Filler Size Research Articles

Pelepasan monomer resin komposit nanofil dan mikrohibrid dengan penyinaran berbeda

Background: Many factors affect the elution of composite resin monomers, such as filler size and light-curing unit used. Objectives: to compare the effect of the filler size and light-curing unit on the elution of monomers. Methods: Subjects were 20 composite resins, consists of 10 microhybrid composite resins and 10 nanofilled composite resins, diameter 4.5 mm and height 2 mm. Composite specimens were cured using halogen light-curing unit 680 mW/cm² or LED 1000 mW/cm², for 20 seconds according to group random allocation. Specimens were put into 1 mL artificial saliva, soaked for 24 hours and then were analyzed with LC-MS/MS, for TEGDMA elution. Results: Two-ways ANOVA test showed there were differences in the influence of filler size and light-curing units type on monomer elution (p < 0.05). The mean of monomer TEGDMA eluted from micro-hal 2.4960 µg/mL ± 0.49318 µg/mL, micro-LED 0.03114 µg/mL ± 2.0820 µg/mL, nano-hal 1.8120 µg/mL ± 0.24273 µg/mL, and nano-LED 1.5000 µg/mL ± 0.0255 µg/mL. Tukey test showed microhybrid composite resin eluted more TEGDMA than nanofilled composite resin (p < 0.05). There were no significant differences in the elution of TEGDMA monomers with the use of light-curing unit halogen or LED (p > 0.05). Conclusion: Different filler size influenced the elution of composite resin monomer. The polymerization of the nanofilled composite resin is better than microhybrid composite resin, proved by less nanofilled composite resin monomer eluted. The use of halogen light-curing unit or LED light-curing unit, showed no difference in the effect on the elution of monomer.

Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour.

Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites. This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison. There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly. A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

Spinodal Decomposition of Filled Polymer Blends: The Role of the Osmotic Effect of Fillers.

The reported work addresses the effect of fillers on the thermodynamic stability and miscibility of compressible polymer blends. We calculate the spinodal transition temperature of a filled polymer blend as a function of the interaction energies between the blend species, as well as the blend composition, filler size, and filler volume fraction. The calculation method relies on the developed thermodynamic theory of filled compressible polymer blends. This theory makes it possible to obtain the excess pressure and chemical potential caused by the presence of fillers. As a main result of the reported work, we demonstrate that the presence of neutral (non-adsorbing) fillers can be used to enhance the stability of a polymer blend that shows low critical solution temperature (LCST) behavior. The obtained results highlight the importance of the osmotic effect of fillers on the miscibility of polymer blends. The demonstrated good agreement with the experiment proves that this effect alone can explain the observed filler-induced change in the LCST.

The strength of particulate polymer composite: A new insight on crystallinity and structural morphology

AbstractWe have demonstrated the significant impact of high density polyethylene (HDPE) crystallinity and structural morphology on the tensile strength of 60/40 NR/HDPE polymer blend composites. Introducing nanoscale Boron Carbide (B4C‐type compounds) fillers noticeably changed the crystallinity and morphology of HDPE, leading to the formation of fine spherulites. Conversely, microscale fillers mainly impacted the crystallinity while preserving a coarse architecture. Although both composites experienced a reduction in crystallinity, the nanocomposites outperformed microcomposites and even the pristine polymer blend in terms of strength, implying the effect of a fine structure. The nanocomposite with a filler loading of 2 wt% exhibited the highest strength. This investigation provides novel insights into the interplay between crystallinity, HDPE structure, and the size of fillers, which heavily influence the strength of polymer blend composites.

Numerical analysis on the direction to improve thermal conductivity of polymer composites filled with spherical particles

The research on thermal conductivity of insulating polymer-matrix composites filled with spherical particles (PMCs-SP) is far below the requirements for industrial utility. To find the improving direction for the thermal conductivity of PMCs-SP (KPMCs-SP), a series of PMCs-SP models filled with randomly distributed spherical particles were established. The PMCs-SP models were validated by comparing the calculated KPMCs-SP with the experimental data. It is found that KPMCs-SP increases with the increasing volume fraction of spherical particles, and the influence of filler size and interfacial thermal resistance on KPMCs-SP shows a significant synergistic effect. The formation of heat conduction chains could effectively improve KPMCs-SP. Increasing the number of heat conduction chains and decreasing the spacing of spherical particles can both increase the KPMCs-SP. To quantify the effect of heat conduction chains on KPMCs-SP, the concept of compactness of heat flow chains (C) was creatively proposed. The KPMCs-SP-C curve presences a threshold value, C0 = 0.6372, beyond which KPMCs-SP could be significantly enhanced. In addition, the theoretical specific thermal resistance of PMCs-SP (Rλ,PMCs-SP) was first calculated. For PMCs-SP with the default parameters, the theoretical minimum Rλ,PMCs-SP converged to ∼ 0.72 m·K·W−1.

