جستجوی مقالات مرتبط با کلیدواژه « برهم کنش پرکننده-پرکننده » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

 Fatigue crack growth (FCG) of rubber composites as controlled by the viscoelastic losses, is strongly dependent on the polymer-filler interfacial phenomena. The type of filler-polymer bonding at the interface and the extent of mobility restriction of rubber chains resulting from the interaction by the filler are of the critical ones. In highly filled rubber compound, the amount of mobility restriction is almost dictated by the filler-filler interaction. Regulating the surface energy of the filler can be an effective method to control the filler-filler interaction, to distinguish the two interfacial phenomena, and to pave the way of studying their significance.

Ultrasil VN3 and solution styrene-butadiene rubber (SSBR) were of the base composite materials. Using two silanes with a short and a long aliphatic chain length, the surface of Ultrasil was modified in our lab to a certain level of grafting density which could bring the required surface energy and the filler-filler interaction. By controlling the surface energy of silica treated in the lab, and by making a systematic comparison of the resulting composites, it was possible to study the role of covalent bonding at the interface, the role of filler-filler interaction and severity of mobility restriction and finally the role of silane chain length.

Fatigue crack growth experiment revealed that the severity of mobility restriction and the filler-filler interaction of the composite have the highest impact on the amount of viscoelastic dissipation and the rate of crack growth.  The covalent bonding at the interface can deviate the crack from growing in the original direction and thus it may act as a physical barrier to improve crack growth resistance. For highly filled compounds where the properties are almost dictated by the filler-filler interaction, the role played by the chain length of silane is minor.

It is demonstrated that silica and carbon black have inhibiting effect by the former and accelerating effect by the latter in the kinetics of sulfur vulcanization of rubber. It seems that in sulfur vulcanization reaction of rubber some kinetic phenomena are not systematically investigated. In this regard, due to the autocatalytic mechanism of vulcanization and the diffusional effect of its chains, it seems that immobilization of rubber chains as a result of the presence of reinforcing fillers has an essential role in changing the kinetics of sulfur vulcanization of rubber. This concept has not been explored in other researches. Kinetics measurements were performed by means of an oscillating disc rheometer. The extent of filler/filler interactions was monitored by means of dynamic-mechanical and electrical conductivity tests for silica and carbon black filled compounds, respectively. It was shown that the autocatalytic nature of the vulcanization remains unchanged regardless of the type and concentration of fillers. It was demonstrated that the vulcanization rate goes through a maximum as the loading of fillers rises, regardless of the type and surface chemistry of the fillers. Consequently, silica can also accelerate the vulcanization rate at low loading and decelerate it above a critical loading. Such critical loading exists for both silica and carbon-black, and it is related to the percolation threshold for filler network formation. Therefore, it is discussed that not only the filler surface chemistry, but also the physical phenomena originating from the filler/filler interactions can alter the vulcanization kinetics of rubbers. Such physical effect is attributed to the immobilization and lack of kinetic energy in the entrapped rubber chains which reduce the probability of reaction between the macro-radicals. Therefore, a single mechanism is introduced here to explain the effect of reinforcing fillers on the vulcanization kinetics of the filled rubber.