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Waste rubber powder (WRP) was modified by microwave, sol-gel method, and both microwave and sol-gel method, respectively. The mechanical and dynamic mechanical properties of natural rubber (NR)/modified WRP composite were investigated. The influence of bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) content on curing characteristics and mechanical properties of vulcanizate was also studied. The results showed that NR/WRP modified by both microwave and sol-gel method composite owned the best mechanical properties. Rubber processing analyzer was used to characterize the interaction between silica and rubber chains and the dispersion of silica. With increase of TESPT content, the Payne effect decreased. Scanning electron microscopy indicated the coherency and homogeneity of in situ generated silica filled vulcanizate. Dynamic mechanical analyzer showed that NR/WRP modified by both microwave and sol-gel method composite with 5 phr TESPT exhibited the lower tan d at temperature range of 50-80 C, compared with composite without TESPT and the higher tan d at temperature of 0 C, compared with the conventional modification of WRP.

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Wet dedusting is the main coal dust suppression technique in coal mines, and coal wettability is the main factor affecting dust suppression efficiency. To investigate the main factors affecting the coal wettability and improve it, the coal–water contact angle was used as an index to characterize the coal wettability, and the wettability of six coal samples with different metamorphic degree was studied by analyzing the relationship between the physicochemical properties and the contact angle. To improve the coal wettability, the nonionic surfactant alkyl polyglycoside (APG), anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and polymer surfactant polyacrylamide (PAM) were applied to the coal samples. The results show that SDBS is the most effective surfactant to improve the coal wettability, followed by APG, while the application of PAM would lead to more hydrophobic coal. It is also found that the coal wettability shows a high–low–high trend with the increase in the metamorphic degree. The wettability of long flame coal is the strongest and that of gas coal is the weakest. Moisture is the main hydrophilic factor of coal, while 1,4-dimethylbenzene is the main hydrophobic factor. The main factors affecting the treatment effect of APG, SDBS, and PAM on wettability are the aromatic methylbenzene, hydroxyl, and hydroxyl content of coal, respectively. Therefore, according to the content of hydroxyl in different coals, an SDBS solution can be prepared to improve the coal wettability. For coal with a low hydroxyl content, a higher concentration SDBS solution could be needed.