A novel methodology for evaluating wear behavior of rubber composites under combination of sliding and rolling conditions

The wear behavior of tire tread rubber composites has attracted widespread attention of researcher duo to its serious environmental pollution and high frequency of occurrence for a long time. Herein, a new test method is developed, an improved Akron friction testing machine on a laboratory scale was utilized to estimate the wear loss and mechanism of the rubber composites under rolling and sliding coupling condition. The results indicated that the wear loss quickly increases with the increase of the relative sliding velocity. The main wear mechanism, including adhesive, thermofatigue, tear and curl wear, was governed by the thermal deposition of the worn surface. Scanning electron microscope analysis showed thermal decomposition tear region gradually expanded on the worn surface by increasing relative sliding velocity. The heat distribution numerical analysis supported the experimental results, which confirmed that the heat distribution of the worn surface is entirely consistent with the distribution of the thermal decomposition tear region.     

高灵敏度Si基纤毛式MEMS湍流传感器

为了满足湍流探测高灵敏度、高分辨率的要求,提出了一种新型纤毛微电子机械系统(MEMS)湍流传感器。基于MEMS技术制作了硅十字梁敏感受力结构,通过橡胶探头的受力振动传递水中的湍流信号,凭借传感器头部的导流罩来保证传感器的高分辨率探测。对MEMS湍流传感器进行理论和仿真分析,其一阶共振频率达到481.04 Hz。经过海洋环境模拟机测试实验,结果显示其在50 MPa压力下保持了完好的结构和良好的性能,验证了其水下的可靠性。在湍流实验平台进行测试,通过比较标定法得出其灵敏度为1.92×10^-4 V·m·s^2/kg,满足海洋湍流测试要求。     

Performance of porous European mix (PEM) pavements added with crumb rubbers in dry process

Crumb rubber modifier, made from scrap tires, has been introduced into the production of different types of hot mix asphalt in either wet or dry process. To determine if the rubberised asphalt mix performs as well as polymer-modified asphalt cement (PMAC), test sections of rubberised and control PMAC porous European mix (PEM) in Georgia were examined through a visual inspection and laboratory testing. The results indicated that the performance of rubberised PEM pavements from visual inspection was almost equal to that of PMAC PEM (as the controls) with no rutting or cracking being found, except that the Cantabro test showed a higher mass loss after 3 years' service. After 5 years' service in I-75 Perry, the rubberised PEM still performed a little better rutting resistance, although the rubberised section experienced about twice cumulative traffic as compared to the control; the other visual inspections remained the same.     

烃链功能改性剂对三元乙丙橡胶/凹凸棒土复合材料性能的影响

采用机械共混法制备三元乙丙橡胶(EPDM)/凹凸棒土(AT)复合材料,考察了不同结构的烃链功能改性剂对复合材料硫化性能、力学性能和应力松弛行为及相结构的影响,探究3种烃链功能改性剂对凹凸棒土在复合材料中分散作用的机理。结果表明,改性剂锚固在AT表面并与EPDM有良好相容性,使AT在EPDM中有更好分散性。改性剂添加量为AT的1%时,对EPDM/AT复合材料的力学性能改善效果最明显,其中,以胺基为端基,相对分子质量为2000左右的改性剂使EPDM和AT两相的界面结合性最好,复合材料的拉伸强度提高了304.34%,综合性能提高最为显著。     

Influence of the weight ratio of polydimethylsiloxane modified gelatin to silicone rubber on the potential performance of asymmetric bilayer membranes as wound dressings

Asymmetric bilayer membranes have been regarded as ideal wound dressings for skin regeneration. Our previous work reported the potential advantages of polydimethylsiloxane modified gelatin/silicone rubber (PGE/SR) asymmetric bilayer membrane as a wound dressing. However, it is still unknown whether the proportion of the two components of the bilayer membrane has a prominent influence on its relevant performance. Herein, various PGE/SR membranes with different PGE:SR weight ratios (100:25, 100:50 and 100:100) were fabricated through a self‐stratification method driven by surface tension gradients. Subsequently, the effects of the PGE:SR ratios on the relevant performance (i.e. porous structure, mechanical properties, degradability and biocompatibility) of PGE/SR membranes were systematically investigated. The current results demonstrate that the separating force between the PGE and SR components was reduced significantly on increasing the content of SR, and in particular the PGE/SR1 membrane (100:25) exhibited a well‐defined asymmetric bilayer structure with high porosity, appropriate toughness, water uptake, swelling ratio and water permeability. Concomitantly, the maximum weight loss for the PGE/SR1 membrane was ca 70.65% after 9 days of enzymatic degradation, which met the typical healing period of a normal skin wound. In addition, both the original and degraded PGE/SR1 membrane possessed favorable cytocompatibility in vitro, suggesting its potential application as a wound dressing. © 2019 Society of Chemical Industry     

Effects of green tea powder on the quality attributes of hard red winter wheat flour and Chinese steamed bread

The effects of green tea powder (GTP) on the properties of hard red winter (HRW) flour and Chinese steamed bread were investigated. GTP was blended with HRW flour at levels of 0.00, 1.00, 2.00, 3.00 and 4.00 g GTP/100 g wheat flour. With the addition of GTP, the maximum torque of flour became stronger. The resilience and degree of green colour of steamed bread increased, while hardness and chewiness decreased, with the addition of GTP. The addition of 1.00% GTP did not significantly affect the specific volume, but remarkably influenced the hardness and resilience of steamed bread. In steamed bread formulated with GTP, the antioxidant activity was 0.84 mm TE per g at 1.00% of GTP and increased with GTP levels. The steamed bread had a pleasant flavour, and the degree of overall liking of steamed bread increased with GTP levels to the maximum used in this work.     

Stabilizing effect of the cyclodextrins additive to spray-dried particles of curcumin/polyvinylpyrrolidone on the supersaturated state of curcumin

Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD.