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Advanced Rubber Composites II

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (20 November 2023) | Viewed by 20802

Special Issue Editors


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Guest Editor
Department of Plastics, Rubber and Fibres, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava, Slovakia
Interests: rubbers; rubber composites; reinforcement; carbon-based fillers; magnetic fillers; biopolymer fillers; filler/rubber interactions; surface modification; vulcanization; analysis of cross-link density; network structure
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E-Mail Website
Guest Editor
Department of Plastics, Rubber and Fibres, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava, Slovakia
Interests: rubber; polymers; polymer blends; composites and nanocomposites; biopolymers; multiphase polymer system structures; surface modification of polymers by chemical and physical methods; plasma treatment; reinforcement; vulcanization; recycling of polymers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Current progress in science and technology shift towards development and fabrication of new materials and products that must often fulfill requirements for specific applications. Rubbers are unique and versatile materials characterized by excellent elasticity, dynamic and mechanical properties. They can be easily processed and shaped into desired products. Thus, they are highly demanded in various spheres ranging from general products to high-tech applications. Final properties of rubbers can be easily tailored by introduction of special additives, different fillers ranging from traditional to special types, by functional modifications of fillers and rubbers or by implementation of processing and manufacturing techniques. Due to increasing demand for protection of the environment, more attention has also been devoted to possibilities of application of biopolymers and materials from renewable resources as additives or fillers into rubber formulations.

Preparation of new materials with unique structure and favorable flexible characteristics requires also new approach to the formation of cross-linked network structure in rubber compounds and study of new vulcanization systems, which can provide spectrum of required mechanical characteristics to rubber-based materials.

Rubber products often represent multiphase and multicomponent composite systems and to better understand correlation between microstructure and macroscopic behavior and property spectrum of innovative, sustainable material concepts, new investigation a simulation methods have been developed. Due to the complexity of rubber products, modern processing methodologies and instrumentation have been implemented.

The special issue “Advanced Rubber Composites II” is devoted to all aspects of rubber science and technology, including, but not limited to rubbers, thermoplastic elastomers, blends, composites, smart materials, eco-friendly materials, fillers, vulcanization systems, rheology, new approaches in testing, methodology, processing and fabrication techniques, 3D-printing, ageing and recycling.

Dr. Jan Kruzelak
Prof. Dr. Ivan Hudec
Guest Editors

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Keywords

  • rubbers
  • fillers
  • reinforcement
  • composites
  • smart materials
  • ecofriendly materials
  • vulcanization
  • 3-D printing
  • rheology
  • testing
  • recycling

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Related Special Issue

Published Papers (11 papers)

