Benefits of using silanes: The chemical bond of the silicas to the polymers is the key factor for green tires ability to withstand high stresses and heavy loads: The silica/silane system reduces roll resistance and improves wet grip, all while ensuring excellent abrasion properties. Unlike with reference carbon black systems, the magic triangle can be expanded by using suitable silica/silane combinations tire performance is increased, and tires are safer and more sustainable.
Goto Shengjia to know more.
This is why industrial carbon black has been gradually replaced in todays tire tread mixtures with the silica/silane system. The combination of precipitated silica and silanes is ideal: Highly dispersible silica is a high-performance filler that provides reliable grip even in wet weather conditions. However, the polar silica is not readily compatible with non-polar polymers. The bifunctional organosilanes create the bridge in the case by coupling the silica to the polymer. Evonik offers them in liquid form (e.g., Si69®) and solid form (e.g., X50-S®). In addition, pre-reacted products are available that are especially ideal for the mechanical rubber goods (MRG) market in particular i.e., silica that has been pre-reacted with silanes to produce the COUPSIL® product line.
Luginsland et al. [54] studied the influence of various silanes on the reinforcement of silica-filled rubber composites. The effect of silane modification on the Payne-effect of silica-filled S-SBR/BR elastomer compound using rubber process analyzer (RPA). Also, it was observed that the breakdown of the filler network and loss of occluded rubber was influenced by the silicas surface area and the silanization degree. Bi-functional silane like TESPT forms an in-rubber structure since it has chemical bonding with rubber matrix during curing. The mechanical properties of silane coupling agents with various functions in the reinforcing of silica-filled natural rubber compounds were studied by Kaewsakul et al. [42]. This research looked at the function of five distinct silane coupling agents in natural rubber, including bis-(triethoxysilylpropyl)tetrasulfide (TESPT), bis-(triethoxysilylpropyl) disulfide (TESPD), octyltriethoxysilane (OTES), vinyltrimethoxysilane (VTMS), and bis-(trimethylsilylmethyl tetra sulfide) (TMSMT) (Table 3). Alkoxy silanes significantly reduce the fillerfiller interaction and viscosity of silica-filled Natural rubber compounds. Alkoxy silanes with sulfur moiety show improvement in overall compound properties. Silanes with no alkoxy group showed poor mechanical properties, and poor filler dispersion (Table 4). Silane with one alkoxy group has better processability and poor mechanical properties than bifunctional silanes [75]. The superior properties of TESPT silane are due to its disproportion at higher mixing temperatures. TESPT can be disproportionate to a mixture of polysulfides with sulfur chain lengths varying from two to eight atoms, depending on reaction time and temperature. The occurrence of such disproportionation reactions during compounding or subsequent processing appears to have little effect on the effectiveness of TESPT as an adhesion promoter. During vulcanization, TESPT can act as an accelerator or add sulfur to rubber compounds [76]. However, this leads to premature scorching and results in poor processability of rubber compounds, such as premature crosslinking and higher viscosity [51]. Apart from these silanes, NXT (3-octanoylthio-1-propyltriethoxy) and MS (Mercaptopropyl trimethoxy) silanes are also available in the market; These silanes can exhibit better dynamic properties, rolling resistance properties, wet grip, etc. compared to the TESPT silanes.
Table 3 Structure of various Organo silanes used for research work with Natural rubber [42]Full size table
Table 4 Effect of different silanes on physio-mechanical properties [42] (Ranking 1- Best and 5- Worst) BRC -Bound Rubber Content and R.I Reinforcement IndexFull size table
If you are looking for more details, kindly visit Hebei Silicon Research Electronic Materials Co., L.
Kosmalska et al. [77] investigated the adsorption of curatives and silica activity toward elastomers and found that Low molecular weight substances of different polarities solubilized in rubber compounds undergo adsorption on the surface of the active filler. It affects the mechanical properties of vulcanizates. This work investigated the effect of accelerators and modified silica in elastomer compounds. Accelerators cause the deactivation of the filler dispersed in EPDM (Ethylene Propylene Diene Monomer Rubber). Crosslinking system or ZnO-modified silica surface decreases the activity of silica towards elastomer. One of the issues with silica-reinforced rubber compounds is the chemisorption of vulcanizing agents on the silica surface because the polar silanol groups of silica can produce strong adsorption with polar chemicals through hydrogen bonding or van der Waals forces [22, 78]. This could negatively affect the characteristics of several important chemical constituents (particularly accelerators) and result in a decrease in crosslink density and end-use properties [79].
If you are looking for more details, kindly visit Scomi Prima 3G/4G/5G Screen.
