No abstract

As an auxiliary agent for rubber processing, polyethylene wax can be used to enhance the diffusion of filler in rubber, improve the extrusion speed of rubber compound and facilitate rubber demoulding, which has good development potential in the field of rubber processing and manufacturing. At present, there is no research on the optimum amount of polyethylene wax in silicone rubber. Therefore, in this paper, we studied the influence of different amount of polyethylene wax on the mechanical and friction properties of silicone rubber. Firstly, silicone rubber composites with different polyethylene wax content were prepared by mechanical mixing and hot pressing. Then, the mechanical properties and friction and wear properties of silicone rubber composites were tested by tensile testing machine and multifunctional comprehensive tester for surface properties of materials. Finally, combined with a series of characterization methods, such as three-dimensional (3D) morphology, scanning electron microscopy (SEM), microscopic observation and energy dispersive X-ray spectroscopy (EDS), the mechanism of polyethylene wax in silicone rubber was studied. The results show that the best addition amount of polyethylene wax in silicone rubber is 0.25 phr, and the friction coefficient of polyethylene wax/silicone rubber composite is the lowest and most stable, and the wear amount is the least. In the process of friction, polyethylene wax can be separated from silicone rubber matrix and distributed on the surface of wear marks, playing a better role in lubrication and wear reduction.

The analysis of progressive failure process is one of the critical issues in the research of composite adhesive joints. In view of this point, acoustic emission (AE) is applied to real-time monitoring of the dynamic damage process of composite adhesive joints in some loading modes such as Mode I (double cantilever beam (DCB)) and Mode II (end notch flexures (ENF)). Furthermore, the high speed camera and scanning electron microscopy are carried to analyses the damage mechanisms of composite bonded joints. Results show that there are significant differences in the load-deflection curves of the specimens under the loads of Mode I and II. The main failure mode of the two types of loading modes is adhesion failure, and the accumulation of damage observed at the edge of the adhesively bonded layer cause defeat of the composite bonded joints. In addition, AE parameters including amplitude, hits, energy, and duration are connected with the fail mechanism. Furthermore, the dynamic characteristics of the AE signal, especially amplitude spectrum distribution, can provide evidences for studying progressive failure behaviors of composite adhesive joints.