A Rapid Method for the Determination of SBS Content Based on the Principle of Orthogonal Testing

The performance of Styrene-butadiene-styrene (SBS) modified asphalt is closely related to the content of SBS modifier. In the production process of modified asphalt, a certain amount of additive such as sulfur and rubber oil may be added to reduce the segregation and promote the swelling of the polymer, but the effect of these additives on determining SBS content in asphalt is not yet clear. This paper presents the calibration curves of SBS content based on rutting factor and creep slope and points out its defects according to the temperature scanning test and the bending beam rheometer test. Subsequently, using Fourier transform infrared spectroscopy (FTIR) for rapid determination of polymer content in SBS modified asphalt based on orthogonal test and then the effects of additives such as asphalt type, SBS content, rubber oil and sulfur on the accuracy of polymer content determination by FTIR were investigated. Moreover, in the orthogonal tests of adding sulfur and rubber oil, the multivariate analysis of variance (MANOVA) was firstly used to analyze the additives influence on the test accuracy of FITR. Results indicated that the influencing degree of different additives is different. The influence of sulfur on the determination accuracy is greater than that of rubber oil. Therefore, the rapid determination method needs further improvement.

Declining Performance of Silicone-Based Magnetorheological Elastomers after Accelerated Weathering

Magnetorheological elastomers (MRE)-based products are usually located in an area directly exposed to sunlight and rain. However, there is no specific research on the behavior of MRE after accelerated weathering. Therefore, in this study, the changes to the chemical and rheological properties of both isotropic and anisotropic MRE after accelerated weathering were examined. Treated and untreated specimens were compared. MRE specimens with 40% by weight CIP were prepared with no current excitation and another sample was prepared with 1.5 T of magnetic flux density. Each specimen was treated in an accelerated weathering machine, Q-Sun Xe-1 Xenon Test Chamber, under a UV light exposure cycle and water spray. A material characterization was carried out using FTIR and a rheometer to determine the changes to the chemical and rheological properties. The morphological analysis results showed that after the weather treatment, the surface was rough and more cavities occurred. The rheometer test results showed a significant decrease in the storage modulus of each treated MRE specimen, unlike the untreated MRE specimens. The decrease in the storage modulus value with currents of 0, 1, 2, and 3 Amperes was 66.67%, 78.9%, 85.2%, and 80.5%, respectively. Meanwhile, FTIR testing showed a change in the wave peak between the untreated and treated MRE specimens. Thermogravimetric analysis (TGA) also showed a decrease in MRE weight for each specimen. However, for both treated and untreated MRE specimens, the decrease in TGA was not significantly different. In all the tests carried out on the MRE samples, weather acceleration treatment caused significant changes. This is an important consideration for developers who choose silicone as the MRE matrix.

Modification Mechanism of Asphalt Modified with Rock Asphalt and Styrene-Butadiene Rubber (SBR)

High-performance asphalt binder plays an important role in the durable asphalt pavement. Asphalt modified by rock asphalt (RA) is one of the high-performance modified asphalt materials. It was used in road engineering as a relatively environmentally friendly material, because rock asphalt takes some advantages of large reserves, easy treatment, and efficient modification. Moreover, the main component of rock asphalt is bitumen, which enables it to substitute part of the binder used in asphalt mixtures. On the other hand, the negative low-temperature performance of RA modified asphalt impeded its application in cold regions. The object of this paper is to improve the low-temperature performance of RA modified asphalt by compound modified with styrene-butadiene rubber (SBR). The 70-penetration grade binder and the RA modified asphalt with 15% RA by weight were applied as the base binder. Five types of RA-SBR modified asphalt were prepared, and the content of SBR was 2%, 4%, 5%, 6% and 8% by weight of BRA modified binder. The Fourier transform infrared spectroscopy (FTIR) tests were utilized to illustrate the reasons for the poor low-temperature performance of BRA modified asphalt and reveal the compound modification mechanism of BRA-SBR modified asphalt. The Brookfield viscosity test, dynamic shear rheometer test, and bending beam rheometer test were adopted to reveal the variation patterns of rheological behavior and low-temperature performance with mass contents of SBR. The test results indicated that the worse of low-temperature performance was caused by the increase of asphaltene content and the stress concentration due to ash in RA modified asphalt. And the compound modification is a physical process. The addition of SBR has improved the low-temperature performance of RA modified asphalt dramatically. And based on the rheological behaviors and low-temperature performance of RA-SBR compound modified asphalt, the optimum content of SBR was determined, which is about 4%∼5%.