A comprehensive study on enhancing effective thermal conductivity of polymer composites with randomly distributed triple fillers

This paper describes a comprehensive study on the effective thermal conductivity (ETC) of triple-filled polymer composites. A very complicated behavior was revealed under various effective factors, such as thermal conductivity (TC), volume fraction (VF), particle distribution, particle size, and filler arrangement. Consequently, some prediction models, which were well validated with numerical results, are first developed. Additionally, the ETC of polymer composite dramatically and non-linearly depends on TC ratios, VF ratios, particle distribution, filler arrangement, and particle size of the triple filler. The mountain shape of the ETC forms and depends on a variety of effective factors. The maximum ETC exists at the given optimum TC ratios ranging from approximately 0.1 to 100. It was also found that the ETC increases with the increase of the VF ratio for a threshold TC ratio; however, this trend changes when TC ratios go beyond the threshold values. Particularly, the ETC of the particle-filled polymer composite also depends on the filler arrangement, even though particles are straightly arranged along the direction of thermal flow. This effect becomes more significant when the difference in VF and TC between particles is larger. The results obtained are very useful in enhancing and maximizing the ETC of polymer composites with triple fillers and even multiple fillers in general.

Analysis of friction and wear performance of eco-friendly basalt filler reinforced polylactic acid composite using the Taguchi approach

The main goal of this research is to utilize sustainable and eco-friendly basalt materials for the fabrication of bio-based thermoplastic composites. This will help to keep up with ecologically balanced factors. There have been several studies on natural fiber reinforced with different polymer matrices during the past 10 years. As a result, the academics and experts expressed concern about the environmental imbalance. By keeping these points, an attempt was made to fabricate basalt fillers reinforced polylactic acid composites with the maximum weight ratio (30 wt %), and the tribological study is conducted for the fabricated composites. In this study, the Taguchi and analysis of variance (ANOVA) approaches have been used to analyze the coefficient of friction (COF) and specific wear rate (SWR) of polylactic acid composite reinforced with constant 30 wt% basalt fillers. The morphology, particle size, and elemental composition of the basalt fillers are examined using scanning electron microscopy, a particle size distribution analyzer, and energy-dispersive X-ray analysis, respectively. The tribology tests are conducted with Pin-on-Disk Tribometer following the ASTM G99 standard, following the L18 orthogonal array design, which was developed using the statistical program MINITAB-19. The selected parameters for the analysis are basalt (wt %), load (N), speed (rpm), and distance (m) under dry conditions. For PLA samples, the optimum parameters in response to COF is found to be 0 wt% basalt, 3 N load, 100 rpm speed, and 100 m distance; for the SWR output, the optimum parameters are 30 wt% basalt, 6 N load, 100 rpm speed, and 150 m distance. The consistent observation is that adding basalt fillers has not significantly reduced COF but has contributed more to SWR reduction with PLA composite. The best COF value for PLA samples is obtained with low sliding distance. The typical observation across all COF graphs is that the COF value first seems to be lower due to a smoothened polymer surface, rises throughout an experiment, and then stabilizes with very little variance. Regardless of the processing parameters, the depth of wear steadily increases with increasing load as observed in 2D depth profiles. The neat PLA polymer morphology that gives the illusion of deep grooves and many tracks dispersed over a single worn surface shows how the maximum parameter influence is more obvious on the surface of the sample. Overall, the results suggest that thermoplastic composites are feasible for the manufacturing of paper mill rollers.

