Silica reinforcement systems

Obviously, if any coupling agent is used, polymer adsorption will naturally occur (Bomo, 1989 Killian etal., 1987) in addition, because of the high polarity of silica, some direct interaction between silica aggregates will also take place and constitute an additional filler-filler network. These effects will not happen in silica-reinforced systems when an appropriate amount of coupling agent is used. 

In silica reinforcement systems containing TESPT, Wolff has suggested that the reaction is similar when the TESPT/silica intermediate is present instead of sulfur, in which case the crosslinking agent is the polysulfidic sulfur chain. Wolff showed that mercaptobenzothiazyl disulfide (MBTS) reacts with the tetrasulfane group, thus forming 2 mol of the polysulfide ... 

Silica compounds are generally processed in conventional internal mixers, preferably with intermeshing rotors. These mixers are designed and optimized for carbon black-fiUed compounds in which mixing is based only on physical processes. When a silica-silane reinforcing system is used, additionally a chemical reaction, the sUanization, occurs. One of the main influencing factors of the silanization reaction is the concentration of ethanol in the compound as well as in the mixer [25,26]. As the silanization finally reaches an equilibrium, low concentrations of ethanol in the compound are expected to enhance the reaction rate. 

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Silica fillers also react with the rubber causing an increase in viscosity and dry and unmanageable processing behaviour. Filler activators need to be added to silica-reinforced compounds to overcome these problems. The usual filler activators used are diethylene glycol, polyethylene glycol and amines such as triethanolamine. Some of these activators not only overcome the problems of processing and accelerator absorption, but depending on the cure system used, will also act as vulcanisation activators. 

Silica reinforced rubber, 22 703 Silica sheets, 22 383-385 Silica-silane system, 22 377-378 Silica sol-gel fiber processing, 23 80 Silica sols, 22 383, 473-474 applications of, 22 394 modification of, 22 393-394 preparation of, 22 392-393 properties of, 22 391-392 purification of, 22 393 Silica, solubility in steam, 23 212-213 Silica-supported activated manganese dioxide, 76 568... 

Introduction of postpolymerization steps to facilitate better interaction with the reinforcement system. This is one of the most radical developments affecting the rubber industry because it enables silica to significantly displace carbon black as the favored reinforcement for the applications. 

High-tensile-strength butyl compounds generally use FEF- or GPF-grade carbon blacks. Vulcanization systems tend to be based on thiazole accelerators such as mercaptobenzothiazole disulfide (MBTS) and thiuram accelerators such as tetramethylthiuram disulfide (TMTD). Low-tensile-sfrengfh compounds will use a clay or silica reinforcing filler in place of carbon black. 

Carbon blacks, clays, and silicas constitute the filler or compound reinforcement system. Optimization of these materials in a formulation depends on the application for which the component is intended for example, tread or sidewall. 

Hui, S., Chaki, T. K., Chattopadhyay, S., Exploring the simultaneous effect of nano-silica reinforcement and electron-beam irradiation on a model LDPE/ EVA-based TPE system. Polymer International 2009,58,680-690. 

In Section 4.4 we saw that the thermoplastic elastomers behave as self-reinforcing systems. Earlier in this chapter, we examined silica- and... 

Very recently, many studies have been conducted to identify new reinforcing systems. These systems are similar to silica compounds and characterized by the use of a coupling agent to chemically bond elastomer chains to filler surface. Many reinforcing systems have been patented alumina oxyhydroxide and oxide [18,19], titanium oxides [20], and silicon nitride/carbide [21]. 

E. P. Plueddemann (VoiO CoAntng) Apparently the textile/adhesive/ rubber system is quite different from the silane reinforced systems dealt in the paper. Consequently the effect of adhesion vs. modulus is not the same. Unmodified silica does not bond to rubber at all. 

Silicone rubber and, in general polar polymers, are by nature materials of choice for preparing silica filled systems however limited to niche applications, with respect to the range of properties that such specialty polymers may offer. In order to develop optimum reinforcing performance with more common diene elastomers, silica must be chemically treated as we will see below, because contrary to carbon blacks, silica particles do not develop spontaneous strong interactions with nonpolar polymers. It is nevertheless interesting to see that, even with comparable size and structure, pure silica does not affect the mechanical properties of vulcanized rubber compounds in the same manner as carbon black. 

One end of such molecules is expected to specifically react with silanols on silica surface, whilst the other end is expected to eventually interact with the vulcanization system (essentially sulfur based) in order to provide chemical bonding with the rubber network. It worth underlining again the fundamental difference between carbon black and silica reinforcement no chemistry is needed with the former but is essential with the latter. 

Silica. The main uses of siUca are in the treads of off-the-road tines for improved chunking and tear resistance and as a component of the bonding system for brass and 2inc-plated steel cord. These are commonly used in radial passenger and tmck tire belt skim stock. In addition the body pHes of steel radial tmck tires, hoses and belts, and footwear use significant volumes of siUca as a reinforcing filler. 

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