Poly Methyl Methacrylate Samples Research Articles

A Bayesian approach to estimate flame spread model parameters over the cylindrical PMMA samples under various gravity conditions

The flammability limit of cylindrical polymethyl-methacrylate (PMMA) samples in an opposed-flow was observed experimentally under various gravity levels at 1G or more utilizing a centrifuge. Flame spread on the sample was observed, and the limiting oxygen concentration (LOC) was measured in various opposed-flow velocities ranging from 5 to 30 cm/s. Two rotating radii of the centrifuge were tested to assess the effects of Coriolis force on the LOC. A scale analysis model, based on an energy balance equation, was evaluated for thermally thick cylindrical samples. The buoyancy-induced flow was modeled in the analytical model. Model parameters were evaluated with a Bayesian approach: The Metropolis Hasting (a Markov Chain Monte Carlo) method. The results indicated that flames were tilted by the Coriolis force when the oxygen concentration was sufficiently rich from the LOC in 4G. However, the effects were negligible under the oxygen concentration conditions near LOC. No significant difference in the LOC was also observed even when the rotating radius of the centrifuge changed. At 1G or higher, the LOC approached to a certain value asymptotically with decreasing the opposed-flow velocity. The LOC also increased with increasing the gravity level and sample diameter. The measured LOCs were used to sample model parameters using MCMC methods. Consequently, a suitable fitting curve of the model to the experimental LOC was obtained. Using the predicted model parameters, the LOC under microgravity, Moon, and Mars conditions were predicted as a function of the opposed-flow velocity. In microgravity, the LOC increased greatly with decreasing the forced flow velocity (the radiative extinction regime), and the minimum LOC (MLOC) was recognized. On Moon, the credible interval of LOC was rather large in the low-velocity region, and the MLOC was also recognized. Moreover, it was possible that the cylindrical PMMA sample exhibited the highest flammability not under microgravity but a partial gravity condition.Novelty and SignificanceFrom observing the limiting oxygen concentration of the flammability limit for cylindrical polymethyl-methacrylate (PMMA) samples in opposed-flows under various gravity conditions, we developed a model of limiting oxygen concentration (LOC) for thick cylindrical samples with the buoyancy induced flow was developed, and we estimated difficult-to-predict parameters using Bayesian statistical methods. Using this model, we can estimate the flammability limits under various gravity conditions of manned space exploration, including Moon and Mars. In addition, the present study shows that the minimum limiting oxygen concentration (MLOC) is the lowest in partial gravity. These results open a new research field for partial gravity combustions, apart from the normal gravity and microgravity and contribute to the understanding on the fire safety on manned space explorations to Moon and Mars.

APPLICATION OF OPTIMIZATION METHOD IN MULTIDIMENSIONAL SPACE TO THE PROBLEM OF DETERMINING FULLERENE CONCENTRATION IN FULLERENE-CONTAINING MIXTURE

The work proposes a method for the quantitative processing of experimental data from ultraviolet spectroscopy of substituted fullerene mixtures, taking into account errors in the experimental data. This task can be written as a system of Vierordt equations (a system of linear equations). The coefficients of the system are the extinction coefficients of individual substituted fullerenes, which are difficult to measure accurately. Therefore, the mathematical model of the problem contains significant errors that affect the reliability and stability of the solution. To minimize the influence of errors, the work [1] proposes a method, which involves reducing the considered system of linear equations to a linear programming problem. This study generalizes the work [1] and proposes to use linear programming problems to find interval values of correction factors for parameters containing errors. Since decreasing the discrepancy reduces the solution error only for well-conditioned coefficient matrices, the values of correction coefficients that minimize the condition number of the coefficient matrix are found in the obtained intervals. The found correction values allowed to significantly improve the conditionality of the system coefficient matrix and obtain a more accurate solution. By using the refined extinction coefficients, the distribution of molar fractions of fullerene fragments and fullerene-containing compounds in the mixture of products formed by the attachment of cyanoisopropyl radicals was obtained, as well as the distribution of molar fractions of fullerene fragments of different degrees of substitution for samples of fullerene-containing polymethyl methacrylate and the distribution of molar fractions of fullerene fragments of different degrees of substitution for samples of fullerene-containing polystyrene. The results are correct and consistent with the theory, both for low-molecular-weight mixtures and for fullerene-containing polymers.

