Continuous ultrasonic devulcanization of carbon black-filled NR vulcanizates

Abstract

The continuous ultrasonic devulcanization of natural rubber (NR) filled with various concentrations of carbon black (CB) indicated a minimum of crosslink density and gel fraction at an intermediate amplitude, which is independent of CB content. An attempt was made to improve the efficiency of devulcanization by use of various chemicals (1,3 Diphenylguanidine, 2‐Mercaptobenzothiazole, Thianaphthene). However, these experiments did not indicate any improvement in comparison with devulcanization without chemicals. An idea of adding fresh CB into devulcanized compound, which has been shown to improve mechanical properties in the case of styrene–butadiene rubber (SBR), was tested in the present study for CB filled NR compound. The obtained result indicated that an addition of fresh CB to devulcanized CB‐filled NR did not lead to an improvement in mechanical properties upon revulcanization. The revulcanization recipe was optimized to improve the mechanical properties of revulcanized CB‐filled NR vulcanizates. It was found that CB‐filled NR upon revulcanization retained its strain‐induced cystallizability with the tensile strength and elongation at break at about 50 and 70% level of the virgin vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2340–2348, 2001

Ultrasonic devulcanization of carbon black–filled ethylene propylene diene monomer rubber

“…It is believed that, because of the reduced mobility, filled rubbers may exhibit an increasing probability of the breakup of the bound chains by the ultrasonic treatment leading to the partial deactivation of the filler. This effect is believed to be the main reason for the observed loss of performance characteristics of rubber after ultrasonic devulcanization in CB‐filled SBR,44 CB‐filled NR,45 and silica‐filled silicone rubber 20. Without the presence of CB in rubber, the performance properties of revulcanized rubbers are improved or do not deteriorate significantly because of the presence of a bimodal network and the absence of the effect of deactivation of filler 19, 21, 46…”

The Role of Carbon Black on Devulcanization of Natural Rubber by Microwaves

“…This technique is widely mentioned by the literature to detect the status of devulcanization of elastomers 4,5,[14][15][16]24,31,32,39,41,[43][44][45][46][47][48][49][50][51][52] . In general, the content of soluble material (sol) increases with the increasing of devulcanization degree, due to the breaks of the cross-linkings and, consequently, the release of these molecules from the three-dimensional network of vulcanized rubber.…”

Devulcanisation of natural rubber vulcanisate through solid state mechanochemical milling at ambient temperature

“…Therefore, 2?5 phr of ZnO and 0?75 phr of stearic acid were used in recipes 3-5 in this work. Hong et al 16 reported that the preexistence of sulphenamide in the devulcanised sample is sufficient to catalyse the added sulphur-activator system and gives a satisfactory degree of curing, so it is unnecessary to add additional accelerator. In order to study the effect of accelerator (CBS) on the mechanical properties of the revulcanisates, the amount of sulphur in the revulcanisation recipe is kept constant at 1?5 phr and the amount of accelerator is varied from 1?5 to 0 phr in recipes 3-5 ( Table 2).…”