Parametric study on producing Fused Deposition Modelling filament made of recovered carbon black reinforced Acrylonitrile Butadiene Styrene plastics

Additive manufacturing is a process that makes three-dimensional object layer by layer. There are many different types of 3D printer and the most commonly used is Fused Deposition Modeling (FDM). There is a need for a new material for Acrylonitrile Butadiene Styrene (ABS) FDM filament to improve filament strength and reduce the usage of plastics. From literature, there are limited studies available on making 3D printer filament reinforced by recycled carbon black. The limitation hinders the potential of using this material in new applications. In this study, recycled carbon black powder (rCB) was added as a filler reinforcement to enhance the properties of ABS. Parameters considered in this study were percentage of filler weight loading and filler size. Tests and characterisation used in this study were tensile test, thickness test, surface roughness test, scanning electron microscopy, density test and water absorption test. There were improvements in mechanical properties such as tensile test and elasticity of the filament compared to the pure ABS plastic. The higher filler percentage can improve the elasticity of filament and lower filler percentage can improve the strength of the filament. The findings could help in improving marketability status and commercialisation potential of rCB reinforced ABS filament for FDM applications.

A developed Takayanagi model to estimate the tensile modulus and interphase characteristics of polymer nanocellulose composites

This study analyzes the tensile modulus of nanocellulose-reinforced composites by developing the Takayanagi model considering the interphase section and filler size. The model accuracy is assessed by reported experimental moduli of composites and by parametric studies. The estimates of advanced model fit to the measured moduli of numerous examples. Also, it is revealed that the treatment of nanocellulose increases the modulus and thickness of interphase in nanocomposites. The relative modulus (Er) as the ratio of nanocomposite modulus to the modulus of matrix significantly changes when nanocellulose modulus (Ef) is raised from 50 to 100 GPa; however, Er unimportantly rises at Ef > 100 GPa. Additionally, nanocellulose radius (R) of 2 nm maximizes the Er to 1.636, though Er decreases to 1.09 at R = 58 nm and the variation of Er is insignificant at R > 20 nm. Furthermore, the interphase moduli (Ei) below 10 GPa meaningfully affect the nanocomposite modulus, but Ei > 10 GPa cannot cause the considerable change in Er. Therefore, Er does not change at the high levels of Ef, R and Ei.

Comparative study on the tribological properties of poly(arylene ether nitrile)/polytetrafluoroethylene composites: The influence of filler size and testing conditions

AbstractIn this work, the influence of polytetrafluoroethylene (PTFE) filler size and testing conditions (i.e., air, water, and lubricating oil) on the tribological properties of poly(arylene ether nitrile) (PEN) was systematically investigated. The results showed that the addition of PTFE was beneficial to improve the tribological properties of PEN‐based composites which was related to the easier formation of transfer film on the surface of friction pair. Samples which were tested in water demonstrated a relatively higher friction coefficient (μ) and wear loss when compared with those tested in dry air and lubricating oil scenarios, which was attributed to the fact that friction induced heat and wear debris could be timely removed by water. In addition, the infiltration of water further reduced the interaction between PTFE filler and PEN, which aggravated the wear loss of sample blocks. When tested in lubricating oil, pure PEN showed the lowest wear loss when compared with that of PEN/PTFE composites. At a given content (20 wt%) of PTFE fillers, PEN/PTFE1.5μm exhibited the lowest μ in lubricating oil whereas PEN/PTFE5μm demonstrated the lowest specific wear loss in air condition (1.18 × 10−6 mm3/N·m). This work provided some useful information for the design and application of PTFE‐containing polymer composites that can be targeted in different lubrication scenarios in industrial fields.

Electromagnetic interference shielding composites and the foams with gradient structure obtained by selective distribution of MWCNTs into hard domains of thermoplastic polyurethane

In this paper, multilayer thermoplastic polyurethane (TPU)/multiwalled carbon nanotubes (MWCNTs) electromagnetic interference shielding composite foams with gradient structure was prepared. The gradient distribution of effective concentration of filler and cell size were realized by selective distribution of MWCNTs into hard domains of TPU, which improved interlayer interface polarization of electromagnetic waves and impedance matching between the material and the air. The average electromagnetic interference shielding efficiency (EMI SE) of TPU/MWCNTs composites with gradient structure is 1.2 times larger than that of homogeneous composites. After foaming, the average EMI SE of the gradient foams was higher than that of the homogeneous foams, with maximum average EMI SE of 35.4 dB. This work is the first time to correlate the interaction of fillers with the soft domains and hard domains of TPU and EMI shielding performance, providing a feasible method for designing lightweight composites with low filler and better EMI shielding performance.