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Research

16 pages, 9785 KiB  
Article
Polyurethane Glycerolysate as a Modifier of the Properties of Natural Rubber Mixtures and Vulcanizates
by Marcin Włoch, Maksymilian Toruńczak and Janusz Datta
Materials 2024, 17(1), 62; https://doi.org/10.3390/ma17010062 - 22 Dec 2023
Cited by 1 | Viewed by 985
Abstract
Chemical recycling of polyurethanes can be realized in several different ways, but the most important methods are glycolysis and glycerolysis. Both methods permit recovery of polyols (when the process is realized with the mass excess of depolymerizing agent) or substitutes of polyols, which [...] Read more.
Chemical recycling of polyurethanes can be realized in several different ways, but the most important methods are glycolysis and glycerolysis. Both methods permit recovery of polyols (when the process is realized with the mass excess of depolymerizing agent) or substitutes of polyols, which contain urethane moieties in the main chains and terminate mainly in hydroxyl groups (when the process is realized with the mass excess of depolymerized polyurethane). Oligomeric products with urethane groups in the chemical structure can also be used as modifiers of rubber mixtures and vulcanizates. The main aim of the presented work is to study the effect of polyurethane glycerolysate on the performance of natural rubber mixtures and vulcanizates. The influence of the modifier on the vulcanization kinetics and swelling of rubber mixtures, and the thermo-mechanical and mechanical properties of rubber vulcanizates, was studied. The prepared materials were also subjected to accelerated thermal aging in air. It was found that polyurethane glycerolysate affects the vulcanization process of rubber mixtures (for example, promotes the activation of vulcanization) and acts as an antidegradant under thermoxidative conditions (higher stability of mechanical properties was observed in comparison to a reference sample without modifier). The obtained results show that chemical recycling products can be valuable modifiers of natural rubber mixtures and vulcanizates, which extends the possible applications of polyurethane chemical recycling products. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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19 pages, 2026 KiB  
Article
Metal Organic Frameworks: Current State and Analysis of Their Use as Modifiers of the Vulcanization Process and Properties of Rubber
by Katarzyna Klajn, Tomasz Gozdek and Dariusz M. Bieliński
Materials 2023, 16(24), 7631; https://doi.org/10.3390/ma16247631 - 13 Dec 2023
Cited by 3 | Viewed by 1323
Abstract
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also [...] Read more.
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also increasing, focusing mainly on the synthesis of MOF-polymer hybrid compounds. Due to the presence of metal ions in their structure, they can also serve as a component of the crosslinking system used for curing elastomers. This article presents the possibility of using zeolitic imidazolate framework ZIF-8 or MOF-5 as activators for sulfur vulcanization of styrene-butadiene rubber (SBR), replacing zinc oxide in conventional (CV) or effective (EF) curing systems to different extents. Their participation in the curing process and influence on the crosslinking density and structure, as well as the mechanical and thermal properties of the rubber vulcanizates, were examined. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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17 pages, 2465 KiB  
Article
Combined Sulfur and Peroxide Vulcanization of Filled and Unfilled EPDM-Based Rubber Compounds
by Ján Kruželák, Mária Mikolajová, Andrea Kvasničáková, Michaela Džuganová, Ivan Chodák, Ján Hronkovič, Jozef Preťo and Ivan Hudec
Materials 2023, 16(16), 5596; https://doi.org/10.3390/ma16165596 - 12 Aug 2023
Cited by 3 | Viewed by 1481
Abstract
The sulfur curing system, peroxide curing system and their combinations were applied for the cross-linking of unfilled and carbon black-filled rubber formulations based on ethylene-propylenediene-monomer rubber. The results demonstrated that the type of curing system influenced the course and shape of curing isotherms. [...] Read more.
The sulfur curing system, peroxide curing system and their combinations were applied for the cross-linking of unfilled and carbon black-filled rubber formulations based on ethylene-propylenediene-monomer rubber. The results demonstrated that the type of curing system influenced the course and shape of curing isotherms. This resulted in the change of curing kinetics of rubber compounds. The cross-link density of materials cured with combined vulcanization systems was lower than that for vulcanizates cured with the peroxide or sulfur system. Good correlation between the cross-link density as well as the structure of the formed cross-links and physical–mechanical characteristics of the cured materials was established. Both filled and unfilled vulcanizates cured with combined vulcanization systems exhibited a higher tensile strength and elongation at break when compared to their equivalents vulcanized in the presence of the peroxide or sulfur curing system. It can be stated that by proper combination of vulcanization systems, it is possible to modify the tensile behavior of vulcanizates in a targeted manner. On the other side, dynamical–mechanical properties were found not be significantly influenced by the curing system composition. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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28 pages, 15194 KiB  
