Recuring Vulcanizates. II. Effect of Added Accelerators

Abstract

Vulcanizates, to which more accelerator has been added by swelling, were recured to study the interaction between the accelerator and the sulfur crosslinks. The addition of benzothiazole, or dithiocarbamyl sulfenamides, to SBR, SBR/ BR, or NR vulcanizates caused more crosslinks to form on recuring. A typical induction period was also noted. The results were essentially the same in all rubbers. Crosslink formation, as measured by modulus development or rheometer torque, increased with increasing loadings of accelerator. Similarly, at a given accelerator loading, crosslink formation increased with increasing length of the polysulfide crosslink. These results indicate that an equilibrium exists between the zinc salt of the accelerator and the polysulfide crosslinks.

Self-Curable Benzoxazine Functional Polybutadienes Synthesized by Click Chemistry

“…In a flask, PB-N 3 (0.3 g), 3-(4-(prop-2-ynyloxy)phenyl)-3,4-dihydro-2H-benzo[e] [1,3]oxazine (4) (0.4 g), copper(I)bromide (0.5 g), 2,2 -bipyridine (0.9 g) and dry CHCl 3 (10 ml) were added. The flask was capped with a septum and purged with dry nitrogen for 10 min.…”

“…The crude product was purified by distillation under reduced pressure (bp 95 • C, 10 mmHg) to afford a colorless and highly viscous liquid, which crystallized into yellowish white crystals after a while in the flask (yield 75%, mp 49-50 • C). [1,3] Oxazine (4) In a 250 ml flask, paraformaldehyde (1.9 g, 63 mmol) in 100 ml dioxane was cooled in an ice bath. To this solution, p-propargyloxy aniline (34 mmol, 5 g) in 25 ml dioxane was added portion-wise.…”

“…Cross-linking is a way to enhance the properties of PB; generally, the crosslinking of rubber materials can be done by the sulfur vulcanization [2][3][4], peroxide curing [5], or resole curing [6]. However, for certain applications the existing systems may be inadequate as they require high temperature and pressure to attain a reasonable rate of the cross-linking reaction.…”

Sulfur Vulcanization of Natural Rubber for Benzothiazole Accelerated Formulations: From Reaction Mechanisms to a Rational Kinetic Model

“…Crosslink Desulfuration. -Desulfuration involves the removal of sulfur from the longer polysulfidic crosslinks and, eventually leads to the formation of more stable di-and monosulfidic SULFUR VULCANIZATON OF NATURAL RUBBER FOR BENZOTHIAZOLE 625 crosslinks, 97,[103][104][105][106] where the sulfur that is removed from the crosslinks is reused in the vulcanization process to produce additional crosslinks. The shortening of crosslink is often accompanied by changes in the positions of sulfur attachment to the olefin moieties.…”

Thiazole Type Accelerator Effects on Silane/Silica Filled Natural Rubber Compound upon Vulcanization and Mechanical Properties

“…Schematic illustration of (1) exchange reaction between polysulfide accelerators [38][39][40][41] ; (2) crosslink desulfuration reaction [42][43][44][45][46] . Figure 12은 충전제와 촉진제 첨가량을 변화시킨 조건 에서 T max-min 와 충전제 첨가량을 각 축에 나타낸 그래프이다.…”