Effect of Carbon Black on Crosslinking

Abstract

For a number of different vulcanization systems, the equilibrium swelling ratios for carbon-black-filled and unfilled samples are shown to be linearly related, as found by Lorenz and Parks, indicating that the degree of crosslinking is not changed by incorporating carbon black. However, filled compounds swell less, and thus the apparent degree of crosslinking is significantly greater. For example, it is about twice as large for compounds containing 50 phr of HAF carbon black. This is confirmed by measurements of the elastic modulus of swollen samples. Relatively strong bonds appear to be formed between rubber molecules and the surface of carbon black particles - bonds that can withstand swelling stresses and temperatures of up to 120 °C. Bonding between rubber and carbon black is also indicated by the limited swelling of filled rubber compounds even before vulcanization, although in this case the apparent degree of crosslinking is smaller. Thus, vulcanization appears to enhance the contribution of rubber-particle bonding to the elastic modulus and restricted swelling of carbon-black-filled vulcanizates. Simple procedures are suggested for estimating the actual degree of crosslinking in filled rubber vulcanizates from measurements of equilibrium swelling or elastic modulus.

The effect of hydrocarbon ageing on the mechanical properties, apparent crosslink density and CO2 diffusion of a hydrogenated nitrile butadiene rubber (HNBR)

“…These uncertainties regarding exact composition of the cured compound lead to underestimating the solvent absorption per unit mass of polymer and, therefore, overestimating M c . Secondly, the presence of reinforcing fillers can greatly reduce local molecular mobility and, therefore, can act in the same way as chemical crosslinks to impede the three dimensional deformation required for swelling to occur [23,40,41]. This could lead to an overestimation of the crosslink density.…”

Effect of carbon nanotubes with different lengths on mechanical and electrical properties of silica-filled styrene butadiene rubber compounds

“…The samples were also stretched up to 100% elongation and retracted repeatedly in order to measure hysteresis losses. The fractional hysteresis (FH), defined as the energy dissipated upon retraction divided by the energy supplied for stretching, was determined from the areas of work done during extension (A ext ) and work done during retraction (A ret ), using the following equation [23]:…”

ModificationIn Situof EPDM Filled with Carbon Black by Glycidyl Methacrylate

“…The incorporation of carbon black into rubber vulcanizates generally gives improved physical and mechanical properties [1] . Such improvements resulting from the addition of carbon black, called ''carbon black reinforcement'', had been widely discussed in the 1950s to the 1990s [2][3][4][5] . In order to exert its beneficial influence on the properties of vulcanizates, carbon black must be sufficiently dispersed in rubber matrix.…”