Effect of aluminum oxide powder reinforcement on degree of conversion, monomer release and flexural strength of heat-cured acrylic resin

Objectives: Effect and correlation of aluminum oxide powder on degree of conversion, residual monomer and flexural properties of heat-cured acrylic resin specimens were studied. Materials and methods: Heat-cured acrylic resin and aluminum oxide powders were used. Specimens of specific dimensions from unreinforced and reinforced acrylic resins using stainless steel plates were prepared. Degree of conversion was determined using FTIR Spectrometer. Released monomer was measured using isocratic high-performance liquid chromatography. Flexural strength was tested using three point-bending test. Results: Aluminum oxide reinforcement showed increased degree of conversion than that of the unreinforced specimens. Released monomer from reinforced specimens was lower than that of unreinforced specimens. Deflection at fracture of reinforced specimens was lower than that of unreinforced specimens. Flexural strength was increased by addition of 2.5 % and 5% aluminum oxide. There was a positive correlation between degree of conversion and flexural strength. There was a negative correlation between degree of conversion and monomer release. Conclusions: Aluminum oxide powder increased degree of conversion and flexural strength but reduced monomer release and deflection at fracture. There was a positive correlation between degree of conversion and flexural strength. There was a negative correlation between degree of conversion and monomer release. Clinical relevance: Aluminum oxide powder could reinforce the week acrylic resin denture base materials. Degree of monomer conversion during processing of acrylic resin denture base materials is very critical in determination of monomer release and mechanical properties of acrylic resin in service.

Influence of Coating on Mechanical Performance of Lap-Spliced Carbon Fiber-Textile Reinforced Mortar (TRM)

In this study, the effect of coating methods in the lap splice area on mechanical performance of lap-spliced carbon textile reinforced mortar (TRM) composites was investigated. The coating methods included textile reinforcement coated with epoxy, textile reinforcement coated with aluminum oxide powder and epoxy, and textile reinforcement coated with aluminum oxide powder, epoxy, and carbon fiber fabrics. It appears that the coated specimens showed higher peak strength and ultimate strain than those of the uncoated one.

Operational properties of chromium coatings obtained from self-regulating electrolyte with addition of nano-dimensional particles

The article presents the results of laboratory studies of microhardness and wear resistance of basic and nanocomposite electroplating chromium coatings. The most effective strengthening phase was chosen - nanosized alumina powder at a concentration of 3 g / l. The use of nano-sized aluminum oxide powder makes it possible to increase the microhardness and wear resistance of nanocomposite coatings by 1.5-1.8 times as compared to the base ones.

Tensile Behaviors of Lap-Spliced Carbon Fiber-Textile Reinforced Mortar Composites Exposed to High Temperature

The tensile behaviors of textile-reinforced mortar (TRM) composites made with carbon fiber textile and alumina cement-based mortar were investigated through direct tensile tests. Three different surface treatment details in the lap splice area were used to improve the tensile behaviors of the TRM composites: carbon fiber textile impregnated by epoxy, carbon fiber textile coated with aluminum oxide powder following epoxy impregnation, and carbon fiber textile coated with aluminum oxide powder following both carbon fiber fabric attachment and epoxy impregnation. Three different lap splice lengths were used 180, 200, and 220 mm. In addition, the tensile properties of TRM composites following exposure to high temperature were investigated as well. In this test, TRM test specimens were exposed to two different temperature histories with maximum values of 250 and 350 °C. The results of the test specimens according to the test parameters were analyzed in terms of initial stiffness, cracking strength, corresponding strain at cracking, modulus of elasticity in the cracked stage, peak strength, and ultimate strain. The influence of lap splice length on the tensile behaviors of the TRM composites was analyzed and discussed. The surface treatment in the overlapping region showed ductile behavior and resulted in a significant improvement of the peak strength and ultimate strain over the untreated lap splice textile. Following exposure to high temperature, the TRM composites showed a reduction of tensile responses compared to those cured at room temperature. In addition, a prediction model developed in the previous study was used to predict the tensile behaviors of the lap-spliced carbon fiber-textile reinforced mortar composites exposed to high temperature, and the prediction by the model showed a good agreement with the experimental results.