Polymethylmethacrylate Powder Research Articles

Powder‐Sintered Hierarchically Porous PMMA with Optimal Pore Parameters for Passive Daytime Radiative Cooling

AbstractPorous radiative cooling polymers have drawn significant attention for passive daytime cooling due to their desirable cooling performance and easy scalability. Since optimal pore parameters (i.e., pore diameter and porosity) will enhance light scattering, polymethyl methacrylate (PMMA) powders are sintered to fabricate samples with different pore parameters by the one‐step full‐dry powder sintering method. These samples have a hierarchically porous structure with pore diameters <5.0 µm. The most porous sample has 43% porosity, 0.964 reflectance in the 0.3–2.5 µm wavelength range, and 0.967 emittance in 8–13 µm wavelength range (which is the atmospheric window). The measured cooling temperature difference decreases when the porosity is low for hierarchically porous PMMA with similar pore size distribution. The high sub‐ambient cooling temperature reduction provided by hierarchically porous PMMA with optimal pore parameters is due to high solar reflectance when illuminated by the sun. Similar cooling trends are evident when sunlight is simulated by a Xenon lamp and an optical filter. The powder‐sintered hierarchically porous PMMA with optimal pore parameters can be an excellent radiative cooler for passive daytime cooling applications.

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.

Impact of Manual Addition of Vancomycin to Polymethylmethacrylate (PMMA) Cements.

(1) Background: The addition of antibiotics to bone cements is a common practice in the treatment of periprosthetic joint infections. In revision cases, the amount and type of antibiotic is often insufficient and additional antibiotics must be added. The addition, however, changes the product itself, and the surgeon becomes the "manufacturer" of the bone cement. PMMAe wished to clarify whether the admixture of antibiotics changes the mechanical stability of the bone cements used and if the added antibiotics were still functional and released in sufficient quantities. (2) Methods: We compared two industrially manufactured vancomycin-containing PMMA cements; the low-viscous VancogenX® (TECRES, Sommacampagna, Italy) and the high-viscous Copal® G+V (Heraeus Medical GmbH, Wehrheim, Germany), with two PMMA cements loaded with aminoglycosides, to which 2.0 g of vancomycin (Hexal CT1631) were manually added-the high-viscous Smartset® GHV and the medium-viscous Antibiotic Simplex with Tobramycin (antibiotic Simplex® T). Test specimens of the bone cements were used to determine mechanical stability (bending strength and bending module), and the release of the antibiotics was determined by HLPC and modified Kirby-Bauer assays. (3) Results: All tested bone cements showed an initial high release within the first hours. Repeated testing after 24 h showed a reduced efficacy of VancogenX® and Smartset® GHV in Kirby-Bauer assays. Long-time release over days showed a release of functional antimicrobial active ingredients over this period of time in anti-microbial assays, but no activity of VancogenX® from day 21 onward. No significant differences in the ISO bending modules could be detected, but in contrast to the bending module, the ISO bending strength was substantially reduced by 10-15 mPal in comparison to both cements of the reference group. The Simplex®T met just the ISO 5833; the Smartset® GHV did not after adding vancomycin. (4) Conclusions: In conclusion, the manual addition of 2 g of vancomycin to 40 g of PMMA powder is recommended for the treatment of methicillin-resistant staphylococci. Vancomycin is released over a period of 42 days with concentrations above the MIC for typical staphylococci. The mechanical properties of the PMMA just met, or did not fulfill, ISO mechanical specification. Copal® G+V showed a better elution than VancogenX® over time.