Visualization experiments and numerical simulation on the growth of fracture height in bedding-rich reservoirs

The development of shale bedding and differences in properties have significant effects on the growth of the fracture height. To investigate the impact mechanism of bedding on the fracture growth height, the visualization fracturing experiments based on polymethylmethacrylate (PMMA) samples were performed to investigate the impact of the injection rates, viscosity and temporary plugging parameters on the growth pattern of hydraulic fractures. Furthermore, the solid–fluid-damage fracturing coupled model considering the vertical distribution of bedding was constructed by the continuous-discontinuous element method, and the impact of key formation parameters and treatment parameters were investigated. The results show that the height growth pattern of PMMA samples was affected by the flow rate and fluid viscosity. The fracture can cross the bedding at high-viscosity fluid. But in low-viscosity fluid the fracture tends to be arrested by the bedding. And the fracture cannot cross the bedding again after In-fracture temporary plugging. The fractures vertical growth pattern mainly includes three types at various stratigraphic parameters and treatment parameters, “工” type fracture, “丰” type fracture, and “I” type fracture, respectively. For vertical stress differentials below 3 MPa or Young's modulus below 20 GPa or injection rates below 1.8 m3/min or the fluid viscosity below 5 mPa·s, the fracture will be limited within the bedding.

Influence of alumina and PMMA on mechanical properties and aging behavior of 3D printed PLA composites: A comparative study

AbstractThis study intends to investigate the mechanical, thermal, and aging behaviors of 3D‐printed PLA (polylactic acid)‐blend with 10% polymethyl methacrylate (PMMA) and 10% alumina polymer composites for biomedical applications using compressive, DSC, and DMA analysis. The experimental results revealed that aged PLA blend with alumina samples increased compressive strength by 60.1% and 37.8% during hydrolytic and enzymatic degradation, respectively, compared to aged PLA samples. Also, it was reported that the PLA blend with PMMA samples increased compressive strength by 51.1% and 24% after hydrolytic and enzymatic degradation, respectively, as compared to aged PLA samples. Furthermore, DSC analysis revealed that alumina blended samples had a higher Tg than pure PLA and PMMA blended samples. In addition, DMA investigation revealed that the Tg of aged neat PLA, PLA/PMMA, and PLA/alumina increased by 4.38%, 4.8%, and 4.6%, respectively, compared to unaged polymer composites. Additionally, PLA/alumina‐aged samples exhibited stronger aging properties than neat PLA and PLA/PMMA blended‐aged samples. It was reported that the weight loss of PLA/Alumina was lowered by 10.7% and 15.6% compared to aged PLA/PMMA samples, for hydrolytic and enzymatic aging respectively. It was found that PLA alumina has better mechanical, thermal, and degradation resistance than PLA materials.Highlights Alumina and PMMA materials were blended with PLA. Examined the aging and mechanical properties of PLA blended composites. Utilized hydrolytic and enzymatic aging for biomedical applications. Evaluated mechanical strength performance of aged and unaged samples. DSC and DMA were utlised for this research.

Comparison of the Antimicrobial Efficacy of Conventional Versus Chitosan Re-inforced Heat-Polymerized Polymethylmethacrylate Dental Material: An In Vitro Study.

