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Results and discussion3.1. Chemical structure characterization of MSaDT by FTIRFig. 1 shows the FTIR spectra of the pure silica and MSaDT of30 C, 40 C, 50 C, 60 C, and 70 C, respectively. The absorptionpeaks at 3440 cm1 and 1650 cm1, corresponding to the stretchingand deforming vibration modes, respectively, are the H–O–Hbonds of the adsorbed water; the absorbance ranging from1000 cm1 to 1150 cm1, assigned to the Si–O–Si stretching mode[25], is obvious. The surface modification of silica is realized bychemical reaction between the hydroxyl groups of silica and thesilanol groups of hydrolyzed TESPT. Therefore, the surface graftingreaction can be easily identified by the appearance of characteristicbond, such as the peak for methylene (–CH2–) [26] at 2850–2900 cm1, in the FTIR spectra of MSaDT. As shown in Fig. 1, afterthe removal of un-reacted TESPT by Soxhlet extraction, the strongabsorbance peaks at 2855 cm1 and 2950 cm1 attributed to the –CH2– vibration of TESPT appear for all samples except pure silica,indicating that TESPT is successfully bonded to the surface of silica.To further investigate the grafting reaction by comparison of theposition of Si-OH peaks near 3400 cm1, it can be found that thepeaks in the FT-IR spectra of MSaDT have shifted in the directionof higher wavenumbers, in a so-called ‘‘blue shift’’ [27]. This ‘‘blueshift’’ suggests that the number of hydroxyl groups decreases afterthe modification of silica with TESPT, resulting in the destruction ofhydrogen bonds on the surface of silica. Generally, the poor dispersionof silica in the rubber matrix is mainly due to the large amountof hydrogen bonds formed among the hydroxyl groups on the silicasurface. Hence, the destruction of hydrogen bonds can improve the characterization. It can be seen that pure silica presents severeagglomeration, with the primary and secondary aggregates at260 nm and 700 nm, respectively, and even larger aggregates at5–6 lm. Compared with the pure silica, the MSaDT shows a smallerparticle size and narrower particle size distribution. With theincrease of modification temperature, the peaks of particle sizeshift toward small size at the temperatures below 50 C, but theshift reverses direction at the temperatures above 50 C. The valuesof average particle size are marked in Fig. 2B, indicating that theMSaDT of 50 C has the smallest particle size of 105 nm. It can beconcluded that the modified temperature of 50 C is beneficial todecrease the particle size and suppress the particle agglomeration.
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