Dominica H. C. Wong, F. Ignatz-Hoover, A. Childress, Grayson L. Jackson, Amrishkumar Padmakumar
High-performance rubber compounds require good dispersion of polymers, fillers, and other additives. However, fine powdery additives such as zinc oxide and insoluble sulfur (IS) are characteristically difficult to disperse, and poor dispersion may lead to large crosslink and modulus gradients in the final vulcanizate. IS dispersion can be assessed directly or indirectly, yet many techniques suffer from a lack of sensitivity and accuracy or are cost prohibitive. Herein, we describe the application of a two-parameter Weibull distribution and population survival analysis of cured rubber tensile strength as a simple technique to evaluate IS dispersion. We use statistical tools to determine the optimum number of sample replicates required to differentiate the quality of dispersion in rubber articles through the Weibull scale and shape estimates (a and b, respectively). We then demonstrate how mixing cycle time and intensity affect the dispersion of two IS grades and show that judicious choice of IS can lead to reduced cycle mix times, productivity improvements, and energy cost savings.
{"title":"QUANTIFYING SULFUR DISPERSION USING POPULATION SURVIVAL ANALYSIS OF TENSILE STRENGTH","authors":"Dominica H. C. Wong, F. Ignatz-Hoover, A. Childress, Grayson L. Jackson, Amrishkumar Padmakumar","doi":"10.5254/rct.23.76946","DOIUrl":"https://doi.org/10.5254/rct.23.76946","url":null,"abstract":"\u0000 High-performance rubber compounds require good dispersion of polymers, fillers, and other additives. However, fine powdery additives such as zinc oxide and insoluble sulfur (IS) are characteristically difficult to disperse, and poor dispersion may lead to large crosslink and modulus gradients in the final vulcanizate. IS dispersion can be assessed directly or indirectly, yet many techniques suffer from a lack of sensitivity and accuracy or are cost prohibitive. Herein, we describe the application of a two-parameter Weibull distribution and population survival analysis of cured rubber tensile strength as a simple technique to evaluate IS dispersion. We use statistical tools to determine the optimum number of sample replicates required to differentiate the quality of dispersion in rubber articles through the Weibull scale and shape estimates (a and b, respectively). We then demonstrate how mixing cycle time and intensity affect the dispersion of two IS grades and show that judicious choice of IS can lead to reduced cycle mix times, productivity improvements, and energy cost savings.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49111983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sonya K Adas, Charles J. Kritkausky, Lorrin A. Ortmann, M. K. Saxena
Migration of wax in a model sidewall formulation was studied by characterization of the compound surface over time. Vulcanizates were prepared with different wax types at equal loadings, including neat paraffinic wax, a 1:1 blend of paraffinic and microcrystalline wax, and neat microcrystalline wax. The amount of wax on the surface was measured by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and was governed by the type of wax included in the formulation. The ATR-FTIR findings were corroborated by the performance of each vulcanizate under ozone aging at static conditions. Despite the distinct differences observed in the quantity of surface wax, gas chromatography (GC) analysis of the surface waxes indicated that the composition of the migrated wax was remarkably similar regardless of the wax type used. Additionally, the degree of similarity between the composition of the constituent wax and wax recovered from the surface film correlated directly with film thickness. These results provide observable evidence in support of the theory that wax migration is governed by the competing effects of solubility and mobility of alkane chains within the rubber matrix and demonstrate a framework for future investigations of rubber oxidation mitigation. The combination of ATR-FTIR and GC, in particular, permits identification of specific wax fractions migrating out of the rubber matrix and quantification of the corresponding film thickness over an extended period of time, resulting in a robust characterization of the compound surface and thorough understanding of optimal wax compositions for various implementations under isothermal, application-specific conditions.
