Abstract
The knowledge of how rubber breakdown on heating in oxidative environment is important in processing and using the material. In the present work, we performed thermogravimetric analysis and utilized three iso-conversional kinetic models to get apparent activation energies of thermal degradation of natural rubber/butyl rubber. Blending of RSS/butyl and additives was done using a laboratory two-roll mill. Cure time of the blended compound was determined by a moving die rheometer. The compound was compression moulded at 160°C with a pressure of 150 kg/cm 2 using a laboratory hot press. Thermogravimetric analysis was carried out from 30°C to 800°C in air flow of 200 ml/min with heating rates of 5, 10, 15, and 20°C/min. The kinetic parameters were determined by three isoconversional models (Kissinger, Doyle, and Flynn–Wall–Ozawa model). The result revealed that the thermal decomposition of the blend occurs in two stages, DTG peaks tends to shift to a higher temperature and the values of DTG peaks increase with the increase of heating rate, and the three isoconversional models gave similar apparent activation energies. The activation energy obtained can be used to predict thermal lifetime of the material.
Highlights
Rubber oxidation rate depends on many factor, such as rubber type, processing methods and service condition of the product
A conventional sulphur vulcanization system was employed with the following formulation: ribbed smoked sheet (RSS) 55 phr, butyl 45 phr, carbon black 50 phr, NPCC 5 phr, TMQ 2 phr, 6PPD 1 phr, wax 0.5 phr, zinc oxide (ZnO) 5 phr, aflux 42 1 phr, paraffinic oil 8 phr, tetramethyl thiuram (TMT) 0.5 phr, mercapto benzothiazole (MBT) 0.5 phr, and sulphur 2.5 phr
It shows the main mass loss stages move in the direction of higher temperature with the increase of heating rate
Summary
Rubber oxidation rate depends on many factor, such as rubber type, processing methods and service condition of the product. Oxidation stability determines the service life of the product because exposure of rubber to oxygen can result deterioration in its mechanical properties. Thermogravimetric analysis is one of the most widely accepted methods for determining the thermal properties of polymeric materials (Martins et al, 2008). It provides approximation of effective kinetic parameters for decomposition reactions of various materials (Wang & Zhao, 2015). Nabil et al (2013) applied the Coats–-Redfern’s method to study thermal analysis of carbon black-filled NR/Virgin EPDM and NR/Recycled EPDM rubber blends It provides approximation of effective kinetic parameters for decomposition reactions of various materials (Wang & Zhao, 2015). Zhao et al (2013) analyzed the degradation kinetics of phenol–formaldehyde resins derived from beetle infested pine barks by using Kissinger and Kissinger–Akahira–Sunose methods. Zheng et al (2015) used the isoconversional Flynn-Wall-Ozawa (FWO) method to calculate the kinetic paramesters of degradation of natural rubber (NR). Nabil et al (2013) applied the Coats–-Redfern’s method to study thermal analysis of carbon black-filled NR/Virgin EPDM and NR/Recycled EPDM rubber blends
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