Abstract:Insoluble sulfur (IS), used as a vulcanizing reagent of rubber, is prepared by the thermal ring-opening polymerization of sulfur (S8). Enhancing its thermal stability and content ratio (yield) is important for the industrial production of IS. The post-heating process at a high temperature of 70 or 90 C of the mixture of IS and S8 enhanced the thermal stability of IS and reduced the yield of IS. Further, the process at 30 C enhanced its thermal stability and maintained its yield. Since the thermal stability of … Show more
“…The endothermic peak formed around 180°C can be attributed to the ring-opening of sulphur. 58 On the other hand, the endothermic peaks of sulphur originated from the crystalline phase disappeared completely for vulcanized EPDM samples including 2.5 and 10 phr sulphur. These findings confirm that there is not any unreacted sulphur after vulcanization process.Figure 10.Differential scanning calorimeter thermograms of ethylene propylene diene monomer compounds and sulphur.…”
Tuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers.
“…The endothermic peak formed around 180°C can be attributed to the ring-opening of sulphur. 58 On the other hand, the endothermic peaks of sulphur originated from the crystalline phase disappeared completely for vulcanized EPDM samples including 2.5 and 10 phr sulphur. These findings confirm that there is not any unreacted sulphur after vulcanization process.Figure 10.Differential scanning calorimeter thermograms of ethylene propylene diene monomer compounds and sulphur.…”
Tuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers.
“…( )3 + ROOH → PD−S O P OR ( )3 + ROH Furthermore, sulfur/nanoparticles can be used to enhance thermal stability of polymers because reinforcing polymers with nanoparticles significantly improves the properties of polymers (Chrissafis and Bikiaris, 2011;Senthil Kumar et al, 2018;Terada et al, 2020).…”
The addition of polymer to a base binder has been documented as a successful approach in terms of improving physical and rheological properties of the base bitumen. However, the main drawbacks of polymer-modified bitumen are incompatibility and degradation of polymer due to aging. This article aims to introduce a bibliometric analysis and review on modifying bitumen with polymers. Additionally, this article intent to highlight the significant gaps and recommendations for future work. Furthermore, another objective of this article is to provide a worth attempt regrading reducing the negative impact of polymer’s drawbacks on the performance of polymer-modified base binder. The findings of this article demonstrated that the test of storage stability for polymer-amended bitumen should be modified, in which the softening point of aluminum tube centerpiece should be measured to introduce a better evaluation for the storage stability of polymer-amended bitumen. In addition, the effects of kinetic factors (mixing sequence, viscosity of blend, shear rate, and time of mixing) on the compatibility of polymer-amended bitumen should be investigated. Moreover, the addition of compatibilizers and stabilizers to polymer-modified binder is recommended to improve compatibility and reduce the effect of aging on degradation of polymer.
Carbon consumption of activated carbon varies with the sulfur-containing products. In this work, differential thermogravimetric (DTG), electron paramagnetic resonance (ESR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) were used to reveal the adsorptionregeneration process of H 2 S and the effect of adsorption products on carbon consumption. H 2 S reacts with the C=C bond to form C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C , about 30 °C higher than the decomposition temperature of H 2 SO 4 . In the thermal regeneration process, the elemental sulfur in the form of monoclinic sulfur (S 8 ) rst breaks into in nitely long chain molecules (S ∞ ) and then into small molecules, nally into sulfur vapor. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H 2 SO 4 . The compressive strength reduces less due to its slight effect on the disordered graphitic structure. H 2 S also reacts with the C=O bond to form H 2 SO 3 or H 2 SO 4 . The desorption of H 2 SO 3 does not require carbon consumption. The decomposition of H 2 SO 4 needs to react with C=C bond to release SO 2 , CO 2 , and CO, and the compressive strength of activated carbon signi cantly decreases. The carbon consumption originates from two aspects, the one from the regeneration of sulfur-containing products is more than twice of the other one from the decomposition of oxygen-containing functional groups.
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