The elastomer is typically mixed with glycols or amines to enhance the curing properties. Diphenyl guanidine (DPG) is frequently utilized for silica-reinforced composites because it works as a catalyst for the silanization reaction between the silica filler and the silica coupling agent synergistic secondary accelerator of sulfur-accelerated sulfur sulfenamide [80,81,82]. The application of DPG increases the silanization reaction rate, namely the hydrolysis of TESPT followed by condensation reaction and the direct condensation reaction of TESPT and silica. DPG might reduce the activation energy of the silanization process from 90.4kJ/mol to 70.8kJ/mol [83].
With the study of the impact of different silica, silane coupling agents, and DPG on the compound properties, Kaewsakul et al. [84] optimized the Rubber Formulation for Silica-Reinforced Natural Rubber Compounds and investigated DPGs dual nature as an activator for silanization and accelerator for curing system. The increase in silane and DPG content favours the physical properties, chemically bound rubber content, reinforcement index, and cure time, along with a negative effect on scorch time. A Higher silica structure results in improved dispersion, smaller aggregate sizes, and, as a result, quicker flocculation. The High Dispersible silica-reinforced-NR vulcanizates have a higher reinforcement index and lower tan delta at 60 degrees C, indicating a lower rolling resistance than standard silica-filled compounds favouring tire application. Although DPG has a dual role in silica-filled rubber compounds, there is a chance for the evolution of aromatic amines like Aniline (toxic) during mixing [85]. There was a demand in search of an alternative to DPG for betterment. Hayichelaeh et al. [52] investigated the impact of amines that could potentially replace DPG on the silanization reaction of the silica-silane system in the model and real-world silica-filled natural rubber compounds. These amines included hexylamine, decylamine, octadecylanime, cyclohexylamine, dicyclohexylamine, and quinuclidine. The primary silanization reaction rate constants of the compound with amine were 3.7 times those of the compound without amine. Linear amines boosted the primary silanization reaction faster than aromatic/cyclic amines. In linear alkyl amine, short alkyl amine showed a higher rate constant of primary silanization reaction than cyclic and long alkyl amines and a lower flocculation constant.
The effects of silica and its various surface treatments on the vulcanization of silica-filled SBR were investigated by Ramier et al. [86]. This study examines the impact of various silica treatments on the vulcanization of rubber packed with silica (SBR). In comparison to the silica-filled compound with DPG, grafting alters the vulcanization kinetics and lowers the cure rate of the substance. A more homogeneous crosslinking may result from the grafting of the filler surface by reducing N-Cyclohexyl-2-Benzothiazole Sulfonamide (CBS) adsorption. Antioxidant functionalized silicas reinforcing and antioxidation effects in styrene-butadiene rubber were studied by Pan et al. [87]. In this study, precipitated silica and an antioxidant coupling agent were combined to create antioxidant functionalized silica via the reactions of 3-Glycidyloxypropyl) trimethoxy silane (A-187) and N-phenyl-1,4-phenylenediamine (PPDA). Above 3.9% of antioxidant content by weight to silica, functionalized silica dramatically improves the thermal and ageing properties by retaining the mechanical properties of the SBR / Silica compound. The functionalized silica-filled compound has reduced viscosity and optimum cure time than the unmodified silica-filled compound. As toxicity is a concern, even aromatic oils as processing oil are banned; currently, TDAE (Treated Distillate Aromatic Extract) is used as a processing aid by tire industries. C. Hayichelaeh et al. [88] found a better bio-based alternative to TDAE. Epoxidized palm oil and amine-modified epoxidized palm oil tend to increase the filler reinforcement, increase the curing rate, and reduce the Payne effect (Fig. 12). Amine-modified EPO also enhances the silanization reaction as it acts as a silanization catalyst [88]. Weng et al. [89] studied the effect of alkalinity of different ionic liquids as a catalyst for silanization reaction. The silanization reaction enhancement significantly improved silica dispersion and interfacial interaction between silica and rubber in SBR composites. The reactivity of ionic liquids is higher for strong alkalinity and lower for weak alkalinity ionic liquids. The reactivity of Ionic liquids for silanization is as follows: 1-butyl-3-methylimidazolium acetate (CIL)>1-butyl-3-methylimidazolium hydroxide (OIL)>1-butyl-3-methylimidazolium tetrafluoroborate (BIL)>1-butyl-3-methylimidazolium hexafluorophosphate (PIL). The presence of short and linear amines and higher alkalinity ionic liquids significantly enhances the rate of silanization. The polar group of silica adsorbs the curatives added to the compound. To retain the equivalent amount of cross linking and cure rate, additional Phr of curatives must be added while designing formulation. Having sulfur-containing silane enhances a crosslink density as it provides additional sulfur for vulcanization; in contrast to the advantages, it leads to processing difficulties (Scorch effect). The non-sulfur-containing silanes have better processabilities with poor mechanical properties.
Fig. 12Effect of synthetic and bio-based oil on Storage modulus and Payne effect of silica-filled elastomer composite [88]
Full size image
If you are looking for more details, kindly visit silica silane.
For more Substitute Shaker Screeninformation, please contact us. We will provide professional answers.