Polymethylmethacrylate (PMMA) is widely used in the fabrication of dentures due to its aesthetic appeal and mechanical strength. However, PMMA's susceptibility to microbial colonization often leads to oral infections such as denture stomatitis. Enhancing the antimicrobial properties of denture materials is crucial for improving patient outcomes.Chitosan, a natural biopolymer, possesses inherent antimicrobial properties and could potentially enhance the microbial resistance of PMMA. This study has investigated thepotential of chitosan-reinforced heat-polymerized PMMA denture material to reduce microbial colonization. The aim of the study was to evaluate and assess the anti-bacterial and antifungal properties of chitosan-reinforced heat-polymerized PMMA with conventional heat-polymerized PMMA Materials and methods:Chitosan-reinforced PMMA samples were fabricated with varying chitosan concentrations (0% control, 5%, 10%, and 15% by weight). The fabrication involved mixing chitosan powder with PMMA powder, adding monomer liquid, followed by mixing, packing, and curing using the conventional heat polymerization technique. The antimicrobial efficacy was assessed in vitro using two common oral pathogens: Streptococcus mutans and Candida albicans. Blood agar plates were used for S. mutans and Sabouraud agar plates were used for C. albicans. Each sample was placed on the respective agar plates inoculated with a standardized microbial suspension and incubated at 37°C for 24 hours. The number of colony-forming units (CFUs) was counted to quantify microbial growth. Statistical analyses, including linear regression analysis, one-way ANOVA test, and Pearson correlation were performed to evaluate the relationship between chitosan concentration and antimicrobial efficacy. The p-value was calculated to determine the statistical significance of the results. The chitosan-reinforced PMMA samples showed significantly greater antimicrobial efficacy compared to the conventional PMMA samples. The CFU counts for both S. mutans and C. albicans decreased with increasing chitosan concentration. Linear regression analysis indicated a strong negative correlation between chitosan concentration and CFU counts, with Pearson correlation coefficients of -0.97 for S. mutans and -0.98 for C. albicans. ANOVA analysis revealed a statistically significant difference in antimicrobial efficacy across different chitosan concentrations (p < 0.001). Incorporating chitosan into heat-polymerized PMMA significantly enhances its antimicrobial properties against S. mutans and C. albicans. The antimicrobial efficacy improves with higher concentrations of chitosan, with the 15% chitosan-reinforced samples showing the most substantial reduction in microbial growth. These results suggest that chitosan-reinforced PMMA dentures could be a superior alternative to conventional PMMA dentures, potentially reducing denture-related infections and improving oral health outcomes for denture wearers.

Enhanced PMMA Denture Bases Using Functionalized MWCNT Fused g-C3N4 Nanocomposites

This study presents the development and analysis of a new metal-free nanocomposite that incorporates functionalized multi-walled carbon nanotubes (f-MWCNTs) with graphitic carbon nitride (g-C3N4) for reinforcing polymethyl methacrylate (PMMA) denture bases. The f-MWCNTs were integrated with g-C3N4 nanoparticles, and their structural and morphological features were examined using various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy. A mechanical blending process was employed to synthesize the nanocomposite by mixing 2 wt% of the f-MWCNT/g-C3N4 with PMMA polymer powder, followed by heat curing to form the composite material. Specimens for mechanical testing were crafted to measure flexural strength, impact resistance, compressive performance, and hardness. The findings revealed that the f-MWCNT/g-C3N4-reinforced PMMA composites outperformed standard PMMA in mechanical robustness. Surface examination of the tested samples through SEM showed distinctive dimpling and roughness, indicating a toughened fracture surface in comparison to pure PMMA and g-C3N4 samples. The study concludes that this innovative f-MWCNT/g-C3N4 composite is a promising reinforcement for PMMA denture bases, enhancing both their mechanical and physical attributes.Keywords: PMMA, functionalization, MWCNTs, Graphitic Carbide Nitride, Mechanical Properties and Denture Base

Compatibilizing and foaming of PC/PMMA composites with nano‐cellular structures in the presence of transesterification catalyst

AbstractCompatibility of polycarbonate (PC) and polymethyl methacrylate (PMMA) alloys was improved by using a transesterification catalyst (SnCl2·2H2O). Modified PC/PMMA alloys exhibit single Tg, and their initial island phase existing in the SEM were transformed into uniform surface. Besides, the transmittance of the modified alloys was increased from original 40% to 85%. Moreover, PC/PMMA alloys and PC foams with micro‐cellular and nano‐cellular structures were prepared by solid‐state CO2 foaming in the presence of transesterification catalyst. Distinctively, there are obvious nano‐cellular structures existing in the PC samples, but no related nanostructures were found in PMMA samples, after treated by same amount of catalyst and foaming process for pure PC and PMMA matrix. Furthermore, the effects of foaming temperature and segment structure on their foaming behavior were also studied. Additionally, a uniaxial stress experiment was conducted at a specific temperature to simulate the biaxial stress during the foaming process for discovering the mechanism of nanopore formation. Therefore, the concept of nano‐cellular structures will point out a direction for the development of high‐performance, heat insulation PC materials of the next generation.Highlights Transesterification catalysts enhanced compatibility between PC and PMMA. Nanopore structures were successfully constructed in PC foams. Segment stretching was the main reason for the formation of nanopores.

Assessing the Color Stability of Polymethyl Methacrylate (PMMA) Dental Restorations Polished With a Novel Polishing Agent Derived From Pulverized Old Alginate Impressions.