Article
Potential Utilization of Ground Eggshells as a Biofiller for Natural Rubber Biocomposites
by Anna Sowińska-Baranowska and Magdalena Maciejewska
Materials 2023, 16(8), 2988; https://doi.org/10.3390/ma16082988 - 9 Apr 2023
Cited by 1 | Viewed by 2550
Abstract
The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and [...] Read more.
The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPTS), were used to increase the activity of ground eggshells in the elastomer matrix and to ameliorate the cure characteristics and properties of NR biocomposites. The influence of ground eggshells, CTAB, ILs, and silanes on the crosslink density, mechanical properties, and thermal stability of NR vulcanizates and their resistance to prolonged thermo-oxidation were explored. The amount of eggshells affected the curing characteristics and crosslink density of the rubber composites and therefore their tensile properties. Vulcanizates filled with eggshells demonstrated higher crosslink density than the unfilled sample by approximately 30%, whereas CTAB and ILs increased the crosslink density by 40–60% compared to the benchmark. Owing to the enhanced crosslink density and uniform dispersion of ground eggshells, vulcanizates containing CTAB and ILs exhibited tensile strength improved by approximately 20% compared to those without these additives. Moreover, the hardness of these vulcanizates was increased by 35–42%. Application of both the biofiller and the tested additives did not significantly affect the thermal stability of cured NR compared to the unfilled benchmark. Most importantly, the eggshell-filled vulcanizates showed improved resistance to thermo-oxidative aging compared to the unfilled NR. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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16 pages, 3029 KiB  
Article
Cross-Linking, Morphology, and Physico-Mechanical Properties of GTR/SBS Blends: Dicumyl Peroxide vs. Sulfur System
by Agata Rodak, Agnieszka Susik, Daria Kowalkowska-Zedler, Łukasz Zedler and Krzysztof Formela
Materials 2023, 16(7), 2807; https://doi.org/10.3390/ma16072807 - 31 Mar 2023
Cited by 4 | Viewed by 1742
Abstract
In this work, ground tire rubber and styrene–butadiene block copolymer (GTR/SBS) blends at the ratio of 50/50 wt%, with the application of four different SBS copolymer grades (linear and radial) and two types of cross-linking agent (a sulfur-based system and dicumyl peroxide), were [...] Read more.
In this work, ground tire rubber and styrene–butadiene block copolymer (GTR/SBS) blends at the ratio of 50/50 wt%, with the application of four different SBS copolymer grades (linear and radial) and two types of cross-linking agent (a sulfur-based system and dicumyl peroxide), were prepared by melt compounding. The rheological and cross-linking behavior, physico-mechanical parameters (i.e., tensile properties, abrasion resistance, hardness, swelling degree, and density), thermal stability, and morphology of the prepared materials were characterized. The results showed that the selected SBS copolymers improved the processability of the GTR/SBS blends without any noticeable effects on their cross-linking behavior—which, in turn, was influenced by the type of cross-linking agent used. On the other hand, it was observed that the tensile strength, elongation at break, and abrasion resistance of the GTR/SBS blends cured with the sulfur system (6.1–8.4 MPa, 184–283%, and 235–303 mm3, respectively) were better than those cross-linked by dicumyl peroxide (4.0–7.8 MPa, 80–165%, and 351–414 mm3, respectively). Furthermore, it was found that the SBS copolymers improved the thermal stability of GTR, while the increasing viscosity of the used SBS copolymer also enhanced the interfacial adhesion between the GTR and SBS copolymers, as confirmed by microstructure evaluation. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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21 pages, 5198 KiB  
Article
Degradation by Electron Beam Irradiation of Some Elastomeric Composites Sulphur Vulcanized
by Elena Manaila, Gabriela Craciun, Ion Bogdan Lungu, Marius Daniel Dumitru Grivei and Maria Daniela Stelescu
Materials 2023, 16(6), 2152; https://doi.org/10.3390/ma16062152 - 7 Mar 2023
Cited by 1 | Viewed by 1470
Abstract
Composites based on natural rubber and plasticized starch obtained by the conventional method of sulfur cross-linking using four types of vulcanization accelerators (Diphenyl guanidine, 2-Mercaptobenzothiazole, N-Cyclohexyl-2-benzothiazole sulfenamide, and Tetramethylthiuram disulfide) were irradiated with an electron beam in the dose range of 150 and [...] Read more.
