Effects Of Ultrasonic Amplitude Research Articles

The effect of ultrasonic extrusion on the structure and properties of BR gum and prepared compounds and vulcanizates

Abstract Ultrasonic extrusion of BR was conducted and processing characteristics were evaluated. Ultrasonic power consumption increased with the increase of ultrasonic amplitude. Die pressure decreased with the increase of ultrasonic amplitude indicating that the imposition of ultrasound can be used to increase extrusion output rate. The effect of ultrasonic amplitude on molecular structure of BR, including molecular weight and gel formation behavior were studied. Depending on the ultrasonic amplitude, structure changes occurred in BR, including a degradation, formation of long-chain branching and gel. Untreated and treated BR were mixed with CB, silica and silica/silane. Bound rubber content and flocculation behavior were studied. Formation of the long-chain branching was shown to increase the bound rubber content and rubber-filler interaction and to reduce the filler-filler interaction and flocculation of BR/silica compound. Both the untreated and treated BR, BR/CB, BR/silica and BR/silica/silane were vulcanized and their crosslink density, gel fraction and mechanical properties were measured. Based on DMA temperature sweep of BR/silica vulcanizate, it was shown that formation of the long-chain branching during ultrasonic treatment reduced the loss tangent at 60 °C, predicting a lower rolling resistance if the rubber used in tires.

Cavitation Bubble Dynamics Induced by Hydrodynamic Pressure Oil Film in Ultrasonic Vibration Honing

During ultrasonic vibration honing (UVH), a thin hydrodynamic oil film formed can seriously affect the cavitation effect in the grinding fluid, but the mechanism is still unclear now. Based on the hydrodynamics theory, a revised cavitation bubble model with oil film pressure is developed, and it has been calculated by the four-order Runge–Kutta method. The calculation results show that the oil film pressure under UVH is a positive–negative alternant pulse pressure, and it can induce the secondary expansion of the bubble, leading to double microjets during the process of the bubble collapsing. The effects of ultrasonic amplitude, ultrasonic frequency, oil film height, and reciprocation speed of the honing stone on the bubble dynamics are discussed. With the increase of ultrasonic amplitude, the amplitude of the bubble expansion is increased, and the oscillation interval is extended. As increasing normalized oil film height, the variation of the bubble first expansion is slight, while the amplitude of the bubble secondary expansion is reduced and the oscillation interval is also shortened. The main effect of ultrasonic frequency and reciprocation speed of the honing stone on the bubble dynamics is connected with the secondary bubble expansion. The bubble secondary expansion is decreased with the increasing reciprocation speed of the honing stone, ultrasonic frequency, and oil film height. The results of the simulations are consistent with the surface roughness measurements well, which provides a theoretical prediction method of cavitation bubbles control.

Effect of Ultrasonic Amplitude on Surface Properties of Anodised Titanium for Biomedical Application

Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It is a simple and low cost method to produce bioactive material. This work describes the effect of ultrasonic amplitude on the surface properties of anodised titanium. Specifically, high purity titanium foils were anodised in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate monohydrate (CA) at 350 V and 70 mA.cm-2 for 10 minutes. The ultrasonic amplitude was varied from 20-60 μm. Next, field emission scanning electron microscopy (FESEM) glancing angle X-ray diffractometer (GAXRD) and atomic force microscopy (AFM) were used to characterise the anodised titanium. The results showed that application of sonication is able to remove the entrapped bubbles on the anode surface and enhance the oxidation process. The pores size and surface roughness were increased as increasing of ultrasonic amplitude. At ultrasonic amplitude ≥ 50 μm, rutile TiO2 was formed on the surface of oxide layer. It was found that the sonication is a simple method to improve the surface properties of anodised titanium for implant applications.

Properties of polyetherimide/graphite composites prepared using ultrasonic twin‐screw extrusion