Graphene oxide-encapsulated baghdadite nanocomposite improved physical, mechanical, and biological properties of a vancomycin-loaded PMMA bone cement

Polymethyl methacrylate (PMMA) bone cement is commonly used in orthopedic surgeries to fill the bone defects or fix the prostheses. These cements are usually containing amounts of a nonbioactive radiopacifying agent such as barium sulfate and zirconium dioxide, which does not have a good interface compatibility with PMMA, and the clumps formed from these materials can scratch metal counterfaces. In this work, graphene oxide encapsulated baghdadite (GOBgh) nanoparticles were applied as radiopacifying and bioactive agent in a PMMA bone cement containing 2 wt.% of vancomycin (VAN). The addition of 20 wt.% of GOBgh (GOBgh20) nanoparticles to PMMA powder caused a 33.6% increase in compressive strength and a 70.9% increase in elastic modulus compared to the Simplex® P bone cement, and also enhanced the setting properties, radiopacity, antibacterial activity, and the apatite formation in simulated body fluid. In vitro cell assessments confirmed the increase in adhesion and proliferation of MG-63 cells as well as the osteogenic differentiation of human adipose-derived mesenchymal stem cells on the surface of PMMA-GOBgh20 cement. The chorioallantoic membrane assay revealed the excellent angiogenesis activity of nanocomposite cement samples. In vivo experiments on a rat model also demonstrated the mineralization and bone integration of PMMA-GOBgh20 cement within four weeks. Based on the promising results obtained, PMMA-GOBgh20 bone cement is suggested as an optimal sample for use in orthopedic surgeries.

Fabrication of poly(vinylidene fluoride)‐based composite powder coating with enhanced adhesion performance

AbstractGiven the environmental benefits, poly(vinylidene fluoride) (PVDF)‐based composite powder coating was developed without using any harmful solvent. However, it still remains poor adhesion to substrates and low compatibility to acrylic resin issues. To address these challenges, PVDF was grafted with glycidyl methacrylate (GMA) through a facile and scalable reactive extrusion method. The resulting product, PVDF‐g‐GMA, was then mixed with different contents of polymethyl methacrylate (PMMA), and the mixing was sprayed onto aluminum substrates. The PVDF‐g‐GMA/PMMA powder coating shows the excellent adhesion and corrosion resistance, particularly when the PMMA content is 30 wt%, owning to the good compatibility of PVDF‐g‐GMA and PMMA. This work opens up a new possibilities for the development of advanced composite powder coatings with improved performance characteristics.

Decreasing polymethyl methacrylate bone cement concentration extends working and setting times in vitro.

To determine setting and temperature properties of diluted polymethyl methacrylate (PMMA) bone cement in vitro to assess utility for vocal fold augmentation in horses. 4 dilutions of PMMA equivalent to volumes of 15 mL, 20 mL, 25 mL, and 30 mL PMMA powder (PMMAp) in 10 mL solvent. For each volume PMMAp, setting times (tset), peak temperatures (Tmax), and times to peak temperature (tmax) were determined using a temperature data logger in a 4-mL volume of PMMA. Injectability was assessed in vitro by documenting the force required to inject 0.2 mL PMMA through an 18-gauge 3.5-inch spinal needle attached to a 6-mL syringe at 1-minute intervals. Working time (twork) was calculated from a linear regression of injectability. Peak temperatures increased with increasing volume of PMMAp: 56 °C, 86 °C, 99 °C, and 101 °C. Times for tset, twork, and tmax were inversely proportional to PMMA concentrations, resulting in tset of 23, 21, 17, and 14 minutes; twork of 22.75, 12.25, 7, and 4 minutes; and tmax of 28, 24, 19, and 16 minutes, respectively, for 15, 20, 25, and 30 mL PMMAp. Pairwise comparisons for all analyses were significant apart from Tmax for 25 and 30 mL PMMAp (P = .96) and twork for 20 and 25 mL PMMAp (P = .06). Decreasing the concentration of PMMA bone cement resulted in longer working times and setting times; however, peak temperatures did not differ between the 2 strongest concentrations. Further research is warranted to quantify diluted PMMA properties for in vivo use for vocal fold augmentation in horses.

Surface, mechanical and chemical properties of modified denture resin using natural biopolymer.