Nanocomposite physics and structure considerations in MCNP proton shielding models

Background Deep space crewed missions require unique radiation shielding considerations. Due to mission duration and the heavy, high-energy nature of deep space radiation, the aluminum alloys that have historically been used for spacecrafts do not provide sufficient protection for crew members. Polymer-based nanocomposites have been proposed as potential radiation shielding materials for deep space applications; however, the high tunability of nanocomposites and the limited number of facilities able to produce representative radiation energies presents barriers to nanocomposite testing. Computational approaches may allow for preliminary investigation and discrimination of nanocomposite parameters like polymer and filler composition, loading percentage, and filler size and structure. Methods This work aims to investigate several modeling methods to perform radiation transport simulations for a nanocomposite, particularly with regards to modeling the filler nanostructure and the involved physics. Published experiments of a polydimethylsiloxane-carbon nanotube nanocomposite in 63 MeV and 105 MeV proton beams were digitally recreated in MCNP6.2 with three different nanocomposite structures. Additionally, several simulations were performed under various physics assumptions. The computationally determined water equivalent thicknesses are compared between modeling methods, as well as between the computational and the published experimental work. Results Nanostructure model complexity had no impact on the computed water equivalent thickness, with <1% difference between the three modeling methods. The inclusion of delta ray production and tracking physics produced a slight decrease in the computed water equivalent thickness and significantly increased the computational time for a single simulation by a factor of 35.7. Computationally determined water equivalent thicknesses are within 5% of published experimentally determined values. Conclusions Shielding capabilities of a polymer/carbon nanotube nanocomposite estimated using Monte Carlo radiation transport models agree well with published experimental results, even with a simplistic representation of the nanocomposite material. Radiation transport settings influenced the resulting water equivalent thickness as well as computational resource needs.

Modified poly(phenylene oxide)/(CaSr)TiO3 composites with ultrahigh permittivity and low loss for microwave substrates

Polymer/ceramic composites used as microwave dielectric combine the excellent dielectric properties of ceramic with the toughness of polymer. The properties of composites are not only determined by the properties of components but also influenced by the polymer-ceramic interface. In this work, we conducted experiments and simulations on the dielectric properties and thermal conductivity of modified poly(phenylene oxide)/(CaSr)TiO3 (mPPO/CST) composites. A comparison of composites filled with different sizes (2.5, 11, and 20 µm) of CST fillers demonstrates that smaller particle (more filler-matrix interface) is beneficial to mechanical properties but detrimental to dielectric properties and heat transfer. The finite element simulation results are in good agreement with the experimental values, which is of significance for guiding future experiments. The composite filled with 80 wt. % CST20 has a high relative density of 97%, an ultrahigh εr of ∼20, and a low tan δ of 0.0019 at 10 GHz. Meanwhile, the mPPO/CST composites are eco-friendly and suitable for mass production and are promising candidates for automotive and aerospace applications.

Effect of fillers on the microphase separation in polyurethane composites: A review

AbstractThe microphase separation behavior of polyurethane (PU) strongly affects its mechanical, thermal, electrical, and other functional properties. Adding fillers to change the degree of microphase separation (DPS) in PU is a convenient and efficient method. Although many scholars have tried to regulate the microphase separation of PU by adding fillers, there are still many controversies about the effect. In this review, we classify commonly used fillers into three categories according to their morphology: spherical fillers, fibrous fillers, and layered fillers, and summarize their effects on the microphase separation behavior of PU. We explore the similarities and differences in the mechanisms by which different fillers affect the microphase separation of PU, and find that the polarity, morphology, size of fillers, and preparation method have a significant impact on the degree of microphase separation in PU. The impact of microphase separation on the mechanical properties of PU has also been summarized to illustrate their close relationship. We hope that these summaries will provide some guidance for the development of new high‐strength and multifunctional PU composites.Highlights Summarized recent research progress on effect of common fillers on DPS of PU. Common fillers are classified into three categories based on their morphology. Common laws of the fillers impact on the DPS are classified and discussed. The close relationship between DPS and mechanical properties is reviewed. Provided information for high‐strength and multifunctional PU development.