{"title":"ANALYTICAL INVESTIGATION OF WAX MIGRATION IN RUBBER COMPOUNDS","authors":"Sonya K Adas, Charles J. Kritkausky, Lorrin A. Ortmann, M. K. Saxena","doi":"10.5254/rct.23.76960","DOIUrl":"https://doi.org/10.5254/rct.23.76960","url":null,"abstract":"\u0000 Migration of wax in a model sidewall formulation was studied by characterization of the compound surface over time. Vulcanizates were prepared with different wax types at equal loadings, including neat paraffinic wax, a 1:1 blend of paraffinic and microcrystalline wax, and neat microcrystalline wax. The amount of wax on the surface was measured by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and was governed by the type of wax included in the formulation. The ATR-FTIR findings were corroborated by the performance of each vulcanizate under ozone aging at static conditions. Despite the distinct differences observed in the quantity of surface wax, gas chromatography (GC) analysis of the surface waxes indicated that the composition of the migrated wax was remarkably similar regardless of the wax type used. Additionally, the degree of similarity between the composition of the constituent wax and wax recovered from the surface film correlated directly with film thickness. These results provide observable evidence in support of the theory that wax migration is governed by the competing effects of solubility and mobility of alkane chains within the rubber matrix and demonstrate a framework for future investigations of rubber oxidation mitigation. The combination of ATR-FTIR and GC, in particular, permits identification of specific wax fractions migrating out of the rubber matrix and quantification of the corresponding film thickness over an extended period of time, resulting in a robust characterization of the compound surface and thorough understanding of optimal wax compositions for various implementations under isothermal, application-specific conditions.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42781946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jesbeer Kallungal, L. Chazeau, J. Chenal, J. Adrien, E. Maire, C. Barrès, B. Cantaloube, P. Heuillet
A novel methodology for characterizing the morphology distribution of filler agglomerates in elastomer composites is presented based on laboratory-sourced X-ray tomography. Various feature extraction methods (via, e.g., image-processing filters, segmentation) and selection tools (Spearman's rank correlation coefficient) combined with K-means unsupervised clustering algorithm were developed for identifying the distinct morphological classes in model materials (carbon-filled ethylene propylene diene monomer rubber). The interest of this methodology was demonstrated by precisely differentiating the materials compounded with different processing parameters. For instance, in this example, thanks to this analysis, it was found that introducing the filler before the elastomer in internal mixer tends to favor more structured agglomerates.
{"title":"QUANTITATIVE ANALYSIS OF CARBON BLACK AGGLOMERATE MORPHOLOGY IN ELASTOMER COMPOSITES BASED ON X-RAY TOMOGRAPHY BY MEANS OF NUMERICAL CLUSTERING","authors":"Jesbeer Kallungal, L. Chazeau, J. Chenal, J. Adrien, E. Maire, C. Barrès, B. Cantaloube, P. Heuillet","doi":"10.5254/rct.22.77979","DOIUrl":"https://doi.org/10.5254/rct.22.77979","url":null,"abstract":"\u0000 A novel methodology for characterizing the morphology distribution of filler agglomerates in elastomer composites is presented based on laboratory-sourced X-ray tomography. Various feature extraction methods (via, e.g., image-processing filters, segmentation) and selection tools (Spearman's rank correlation coefficient) combined with K-means unsupervised clustering algorithm were developed for identifying the distinct morphological classes in model materials (carbon-filled ethylene propylene diene monomer rubber). The interest of this methodology was demonstrated by precisely differentiating the materials compounded with different processing parameters. For instance, in this example, thanks to this analysis, it was found that introducing the filler before the elastomer in internal mixer tends to favor more structured agglomerates.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43176777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Rigotti, A. Dorigato, F. Valentini, A. Pegoretti
Ground tire rubber (GTR) from end-of-life tires was mechanically devulcanized in a lab-made two-roll machine. Parameters such as rolling speed and number of rolling cycles were systematically changed, and their effects on the degree of devulcanization and on the chemical structure of the resulting materials were investigated. Milder devulcanization conditions promoted a selective scission of S–S bonds inside the macromolecular structure of GTR, whereas harsher processing parameters led to a more pronounced and undesired C–C and C–S scission in the rubber main chains. Next, two different amounts of GTR and devulcanized GTR (dGTR) were added through melt compounding to an EPDM. The effect of the devulcanization parameters and of the GTR/dGTR loading on the microstructural and thermomechanical properties of the resulting compounds was systematically investigated. A better interface was found for dGTR than GTR, due to revulcanization in which the restored cross-link sites could form chemical bonds with the EPDM matrix; thus, energy absorption and strain at break increased. The possibility to produce novel environmentally friendly EPDM compounds with tailorable properties with respect to the neat matrix and with a lower cost and raw material amount has thus been demonstrated.
