✍ Scribed by Skander Mani; Philippe Cassagnau; Mosto Bousmina; Philippe Chaumont
No coin nor oath required. For personal study only.
The aim of the present work is to study the free-radical kinetics of PDMS rubber crosslinking in the presence of 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) nitroxide. For this purpose a new method based on the relationship between the kinetics of the macro-radicals coupling [R cc (t)] was derived from a fundamental kinetic model and the viscoelastic changes of the complex shear modulus (G 0 (t) u and G 00 (t) u ). The kinetic model takes into account the initiator (Dicumyl peroxide in the present study) decomposition and the trapped PDMS macro-radicals in the presence of a radical scavenger such as TEMPO. Activation energy E ac and collision frequency factor A 0c for the bimolecular termination reaction coefficient rate k cc have been derived from the anisothermal DSC results according to the Kissinger method. Furthermore, it was observed that addition of TEMPO nitroxide can boost the initiator efficiency. The concentration variation of the active PDMS carbon-centred radicals [R p (t)] act and the [R cc (t)] with reaction time were predicted using this kinetic model. On the other hand, the influence of TEMPO concentration in formulation ([N] 0 ) and effect of temperature on viscoelastic variations are studied. As a main result, the rheological modelling shows that this new method accurately predicts the time variation of complex shear modulus at any temperature and [TEMPO]/[DCP] ratio.
📜 SIMILAR VOLUMES
The stable nitroxide TEMPO is shown to react with styrene and polystyrene models under conditions typically used for polymerizations. These results show that the nitroxide is not inert at the elevated temperatures necessary to conduct polymerizations. The implications of hydrogen abstraction and ole
## Abstract Bulk radical polymerization of styrene in the presence of nitronyl nitroxides (2‐(4‐substituted phenyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydroimidazolyl‐1‐oxyl 3‐oxide) was studied. All nitronyl nitroxides, like other nitroxyl radicals such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl radical (TEMP