Kinetics of the Formation of Nitroso Radicals in the System of Butyl Rubber Curing in the Presence of Sterically Hindere
- PDF / 805,991 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 88 Downloads / 174 Views
tics of the Formation of Nitroso Radicals in the System of Butyl Rubber Curing in the Presence of Sterically Hindered 2,4,6-Tri-tert-butylphenol E. Kh. Afiatullova, T. A. Chapkoa, and L. N. Gur’evaa,* a
Research Institute of Polymer Materials, Joint-Stock Company, Perm, 614101 Russia *e-mail: [email protected] Received October 5, 2018; revised September 7, 2020; accepted September 17, 2020
Abstract—The kinetics of the activity of the butyl rubber (BR) curing system without and with various amounts of antioxidant P-23 at temperatures of 55 and 80°C was studied. The induction period of the vulcanization of the BR samples in the presence of sterically hindered phenol was found to exceed that for the samples without phenol. With rising temperature the rate of the rubber vulcanization tends to increase due to an increase in the initiation rate. Keywords: kinetics, reaction mechanism, vulcanization, butyl rubber, nitroso radical, sterically hindered phenol, 2,4,6-tri-tert-butylphenol
DOI: 10.1134/S1070363220090352 One of the lines of efforts aimed at development of a composite material entails the use of high-molecularweight plasticized butyl rubber (BR) as a binder. Even in small amounts, BR affords high physicomechanical properties of a composite and offers a number of advantages over other known elastomeric binders. The manufacture of BR-containing industrial products employs, among other curing systems, that in which the actual curing agent for BR in the redox reaction of vulcanization is p-nitrosobenzene (p-DNB), the product of oxidation of paraquinone dioxime (PQD) with manganese dioxide (MnO2), crosslinking the rubber molecule. To prevent premature curing of BR, it is necessary to add curing inhibitors. To be suitable for this purpose, a compound should meet the following criteria. First, the reaction of the inhibitor with the active site should give a product (most often, a radical) which is not involved in the chain propagation, since only in this case the inhibitor, while entering into reaction, terminates the chain. Second, the inhibitor must be highly reactive toward at least one of the active sites leading the chain, because only this allows it to successfully compete with the reactants entering in the chain propagation acts with the active sites. Third, the inhibitor itself and the products it forms during the reaction should not exert a noticeable initiating effect, since in this case the reaction rate would increase due to an increase in the initiation rate [1].
The inhibitor used in this study was 2,4,6-tri-tertbutylphenol (P-23) antioxidant, an aromatic compound characterized by a relatively weak O–H bond (Scheme 1). The antioxidant is produced via a multistage synthesis process based on homogeneous or heterogeneous catalytic alkylation of phenol with isobutylene, followed by distillation of the synthesis products and purification by multiple recrystallization. Each stage of the process can have an impact on the quality and purity of the resulting product. Use of P-23 enables controlling the length of
Data Loading...