This laboratory study determined the surface, mechanical and chemical properties of polymethyl methacrylate (PMMA) denture resin reinforced with micron-sized Gum Arabic (GA) powder in different weight ratios. This laboratory study was conducted at the Dental Health Department of the College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia from November 2022 to February 2023. Three experimental denture resins were prepared by incorporating GA powder in heat-polymerized PMMA powder using different wt.% (5, 10, and 20 wt.%). While pristine PMMA served as the control group. A total of ten bar-shaped specimens with dimensions of 65 mm × 10 mm × 3.5 mm were prepared for each study group. The surface properties (micro CT and SEM evaluation), mechanical properties (Nanohardness, elastic modulus and flexural strength) and chemical properties (FTIR) were conducted. The data were statistically analyzed using the one-way analysis of variance and Tukey's post hoc tests (p<0.05). The surface and bulk properties of experimental GA-reinforced PMMA resin materials deteriorated while the mechanical properties were also negatively altered using GA-based PMMA denture resin. A linear correlation was observed between weak mechanical properties and increasing wt.% of GA in denture resin. The incorporation of GA powder in denture resin might not be a viable option. The surface and mechanical properties of experimental PMMA composites were adversely affected compared to the control group.

Bone Cement Waste in Total Knee Arthroplasty: A Preliminary Study of Scope and Cost.

Medical waste is both costly and detrimental to the environment, and operating room waste represents a substantial portion of this. To the authors' knowledge, bone cement waste in total knee arthroplasty (TKA) has not previously been studied. The vast majority of TKA are cemented, and the volume of TKA is forecast to increase. Given this, we studied the waste resulting from the routine use of 2 40-gram bags of polymethyl methacrylate (PMMA) powder during cementing in primary TKA. We first studied the yield of commercially available plain and gentamicin medium-viscosity bone cement powder and calculated the cost/gram of product. We then collected the PMMA remaining after primary TKA to determine the average amount of waste, its cost, and possible correlations with patient and implant metrics that could improve efficiency and reduce waste of PMMA. Overall, PMMA waste averaged 59% per TKA, at a median cost of $129 per case. Cost of waste was greater when gentamicin cement was used, as its cost was 2.5X that of plain cement. Implant sizes and surface area ranges were identified that could reliably allow the use of a single 40-gram package of powder, potentially reducing PMMA waste. While it is acknowledged that zero-waste cementing is not practical, any reduction in waste that does not compromise either the flow of surgery or the adequacy of fixation would be beneficial. Reevaluation of PMMA techniques could reduce waste, resulting in both cost savings and improved sustainability in arthroplasty.

Influence of the content of polymethyl methacrylate on the properties of porous Si3N4 ceramics fabricated by digital light processing

Porous Si3N4 ceramics are highly regarded as ideal materials for radomes due to their unique characteristics. However, the slurry used for the preparation of porous Si3N4 ceramics suffers from a low cure depth, making it challenging to fabricate ceramic components using DLP technology. In this study, porous Si3N4 ceramics were prepared by combining DLP technology with pore-forming agent method. The addition of polymethyl methacrylate (PMMA) powders with lower refractive index than that of Si3N4 powders can improve the penetration depth of ultraviolet light in the Si3N4 slurry. A systematic study was conducted to investigate the influence of the addition of PMMA powders on the properties of Si3N4 slurries and porous Si3N4 ceramics. When PMMA powders were added at 10 wt%, the slurry with a lowest viscosity of 0.13 Pa s (the shear rate is 30 s−1) and cure depth of 40.0 μm (the exposure energy is 600 mJ/cm2) was obtained. With the increase of PMMA content, porous Si3N4 ceramics experienced a gradual decrease in both the flexural strength and bulk density, while the porosity increased from 14.41% to 27.62%. Specifically, when 20 wt% PMMA was added, the resulting porous Si3N4 ceramics had a lowest bulk density (2.41 g/cm3), a maximum porosity (27.62%), and a flexural strength (435.87 MPa). The study is of great significance in establishing an experimental foundation for fabricating porous Si3N4 ceramics by using DLP technology.

