Curing, rubber tread

Following this scheme, Coz and Baranwal [80] have reported the reverse engineering of four unknown cured rubber compounds, representing a radial passenger tyre tread, a radiator hose, an oil pan seal and an engine gasket. 

TESPT remained the industry standard coupling agent for sulfur cured rubber into the 1990s. With the development of HDS came expanded applications for silica-based compounds, particularly in high performance passenger tire treads which needed a combination of tread wear, low rolling resistance, and good wet traction (73). This combination of performance attributes can be simultaneously optimized to unique levels with silica. Recipes with 50-100 phr silica were now permissible and desirable. 

Although direct analysis of rubber compounds yields simultaneously information about polymer and additives, a quantitative determination of the additives is difficult. This requires separation of these components from the polymer and fillers by means of extraction. Following the standard procedure at Akron Rubber (cfr Chp. 2.2 of ref. [3a]), Coz et al. [25] have examined four unknown cured rubber compounds (radial passenger tyre tread, radiator hose, oil pan seal and engine gasket). Tables 6.7 and 6.8 compare the reconstructed formulations and actual recipes for the tyre and radiator hose. 

HMMM can also be used with reinforcing novolac phenol formaldehyde resins to harden a cured rubber compound. For example, these reactive PF resins might be used in the bead area or the tread compound of a tire in order to increase hardness. 

A pre-cured tread with pattern is prepared by moulding. A thin strip of unvulcanised cushion rubber compound is inserted between the casing and the tread rubber to form the bonding agent between the new and old components. The tread is then applied to the casing and consolidated by pressure. The cushion rubber is then vulcanised. This is also known as cold retreading . 

Overcuring is encountered to some degree in all compounds of any thickness because of the slow conductance of heat through rubber. Earthmover tires may have tire shoulder gauges in excess of 0.3 m (M2 in.). The outside/inside are overcured to effect a satisfactory state-of-cure in the tread rubber. 

Tyres are normally cured in a modification of the compression mould where a bladder or an inflated airbag forces and holds the green rubber stock of the tyre against the mould surface during vulcanization. This force reproduces the design of the tyre tread and the heat from the steam is introduced into the bladder to effect the vulcanization. Small size rubber expansion joints used in piping systems are moulded by compression moulding... 

Rubbers are also being extruded, in a not essentially different way from plastics. Cooling of the extrusion cylinder is necessary to prevent premature vulcanisation as a result of the heat developed by internal friction. The extruder is fed by ribbons, obtained from milled sheets. End products are hoses, profiles, and cable mantles. On-line vulcanisation can be achieved by passing the extrudate through a steam channel, while the rate of extrusion is adjusted to the rate of curing. For this purpose high-rate vulcanisation recipes have been developed. Steam temperatures of about 200 °C are being applied (15 bars pressure). Treads for motorcar tyres are also extruded they are wrapped round the pre-formed carcass and then formed and vulcanised in a press. 

The compounded rubber stock will be further processed for use. The process could be injection or transfer molding into a hot mold where it is cured. Tire curing bladders are made in this fashion. Extrusion of the rubber stock is used to make hose or tire treads and sidewalls. Another common process is calendaring, in which a fabric is passed through rolls where rubber is squeezed into the fabric to make fabric-reinforced rubber sheets for roofing membranes or body plies for tires. The actual construction of the final product can be quite complex. For example, a tire contains many different rubber components some of which are cord or fabric reinforced. All of... 

Blends of elastomers are routinely used to improve processability of unvulcanized rubbers and mechanical properties of vulcanizates like automobile tires. Thus, cis-1,4-polybutdiene improves the wear resistance of natural rubber or SBR tire treads. Such blends consist of micron-sized domains. Blending is facilitated if the elastomers have similar solubility parameters and viscosities. If the vulcanizing formulation cures all components at about the same rate the cross-linked networks will be interpenetrated. Many phenolic-based adhesives are blends with other polymers. The phenolic resins grow in molecular weight and cross-link, and may react with the other polymers if these have the appropriate functionalities. As a result, the cured adhesive is likely to contain interpenetrating networks. 

Uses Post vulcanization stabilizer for sulfur cures of NR, IR, SBR, and NBR used in tire treads, sidewalls, and general industrial prods, incl. belting and inj. molded goods bonding promoter for rubber-based steel adhesion Trade Name Synonyms Duralink HTS [Flexsys http //www.fiexsys.com, Harwick Std. Distrib. http //WWW. harwickstandard. com]... 

Dry RubbGr. Because of its enhanced crystallizability, guayule rubber can exhibit superior failure properties in unfilled rubber compositions. As a double network, an elastomer cured a second time while in a deformed state guayule rubber exhibits substantially better fatigue resistance than deproteinized Hevea rubber (118). When compounded with carbon black, guayule rubber and Hevea rubber behave similarly (119). In tread and wire skim stocks, the compoimding and performance behavior of guayule rubber was comparable to that of Hevea rubber (Tables 7, 8) (120). 

When compared to synthetic rubbers, NR requires lower curing temperatures, and therefore, longer vulcanization time. It has also poorer abrasion resistance and ageing properties, and cracks easily in tread grooves and tyre side walls. 

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