Optimization of the alkali treatment on the tempo‐modified cellulosic nanoreinforcement in autoclaved epoxy matrix

AbstractInvestigators increased interest in composites with novel natural fibers beholds significant progress globally over the past decade. Moringa oleifera seed filler is among the few newly known novel fiber‐rich in cellulose and meagrely used in commercial industries. This research article used a broad characterization of 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO)‐modified Moringa oleifera cellulosic nanoreinforcement/epoxy composites to verify its potential as a feasible substitute for synthetic fibers in polymer composites. Composites were fabricated at a fixed filler size of 300–500 nm with a loading of 15 wt% untreated and alkali‐treated composites through the two processes: hand lay‐up followed by autoclave curing. The properties, such as, static and dynamic mechanical properties and thermal stability, have been studied for untreated and treated composites. Composites with 5 wt% alkali treatment TEMPO‐modified nano‐cellulosic filler (TMCF) loading possesses superior water resistance, interfacial surface chemistry, and mechanical property compared to autoclaved epoxy and the untreated composite. Four isoconversional methods, Friedman, Coats‐Redfern, Broido, and Kissinger, were utilized to investigate the degradation behavior and kinetic parameters like activation energy of composites. Composites that have been 5 wt% mercerized exhibit greater thermal resilience and activation energy of 250 kJ/mol, which is 20% greater than the untreated sample. This study validates the 5 wt% alkali treated TMCF as a novel sustainable and bio‐reinforcement in polymer composite for semi‐structural applications.

An Investigation on Filler Particle Size and Its Distribution in Glass-Epoxy Hybrid Composites Using Image Processing

Analysis of filler particle size and distribution plays a vital role in achieving a good balance of polymer composites’ electrical, thermal, and mechanical properties. Such assessments help understand the relationship between microstructure and the physical nature of polymer composites reinforced with fillers. In this investigation, glass epoxy composites with different nano and micro-sized fillers, namely SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , graphite and cenosphere, are fabricated by hand-lay technique with bagging. Particle analysis is carried out by employing image processing techniques using ImageJ. To understand the nature of hybrid filler size distribution, a comprehensive assessment of the micro and nanofiller particle distribution and the average shortest and longest separation distance between the nano and micron particles is estimated. From the particle size distribution analysis, it is observed that the micron particles are more evenly distributed than nanoparticles. The average distance between micron and nanofiller particles is observed depending on the type of filler used. The microparticles tend to surround the nanoparticles, which is desirable for decreasing the free space distances between the filler particles. Also, statistical analysis is carried out to study the experimental and estimated micron and nanofiller particle sizes used in the composites.

Post-consumer recycling of Tetra Pak®: Starting a “new life” as filler in sustainable polyurethane foams

Tetra Pak® is a laminated packaging consisting in cardboard, aluminum and LDPE layers, used to preserve several food products and beverages. Recycling of such material is not trivial; usually packages end up in the landfill. In this study, Tetra Pak® scraps were used as reinforcing filler for sustainable composite polyurethane (PU) foams, without components separation. Foams were prepared through polyaddition reaction between di-isocyanate source and biobased polyols, in presence of suitable additives and blowing agents, and by loading Tetra Pak® at 5 wt% and 20 wt%, respectively. The effect of filler size, shape and concentration on thermal, morphological and mechanical characteristics of the foams was investigated. The intercalation of Tetra Pak® corresponded to compressive stress (3 times more) and the flexural stress (50% more) increases with respect to the unloaded foam. The so-obtained foams can be used in food packaging (as containers) and in other applications.

Surface Properties of Resin Composites and CAD/CAM Blocks After Simulated Toothbrushing.