Interim restorations are essential in restorative dentistry, serving as temporary solutions until permanent restorations can be placed. Polymethyl methacrylate (PMMA) is a promising solution for customizing teeth for removable dentures to match the exact requirements of patients. The color stability of these restorations is critical for patient satisfaction. PMMAis a widely used material for interim restorations due to its favorable properties. The study compares the color stability of PMMA interim restorations polished using traditional pumice versus Algishine, a novel polishing agent derived from pulverized old alginate impressions. The 3-D design software Geomagic Design X (3D Systems, Rock Hill, CA) created a standard tessellation language file of 2-cm radius circles. Sixty PMMA samples were milled and divided into two groups of 30 each. Group A samples were polished using pumice, while group B samples were polished with Algishine. Baseline color measurements were taken using a spectrophotometer (VITA Easyshade V, VITA Zahnfabrik, Bad Säckingen, Germany). The samples were then subjected to staining with coffee, tea, and red wine solutions for 30 days, simulating oral conditions. Post-staining color measurements were taken, and color changes (ΔE) were calculated at the seven-day (t1) and one-month (t2) mark. The Shapiro-Wilk test assessed normality, followed by a two-way ANOVA testto compare color change values at different time points. At t1 (seven days), there were no significant differences between groups A and B in the coffee and tea staining groups. However, significant differences were observed in red wine staining, with group B exhibiting lower ΔE values (0.14 ± 0.067) compared to group A (0.38 ± 0.076) (p < 0.01). At t2 (30 days), significant differences were noted in all staining groups. Group B consistently showed lower ΔE values: coffee (0.125 ± 0.084 vs. 0.236 ± 0.015, p < 0.01), tea (0.254 ± 0.087 vs. 0.391 ± 0.015, p < 0.01), and red wine (1.174 ± 0.045 vs. 1.309 ± 0.074, p < 0.01), indicating superior resistance to staining compared to group A. The results suggest that Algishine is more effective than pumice in maintaining the color stability of PMMA interim restorations. The novel polishing agent derived from old alginate impressions enhances esthetic longevity and provides an eco-friendly solution for recycling dental material waste. Algishine performs superiorly in preserving the color of PMMA interim restorations against common staining agents. Its application can potentially improve patient satisfaction and contribute to sustainable dental practices.

Failure assessment of eccentric circular holes under compressive loading

The present work aims to investigate the failure size effect on flattened disks containing an eccentric circular hole under mode I loading conditions. For this purpose, uniaxial compression tests are carried out on polymethyl methacrylate (PMMA) samples with holes. Depending on the hole radius and eccentricity, the energy release rate is either an increasing or decreasing function of the crack length, thus affecting the stability of crack propagation. Experimental results are interpreted and discussed through the coupled stress and energy criterion of Finite Fracture Mechanics. The approach lies on the assumption of a finite crack advance and it is implemented through the numerical estimation of the stress field and the Incremental Energy Release Rate functions. Finally, stability and crack speed propagation are discussed under the assumption of Linear Elastic Fracture Mechanics. Theoretical predictions reveal in agreement with experimental results thus demonstrating that the Coupled Criterion effectively captures the failure condition.

Cure State Sensing of Polymethylmethacrylate Using a Vibrating Axial Probe.

A new axially vibrating sensor based on an audio voice coil transducer and a lead zirconate titanate (PZT) piezoelectric disc microphone was developed as a probe for the measurement of in vitro rheological fluid properties, including curing progress for polymethylmethacrylate (PMMA) mixtures with important uses as bone cement in the field of orthopedics. The measurement of the vibrating axial sensor's acoustic spectra in PMMA undergoing curing can be described by a damped harmonic oscillator formalism and resonant frequency (ca. 180 Hz) shift can be used as an indicator of curing progress, with shifts to the blue by as much as 14 Hz. The resonant frequency peak was measured in 19 different 4.0 g PMMA samples to have a rate of shift of 0.0462 ± 0.00624 Hz·s-1 over a period of 400 s while the PMMA was in a dough state and before the PMMA transitioned to a hard-setting phase. This transition is unambiguously indicated by this sensor technology through the generation of a distinct circa 5 kHz high-Q under-damped ring-down response.

