Based on the model of a freely hinged chain, the theoretical analysis of the configuration statistics of the ensemble of two freely hinged chains with entanglements was carried out. It was found that the laws of the chain ensemble deforming (at the micro level) and the deforming of the continuum element (at the macro level) could be described by similar relationships. The variation of constraints due to entanglements for the chain ensemble and the element surface area due to deformations 1 and 2 was similar. Based on that law, a method to describe constraints caused by entanglements for the chain ensemble was proposed. The theoretical derivation of an equation for the free energy of networks with entanglements in the absence of physical crosslinks was rendered, the obtained equation coinciding with the empirical potential of Mooney-Rivlin in its form. The description of stresses in real networks with consideration for constraints due to entanglements and physical crosslinks was suggested. For the description of constraints due to physical crosslinks, the Flory-Erman theory of constrained junctions(CJ) was employed. A real network description was provided by modifying the CJ theory based on the results of the theoretical analysis of ideal networks with entanglements(the MCJ theory). The verification of the stress dependence description was carried out proceeding from the reciprocal of the extension ratio using the experimental data of Pak and Flory by simple extension-compression of polydimethylsiloxane networks with a different density of chemical crosslinks. The adequacy of the MCJ theory equation system for the calculation of the polymer stress-strain states was demonstrated. 43 refs.

The effect of adhesion-promoter resins, used in the belt compound of tires, on the mechanical properties of the rubber compounds was studied. It was proposed that the presence of certain adhesion-promoting resins could lead to the formation of a copper sulphide adhesion layer that might protect the residual brass from corrosion during humidity-ageing conditions. Highly polished brass coupons were cured against the NR compounds and the cured rubber was later removed using ortho-dichlorobenzene solvent. To test the proposed theory, the crystal structure of the copper sulphide adhesion layer was studied using synchrotron source grazing incidence angle X-ray diffraction. Confirmation was obtained of the authors' previously-proposed theory that the presence of adhesion-promoting resins altered the crystal structure of the adhesion layer resulting in durable rubber-to-brass bonding during ageing conditions. 31 refs. (ACS Rubber Division, Fall Meeting, Columbus, Ohio, USA, Oct.2004)

The use of aramid short fibres, e.g. poly-para-phenylene terephthalamide (Twaron), poly-meta-phenylene isophthalamide (Conex) and co-poly-(para-phenylene/3,4'-oxydiphenylene) terephthalamide (Technora), in typical truck tread compounds has been studied with the aim of improving hysteresis, thereby reducing rolling resistance. The results of the author's latest research in this area are presented, focusing on improvement in rolling resistance, heat build-up, flexural and dynamic properties. Compounds were engineered to improve the hysteresis characteristics with a positive effect on wear and tear resistance. Furthermore, the levels of fibres and their sizes were varied to obtain best performance advantage. The advantages that can be obtained by addition of a small amount of fibres, often in a way that is impossible with conventional particulate fillers or with other fibres, are described. 8 refs. (ACS Rubber Division, Spring Meeting, Grand Rapids, MI, USA, May 2004)

NR was blended with different amounts of recycled rubber (RR, recycled tyre tread) and a fixed amount of carbon black reinforcement filler (60 phr) was loaded into the blends. The blends were vulcanised either by microwave irradiation (MW) or by conventional thermal (CT) systems. The results suggested that the tensile modulus and hardness of the vulcanisate could be enhanced by increasing the RR content, whereas the tensile stress, elongation at break and tear strength decreased with RR loading. The mechanical properties of the vulcanisates produced by the CT method were higher than those from the MW method. The vulcanisates from the MW method had a higher resistance to toluene penetration than those from the CT method. The differences between the properties produced by the two methods were smaller at higher RR contents. The sensitivity of the property changes of the vulcanisates due to the addition of the RR content was greater for the CT than for the MW method. The observed differences between the curing systems were explained in terms of the density and types of crosslinks in the vulcanisates. 18 refs.