{"title":"DEVULCANIZATION PARAMETERS AND MECHANICAL PROPERTIES OF EPDM/GROUND TIRE RUBBER COMPOUNDS","authors":"D. Rigotti, A. Dorigato, F. Valentini, A. Pegoretti","doi":"10.5254/rct.23.77949","DOIUrl":"https://doi.org/10.5254/rct.23.77949","url":null,"abstract":"\u0000 Ground tire rubber (GTR) from end-of-life tires was mechanically devulcanized in a lab-made two-roll machine. Parameters such as rolling speed and number of rolling cycles were systematically changed, and their effects on the degree of devulcanization and on the chemical structure of the resulting materials were investigated. Milder devulcanization conditions promoted a selective scission of S–S bonds inside the macromolecular structure of GTR, whereas harsher processing parameters led to a more pronounced and undesired C–C and C–S scission in the rubber main chains. Next, two different amounts of GTR and devulcanized GTR (dGTR) were added through melt compounding to an EPDM. The effect of the devulcanization parameters and of the GTR/dGTR loading on the microstructural and thermomechanical properties of the resulting compounds was systematically investigated. A better interface was found for dGTR than GTR, due to revulcanization in which the restored cross-link sites could form chemical bonds with the EPDM matrix; thus, energy absorption and strain at break increased. The possibility to produce novel environmentally friendly EPDM compounds with tailorable properties with respect to the neat matrix and with a lower cost and raw material amount has thus been demonstrated.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42898784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Surya, S. Sharma, T. Mondal, K. Naskar, A. Bhowmick
A substantial knowledge gap persists in the material development of smart tires for future self-driving automobiles, which can increase both the vehicles' performance as well as the safety of the passengers. Due to the very high stiffness of conventional strain sensors compared to the softer rubber compound used as the tire tread material, an inaccurate representation of tire deformation characteristics is anticipated. Here, a comprehensive characterization of the electrical conduction and strain sensing behavior of a natural rubber (NR)-based commercial tire tread composite combining the reinforcement of a carbon black-conductive nanofiber dual filler system was carried out for the very first time. The incorporation of as low as 2 wt.% of carbon nanotubes (CNT) and graphite nanofibers (GNF) could increase the electrical conductivity of the control compound by two orders of magnitude compared to the control compound. The gauge factor observed was much higher than the value reported for metallic or polyvinylidene difluoride (PVDF) based stain sensors developed for this application. A 25% enhancement in thermal conductivity was also observed. Thus, the developed composites have the potential to be used as in situ strain sensors so that the problems of debonding and heating differences in the sensor–rubber interfaces in tires can be avoided in future.