Assessment of the Antifungal Activity of PMMA-MgO and PMMA-Ag Nanocomposite

Orthodontic acrylic resin is used in the construction of orthodontic appliances. It lacks antimicrobial properties and is prone to microbial infection. So, the infection associated with it can be reduced via modification of orthodontic acrylic resin with nanoparticles (NPs) incorporation. The study directed to evaluate the antifungal properties of modified orthodontic acrylic resin incorporated with magnesium oxide (MgO)-NPs and silver (Ag)-NPs. NPs were mixed with polymethylmethacrylate (PMMA) in ethanol-assisted mixing method. Disc samples (10 mm in diameter and 2 mm thick) of PMMA-MgO, PMMA-Ag nanocomposites and PMMA alone (as control) were prepared. Then, C. albicans was isolated and identified clinically through taking swabs from acrylic denture base orthodontic appliances, cultured on a Sabouraud Dextrose Agar medium, followed by transferring on HiCrome™ candida Differential agar which is a selective and differential medium to distinguish distinct Candida species. The polymerase chain reaction was performed and the amplicon was separated by 2% gel electrophoresis and then visualised by ethidium bromide. DNA sequencing was performed on the sample at Sanger sequencing/ ABI 3500. Antifungal activity of PMMA-MgO and PMMA-Ag (1%, 3% and 5% of NPs) was conducted through disc diffusion assay and colony forming unit counts. The result showed a decrease in the number of adhered Candida albicans (C. albicans) of all concentrations of both nanocomposite and the decrease was statistically significant (P&lt;0.05) in all experimental groups except MgO-NPs 1% and 3%. Increasing the concentration of NPs was associated with decrease in the adhered C. albicans. It was concluded that PMMA-MgO and PMMA-Ag nanocomposites showed anti-adherence activities against clinically isolated C. albicans in concentration dependent manner.

Exploring the Use of Cold Atmospheric Plasma for Sound and Vibration Generation.

In this study, we investigate the potential of cold atmospheric plasma (CAP) as a non-contact excitation device, comparing its performance with an ultrasound transmitter. Utilizing a scanning Laser Doppler Vibrometer (LDV), we visualize the acoustic wavefront generated by a CAP probe and an ultrasound sensor within a designated 50 mm × 50 mm area in front of each probe. Our focus lies in assessing the applicability of a CAP probe for exciting a small polymethyl methacrylate (PMMA) sample. By adjusting the dimensions of the sample to resonate at the excitation frequency of the probe, we can achieve high vibrational velocities, enabling further mechanical analysis. In contrast with traditional vibration excitation techniques such as electrodynamical shakers and hammer impact excitation, a plasma probe can offer distinct advantages without altering the structure's dynamics since it is contactless. Furthermore, in comparison with laser excitation, plasma excitation provides a higher power level. Additionally, while pressurized air systems are applicable for limited low frequencies, plasma probes can perform at higher frequencies. Our findings in this study suggest that CAP is comparable with acoustic excitation, indicating its potential as an effective mechanical excitation method.

Cyclical hydraulic pressure pulses reduce breakdown pressure and initiate staged fracture growth in PMMA

Using unique experimental equipment on large bench-scale samples of Polymethylmethacrylate, used in the literature as an analogue for shale, we investigate the potential benefits of applying cyclical hydraulic pressure pulses to enhance the near-well connectivity through hydraulic fracturing treatment. Under unconfined and confined stresses, equivalent to a depth of up to 530 m, we use dynamic high-resolution strain measurements from fibre optic cables, complemented by optical recordings of fracture development, and investigate the impact of cyclical hydraulic pressure pulses on the number of cycles to failure in Polymethylmethacrylate at different temperatures. Our results indicate that a significant reduction in breakdown pressure can be achieved. This suggests that cyclic pressure pulses could require lower power consumption, as well as reduced fluid injection volumes and injection rates during stimulation, which could minimise the occurrence of the largest induced seismic events. Our results show that fractures develop in stages under repeated pressure cycles. This suggests that Cyclic Fluid Pressurization Systems could be effective in managing damage build-up and increasing permeability. This is achieved by forming numerous small fractures and reducing the size and occurrence of large fracturing events that produce large seismic events. Our results offer new insight into cyclical hydraulic fracturing treatments and provide a unique data set for benchmarking numerical models of fracture initiation and propagation.