Analysis of the Multiwalled Carbon Nanotubes Reinforced Polymethyl Methacrylate Bone Cement’s Characteristics and In Vitro Bioactivity to Prolong Its Functionality in Orthopedic Application

Polymethyl methacrylate (PMMA) bone cement is being used to fill voids that are created due to vertebral compression fractures. It is also a grouting medium in orthopedic joint replacement surgeries as they possess fast primary fixation to the bone. Considering the cement properties and in vitro bioactivity of bone cement is essential for cemented hip and knee joint replacement surgeries. In this study, commercial Simplex P bone cement (SPBC) is modified with carboxyl- (-COOH-) functionalized multiwalled carbon nanotubes (MWCNTs) to overcome high polymerization temperature, volumetric shrinkage, surface wettability, and in vitro bioactivity. A geometric dilution method is used to incorporate MWCNTs with the PMMA powder, which is in unequal proportions. The PMMA/MWCNT nanocomposite with different concentrations of reinforcements, such as 0.1, 0.3, 0.5, and 0.7 weight percentages, is prepared for the investigation. It was observed that the MWCNTs had a beneficial impact on PMMA bone cement (PMMA-BC) by enhancing its setting time (2.94%↑) and surface wettability (23.58%↑). Also, diminished polymerization temperature (29%↓) and volumetric shrinkage (40.9%↓) are observed for an optimum concentration of 0.7 wt. %. The bioactivity of the cement surface is validated by the in vitro bioactivity observed in simulated body fluid (SBF) through the development of primary and secondary apatite. It is concluded that the synthesized PMMA/MWCNT nanocomposites are found to have enhanced cement properties compared to PMMA-BC.

Dispersion and Homogeneity of MgO and Ag Nanoparticles Mixed with Polymethylmethacrylate.

This study aims to examine the impact of the direct and indirect mixing techniques on the dispersion and homogeneity of magnesium oxide (MgO) and silver (Ag) nanoparticles (NPs) mixed with polymethylmethacrylate (PMMA). NPs were mixed with PMMA powder directly (non-ethanol-assisted) and indirectly (ethanol-assisted) with the aid of ethanol as solvent. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscope (SEM) were used to evaluate the dispersion and homogeneity of MgO and Ag NPs within the PMMA-NPs nanocomposite matrix. Prepared discs of PMMA-MgO and PMMA-Ag nanocomposite were analyzed for dispersion and agglomeration by Stereo microscope. XRD showed that the average crystallite size of NPs within PMMA-NP nanocomposite powder was smaller in the case of ethanol-assisted mixing compared to non-ethanol-assisted mixing. Furthermore, EDX and SEM revealed good dispersion and homogeneity of both NPs on PMMA particles with ethanol-assisted mixing compared to the non-ethanol-assisted one. Again, the PMMA-MgO and PMMA-Ag nanocomposite discs were found to have better dispersion and no agglomeration with ethanol-assisted mixing when compared to the non-ethanol-assisted mixing technique. Ethanol-assisted mixing of MgO and Ag NPs with PMMA powder obtained better dispersion, better homogeneity, and no agglomeration of NPs within the PMMA-NP matrix.