Laboratory Investigation of Rubberized Asphalt Using High-Content Rubber Powder

Rubberized asphalt (RA) has been successfully applied in road engineering due to its excellent performance; however, the most widely used rubber content is about 20%.To improve the content of waste rubber and ensure its performance, seven rubberized asphalts with different powder content were prepared by high-speed shearing. Firstly, penetration, softening point, and ductility tests were carried out to investigate the conventional physical features of high-content rubberized asphalt (HCRA). Then, the dynamic shear rheometer test (DSR) was conducted to estimate the high-temperature rheological properties. The bending beam rheometer test (BBR) was carried out to evaluate the low-temperature rheological performance. Finally, combined with the macroscopic performance test, the modification mechanism was revealed by the Fourier transform infrared reflection (FTIR) test, and scanning electron microscope (SEM) analysis was used to observe the microscopic appearance before and after aging. The results show that rubberized asphalt has excellent properties in high- and low-temperature conditions, and fatigue resistance is also outstanding compared with neat asphalt. As the crumb rubber content increases, it is evident that the 40% RA performance is the best. The low-temperature properties of HCRA are better than the traditional 20% rubberized asphalt. This study provides a full test foundation for the efficient utilization of HCRA in road engineering.

Comparing Test Methods for the Intra-ply Shear Properties of Uncured Prepreg Tapes

To achieve cost-efficient manufacturing and a high part quality in Thermoset Automated Fiber Placement (TS-AFP), knowledge about the interaction between material and process parameters is of special interest. Material properties of prepregs are well known at the cured state of the resin. However, there are no standardized test procedures for the mechanical behavior of the uncured prepreg tapes. To investigate the intra-ply shear deformation behavior of uncured unidirectional prepreg tapes, we compared several measurement procedures and conducted experiments for rheometer based tests using 8552/AS4 material. We identified a rotational parallel platens rheometer test method and a torsion bar rheometer test method to be suitable. Experiments using both methods revealed that the Torsion Bar Test has a higher repeatability and the analysis is less complex. Furthermore, first results show that changes in material properties caused by aging can be analyzed using this method. In the future,we will use the Torsion Bar Test to characterize changes in deformation behavior due to material aging as well as material modifications. By this, we will be able to provide data for the material modeling thus enabling the prediction of lay-up defects such as buckling due to steering.

The Impact of Erythrocytes Injury on Blood Flow in Bionic Arteriole with Stenosis Segment

Ventricular assist device (VAD) implantation is an effective treatment for patients with end-stage heart failure. However, patients who undergo long-term application of VADs experience a series of VAD-related adverse effects including pump thrombosis, which is induced by rotate impeller-caused blood cell injury and hemolysis. Blood cell trauma-related flow patterns are the key mechanism for understanding thrombus formation. In this study, we established a new method to evaluate the blood cell damage and investigate the real-time characteristics of blood flow patterns in vitro using rheometer and bionic microfluidic devices. The variation of plasma free hemoglobin (PFH) and lactic dehydrogenase (LDH) in the rheometer test showed that high shear stress was the main factor causing erythrocyte membrane injury, while the long-term exposure of high shear stress further aggravated this trauma. Following this rheometer test, the damaged erythrocytes were collected and injected into a bionic microfluidic device. The captured images of bionic microfluidic device tests showed that with the increase of shear stress suffered by the erythrocyte, the migration rate of damaged erythrocyte in bionic microchannel significantly decreased and, meanwhile, aggregation of erythrocyte was clearly observed. Our results indicate that mechanical shear stress caused by erythrocyte injury leads to thrombus formulation and adhesion in arterioles.