Characteristics of Electromagnetic Radiation from Quartz, Lithium Niobate, and Polymethyl Methacrylate Samples Subjected to Impact Loading

Characteristics of Electromagnetic Radiation from Quartz, Lithium Niobate, and Polymethyl Methacrylate Samples Subjected to Impact Loading

The effect of dilatational and distortional strain energy density on crack initiation

AbstractTo investigate the distinct influences of dilatational strain energy density (Dil‐SED) and distortional strain energy density (Dis‐SED) on crack initiation, quasi‐static loading tests were performed on centrally cracked polymethyl methacrylate samples, employing digital image correlation equipment. Our findings unveiled that the Dil‐SED promotes crack initiation, while the Dis‐SED inhibits it. Additionally, it was found that the direction obtained by the ratio of these two strain energy densities was closer to the crack initiation direction than the direction associated with the maximum Dil‐SED and minimum Dis‐SED values. Furthermore, experimental and finite element method (FEM) results indicated that the distribution of these two strain energy densities remains relatively insensitive to the core region's radius . By understanding Dil‐SED and Dis‐SED magnitudes and their impacts on crack initiation, material failure can be predicted and prevented.

Migration behavior of space charge packet researched by using electron beam irradiation and real-time space charge distribution measurement in piezo-pressure wave propagation (PWP) method

The space charge packet is a special sort of space charge phenomenon that is characterized by the migration of aggregated space charge in the form of a packet in the sample. Currently, most of the experimental and simulation studies on the generation and migration of space charge packets focus on the space charge packets with positive polarity in polyethylene and their cross-linking products, while the characteristics of the space charge packets with negative polarity still need studying. This paper presents an integrated experimental system for studying space charge packet with negative polarity, which enables experimental studies combining electron beam irradiation technique and real-time space charge distribution measurement. The beam flux for electron beam irradiation is controlled by a metal grid with an optical fiber-electric relay, and the space charge distribution measurement is performed by the piezo- pressure wave propagation method. The system achieves a withstand voltage value of 17 kV and a measuring resolution of 25 ns for space charge distribution measurement and is suitable for experimental studies of various material samples with different thickness ranges under different electric fields. In this work, the migration behaviors of space charge packets with negative polarity in polypropylene (PP) and polymethyl methacrylate (PMMA) samples under different applied electric fields (15, 20, 25, 30 kV/mm) are studied by using the experimental system. The relationship between the migration properties of carriers with negative polarity (electrons) and the electric field can be extracted from the experimental results. The “negative differential mobility” phenomenon is found for both materials, i.e. the migration rate decreases with the increase of the electric field. The threshold electric field for the “negative differential mobility” phenomenon of electrons in PP sample is about 26.0 kV/mm while the threshold electric field for the “negative differential mobility” phenomenon of electrons in PMMA sample is 19.5 kV/mm, and the phenomenon disappears at an electric field of 27.5 kV/mm. The electric field where the "negative differential mobility" phenomenon of electrons appears and disappears in different materials can be extracted by using the experimental system proposed in this paper.

Effect of Nystatin Coated Copper Oxide (CuO) Particles on Mechanical, Thermal, and Antifungal Properties of Polymethyl Methacrylate (PMMA)–Based Denture Materials

Polymethyl methacrylate (PMMA) has garnered significant attention in the field of dentistry due to its wide applications. This paper proposes the incorporation of the nystatin coated copper oxide (CuO) particles having desirable conductivity and antifungal properties, as a filler in the PMMA denture to address their low thermal conductivity, low impact strength, low fatigue resistance, and microbial adhesion. The prepared nystatin coated CuO particles were characterized with several analytical techniques. The nystatin coated CuO particles were mixed in different ratios (0%, 1%, 2%, and 4%) in PMMA corresponding to groups C, E1, E2, and E3, respectively. The prepared samples of composite PMMA with nystatin coated CuO were evaluated to determine their transverse strength, impact strength, Vickers hardness (HV), and thermal conductivity. Furthermore, antifungal properties of CuO particles, nystatin coated CuO particles, and their acrylic composites were evaluated against Candida albicans. Scanning electron microscopy (SEM) analysis confirmed the particles’ spherical and irregular shapes. The particle sizes range from nano to micron level. Fourier‐transform infrared spectroscopy (FTIR) and energy dispersive X‐ray spectroscopy (EDX) analysis confirmed the coating of nystatin on CuO. X‐ray diffraction (XRD) analysis showed the diffraction patterns and planes of CuO monoclinic shape structure. The composite prepared to have higher values of HV (19.53 ± 0.65, 20.16 ± 0.37, and 21.11 ± 0.75, respectively) as compared to the control. The impact strength values were measured high at 14.12 ± 5.55 kJ/m2 for 2% containing nystatin coated CuO acrylic resins compared to control and other groups. The conductivity increased linearly with the addition of CuO particles. The addition of CuO particles causes a reduction in flexural strength as compared to the control group. As the concentration of nystatin coated CuO (1%, 2%, and 4%) in acrylic samples increased, the antifungal properties were improved. Thus, the incorporation of optimized concentrations of nystatin coated CuO particles in acrylic resin resulted in the improved mechanical, thermal, and antifungal properties.