ABSTRACTThe dispersion of various graphites in polymers is a challenging problem limiting their potential use. To solve this problem, an ultrasound assisted twin‐screw extruder was developed and utilized to compound polyetherimide (PEI) with untreated nature graphite (UG), modified graphite (MG) and expanded graphite (EG) at concentrations up to 10 wt %. The effect of ultrasonic amplitude on rheological, mechanical and electrical properties of the PEI composites was investigated. Ultrasonic treatment of PEI/UG composites showed little effect on these properties. In contrast, ultrasonic treatment of PEI/MG and PEI/EG composites led to an increase of the storage (G′), loss (G″) moduli and complex viscosity and to a decrease of the damping characteristics. In particular, the PEI/5 wt %EG composite ultrasonically treated at an amplitude of 10 μm showed a 45% higher complex viscosity than the untreated composite at a frequency of 0.5 rad/s. Also, the PEI/5 wt % EG composite treated at an amplitude of 10 μm showed a reduction in the electrical volume resistivity by almost three orders of magnitude leading to a lower percolation threshold. The untreated and treated PEI/UG and PEI/MG composites did not show any percolation within all graphite concentrations studied, due to large size of particles of UG and MG and their strong agglomeration. The ultrasonic treatment showed slight effect on mechanical properties of all these composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41397.

Ultrasound-assisted Suzuki coupling reaction for rapid synthesis of polydihexylfluorene

Ultrasound-assisted synthesis of conjugated polymer is reported taking PF as an example. It is found that ultrasound can dramatically accelerate the Suzuki coupling reaction. The effects of ultrasonic amplitude, time, monomer and catalyst's concentration on the polymerization have been investigated. PF with high Mw of 39,100 g/mol is obtained in 20 min under optimized condition.

ULTRASONIC AIDED EXTRUSION OF CNT- AND CNF-FILLED SBR COMPOUNDS AND PROPERTIES OF THEIR VULCANIZATES

Abstract Ultrasonically assisted single screw extrusion of styrene–butadiene rubber (SBR) compounds filled with multiwall carbon nanotubes (CNT) up to 20 phr and carbon nanofibers (CNF) up to 35 phr was carried out. The effects of ultrasonic amplitude on processing characteristics, rheology, extractable amount, vulcanization behavior, mechanical properties, abrasion, electrical resistivity, and morphology were investigated. Ultrasonically treated compounds showed an increase in viscosity and unextractable content in both CNT- and CNF-filled compounds. A decrease in the induction time of curing with amplitude was observed in CNT-filled compounds. However, the induction time of CNF-filled compounds showed more complex behavior with amplitude. The final cure torque, crosslink density, modulus, and tensile strength showed a maximum at an intermediate amplitude in filled vulcanizates. An increase in the glass transition temperature (Tg) and a decrease in tan δ at Tg with amplitude were observed in CNF- and CNT-filled vulcanizates. At the same time, tan δ in the range of 0–60 °C of these vulcanizates showed, respectively, a minimum and a continuous increase with amplitude. CNF-filled vulcanizates exhibited improved abrasion resistance with optimum results at an amplitude of 5.0 μm. The effect diminished with increasing CNF loadings. Improvements in abrasion resistance of CNT-filled vulcanizates were observed at certain amplitudes at low CNT loadings only. Ultrasonic treatment caused a significant reduction in the electrical percolation threshold of CNF- and CNT-filled vulcanizates. Atomic force microscope analysis showed a generation of unique CNT agglomerates by ultrasonic treatment, suggesting an increase of rubber–filler interaction. High resolution scanning electron microscopy analysis of vulcanizates showed better dispersion of ZnO by ultrasonic treatment.

ULTRASONIC AIDED EXTRUSION OF CARBON BLACK-FILLEDSBR COMPOUNDS

Abstract Ultrasonically assisted single screw extrusion of carbon black (CB)-filled styrene–butadiene rubber (SBR) compounds up to 60 phr was carried out and its processing characteristics were measured. The effects of ultrasonic amplitude on rheology, extractable amount, vulcanization behavior, mechanical properties, abrasion, electrical resistivity, and morphology were investigated. Increasing ultrasonic amplitude led to a reduction of extractable content with the effect diminishing with increasing CB loading. Treated compounds showed an increase in viscosity at certain amplitudes. Cure curves revealed reduced induction times with increasing amplitude, except at the highest CB content. The maximum torque of the cure curve, crosslink density, and mechanical properties of vulcanizates all showed an increase at certain ultrasonic amplitudes. An increase in the glass transition temperature (Tg) and a decrease in tan δ at Tg were observed with increasing amplitude. Ultrasonically treated unfilled and CB-filled compounds led to vulcanizates with significant and slight improvements in abrasion, respectively. Ultrasonic treatment caused a significant reduction in the electrical percolation threshold of vulcanizates. Morphological study by atomic force microscope revealed a creation of unique CB agglomerates, suggesting the strong interactions between the SBR and CB aggregates in treated compounds, leading to reinforcing effects in vulcanizates.