The development of a domestic civil aviation tyre industry in China, which is currently dominated by international companies, through increased research, development of new aircraft tyres, increased market competitiveness and expanded market share, is discussed.

Advances in tyre inner liner technology are discussed, focusing upon the use of nanocomposites for inner liner production. The basic properties of a nanocomposite inner line must meet are determined and an assessment is made of how a nanocomposite inner liner might perform in a tyre relative to a conventional halobutyl rubber. A comparison is made of a bromobutyl 2255 truck tyre inner liner compound with a nanocomposite inner liner and the effects of formulation and compounding variables on the properties of the nanocomposite-based inner liner are examined. The benefits achievable through the use of nanocomposites in inner liners, particularly in the area of permeability reduction, are also considered. 10 refs.

A brief report is presented on the use of dielectric preheating of rubber bales to reduce energy consumption during the mixing of rubbers in tyre processing. 2 refs.

The development of a tyre tread compound consisting of a blend of NR and polybutadiene and a novel filler system composed of Rubber Coated Carbon Black and silica is reported. A comparison is made of this filler combination with a carbon black/silica combination in the tyre tread compound and the benefits offered by this new filler system, which include enhanced rolling resistance and wet grip, are indicated. 17 refs.

The development of a finite element kinetic model for numerical simulation of thermal oxidation in automotive tyres, based on the Basic Autoxidation Scheme and incorporating mass transport limitations related to the diffusion of oxygen into the layered elastomer system is described. The extent of oxidation is calculated at different locations within the tyre as a function of time and temperature, and results for ageing are compared to experimental data for crosslink density, elongation at break and modulus variation derived from accelerated testing. 30 refs.

The use of coagulated styrene-vinyl pyridine-butadiene terpolymer latex (VP latex) as a secondary accelerator in the curing of natural rubber and synthetic, butadiene rubber and styrene-butadiene rubber-based compounds with the sulphonamide-sulphur curing system was investigated by cure rheometry. The effects of the addition of VP latex on curing reaction rate and activation energy are discussed. 15 refs.

The cure characteristics of compounds of natural rubber with ground rubber tyres, devulcanised using a counter-rotating twin screw extruder, sulphur, N-cyclohexyl-2-benzothiazyl sulphenamide as accelerator and various proportions of carbon black was investigated using a cure rheometer. The effects of carbon black content on the mechanical properties of the vulcanisates were studied and the results are discussed. 20 refs.

There has been an unabated influx of international tyre majors into China, which is witnessing an unprecedented boom in automobiles and radial tyre production. At present, nine of the world's top ten tyre companies have manufacturing facilities in China. There are over 20 tyre units set up with foreign capital, either independent or joint ventures, involving a total investment of 3bn US dollars. Their market share in the Chinese tyre market is an amazing 80% in radial tyres, inclusive of 20% in truck radials and 50% in exports. The activities of these tyre majors are outlined.

Sales of run-flat tyres are running well below expectations. For the carmaker, the attraction is the space-saving issue, while for motorists there is the guarantee of greater safety and convenience. However, not many tyres deflate so suddenly that the vehicle cannot be brought to a safe stop, so standard-fit tyre pressure monitoring systems combined with modified wheels could provide adequate advance warning of a deflation problem no doubt more cheaply. The refining of the car tyre continues. More recently, tyre noise has been the big challenge and new regulations for wet grip are on the way. A bigger agenda is rolling resistance and therefore better fuel economy. Without the correct air pressure, rolling resistance is a valueless objective, and this is where tyre pressure monitoring systems come to the fore again.

Bridgestone knocked Hutchinson SA out of the top spot, while some other companies switched positions, in the latest rankings of the world's largest non-tyre rubber product makers. Bridgestone, which was ranked third in 2004, had an estimated 3175m US dollars in sales to Hutchinson's 3130m US dollars. Freudenberg Group, in second place in 2004, fell to third, while Continental AG jumped to fourth from sixth.