The limiting oxygen volume fraction for opposed flame spread extinction

The limiting oxygen volume fraction (LOC) for flame spread is a parameter used to determine flammability and fire hazard. The LOC depends on the solid material, geometry, and environmental conditions. It is important to understand the relationship between these conditions and the LOC, particularly for environments different than Earth atmospheres. Future spacecraft will have sub-atmospheric cabin pressures designed to reduce preparation time for extravehicular activities. This work attempts to provide further information on this aspect of solid fuel flammability by conducting experiments to determine the effect of ambient pressure and external radiant flux for flames spreading downward over cylindrical samples of black polymethyl methacrylate (PMMA). The experimental methodology is based on test methods ASTM 2863 (LOI) and ASTM E-1321 (LIFT), that are used to determine some aspects of material flammability, specifically extinction and flame spread under external radiant heating. Experiments are conducted in a pressure chamber at pressures from 40 to 100 kPa with radiant heating from 0 to 3.3 kW/m2. Results show that decreasing either the ambient pressure or the external radiant flux increases the LOC of the PMMA. The results are correlated in terms of the ratio of the partial pressure of oxygen, radiant flux, and ambient pressure with an equation that includes the LOC at atmospheric pressure. It is found that the heat transfer and chemical kinetic mechanisms that control the flame spread are primarily dependent on the oxygen molar fraction, explaining the experimental observations. The data from this work will be compared with experiments to be conducted in the International Space Station (ISS) under the SoFIE-MIST project to provide further understanding of the effect spacecraft environments have on the LOC of materials. The results will give further insight into the flammability of materials, particularly at sub-atmospheric ambient pressures found in spacecraft, aircraft, and high-altitude locations.

Mechanical and tribological properties of nano clay/PMMA composites extruded with a twin-screw extruder

An analysis has been done on the strength and wear of the nanocomposites. The synthesis of nano clay or poly-methyl methacrylate (PMMA) nanocomposites by using a twin-screw extruder is discussed here. During the synthesis of nanocomposites, a compatibilizer was added to improve the bonding between the clay and matrix between the five different types of composites. The samples obtained are then used for tensile testing after being molded into dog-bone-shaped samples. The tensile test is done by using a UTM (Universal Testing Machine) and tensile strength and tensile modulus were recorded. Then flexural strength and modulus were recorded by conducting a flexural test. The rectangular part of the dog-bone samples is sliced for this test. Similarly, testing of wear was done using a pin-on-disc apparatus. After the flexural test and wear test analysis, scanning electron microscope imaging of the failed and worn-out surfaces is recorded. It was concluded that the pure PMMA sample has lesser strength than the 2.5 wt% sample. But the pre PMMA sample exhibits higher tensile strength and flexural modulus. And on boosting the filler content in the composite material, the strength reduces but the wear resistance of the composite improves.

Influence of PMMA 3D Printing Geometries on the Mechanical Response

This work presents a study regarding the mechanical characterization of polymethyl methacrylate (PMMA) patterned samples manufactured via material-extruded additive manufacturing. In recent years, literature about mechanical analysis in additive manufacturing has been growing increasingly, especially for material extrusion-based techniques. However, this trend surpasses the speed of information released by standard councils, existing no clear specifications for polymer characterization apart from conventional techniques. This issue has led to premature breakage as well as fracture not located in the constant cross-section region of samples. The main purpose of this present research is focused on the analysis of diverse modifications of the standard injection geometries to tackle the mentioned problems. Several printing methodologies were compared, changing slicing and geometrical parameters such as number of walls, and fillet radius. Then, the manufacturing of PMMA samples with a material extrusion printer took place to characterize both the material and the effective properties of the structures. With the information post-processed from tensile and compression tests, disparities were found between different geometrical designs for both elastic modulus and ultimate stress. Moreover, diverse location of fractures were observed for the studied geometries. The data obtained from the analysis was valuable to establish a proper protocol for further studies. The experiments suggest that for tensile tests the golden standard is selecting rectangular specimens since they do not induce premature breakage nor fracture outside of gauge length.