Análise antifúngica da incorporação do óleo essencial de Cymbopogon citratus (d.c.) Stapf em polimetacrilato de metila

ABSTRACT Objective: Evaluated the antifungal effect of the incorporation of different concentrations of the essential oil Cymbopogon citratus (capim santo), into polymethylmethacrylate (PMMA) against Candida albicans. Methods: Fifty specimens were fabricated and divided into five groups: Group 1, PMMA + 10% essential oil (n=10); Group 2, PMMA + 15% essential oil (n=10); Group 3, PMMA + 20% essential oil (n=10); Group 4, PMMA + 25% essential oil (n=10); Group 5, PMMA (n=10). PMMA powder was mixed with the monomer and the mixture was placed in disc-shaped cavities measuring 15 mm in diameter, 2 mm thick. To evaluate the antifungal activity of the experimental specimens, the standard strain of Candida albicans was tested. After incubation, the colony count of each plate was performed using a digital colony counter, obtaining the number of colony forming units (CFU) and the Kruskal-Wallis test was applied. Results: There was statistically significant difference in the CFU count of Candida albicans as a consequence of the addition of Cymbopogon citratus essential oil to PMMA (p &lt; 0.001) and values were significantly higher in comparison with those of all the other groups, when the essential oil was incorporated as incorporated into the PMMA in the concentration of 20%. In the other concentrations, no difference in values was observed in comparison with the Control Group without essential oil of Cymbopogon citratus. Conclusion: The acrylic resin with the essential oil incorporated into it in different concentrations provided no effect against development of the genus Candida.

Preparation of Bio-Composite Coatings on Titanium Substrate by Electrostatic Spray Deposition

In this research, the most modern deposition technique used will be utilized for biomedical applications is Electrostatic Spray Deposition (ESD), which focused on enhancing the corrosion resistance as well as biocompatibility of commercially pure titanium substrate by constructing bio composite coating, various percentages (2, 6, and 10) wt.% of Hydroxyapatite (HAP) powder were combined with (98, 94, and 90) wt.% of polymethyl methacrylate (PMMA) powder, and the same percentages (2, 6, and 10) wt.% of Nickel Oxide (NiO) powder also combined with (98, 94, and 90) wt.% of PMMA. The effects of HAP and NiO percentages in the PMMA matrix on the surface characteristics of titanium were analyzed. The FESEM, XRD, contact angle, and anti-bacterial test demonstrated that the coating layer was successfully made consistent throughout and devoid of cracks. the samples exhibited favorable wetting qualities and inhibited bacterial growth.

Particle emissions and respiratory exposure to hazardous chemical substances associated with binder jetting additive manufacturing utilizing poly methyl methacrylate

BackgroundDuring industrial scale binder jetting utilising poly methyl methacrylate (PMMA) hazardous chemical substances (HCSs) such as PMMA powder particles, methyl methacrylate (MMA) and acetone may be emitted and potentially inhaled by Additive Manufacturing (AM) operators. MethodsPhysical and chemical characterisation of virgin and used PMMA powder samples were characterised in terms of their size, shape and chemical composition. Direct reading particle counting instruments were used to determine particle emissions and emission rates (ER). Internationally recognised methods were used to monitor HCSs in the ambient workplace environment and personal respiratory exposure of the AM operators. ResultsThere were no differences between the median powder size distributions of virgin and used PMMA powders. Scanning Electron Microscopy images indicated the presence of <10 µm and <4 µm sized particles in virgin and used powders. Particle ERs as high as 3.33 × 106 particles/min for 0.01 - ∼1.00 µm sized particles were measured during the post-processing phase. Inhalable and respirable particles, acetone, pentane and toluene were detected in ambient air and AM operators were exposed to quantifiable concentrations of these HCSs. ConclusionsParticles sized 0.01 - ∼1.00 µm were the most prevalent particles emitted, with a maximum ER of 3.33×106 particles/min. Eight-hour Time Weighted Average personal exposures were below their respective Occupational Exposure Limit (OELs), with the exception of inhalable particles (mean >50% of the South African OEL). Recommendations were made to reduce exposure to inhalable particles, which could be applied to other AM facilities.

