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[CABRUSTM]*1 is a silane coupling agent of the polysulfide type that is added to tires with low fuel consumption. In Europe, where they have gained a lot of popularity, tires with sillica and a polysulfide silane coupling agent can reduce CO2 emissions and consume less fuel.
Silicone production begins with silanes, which are also the main ingredients. WACKER was the first company to produce silanes and was a pioneer in the production of silicones. A silane coupling agent acts as a sort of link between organic and inorganic substances. This property makes silane coupling agents useful for modifying resin and surfaces, enhancing adhesion, and increasing the mechanical strength of composite materials.
Silane coupling agent is frequently used to boost silica’s reinforcing power. Numerous silane coupling agents have recently been developed, and their effects on reinforcing improvement in numerous rubbers have been investigated.
Covalent bonds are formed between the repair resin and the surface coated with silane, which is more reactive to it. Additionally, silanes improve the bonding agent’s ability to penetrate the surface microretentions by increasing the surface’s wettability.
The Global tire silane coupling agent market accounted for $XX Billion in 2022 and is anticipated to reach $XX Billion by 2030, registering a CAGR of XX% from 2023 to 2030.
GE The silane’s blocked mercapto and mercapto mercapto groups have distinct coupling reactivity with the polymer. During the phase of ineffective mixing, the mercapto group reacts with the polymer, and the blocked mercapto group aids in the silica’s dispersion.
Additional mercapto silane is produced when the octanoyl-blocking group is removed during the productive mixing stage and curing step. The vulcanization ingredients’ proton-donors(2) aid in the removal of the octanoyl-blocking group. During vulcanization, these newly formed mercapto groups interact with the polymer to strengthen the bond between silica and polymer.
In a typical tread compound filled with silica, NXT Z silane was tested. Table 1 outlines the formula. The traditional tetrasulfide coupling agent, Silquest* A-1289 silane, was mixed into the control compound in two non-productive mix steps at 160°C.
One non-productive mixing step was performed at 170°C between compounds containing NXT* and NXT Z silanes. Similar to NXT silane, NXT Z silane has excellent processing characteristics. 12 minutes were needed to mix both the old NXT silane and the new NXT Z silane. Between the two ineffective mix steps, the control compound with Silquest A-1289 silane required an 18-minute cool down step.
Compared to most conventional sulphur silanes, Momentive has chosen NXT silanes because they can provide better processing in silica compounds. A blocked mercaptosilane is what NXT silanes are.
This improves the thermal stability of NXT silanes, enabling greater mixing temperatures with shorter mixing cycles in most situations. It may also increase a mixer’s total throughput and decrease waste.
When compared to most conventional sulphur silanes, NXT silanes have a lower compound viscosity due to the plasticizing impact of the molecule, which could also result in fewer total mix cycles.
Reduced compound viscosity may also have a favourable impact on extrusion and milling, two downstream processes. Additionally, compounds containing NXT silane show enhanced ageing viscosity stability, which usually permits a green compound to remain on the production line.
The invention that brought highly loaded silica tyres to market was the development of extremely dispersible silica combined with polysulfide bis-alkoxysilanes. These silanes provide some processing flexibility while giving the product good reinforcing characteristics. Viscosity may rise as a result of crosslinking and sulphur donation “in-situ” caused by these polysulfide silanes at higher mixing temperatures.
Highly filled silica/rubber compounds are intended to employ HENGDA silane, a thiocarboxylate functional silane. The octanoyl group (B) of the molecule (A) blocks the mercaptosilane portion, resulting in a blocked mercaptosilane.
Lower silane reactivity with rubber during processing is caused by the blockage of the mercapto group. Furthermore, it allows for mixing at high temperatures without increasing viscosity or creating premature vulcanization.
The temperature at which the silane donates sulphur can only be reached so far before it becomes unstable in the polysulfide functional group. Sulphur donation happens during mixing if the temperature is higher above the threshold, which might cause crosslinking and ultimately scorch issues. This constraint means that in order to scatter and silanized the silica surface without sulphur donation and scorching, S4 (TESPT) and S2 (TESPD) silanes need to be re-milled several times.
In contrast, the octanoyl group blocks the single sulphur atom present in HENGDA silane. This provides HENGDA silane with the hydrophobicity and high temperature stability required to rapidly establish compatibility between the silica and polymer.
Processing is made easier by the blocking octanoyl group in HENGDA silane, which is intended to de-block when the requirements for vulcanization are met. The type of the SBR it reacts with or the presence of specific additives can affect the de-blocking or coupling mechanisms of HENGDA silane. The reinforcing levels obtained with HENGDA silane, in the absence of any additives, are comparable to those obtained with polysulfide silanes.
