Summary: Dichlorocarbene modified butadiene rubber (DCBR) was prepared from butadiene rubber (BR) via an alkali hydrolysis of chloroform with using cetyltrimetylammonium bromide (CTAB) as a phase transfer agent. The chemical structure of DCBR was characterized by a fourier transform infrared spectroscopy and 1 H-and 13 C-nuclear magnetic resonance spectroscopy. The chlorine content in DCBR matrix was extracted by acid digestion method and estimated based on a volhard method. The chlorine content of DCBR increased with the increase of reaction time. The glass transition temperature (T g ) of DCBR (T g ¼ À3.4 C) was shifted to the higher temperature compared to T g value of BR (T g ¼ À102.8 C) due to the presence of dichlorocarbene group. Moreover, thermogravimetric analysis was used to study the decomposition profile of BR and DCBR. The thermal stability of DCBR was decreased compared to that of BR, while the flame retardant of NR/DCBR blend was improved due to the presence of chlorine in DCBR. The chlorine char from dichlorocarbene group acted as a thermal insulator for rubber.
Dichlorocarbene modified butadiene rubber (DCBR) was prepared via the addition of the dichlorocarbene group in the presence of 2 phase transfer agents (cetyltrimethylammonium bromide and tetraethylammonium chloride). The effects of the reaction temperature and time, amount of dichlorocarbene precursor, and the type and amount of phase transfer agent on the chlorine content were investigated. The highest chlorine content (30%) in DCBR was obtained using 0.062 mol chloroform and 0.003 mol cetyltrimethylammonium bromide at room temperature for 19 hours although 27.9% was obtained after 12 hours. The kinetics of this dichlorocarbene modification was best described by the pseudo-first order rate law with 2 rate constants. For practical applications, the DCBR with chlorine contents of 10%, 20%, or 30% were blended with natural rubber (NR) and then vulcanized using the sulfur-curing system. Although the polarity of DCBR was increased, a good compatibility between NR and DCBR still existed, resulting in improved mechanical properties. The oil resistance, flame retardant, and ozone resistance properties of the NR/DCBR blend vulcanizates were enhanced compared to those of a NR/butadiene rubber blend vulcanizate, which was related to the amount of chlorine incorporated into the DCBR. KEYWORDS mechanical properties, oxidation, rubber, thermal properties | INTRODUCTIONRubber products have recently been extensively used in tire production, healthcare supplies, household supplies, interior construction, and transportation. Therefore, there is a demand for flame retardant, ozone, and oil resistance properties of these rubber products. Because rubber molecules contain carbon-carbon double (C═C) bonds, which are reactive to free radicals, ozone, and oxygen, rubber compounds alone have some disadvantages, especially their poor thermal properties and low ozone resistance. modification of rubber is another method of improving the properties of rubber containing C═C bonds. This modification reduces the number of C═C bonds in the rubber structure and introduces the polar dichlorocarbene group into the rubber molecules. Although the increased polarity may cause mixing problems in rubber blends, partially dichlorocarbene modified rubber is less polar than halogenated rubber, which often has a mixing problem. Thus, modification by dichlorocarbene may cause reduced mixing problems compared to halogenated rubber, and so dichlorocarbene modification was chosen for this study. and tetraethylammonium chloride (TEAC) were purchased from AjaxFinechem Pty Ltd (New Zealand) and Sigma-Aldrich Co LLC (USA), respectively. The chemical structures of CTAB and TEAC, the phase transfer agents, are shown in Figure S1. All chemical reagents were used as received. Zinc oxide (ZnO) and stearic acid were used as activators. N-cyclohexyl-2-benzothiazol-sulfenamide (CBS) and sulfur were used as an accelerator and a crosslinking agent, respectively. All vulcanizing agents were purchased from PAN Innovation Industry Ltd (Thailand). | Preparation of DCBRThe DCBR ...
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