Surface feature of PMMA films on NiTi alloy substrate by the spin coating method

Polymethylmethacrylate (PMMA) films are deposited on NiTi shape memory alloy by using the spin coating method. Different ratios of PMMA powder to Toluene were mixed with magnetic stirrer for a duration of 12 h. The various concentrations of solution (mol. %) were used for the spin coating method on the substrate NiTi to produce thin films. The samples were cured in various environment from room to furnace temperature. The surface features of PMMA films were investigated by using an optical microscope. Thermal and mechanical behavior of the NiTi substrate and composites was and studied in the paper. The spin coating and post-processing conditions determined the surface morphology that is featureless or dominate by pinholes and other surface defects. The spin-coated coating at 200 rpm improved film surfaces with 4 mol % PMMA solution. Surface defects in the form of pinholes appear on the surface of the film obtained by spin-coating at 3200 rpm from 8 mol % solution and post-baked at 80 °C for 60 min on a hot plate in an oven inside a vacuum chamber. Different coating properties depends on the preparation parameters by spin coating and thermal and microstructural, mechanical properties are explained and discussed in the paper.

Influence of Incorporating 5% Weight Titanium Oxide Nanoparticles on Flexural Strength, Micro-Hardness, Surface Roughness and Water Sorption of Dental Self-Cured Acrylic Resin.

Background: Polymethyl methacrylate (PMMA) is used in fabricating acrylic denture bases. Repairing a fractured acrylic denture base can be done by self-cured PMMA, yet this is still a weak point after repair. The aim of this study was to evaluate the effect of incorporating 5% weight titanium oxide nanoparticles (TiO2) to self-cured PMMA on flexural strength, surface micro-hardness, roughness, and water sorption. Methods: A total of 160 acrylic–resin specimens were used in this study. They were divided in two main groups; (a) control group, prepared by mixing self-cured PMMA powder to its liquid monomer, (b) treated group, prepared by blending 5% weight TiO2 nanoparticles to self-cured PMMA powder then this blend was mixed with the liquid monomer. Flexure strength, surface micro-hardness, roughness, and water sorption were evaluated. Data were analyzed using independent sample t-tests (p ≤ 0.05). Results: There was a significant increase in the flexural strength of PMMA of the treated group after the addition of TiO2 (137.6 MPa) compared with the control (75.4 MPa) (p ≤ 0.001). No significant difference between the two groups in terms of micro-hardness (p = 0.385) and surface roughness (p = 0.269). Water sorption showed a significant reduction in the treated group (p ≤ 0.001). Conclusions: Addition of 5% weight TiO2 nanoparticles to the self-cured acrylic resin improved its flexural strength and reduced its water-sorption without impairing the surface micro-hardness and roughness.

Fabrication of Alq3/PMMA nanocomposite sheet and its potential applications as radiation dosimeter

Tris (8-hydroxyquinoline) aluminum (Alq3) is a highly luminescent organometallic compound, and therefore has numerous applications in electronic devices. Its unique optical property is suitable for organic light-emitting diodes, optoelectronic, and photodiodes. Despite its numerous potentials, no study investigated its response to ionizing radiation, particularly in its nanostructure form. In this work Alq3 were incorporated in a highly transparent polymethyl methacrylate (PMMA) polymer sheet using chloroform as a proper solvent for both materials. The ratio of Alq3 to PMMA powders was fixed at 1:10. The resulting composite showed recrystallized fine nanoparticles of Alq3, uniformly embedded in the PMMA sheet. Then small pieces of this nanocomposite sheet were exposed to various doses of X-ray and electron beam (E-beam) radiation doses in the range of 5–20 Gy. The molecular fingerprint and optical emission properties of the pristine and irradiated nanocomposite sheets were evaluated using Raman and PL spectroscopy. A systematic increase in the PL and Raman signals with increasing radiation doses were recorded. In addition, blueshift in the PL peak positions of nearly 6 and 9 nm for X-ray and E-beam irradiated sheets, respectively were also observed. These increments were attributed to the formation of radiative vacancies in the Alq3 molecules while the blueshift might be related to possible weakening of some of the Alq3 bonds such as C-O, C-C, C-H and Al-O, respectively. Therefore, the systematic changes in the optical properties might serve as preliminary parameters to investigate its potential use in radiation dosimetry following its nearly excellent linear dose dependence on signal intensities, which are quite encouraging.

