubes (MWCNT) to assess its influence on mechanical properties and self-healing performance. The MWCNT loading varied to 0, 2, 4, 6, and 8 phr. The Equilibrium swelling test was used to quantify the amount of ionic and covalent crosslinks formed. Fourier Transform Infrared (FTIR) spectra were used to detect the presence of MWCNT in the compound. The mechanical properties computed by the tensile and tear strength tests showed that the incorporation of MWCNT increased both properties up to three and twofold, respectively. However, as expected, the elongation at break (Eb) value was reduced. The unfilled sample showed that it can heal up to ∼98 %, measured from the tensile strength. However, the healing efficiency obtained from tensile strength reduces to ∼88 % by incorporating 2 phr MWCNT. The Eb and its self-healing efficiency gradually decreased as the MWCNT amount increased. All samples showed outstanding properties under the tearing mode, where the healed samples produced higher tear strength (>100 % healing) than the initial value. Scanning Electron Microscopy (SEM) micrographs revealed a noticeable gap along the healed cut line with increased MWCNT numbers, possibly due to the lower reaction between polymerized zinc thiolate (PZTh) radicals with zinc thiolate (ZT) and rubber molecules. The work aims to investigate the influence of MWCNTs on the mechanical and healing performance of self-healing NR composites by comparing them to their unfilled sample.

Tensile Strength and Mode I Fracture Toughness of Polymer Concretes Enhanced with Glass Fibers and Metal Chips.

This study experimentally investigates the influence of metal chips and glass fibers on the mode I fracture toughness, energy absorption, and tensile strength of polymer concretes (PCs) manufactured by waste aggregates. A substantial portion of the materials employed in manufacturing and enhancing the tested polymer concrete are sourced from waste material. To achieve this, semi-circular bend (SCB) samples were fabricated, both with and without a central crack, to analyze the strength and fracture behavior of the composite specimens. The specimens incorporated varying weight percentages comprising 50 wt% coarse mineral aggregate, 25 wt% fine mineral aggregate, and 25 wt% epoxy resin. Metal chips and glass fibers were introduced at 2, 4, and 8 wt% of the PC material to enhance its mechanical response. Subsequently, the specimens underwent 3-point bending tests to obtain tensile strength, mode I fracture toughness, and energy absorption up to failure. The findings revealed that adding 4% brass chips along with 4% glass fibers significantly enhanced energy absorption (by a factor of 3.8). However, using 4% glass fibers alone improved it even more (by a factor of 10.5). According to the results, glass fibers have a greater impact than brass chips. Introducing 8% glass fibers enhanced the fracture energy by 92%. However, in unfilled samples, aggregate fracture and separation hindered crack propagation, and filled samples presented added barriers, resulting in multiple-site cracking.

Fabrication and Mechanical Testing of Glass Fiber Reinforced Epoxy Matrix Composites Modified with Powdered Metallic Fillers

Composite materials made up of polymer matrix reinforced with synthetic fibers have gained popularity of late owing to their enhanced mechanical properties. However, very little work is reported to date on metals being used as filler material. Research gaps were obtained pertaining to the use of metallic fillers in synthetic fiber reinforced polymer composites. This paper demonstrates an attempt to fabricate composites made of Epoxy polymer matrix and E-glass fiber reinforcement with Mild Steel in its powdered form as fillers. Composites are prepared in varying weight percentages of the filler in the order of 2 wt. %, 4 wt. % and 6 wt. %. Hand layup method is employed for fabricating these composites which are later subjected to compression. Further, the samples are machined according to ASTM D3039 standard for tensile test and ASTM D256 standard for Izod impact test. Hardness test is also performed using a Shore D Durometer and these properties are compared with the unfilled samples. The results indicated that the weight percentage of the filler clearly influenced the mechanical properties of the developed composites. This study also revealed that the hardness and tensile strength of these composites improved with the incorporation of fillers up to 2 wt. % whereas, the impact strength improved up to 4 wt. %. Thereafter, there was a decline in their impact and tensile properties. However, hardness marginally increased beyond 4 wt. %. This area is open for research with regard to their usability under tribological, high temperature or magnetic conditions.

Comparative Investigation of Nano-Sized Silica and Micrometer-Sized Calcium Carbonate on Structure and Properties of Natural Rubber Composites.

