Butyl rubber reclamation by combined microwave radiation and chemical reagents

Abstract

Rubber recycling is growing worldwide because of increasing raw material costs. In addition, extensive use of rubber articles and their eventual disposal is a major concern for the environment. Butyl rubber (IIR) was devulcanized by microwave radiation with the aid of devulcanizing reagents and oil. The effect of several devulcanizing reagents, hexadecylamine (HAD), diphenyl disulfide (DPDS), N‐cyclohexyl‐2‐benzothiozyl sulfenamide (CBS), and tetramethylthiuram disulfide (TMTD) on devulcanization process, was studied. The investigation was carried out in various microwave radiation temperatures and different amounts of aromatic and paraffinic oils. The results showed that waste rubber powder with a median particle size of 279 normalμnormalm was devulcanized efficiently. It was confirmed when devulcanization % of the devulcanizates were measured by swelling tests. Among of the devulcanizing reagents and based on Horix analysis, HDA with the sol fraction, crosslink density (CLD), and devulcanization percent of 14%, 25 normalmol/normalm3 and 64%, respectively, was the most suitable devulcanizing reagent. In addition, compound with 30 and 6 phr paraffinic oil and HDA in formulation, respectively, had maximum devulcanization % (83%). The devulcanizing temperature of this compound was 180 °normalC . For the most of all compounds, during microwave radiation, a part of disulfides crosslinks were broken and released sulfurs giving new mono and polysulfides bridges. This resulted in the higher CLDs for some compounds when they compared with CLD of the initial waste rubber. In the morphological study of the devulcanized compounds, vulcanized rubbers clearly showed in the SEM micrographs surrounded by a matrix of devulcanized rubber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43363.

Reclaiming waste tire rubber by an irradiation technique

“…The particle size of the waste powder is an important factor for controlling devulcanization temperature as it was found by authors earlier [22,23]. For large particles, i.e.…”

“…The reason may refers to a group of new main chain reactions named "main chain un saturation volatile formation crosslinking" [30] and or the formation of new mono and polysulphide sulphur bridges as it is shown in Table 6. Scheme 5 [23] clearly describes the formed radicals after microwave radiation and subsequent chain and sulphur crosslinks growth. Our founds are in conformity with the other's report [31].…”

“…Note, in this study and to increase the efficiency of SeS di bonds breakage, hexanethiol replaced with cyclohexanethiol. Mechanism of sulphur crosslinks breakage by 2-propanethiol þ n-hexylamine and cyclohexanethiol þ n-hexylamine are depicted in Scheme 2-a and 2-b, respectively [23]. Mono, di and polysulphide % in sulphur bridges for selected rubber compounds were presented in Table 6.…”

“…The devulcanization mechanism for HDA is ionic. Here, the polymer chains with the aid of HDA and microwave radiation divide in to two ions through their sulphur crosslinks [23].…”

“…In addition, there is not any report that compares the effect of the various chemical agents on microwave devulcanization of the waste rubber. Authors [22,23] already studied the effect of various operative parameters including several devulcanizing agents on microwave devulcanization of ethylene-propylene-diene monomer (EPDM) and butyl rubber. In this study, the same parameters along with some more complementary aspects on tire rubbers will be considered and discussed.…”