{"title":"THERMALLY CONDUCTIVE DURABLE STRAIN SENSORS FOR NEXT-GENERATION INTELLIGENT TIRES FROM NATURAL RUBBER NANOCOMPOSITES","authors":"K. Surya, S. Sharma, T. Mondal, K. Naskar, A. Bhowmick","doi":"10.5254/rct.23.76951","DOIUrl":"https://doi.org/10.5254/rct.23.76951","url":null,"abstract":"\u0000 A substantial knowledge gap persists in the material development of smart tires for future self-driving automobiles, which can increase both the vehicles' performance as well as the safety of the passengers. Due to the very high stiffness of conventional strain sensors compared to the softer rubber compound used as the tire tread material, an inaccurate representation of tire deformation characteristics is anticipated. Here, a comprehensive characterization of the electrical conduction and strain sensing behavior of a natural rubber (NR)-based commercial tire tread composite combining the reinforcement of a carbon black-conductive nanofiber dual filler system was carried out for the very first time. The incorporation of as low as 2 wt.% of carbon nanotubes (CNT) and graphite nanofibers (GNF) could increase the electrical conductivity of the control compound by two orders of magnitude compared to the control compound. The gauge factor observed was much higher than the value reported for metallic or polyvinylidene difluoride (PVDF) based stain sensors developed for this application. A 25% enhancement in thermal conductivity was also observed. Thus, the developed composites have the potential to be used as in situ strain sensors so that the problems of debonding and heating differences in the sensor–rubber interfaces in tires can be avoided in future.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42782699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bettina Strommer, A. Battig, D. Schulze, L. Jácome, B. Schartel, M. Böhning
The addition of nanoparticles as reinforcing fillers in elastomers yields nanocomposites with unique property profiles, which opens the door for various new application fields. Major factors influencing the performance of nanocomposites are studied by varying the type and shape of nanoparticles and their dispersion in the natural rubber matrix. The industrial applicability of these nanocomposites is put into focus using two types of graphene and a nanoscale carbon black, all commercially available, and scalable processing techniques in the form of a highly filled masterbatch production via latex premixing by simple stirring or ultrasonically assisted dispersing with surfactant followed by conventional two-roll milling and hot pressing. Different processing and measurement methods reveal the potential for possible improvements: rheology, curing behavior, static and dynamic mechanical properties, swelling, and fire behavior. The aspect ratio of the nanoparticles and their interaction with the surrounding matrix prove to be crucial for the development of superior nanocomposites. An enhanced dispersing method enables the utilization of the improvement potential at low filler loadings (3 parts per hundred of rubber [phr]) and yields multifunctional rubber nanocomposites: two-dimensional layered particles (graphene) result in anisotropic material behavior with strong reinforcement in the in-plane direction (157% increase in the Young's modulus). The peak heat release rate in the cone calorimeter is reduced by 55% by incorporating 3 phr of few-layer graphene via an optimized dispersing process.
{"title":"SHAPE, ORIENTATION, INTERACTION, OR DISPERSION: VALORIZATION OF THE INFLUENCE FACTORS IN NATURAL RUBBER NANOCOMPOSITES","authors":"Bettina Strommer, A. Battig, D. Schulze, L. Jácome, B. Schartel, M. Böhning","doi":"10.5254/rct.23.77961","DOIUrl":"https://doi.org/10.5254/rct.23.77961","url":null,"abstract":"\u0000 The addition of nanoparticles as reinforcing fillers in elastomers yields nanocomposites with unique property profiles, which opens the door for various new application fields. Major factors influencing the performance of nanocomposites are studied by varying the type and shape of nanoparticles and their dispersion in the natural rubber matrix. The industrial applicability of these nanocomposites is put into focus using two types of graphene and a nanoscale carbon black, all commercially available, and scalable processing techniques in the form of a highly filled masterbatch production via latex premixing by simple stirring or ultrasonically assisted dispersing with surfactant followed by conventional two-roll milling and hot pressing. Different processing and measurement methods reveal the potential for possible improvements: rheology, curing behavior, static and dynamic mechanical properties, swelling, and fire behavior. The aspect ratio of the nanoparticles and their interaction with the surrounding matrix prove to be crucial for the development of superior nanocomposites. An enhanced dispersing method enables the utilization of the improvement potential at low filler loadings (3 parts per hundred of rubber [phr]) and yields multifunctional rubber nanocomposites: two-dimensional layered particles (graphene) result in anisotropic material behavior with strong reinforcement in the in-plane direction (157% increase in the Young's modulus). The peak heat release rate in the cone calorimeter is reduced by 55% by incorporating 3 phr of few-layer graphene via an optimized dispersing process.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42931098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Glanowski, M. Le Saux, V. Le Saux, B. Huneau, C. Champy, P. Charrier, Y. Marco
The properties of elastomeric materials are strongly influenced by the inclusions resulting from the ingredients and the elaboration process. A methodology is proposed to differentiate the inclusions harmful for fatigue (larger than a few micrometers) in elastomers according to their chemical nature, and to characterize them quantitatively with sufficient statistics. Three techniques are used and compared: digital optical microscopy (OM), scanning electron microscopy (SEM) associated with energy dispersive X-ray spectroscopy, and X-ray micro-computed tomography (μ-CT). Six materials are used to challenge the methodology. In addition to the usual metal oxides and carbon black agglomerates, three atypical types of inclusions are highlighted, generating specific detection difficulties. A relevant image analysis procedure is developed to automatically detect the inclusions from the acquired images, more objectively and accurately than with the classical thresholding methods. The morphology and the spatial distribution of the different inclusions populations are then determined. μ-CT is the most comprehensive and accurate method for classification and statistical characterization of inclusions. Furthermore, relevant data on the size distribution of inclusions can be obtained using backscattered electrons (SEM-BSE) or digital OM. SEM-BSE provides more accurate results than digital OM.