Fillers have been widely used in natural rubber (NR) products. They are introduced to serve as a strategy for modifying the final properties of NR vulcanizates. Silica and calcium carbonate (CaCO3) are among the fillers of choice when the color of the products is concerned. In this case, a special focus was to compare the vulcanizing efficiency of NR filled with two different filler types, namely nano-sized silica and micrometer-sized CaCO3. This study focused on the effects of the loading level (10-50 parts per hundred parts of rubber, phr) on the final properties and structural changes of NR composites. The results indicated that increased filler loading led to higher curing torques and stiffness of the rubber composites irrespective of the type of filler used. The better filler dispersion was achieved in composites filled with CaCO3 which is responsible for less polarity of CaCO3 compared to silica. Good filler distribution enhanced filler-matrix interactions, improving swelling resistance and total crosslink density, and delaying stress relaxation. The modulus and tensile strength of both composites also improved over the content of fillers. The CaCO3-filled composites reached their maximum tensile strength at 40 phr, exceeding, by roughly 88%, the strength of an unfilled sample. Conversely, the maximum tensile strength of silica-filled NR was at 20 phr and was only slightly higher than that of its unfilled counterpart. This discrepancy was ascribed to the stronger rubber-filler interactions in cases with CaCO3 filler. Effective rubber-filler interactions improved strain-induced crystallization, increasing crystallinity during stretching and reducing the strain at which crystallization begins. In contrast, large silica aggregates with poor dispersion reduced the overall crosslink density, and degraded the thermomechanical properties, tensile properties, and strain-induced crystallization ability of the NR. The results clearly indicate that CaCO3 should be favored over silica as a filler in the production of some rubber products where high performance was not the main characteristic.

INFLUENCE OF FILLERS ON THE STRUCTURE AND PROPERTIES OF POLYMER MATRIX

Purpose. Enhancement of the mechanical properties of the polymer matrix through the incorporation of finely dispersed fillers, namely aluminum oxide and talc, as potential modifiers.
 Research methods. Research was conducted on polymer specimens subjected to tensile testing according to DSTU EN ISO 527-5:2018. The tests were performed using a URM-5 tensile testing machine with a maximum force of 50 kN. Metallographic analysis was carried out using a KEYENCE VHX microscope at magnifications of 50 and 500. The microstructure of the polymer matrix was assessed through etching-free procedures.
 Results. The study demonstrates that the incorporation of finely dispersed aluminum oxide particles increased the strength parameter from 4.69 MPa to 13.07 MPa, as compared to the unfilled sample. Additionally, it was observed that the introduction of finely dispersed talc particles at a concentration of 0.75 % by mass led to an enhancement in strength values from 4.69 MPa to 12.74 MPa, in comparison to the unfilled sample.
 Scientific novelty. A polymer matrix with enhanced mechanical properties was achieved through the addition of fillers acting as modifiers. The optimal concentration of aluminum oxide and talc additives was determined. By comparing the results with previous studies involving aluminum oxide and talc at various concentrations in different types of polymer matrices, it can be concluded that the investigated concentrations of modifiers with epoxy resin ED-20 led to the production of a polymer composite with superior mechanical characteristics. The obtained results underscore the significant potential of aluminum oxide and talc as effective modifiers for improving the strength and other crucial properties of composite materials.
 Practical value. The obtained results highlight the significant potential of utilizing aluminum oxide and talc as modifiers for polymer matrices to enhance their mechanical characteristics. From a practical standpoint, the use of these fillers can exert a substantial impact on the development of new composite materials with improved properties, finding application in composite reinforcement production. Considering the heightened strength and resilience of the resulting materials, these composites can be effectively employed to create lighter and stronger structures in construction and other industries. Additionally, their application may lead to reduced repair and maintenance costs due to increased durability and resistance to mechanical loads. Thus, the implementation of the obtained results could have a substantial influence on the practice of composite material manufacturing, ensuring the creation of products with enhanced characteristics for various applications.

Multifunctionality of MWCNT and TiC hybrid filler silicone composite for energy harvesting and strain sensing

AbstractThe flexible silicone elastomer‐conductive composite was developed with enhanced energy harvesting and strain sensing. A hybrid nanofiller system with multi‐walled carbon nanotubes (MWCNTs) and titanium (IV) carbide (TiC) was used as reinforcing agents for the elastomer. The 4 MWCNT +5 TiC composite has 1.34 MPa tensile strength, 136.85% higher than unfilled silicone rubber (SR) matrix. The unfilled sample has a 1.558 MPa compressive modulus, while 4 MWCNT +5 TiC has 3.87 MPa. The machine and finger presses were utilized to test the energy harvesting of the composite. With greater cyclic stability, the 4 MWCNT +5 TiC sample performed exceptionally well in the machine press in the output voltage range of around 120 mV. Among the thumb presses, 2 MWCNT +5 TiC yielded the best results, with a voltage of about 100 mV. The 3 MWCNT +5 TiC sample produced 9044% more energy than the single filler 3 phr MWCNT sample from our previous work. Higher MWCNT content enhanced composite stiffness, making finger pressing harder and decreasing energy output. The strain sensing test on the 4 MWCNT +5 TiC composite showed high gauge factors (GF = 7.532 and 23.944) and good linearity (R2 = 0.909 and 0.939) over a strain range of Δε = 0%–14% and 14%–22%. Silicone composites' mechanical, energy harvesting, and strain sensing performance improved greatly with the MWCNT and TiC hybrid fillers. These composites could be used in self‐powered wearable electronics, machine or structural deformation monitoring, and human motion sensing.Highlights A stretchable device was developed with improved energy harvesting and strain sensing. Rubber composites were fabricated from MWCNTs, TiC hybrid fillers, and SR matrix. The energy harvesting was 9044% higher for hybrid filler compared to MWCNT as the only filler. Robust strain sensing properties with a gauge factor of 23.9, linearity of 0.91, and relaxation time of 0.1 s. The final composites are useful for self‐powered wearable electronics, health monitoring, and human motion sensing.