This study aimed to evaluate the surface gloss, surface roughness, and color change of restorative materials after a three-body wear abrasion. Four resin composites with different filler particle size (Gracefil Flo [GFF, 0.7 μm], Gracefil LoFlo [GFL, 0.25 μm], Gracefil ZeroFlo [GFZ, 0.15 μm], and Gracefil Putty [GFP, 0.3 μm]), two CAD/CAM resin composite blocks with different filler particle size (Cerasmart 300 [CS3, 0.7 μm] and Cerasmart Prime [CSP, 0.3 μm], GC), and one CAD/CAM lithium disilicate glass-ceramic block (Initial LiSi Block [ILS], GC) as a control were evaluated. Twenty slab-shaped specimens were obtained from each material. Ten specimens were subjected to 80,000 toothbrushing strokes and measured for surface gloss (Gloss Unit, GU), surface roughness (Ra, μm), and color (L*, a*, and b* values) before toothbrushing and at every 20,000 strokes. Color differences (ΔL*, Δa*, Δb*, and ΔE00) before and after toothbrushing were calculated. After 80,000 strokes, abraded surfaces were observed using scanning electron microscopy. The other 10 specimens were measured for Vickers microhardness (VHN). After 80,000 toothbrushing strokes, the mean GU ranged from 60.43 to 16.12 (the highest for ILS and lowest for GFL), and the mean Ra ranged from 0.079 to 4.085 (the lowest for ILS and highest for GFL). At all measuring stages, the calculated ΔE00 values ranged from 0.31 to 0.92 for all materials. The mean VHN ranged from 632.34 to 39.08 (the highest for ILS and lowest for GFZ). The resin composite containing the largest filler particle (GFF) showed significantly lower Ra and higher VHN than other resin composites (GFL, GFZ, and GFP). The CAD/CAM resin composite block containing a smaller filler particle (CSP) retained significantly higher GU than that containing a larger filler particle (CS3). A negative correlation between GU and Ra was detected. Based on the findings, toothbrush abrasion induced a decrease in GU and an increase in Ra for all resin-based materials tested. Resin-based materials with larger filler size tended to show lower Ra, while resin-based materials with smaller filler size tended to show a smaller reduction in GU. These were more pronounced for light-cure resin composites than for resin composite blocks for CAD/CAM.

Comparative analysis between size and mass ratio of nano-Al2O3 in the performance of dental composite and finding the optimum composition

Dental composites provide better bonding with tooth tissue as compared to other traditional materials such as amalgam. However, the development of dental composites relies on experimental results of physical, mechanical and thermal properties of the dental composite obtained after applying the strategy of filler technology, i.e., changing size, shape, surface modification and mass ratio of filler or reinforcement. In the present research, nano-Al2O3 particle size and filler mass ratio were varied to study their effect on the physical, mechanical and thermal behaviour of dental composite. The particle size was varied in the range of 30 nm, 50 nm and 70 nm. Nano-Al2O3 filler mass ratio was varied in the range of (0, 5, 10 and 15 wt. %). Fourier transform infrared analysis was done to check variations in absorption peak and band in the spectrum due to variation in the filler mass ratio and size. Physical properties, mechanical properties and thermal properties were investigated. It was observed that hardness, compressive strength, diametral tensile strength, flexural strength and stress intensity factor were increased by 133%, 13.6%, 27.4%, 25% and 20%, respectively, on adding 5 wt. % of nano-Al2O3 and decreased by 13.5%, 8.1%, 15.3%, 13.9% and 10.3%, respectively, on increasing particle size from 30 nm to 50 nm. The thermal degradation temperature was increased by 31.8% and 36% on adding 5 wt. % and increasing particle size from 30 nm to 50 nm, respectively. It can be concluded that in the case of nano-sized particulate filler, mass ratio played a more significant role than filler size in regards to optimization of physical, mechanical and thermal properties.

Effect of ionizing radiation on thermal and mechanical properties of filled-epoxy adhesives

Stave assemblies at the Large Hadron Collider and other high-energy physics experiments require radiation-resistant adhesives composed of light elements with high thermal conductivity and low interfacial resistance. Porous carbon foams are currently bonded to carbon fiber faceplates with graphite-filled epoxy. Low-viscosity epoxies are used to increase the amount of filler in order to double the thermal conductivity without impacting the properties of the material under irradiation. Promising new adhesive formulations showed no degradation in thermal conductivity after exposure to a fluence of 1016 n/cm2 (>0.1 MeV neutrons) or 10 Gy gamma radiation, but showed variable degradation, compared to the currently used adhesive, after exposure to a fluence of 1015 p/cm2 (1 MGy, 67.5 MeV protons). Adhesives with more than double the irradiated thermal conductivity of the baseline material showed marked improvement in thermal transport in graphite/epoxy/foam/epoxy/graphite structures based on thermal diffusivity measurements. Silicon carbide particles can be added to graphite to stiffen the modulus of the filled epoxy. When spherical AlN was used as a filler, the degradation in thermal conductivity under proton irradiation varied based on the size of the ceramic filler. Options for improving the thermal performance of irradiated adhesives for high-energy physics experiments are discussed.