{"title":"COMBINED TECHNIQUES AND RELEVANT IMAGE PROCESSING FOR QUANTITATIVE STATISTICAL CHARACTERIZATION OF INCLUSIONS IN ELASTOMERS","authors":"T. Glanowski, M. Le Saux, V. Le Saux, B. Huneau, C. Champy, P. Charrier, Y. Marco","doi":"10.5254/rct.22.22970","DOIUrl":"https://doi.org/10.5254/rct.22.22970","url":null,"abstract":"The properties of elastomeric materials are strongly influenced by the inclusions resulting from the ingredients and the elaboration process. A methodology is proposed to differentiate the inclusions harmful for fatigue (larger than a few micrometers) in elastomers according to their chemical nature, and to characterize them quantitatively with sufficient statistics. Three techniques are used and compared: digital optical microscopy (OM), scanning electron microscopy (SEM) associated with energy dispersive X-ray spectroscopy, and X-ray micro-computed tomography (μ-CT). Six materials are used to challenge the methodology. In addition to the usual metal oxides and carbon black agglomerates, three atypical types of inclusions are highlighted, generating specific detection difficulties. A relevant image analysis procedure is developed to automatically detect the inclusions from the acquired images, more objectively and accurately than with the classical thresholding methods. The morphology and the spatial distribution of the different inclusions populations are then determined. μ-CT is the most comprehensive and accurate method for classification and statistical characterization of inclusions. Furthermore, relevant data on the size distribution of inclusions can be obtained using backscattered electrons (SEM-BSE) or digital OM. SEM-BSE provides more accurate results than digital OM.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70683618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Wen, Bin Wang, Aiqin Wu, Qing-zhi Zhang, Wenrong Zhao, Weijie Jia
A 2-thiobenzothiazole/p-phenylenediamine vulcanization intermediate has been characterized by means of ultra-high-performance liquid chromatography–tandem quadrupole time-of-flight mass spectrometry. Pregenerated 2-thiobenzothiazole/p-phenylenediamine intermediate has a clear effect on accelerating the sulfur crosslinking reaction. Therefore, the generation of vulcanization active species can act as a proof that p-phenylenediamine antioxidant could exert an influence on the vulcanization process via a reaction with the accelerator. Based on an analysis of samples from different curing stages, it is speculated that the intermediate is most likely generated in the vulcanization induction period. This research also provides indirect evidence of the effect of zinc oxide on vulcanization. The intermediate can be detected in both solution and vulcanizate. Its formation is likely to be a zinc ion–mediated reversible mechanism involving a radical course.