Effect of 3D-Printed Honeycomb Core on Compressive Property of Hybrid Energy Absorbers: Experimental Testing and Optimization Analysis.

This paper presents an innovative method of constructing energy absorbers, whose primary function is to effectively transform kinetic energy into strain energy in events with high deformation rates. Hybrid specimens are proposed considering thin-walled windowed metallic tubes filled with 3D-printed hexagonal honeycombs made of PET-G and ABS thermoplastic. The patterned windows dimensions vary from 20 × 20, 20 × 30, 15 × 20 and 15 × 30 mm2. Although using polymers in engineering and thin-walled sections is not new, their combination has not been explored in this type of structure designed to withstand impacts. Specimens resist out-of-plane quasi-static axial loading, and test results are analyzed, demonstrating that polymer core gives the samples better performance parameters than unfilled samples regarding energy absorption (Ea), load rate (LR), and structural effectiveness (η). An optimization procedure using specialized software was applied to evaluate experimental results, which led to identifying the optimal window geometry (16.4 × 20 mm2, in case) and polymer to be used (ABS). The optimized sample was constructed and tested for axial compression to validate the optimization outcomes. The results reveal that the optimal sample performed similarly to the estimated parameters, making this geometry the best choice under the test conditions.

Effect of nanosilica on low‐velocity impact and compression after impact properties of continuous carbon fiber‐reinforced epoxy composites manufactured by 3D printing

AbstractTo improve the low‐velocity impact (LVI) and compression after impact (CAI) properties of three‐dimensional (3D)‐printed continuous carbon fiber‐reinforced epoxy composites (CFRC), nanosilica (NS) was incorporated into these composites. NS (0.5 and 1 wt%) was dispersed in a liquid epoxy matrix by ultrasonication and mechanical stirring before mixing in a planetary mixer. The addition of NS up to 1 wt% did not render any processing barrier during the extrusion followed by the automated tape placement (ATP) method, adopted in this study. The resulting “hybrid” laminates showed void content <1% and had minimal internal defects as ensured by nondestructive technique (C‐scan) and scanning electron microscopy. The neat and NS‐loaded CFRPs were subjected to an impact energy of 6 J mm−1. The rebound energy increased by ~36% with the addition of 1 wt% NS as compared to unfilled samples, obtained from the LVI test. The CAI results suggest that with 1 wt% NS the residual compressive strength increased by ~13% in comparison with the neat CFRP laminates. After impact, the damage area was reduced significantly, that is, ~62% with the addition of 1 wt% NS in comparison with the neat CFRP laminates.

Experimental Study on Acoustic Emission Characteristics of Uniaxial Compression of MICP-Filled Sandstone.

Rock masses are inherently heterogeneous, with numerous fractures that significantly affect their mechanical properties, fracture characteristics, and acoustic emission features due to the interactions between fractures or between fractures and the rock mass. Microbially induced calcite precipitation (MICP) technology, as an emerging non-destructive biological grouting reinforcement method, can repair fractured rock masses and alter their internal conditions. To investigate the mechanical properties, failure process evolution, and MICP repair effects of sandstone before and after repair, uniaxial compression tests were conducted on prefabricated, fractured (0.7-2.0 mm width) filled and unfilled rock samples, with acoustic emission monitoring throughout the process. Acoustic emission signal characteristics of the rock samples under stress were comparatively analyzed, determining the rock failure process and the microscopic failure types at compression-density stages, elastic stages, and destruction stages. The results show that the properties of the filled specimens improved, the failure process was mitigated, and the final failure stage was dominated by tension signals, accounting for over 60% of the total. The filling effect was better than 1.5-2.0 mm when the fracture width was 0.7-1.0 mm. The study deeply reveals the evolutionary process of compressive failure of the two types of rocks under different fracture widths, and by correlating the acoustic emission parameters with the stress-strain process, it provides a theoretical basis for repairing rock fractures using microbial engineering technology and offers experimental evidence and possible directions for the improvement and optimization of MICP technology.

