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OBJECTIVE: The objective was to review literature with regard to secondary caries around composite restorations to obtain better insights in the mechanisms behind secondary caries with composites. BACKGROUND: Secondary caries, the...
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OBJECTIVE: The objective was to review literature with regard to secondary caries around composite restorations to obtain better insights in the mechanisms behind secondary caries with composites. BACKGROUND: Secondary caries, the lesion at the margin of a restoration, has been widely considered as the most important and common reason for restoration replacement, regardless of the restorative material type. The Federation Dentaire Internationale defined secondary caries as a 'positively diagnosed carious lesion, which occurs at the margins of an existing restoration'. Due to its importance to the longevity of the restorations and human oral health, over the past few decades, multiple studies have been conducted both in vivo and in vitro to understand and prevent secondary caries, including the etiology and histopathology of secondary caries, the detective and diagnostic methods of secondary caries, the relationship between micro leakage and secondary caries, as well as the cariostatic effects of various restorative materials. REASON: The review is done in order to suggest that the restorative material might influence the development of secondary caries in different ways and the preventive measures to reduce secondary caries.
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Creating biodegradable polymer compositions is an urgent problem. In this research, the processing parameters and physicomechanical properties of materials based on secondary polypropylene and secondary polyethylene filled with pl...
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Creating biodegradable polymer compositions is an urgent problem. In this research, the processing parameters and physicomechanical properties of materials based on secondary polypropylene and secondary polyethylene filled with plant-based fillers are studied. It is estimated that the introduction of a filler leads to an increase in the maximal torsion torque; the lowest resistance against filler introduction is observed in the use of secondary polyethylene. Similar regularities are observed during the study of the minimal torsion torque; however, in this case, the lowest resistance is observed for the sample of secondary polypropylene. It is shown that the introduction of 10-15 parts by the mass of the filler leads to an increase in the elastic modulus and an insignificant decrease in the values of rupture stress and elongation upon breaking.
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In this study, hybrid composites based on carbon fiber (CF) and polypropylene (PP) were fabricated by melt mixing techniques. The composite with optimum fiber length (8 mm) was chosen as a reference material, and to it, CF of vari...
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In this study, hybrid composites based on carbon fiber (CF) and polypropylene (PP) were fabricated by melt mixing techniques. The composite with optimum fiber length (8 mm) was chosen as a reference material, and to it, CF of various lengths (6 mm, 100 mu m, 60 mu m and 100 nm) were added as secondary filler. To understand the synergism effect of these fibers, electrical, rheological, thermal and morphological properties of composites were studied. The surface resistivity of the neat PP is in the order of 10(17) ohm/square. It is observed that surface resistivity of a single fiber filled composite is in the range of 10(4) ohm/square, while it further decreased by threefold (10(1) ohm/square) in the case of secondary fiber filled composites, indicating that the electrical network remains intact. Thermal analysis shows variation in crystallization of hybrid composites that can correlate to the lengths of secondary fibers. The rheological analysis shows that the frequency dependence of storage modulus (G') and loss modulus (G '') in the lower frequency region indicates an elastic solid like behavior of these composites. The morphological behavior showed that the CFs are well dispersed and form a good adhesion with the polymer matrix.
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The current solid polymer electrolytes suffer from poor conductivity, low mechanical and electrochemical stability toward the lithium electrodes. To improve the performance of solid polymer electrolytes, the addition of nanopartic...
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The current solid polymer electrolytes suffer from poor conductivity, low mechanical and electrochemical stability toward the lithium electrodes. To improve the performance of solid polymer electrolytes, the addition of nanoparticle fillers to the polymer electrolyte is being extensively investigated. In this paper, a brief review on the state of art of solid fillers for lithium battery electrolytes is presented.
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Secondary sludge from pulp and paper mills can be considered as a potential filler for composite industry. The surface thermodynamics of the secondary sludge from two different pulp and paper mills, processing capability, and mate...
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Secondary sludge from pulp and paper mills can be considered as a potential filler for composite industry. The surface thermodynamics of the secondary sludge from two different pulp and paper mills, processing capability, and material characteristics of biocomposites filled by secondary sludge were studied in this study. Inverse gas chromatography (IGC) has been employed to study the surface characteristics of the secondary sludge. Also, the cellular biopolymers were extracted and their surface energy determined by IGC. Based on the surface thermodynamics and the chemical structure of the secondary sludge, Nylon II was selected as the polymeric matrix. The dispersive component of surface energy for the secondary sludge samples was obtained in the range 60-42 mJ/m~2 measured at 313-373 K, which is high enough to allow the biosolid to be coupled with conventional polymeric resins. The manufactured nylon/sludge composites showed acceptable, yet not improved, mechanical strength. Also, 10% of dried sludge as filler proved to be an effective amount, which is sufficient to fill but not deteriorate the tensile and flexural strengths of the composite. Sludge-filled composites compounded by a twin-screw extruder exhibit considerably better tensile properties than those compounded by the K-mixer. Maleated polyolefins used as coupling agents also improved the composite's mechanical properties significantly.
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The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service tempera...
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The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service temperatures by using pendulum type impact testing machine. Specimens were tested with two notch configurations such as notch along the laminate and notch across the laminate. The composite laminates were fabricated by using a hand lay-up technique and the experimentations were carried out according to the ASTM standards. The results showed that the specimen subjected to high temperature requires higher breaking impact toughness till 60 °C, further increase in temperature leads to decrease in required breaking impact toughness. The notch along the laminate is highly prone to catastrophic failure and notch across the laminate sustains the impact load to a considerable amount.
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摘要 :
The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service tempera...
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The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service temperatures by using pendulum type impact testing machine. Specimens were tested with two notch configurations such as notch along the laminate and notch across the laminate. The composite laminates were fabricated by using a hand lay-up technique and the experimentations were carried out according to the ASTM standards. The results showed that the specimen subjected to high temperature requires higher breaking impact toughness till 60 °C, further increase in temperature leads to decrease in required breaking impact toughness. The notch along the laminate is highly prone to catastrophic failure and notch across the laminate sustains the impact load to a considerable amount.
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The preparation of fluororubber foam has always been a promising task because of its easy shrinkage characteristic, a promising way to overcome this challenge is to implement collaborative technology. Fluororubber foam with stable...
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The preparation of fluororubber foam has always been a promising task because of its easy shrinkage characteristic, a promising way to overcome this challenge is to implement collaborative technology. Fluororubber foam with stable properties were successfully developed by irradiation pre‐crosslinking, followed by supercritical foaming and secondary cross‐linking in the oven using supercritical N2 as foaming agent. The cross‐linking degree and tensile modulus of fluororubber foam enhanced with the increased absorbed dose (40, 50, and 70?kGy), and the second cross‐linking effect was better at the dose of 40?kGy in fluororubber foam. The fluororubber foam without secondary cross‐linking would shrink gradually, however it could reach a stable state after secondary cross‐linking. Fluororubber filled with carbon black (5, 10, 15, and 20?phr) showed different modulus change trend in different strain range. Better fluororubber foam was obtained after secondary crosslinking, where the addition of carbon black promoted the fluororubber foams with more uniform cell structure. The secondary cross‐linking had a good stabilizing effect on fluororubber foam filled with carbon black, which had an important guiding significance in practical production.
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