Silica compounds tensile properties

In all of the rheometer testing of the uncured compounds, the commercial silica AZ showed the highest values with the B1 and B3 samples having the highest values among the B-series silica samples. The Mooney viscosity at 100°C increases as the number of particles in the aggregates increases. The same compounds were cured and tested, measuring tensile properties, tear resistance. 

This method allows the sol-gel siliea NR latex eompound to be moulded into the desired shape. TESPT was eo-mixed with TEOS and eoneentrated NR latex. Ammonia which functioned as base catalyst was added into the concentrated NR latex. The silica-TESPT-NR latex compound was then subjected to heat to complete the sol-gel silica conversion process. The dried sol-gel silica-NR mixture was compounded as per normal mixing procedure. A good dispersion of silica particles of the size between 100 and 500 nm was achieved. Using the two-level factorial design, it was concluded that the mechanical properties, i.e. tensile properties and tear strength, were significantly affected by the TEOS loading. It was also found that the amount of ammonia present in the concentrated latex, i.e. 0.7% (w/w) was sufficient to convert TEOS into silica. 

The effectiveness of organoclay in NR was observed and reported by Carli et They evaluated the technical feasibility of NR nanocomposites with Cloisite 15A, a commercial organoclay to substitute conventional silica (Si02) filler. TEM analysis indicated that the OMt was homogeneously dispersed in the rubber matrix. A shift of the characteristic peaks to lower angles was observed in XRD, attributed to the intercalation of the OMt by macromolecular rubber chains. Based on the mechanical properties of the compounds they concluded that 50 phr of silica can be replaced by 4 phr of OMt with a reduction in the filler content by 12.5 times, without adversely affecting the tensile properties of the final material even after ageing. 

The various properties of the silica filled compounds were improved compared to the unfilled compounds. The torque values of the filled compounds were increased due to the increase in viscosity. The scorch time and optimum cure time significantly decreased due to the heat conduction of filler particles. Tear and tensile properties of the silica filled compounds were considerably higher because of the effects of strain amplification and hysteresis of the silica filled vulcanizates. ... 

Filler dispersion is a property that determines how well the filler partciles in a given rubber compound are dispersed as a result of the mixing process. This relates to carbon black dispersion as well as the dispersion of nonblack fillers such as silica, clay, calcium carbonate, titanium dioxide, etc. Also rubber curatives such as sulfur and accelerators can be poorly dispersed (commonly these ingredients are added late in the mixing cycle). Poor dispersion makes a mixed stock less uniform, and commonly the cured ultimate tensile strength will have more variability. Poor dispersion can affect other important cured physical properties such as abrasion, tear, and fatigue resistance, flexometer heat buildup, and other dynamic properties. 

To illustrate the influence of surface hydroxyl groups and hydration levels on rubber properties, Wagner (1976) took a series of silicas of different surface areas, hydroxylated to different extents, and then added them to an SBR compound at 50phr (Table 9.19). The author concluded that a reduction in silanol level as a result of an increase in absorbed water will decrease cure time, tensile strength, and abrasion resistance. 

Properties. The mechanical properties of E-SBR vulcanizates depend on the type and level of filler in the compound. Unfilled gum vulcanizates have very poor tensile strength and ultimate elongation, because the rubber lacks self reinforcing of the type found NR rubber vulcanizates, i.e., strain-induced crystallization. This inadequacy is offset by the addition of reinforcing fillers, i.e., carbon black or chemically coupled silica. At optimum loadings with reinforcing carbon black, mechanical properties similar to those of NR can be achieved. However, NR compounds exceed SBR compounds in tear strength because of NR s strain-induced crystallization. 

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