Potential Utilization of Ground Eggshells as a Biofiller for Natural Rubber Biocomposites.

The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPTS), were used to increase the activity of ground eggshells in the elastomer matrix and to ameliorate the cure characteristics and properties of NR biocomposites. The influence of ground eggshells, CTAB, ILs, and silanes on the crosslink density, mechanical properties, and thermal stability of NR vulcanizates and their resistance to prolonged thermo-oxidation were explored. The amount of eggshells affected the curing characteristics and crosslink density of the rubber composites and therefore their tensile properties. Vulcanizates filled with eggshells demonstrated higher crosslink density than the unfilled sample by approximately 30%, whereas CTAB and ILs increased the crosslink density by 40-60% compared to the benchmark. Owing to the enhanced crosslink density and uniform dispersion of ground eggshells, vulcanizates containing CTAB and ILs exhibited tensile strength improved by approximately 20% compared to those without these additives. Moreover, the hardness of these vulcanizates was increased by 35-42%. Application of both the biofiller and the tested additives did not significantly affect the thermal stability of cured NR compared to the unfilled benchmark. Most importantly, the eggshell-filled vulcanizates showed improved resistance to thermo-oxidative aging compared to the unfilled NR.

Flexible polyurethane foams reinforced with graphene and boron nitride nanofillers

AbstractThe effect of three types of nanofillers on the physical, mechanical, and thermal properties of flexible polyurethane foams (FPUF) was studied. FPUF with nanofillers are of interest to the automotive industry due to their potential for enhancing compression properties and enabling sustainable foams. Holey and wrinkled flash graphene, and untreated and silane coated boron nitride were tested as fillers up to 0.1 wt% loading level. Flash graphene filled FPUF showed significant improvement in compressive properties, especially at the 0.025 wt% loading level, showing a 22% increase in compressive force deflection at 25% strain and a 17% increase at 50% strain compared to the unfilled control foam sample. Boron nitride nanoparticles, treated and untreated, were shown to be an effective means of reducing wet compression set properties, addressing a key area of concern for sustainable polyols. Wet compression set was reduced by 20%–30% for most boron nitride foams compared to their unfilled control samples. Boron nitride may enable implementation of more sustainable polyols in automotive FPUF. Nanofillers did not significantly improve thermal stability of FPUF.

Filler loading effect of Al2O3/TiO2 nanoparticles on physical and mechanical characteristics of dental base composite (PMMA)

Although dental raw PMMA has unique features such as its ease and aesthetic fabrication, low cost, and a favorable physical and mechanical properties. Nonetheless, these are insufficient to provide the necessary wear resistance, hardness, and mechanical strength. Wherefore, dental applications are less suited to pure PMMA. The present article focuses on using hybrid filler of Al2O3 and TiO2 NPs with various loading content to evaluate and minimize the wear rate. The tribological characteristics of the nanocomposites were evaluated by a reciprocating tribometer. And the wear resistance was assessed with 3D microscopic images and SEM. The PMMA nanocomposite samples containing 0.4%, 0.8%, 1.2%, 1.6%, and 2.0 wt% filling content of hybrid Al2O3 and TiO2 NPs to compared to an unfilled sample, were fabricated. The hardness of the nanocomposites was found using Shore D durometer. The XRD, density, modulus of elasticity, compressive yield strength, and fracture toughness were performed experimentally. Results showed that the incorporation of hybrid of Al2O3 and TiO2 NPs showed a good enhancement in the mechanical and tribological properties of PMMA composites. Experimental results illustrated that, the nanocomposites with 0.8 wt% of filler content recorded a distinct performance among other filler amounts. COF and Wear rate are reduced up to 20% and 28%, respectively.

A pre-screening study of honeycomb sandwich structure filled with green materials for noise reduction

To maximize the potential of the lightweight and high structural performance of composite and to integrate noise reduction function at the same time, the paper reports a noise reduction composite based on honeycomb sandwich structure by filling the honeycomb with different plant and synthetic fibers and utilizing micro-perforated plate (MPP) as the face sheet. The sound-absorbing effect of these structural samples was characterized and compared. The porosity and density of the filler material and the fiber cloth configuration were calculated and measured. The results show that the filling in the honeycomb significantly increases the sound absorption coefficient and widens the sound absorption band. Meanwhile, the MPP parameter determines the peak frequency of the sound absorption curve. Especially in the range of 125 Hz-4000 Hz, cotton and polyester filling provide the highest average sound absorption coefficients of 0.532 and 0.483 among the five materials pre-studied, while the absorption coefficient of the unfilled sample is about 0.15. The results reveal that a filled honeycomb structure with an MPP face sheet can reduce noise while maintaining mechanical properties. The noise-reduction function-integrated structures can potentially influence construction, transportation, and infrastructure as lightweight and space-saving solutions.