{"title":"CHARACTERIZATION OF 2-THIOBENZOTHIAZOLE/P-PHENYLENEDIAMINE VULCANIZATION INTERMEDIATE AND ITS INFLUENCE ON VULCANIZATION","authors":"S. Wen, Bin Wang, Aiqin Wu, Qing-zhi Zhang, Wenrong Zhao, Weijie Jia","doi":"10.5254/rct.22.78973","DOIUrl":"https://doi.org/10.5254/rct.22.78973","url":null,"abstract":"\u0000 A 2-thiobenzothiazole/p-phenylenediamine vulcanization intermediate has been characterized by means of ultra-high-performance liquid chromatography–tandem quadrupole time-of-flight mass spectrometry. Pregenerated 2-thiobenzothiazole/p-phenylenediamine intermediate has a clear effect on accelerating the sulfur crosslinking reaction. Therefore, the generation of vulcanization active species can act as a proof that p-phenylenediamine antioxidant could exert an influence on the vulcanization process via a reaction with the accelerator. Based on an analysis of samples from different curing stages, it is speculated that the intermediate is most likely generated in the vulcanization induction period. This research also provides indirect evidence of the effect of zinc oxide on vulcanization. The intermediate can be detected in both solution and vulcanizate. Its formation is likely to be a zinc ion–mediated reversible mechanism involving a radical course.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49354276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Because cis-polybutadiene rubber (BR) can improve the fatigue crack growth (FCG) resistance of natural rubber (NR) in the low-tearing-energy (G) range, a blending system of NR/BR is often used in tire materials. In this study, based on relationship of (FCG rate (dc/dN) − G) established from the perspective of fracture mechanics and then inspired by Persson's theory and starting from the perspective of viscoelasticity, the FCG behavior and mechanism of NR/BR were investigated. NR/BR with different blending ratios were prepared, and dc/dN under different G inputs (500/1500 J/m2) was measured. According to the viscoelastic parameters (storage modulus E′, loss factor tan δ, and loss compliance modulus J″) recorded in situ, energy dissipation distribution at the crack tip (energy consumption for FCG inside crack tip: G0 and energy loss in linear viscoelastic zone near crack tip: G0f [v, T]) was determined, and the relationship of (viscoelasticity − dc/dN) was finally set up. When G = 500 J/m2, blending BR can reduce dc/dN as compared with pure NR. On one hand, with a higher BR fraction, an increased cross-linking density and enhanced filler network provided greater rigidity, which increased E′; on the other hand, a low glass transition temperature and flexible chain of BR reduced hysteresis, which decreased tan δ. The joint action led to a decrease in J″, which caused more G0f (v, T) and less G0, resulting in the ultimate reduction of dc/dN. In contrast, for G = 1500 J/m2, when the BR content was >50 phr, dc/dN showed a significant increase. Although more BR evidently decreased J″ and then led to a large amount of G0f (v, T), due to absence of strain-induced crystallization, the chain orientation of BR was hard to resist FCG when G increased. Finally, the morphology of the crack tip propagation path was captured to corroborate the different orientation characteristics of NR and BR and their effects on FCG behavior.
{"title":"VISCOELASTICITY AND DYNAMIC FATIGUE CRACK GROWTH BEHAVIOR OF NATURAL RUBBER/CIS-POLYBUTADIENE RUBBER COMPOSITES","authors":"Qingyuan Han, Youping Wu","doi":"10.5254/rct.22.78925","DOIUrl":"https://doi.org/10.5254/rct.22.78925","url":null,"abstract":"\u0000 Because cis-polybutadiene rubber (BR) can improve the fatigue crack growth (FCG) resistance of natural rubber (NR) in the low-tearing-energy (G) range, a blending system of NR/BR is often used in tire materials. In this study, based on relationship of (FCG rate (dc/dN) − G) established from the perspective of fracture mechanics and then inspired by Persson's theory and starting from the perspective of viscoelasticity, the FCG behavior and mechanism of NR/BR were investigated. NR/BR with different blending ratios were prepared, and dc/dN under different G inputs (500/1500 J/m2) was measured. According to the viscoelastic parameters (storage modulus E′, loss factor tan δ, and loss compliance modulus J″) recorded in situ, energy dissipation distribution at the crack tip (energy consumption for FCG inside crack tip: G0 and energy loss in linear viscoelastic zone near crack tip: G0f [v, T]) was determined, and the relationship of (viscoelasticity − dc/dN) was finally set up. When G = 500 J/m2, blending BR can reduce dc/dN as compared with pure NR. On one hand, with a higher BR fraction, an increased cross-linking density and enhanced filler network provided greater rigidity, which increased E′; on the other hand, a low glass transition temperature and flexible chain of BR reduced hysteresis, which decreased tan δ. The joint action led to a decrease in J″, which caused more G0f (v, T) and less G0, resulting in the ultimate reduction of dc/dN. In contrast, for G = 1500 J/m2, when the BR content was >50 phr, dc/dN showed a significant increase. Although more BR evidently decreased J″ and then led to a large amount of G0f (v, T), due to absence of strain-induced crystallization, the chain orientation of BR was hard to resist FCG when G increased. Finally, the morphology of the crack tip propagation path was captured to corroborate the different orientation characteristics of NR and BR and their effects on FCG behavior.