Improving flexural properties of polymethyl methacrylate denture filled by carbon nanofibers under low filling content

In this article, we chose carbon nanofibers (CNFs) with high aspect ratio and excellent mechanical strength to investigate the evolution of the assemble behavior belong to the nanofillers and its effect on mechnaical properties of CNFs enhanced polymethyl methacrylate (PMMA) base denture resins. Test specimens were manufactured by mixing 0.5%, 1% and 3% content of CNFs with PMMA powder and the flexural properties of the specimens were tested by three-points testing. Comparing with the low flexural strength of pure PMMA base denture resins, Statistical evaluation results revealed that CNFs fillers highly improved the flexural strength of the composite resins to 66.44 ± 1.40 MPa, 68.75 ± 6.82 MPa and 89.26 ± 1.97 MPa at content reached 0.5%, 1% and 3%, respectively. Flexural modulus of neat PMMA was 2.79 ± 0.48 GPa, and the flexural modulus of the sample contains 0.5%, 1% and 3% reached 6.42 ± 0.75 GPa, 5.95 ± 0.29 GPa and 6.27 ± 0.14 GPa, respectively. Scanning electron microscopy revealed the aggregation of CNFs fillers, which is considered a stereoscopic framework that played the role of a special enhancing reinforcement under low filler content, and this strategy is considered to be expanded and developed to a common strategy that guiding our design in composite denture resins.

Measurement of the deposit formation during pneumatic transport of PMMA powder

Deposit formation poses severe hazards and negatively affects the functionality of pneumatic powder transport systems. A novel test-rig was developed for the measurement of the deposition of polymethylmethacrylate powder in a horizontal, turbulent flow through a duct of a square cross-section. The parameters under investigation are the particles’ size, shape, and mass flow rate, the conveying air’s Reynolds number, relative humidity, and temperature, and the duct material. A continuous weighing method is used to quantify the particle deposition and resuspension rate and a Faraday cup is positioned at the duct outlet to measure the specific powder charge. For the considered conditions, the air humidity exhibits a strong influence, especially on the smallest particles. For small particles, a high charge even leads to deposition at the ceiling of the PC duct. Larger particles tend to settle at the center of the duct and smaller ones preferably at its corner.

Исследование механолюминесценции композиционных материалов на основе полимера и порошка люминофора, возбуждаемой воздействием механического ударника, стилуса и лазерного импульса

The mechanoluminescence of the composite materials based on polymethyl-methacrylate and fine-dispersed powders of Sr4Al14O25:(Eu2+,Dy3+) phosphor with a centrosymmetric crystal structure of microcrystals and SrAl2O4:(Eu2+, Dy3+) phosphor with noncentrosymmetric crystalline structure were investigated. To study of mechanoluminescence, the composite layer with a thickness of ~250-300 μm was deposited on the surface of polymethyl-methacrylate substrate transparent in the visible spectral region. The mechanoluminescence of the composite layer was excited by the action of a mechanical striker, short laser pulses in air and water, and dynamic pressure of the stylus sliding over the surface of the mechanoluminescent layer. It is shown that the composite material based on a polymer and SrAl2O4:(Eu2+,Dy3+) powder with a noncentrosymmetric crystal lattice has a pronounced mechanoluminescence, while the composite material with Sr4Al14O25:(Eu2+,Dy3+) powder does not exhibit of the mechanoluminescent properties. It was shown that the excitation of mechanoluminescence in water begins at a much lower power density of the laser pulses than in air. The produced composite layer is shown to exhibit a high efficiency of “mechanooptical” transformation and can be used for recording and visualizing mechanical effects in mechatronic systems.