Grafting hydroxy‐terminated polybutadiene onto nanosilica surface for styrene butadiene rubber compounds

Abstract

Hydroxy teminated polybutadiene (HTPB) was grafted onto the surface of nanosilica particles via toluene di-isocyanate (TDI) bridging to reduce filler-filler interactions and improve dispersion of nanosilica in rubber. Also, this prepolymer as modifier contains double bonds which participate in sulfur curing of styrene butadiene rubber (SBR) matrix to enhance filler/polymer interaction and reinforcement effects of silica. The reactions were characterized by titration and Fourier transforms infrared spectroscopy. Thermogravimetric analysis was utilized to evaluate the weight percentage of grafted TDI and HTPB. About 60% of the hydroxyl sites of silica were reacted with excess TDI in the first reaction. In the second reaction, HTPB as desired reactive coating was grafted on the functionalized nanosilica to constitute about 24 wt % of the final modified silica. The sedimentation experiments showed good suspension stability for the modified nanosilica in the organic media. Scanning electron microscopy revealed nanoscale dispersion of modified silica aggregates in the SBR matrix at concentration of about 14 phr. Also, vulcanization characteristics and mechanical properties of compounds demonstrated that HTPB grafting improved dispersion of nanosilica as well as its interaction to the rubber matrix as an efficient reinforcement.

Use of TBzTD as Noncarcinogenic Accelerator for ENR/SiO2 Nanocomposites: Cured Characteristics, Mechanical Properties, Thermal Behaviors, and Oil Resistance

“…The characteristic peaks of NR (Figure 1(a)) that appeared at 3037, 2850, 1660, 1450, 1375, and 835 cm −1 are assigned to the =C-H stretching, C-H stretching, C=C stretching, C-H bending of CH 2 , C-H bending of CH 3 , and =C-H bending, respectively [3,8,15,24]. The new characteristic peaks that appeared at 1240 and 870 cm −1 (Figure 1(b)) are assigned to the symmetric stretching and asymmetric stretching of epoxide ring, respectively [5,8,15,16,18,[24][25][26][27]. This confirmed the formation of epoxide or oxirane rings from the reaction of performic (generated in situ by the reaction of HCOOH and H 2 O 2 ) with the C=C on the NR molecules.…”

“…The peak at 1590 cm −1 is attributed to the bending vibration of the O-H bond in the adsorbed water molecules on nSiO 2 surfaces. The intensive peaks at about 1083 cm −1 , together with the less intensive peaks at 800 and 455 cm −1 , are attributed to the asymmetric stretching vibration, symmetric stretching vibration, and asymmetric bending vibration of Si-O-Si, respectively [24][25][26].…”

“…However, the CRI of the ENR 40 nanocomposite with 1 phr nSiO 2 was lower than that of the neat ENR 40, indicating a slower rate of vulcanization. This is attributed to the adsorption of the basic accelerator on the -OH groups of the nSiO 2 surface and so lowered the vulcanization rate of the nanocomposites [9,25]. Further increase in the nSiO 2 loading to 2 phr resulted in longer s2 and t 90 , and a lower CRI because of the higher level of the adsorbed accelerator on the nSiO 2 surface, which subsequently reduced the accelerator efficiency.…”

“…H − L is a measure of the dynamic shear modulus, which indirectly indicates the extent of crosslinking (crosslink density) of the vulcanizate [9,10,18,25]. The L , H , and H − L values of the ENR 40 were found to be lower than those of the NR (Table 2), indicating the lower viscosity of the uncured ENR 40 and also the lower elastic modulus and crosslink density of the ENR 40 vulcanizate.…”

“…With this respect, the TBzTD, a fast curing accelerator with no secondary amine, has been developed to replace the TMTD, resulting in the nitrosamine free cure. Recently, reinforcement of rubbers with inorganic nanoparticles, even at a very low loading, can significantly improve their mechanical and thermal properties [9,10,19,[21][22][23][24][25]. To achieve the desired properties, the nanofillers must sufficiently disperse in the rubber matrix, as poor dispersion leads to the obvious decrease in the performance properties of the nanocomposites.…”