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45672706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Butyl and bromobutyl inner tubes, specified by the Aerospace Standard AS50141 for military aircraft, were thermally aged from 40 to 120 °C for varying lengths of time and then their hardness and mechanical properties were measured. 1H double quantum nuclear magnetic resonance (DQ NMR) was used to elucidate crosslink density and distribution changes. Time–temperature superposition of the aged data coupled with the Arrhenius approach was used to determine an approximate shelf life. High (80–120 °C) and low (40–80 °C) temperature oxidation processes were occurring for both rubbers. Below 80 °C, an increase in crosslink density, hardening, stiffening, and loss of elongation was observed. Plasticizer and volatile loss contributes to compound stiffening. Sulfur crosslink network modifications during thermal aging can explain ultimate property loss and stiffness increase. Diffusion limited oxidation was taking place above 80 °C, with the development of a thin oxidized layer composed of ionic crosslinking that affected both hardness and mechanical properties. For butyl rubber, the hardness rise stabilizes as do the ultimate properties, likely due to the proliferation of chain scission reactions, whereas crosslinking reactions prevailed over chain scission events for bromobutyl rubber. Crosslink density and defect fractions B and C as measured through DQ NMR were in agreement with the physical property testing results. The degree of heterogeneity of the network as perceived visually through DQ NMR regularization increases upon exposure to higher temperatures and longer aging times due to the broadening of the crosslink density distribution. Similar Arrhenius activation energies were calculated for the low and high temperature oxidation process for butyl and bromobutyl rubbers. The projected shelf life for the butyl and bromobutyl inner tubes was 10 and 20 yr, respectively. For the first time, DQ NMR testing results (crosslink density and its distribution, defect level) have been successfully applied to support a shelf life determination.
{"title":"Accelerated Heat Aging of Butyl and Bromobutyl Aircraft Inner Tubes for Shelf Life Determination","authors":"G. Germain, Na Li,, R. Pazur","doi":"10.5254/rct.22.78935","DOIUrl":"https://doi.org/10.5254/rct.22.78935","url":null,"abstract":"\u0000 Butyl and bromobutyl inner tubes, specified by the Aerospace Standard AS50141 for military aircraft, were thermally aged from 40 to 120 °C for varying lengths of time and then their hardness and mechanical properties were measured. 1H double quantum nuclear magnetic resonance (DQ NMR) was used to elucidate crosslink density and distribution changes. Time–temperature superposition of the aged data coupled with the Arrhenius approach was used to determine an approximate shelf life. High (80–120 °C) and low (40–80 °C) temperature oxidation processes were occurring for both rubbers. Below 80 °C, an increase in crosslink density, hardening, stiffening, and loss of elongation was observed. Plasticizer and volatile loss contributes to compound stiffening. Sulfur crosslink network modifications during thermal aging can explain ultimate property loss and stiffness increase. Diffusion limited oxidation was taking place above 80 °C, with the development of a thin oxidized layer composed of ionic crosslinking that affected both hardness and mechanical properties. For butyl rubber, the hardness rise stabilizes as do the ultimate properties, likely due to the proliferation of chain scission reactions, whereas crosslinking reactions prevailed over chain scission events for bromobutyl rubber. Crosslink density and defect fractions B and C as measured through DQ NMR were in agreement with the physical property testing results. The degree of heterogeneity of the network as perceived visually through DQ NMR regularization increases upon exposure to higher temperatures and longer aging times due to the broadening of the crosslink density distribution. Similar Arrhenius activation energies were calculated for the low and high temperature oxidation process for butyl and bromobutyl rubbers. The projected shelf life for the butyl and bromobutyl inner tubes was 10 and 20 yr, respectively. For the first time, DQ NMR testing results (crosslink density and its distribution, defect level) have been successfully applied to support a shelf life determination.","PeriodicalId":21349,"journal":{"name":"Rubber Chemistry and Technology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49340460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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