Composites based on natural rubber and plasticized starch obtained by the conventional method of sulfur cross-linking using four types of vulcanization accelerators (Diphenyl guanidine, 2-Mercaptobenzothiazole, N-Cyclohexyl-2-benzothiazole sulfenamide, and Tetramethylthiuram disulfide) were irradiated with an electron beam in the dose range of 150 and 450 kGy for the purpose of degradation. The vulcanization accelerators were used in different percentages and combinations, resulting in four mixtures with different potential during the cross-linking process (synergistic, activator, or additive). The resulting composites were investigated before and after irradiation in order to establish a connection between the type of accelerator mixture, irradiation dose, and composite properties (gel fraction, cross-linking degree, water absorption, mass loss in water and toluene, mechanical properties, and structural and morphological properties). The results showed that the mixtures became sensitive at the irradiation dose of 300 kGy and at the irradiation dose of 450 kGy, and the consequences of the degradation processes were discussed. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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21 pages, 4153 KiB  
Article
Application of Plasticizer Glycerol in Lignosulfonate-Filled Rubber Compounds Based on SBR and NBR
by Ján Kruželák, Klaudia Hložeková, Andrea Kvasničáková, Michaela Džuganová, Ivan Chodák and Ivan Hudec
Materials 2023, 16(2), 635; https://doi.org/10.3390/ma16020635 - 9 Jan 2023
Cited by 1 | Viewed by 1480
Abstract
The work deals with the application of biopolymer fillers in rubber formulations. Calcium lignosulfonate was incorporated into styrene–butadiene rubber and acrylonitrile–butadiene rubber in a constant amount of 30 phr. Glycerol in a concentration scale ranging from 5 to 20 phr was used as [...] Read more.
The work deals with the application of biopolymer fillers in rubber formulations. Calcium lignosulfonate was incorporated into styrene–butadiene rubber and acrylonitrile–butadiene rubber in a constant amount of 30 phr. Glycerol in a concentration scale ranging from 5 to 20 phr was used as a plasticizer for rubber formulations. For the cross-linking of the compounds, a sulfur-based curing system was used. The study was focused on the investigation of glycerol in the curing process; the viscosity of rubber compounds; and the cross-link density, morphology, physical–mechanical, and dynamic mechanical properties of vulcanizates. The study revealed that the application of glycerol as a plasticizer resulted in a reduction in the rubber compounds’ viscosity and contributed to the better dispersion and distribution of the filler within the rubber matrices. The mutual adhesion and compatibility between the filler and the rubber matrices were improved, which resulted in the significant enhancement of tensile characteristics. The main output of the work is the knowledge that the improvement of the physical–mechanical properties of biopolymer-filled vulcanizates can be easily obtained via the simple addition of a very cheap and environmentally friendly plasticizer into rubber compounds during their processing without additional treatments or procedures. The enhancement of the physical–mechanical properties of rubber compounds filled with biopolymers might contribute to the broadening of their potential applications. Moreover, the price of the final rubber articles could be reduced, and more pronounced ecological aspects could also be emphasized. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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11 pages, 1706 KiB  
Article
Tuning the Curing Efficiency of Conventional Accelerated Sulfur System for Tailoring the Properties of Natural Rubber/Bromobutyl Rubber Blends
by Marek Pöschl, Shibulal Gopi Sathi and Radek Stoček
Materials 2022, 15(23), 8466; https://doi.org/10.3390/ma15238466 - 28 Nov 2022
Cited by 1 | Viewed by 1906
Abstract
The state of cure and the vulcanizate properties of a conventional accelerated sulfur (CV) cured 50/50 blend of natural rubber (NR) and bromobutyl rubber (BIIR) were inferior. However, this blend exhibits a higher extent of cure with remarkable improvements in its mechanical properties, [...] Read more.
The state of cure and the vulcanizate properties of a conventional accelerated sulfur (CV) cured 50/50 blend of natural rubber (NR) and bromobutyl rubber (BIIR) were inferior. However, this blend exhibits a higher extent of cure with remarkable improvements in its mechanical properties, particularly the tensile strength, modulus and hardness after curing with a combination of accelerated sulfur and three parts per hundred rubber (phr) of a bismaleimide (MF3). Moreover, with the use of 0.25 phr of dicumyl peroxide (DCP) along with the CV/MF3 system, the compression set property of the CV-only cured blend could be reduced from 68% to 15%. The enhanced compatibility between NR and BIIR with the aid of bismaleimide via the Diels–Alder reaction was identified as the primary reason for the improved cure state and the mechanical properties. However, the incorporation of a certain amount of bismaleimide as a crosslink in the NR phase of the blend, via a radical initiated crosslinking process by the action of DCP, is responsible for the improved compression set properties Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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16 pages, 6729 KiB  
Article
Physical Properties and Biodegradability Evaluation of Vulcanized Epoxidized Natural Rubber/Thermoplastic Potato Starch Blends
by Zhejing Cai, Drahomír Čadek, Michaela Jindrová, Alena Kadeřábková and Antonín Kuta
Materials 2022, 15(21), 7478; https://doi.org/10.3390/ma15217478 - 25 Oct 2022
Cited by 5 | Viewed by 2722
Abstract
The sustainable material—thermoplastic potato starch (TPS)—was blended with modified natural rubber–epoxidized natural rubber (ENR). The poor mechanical properties of the ENR/TPS blends limited the application. Sulfur vulcanization is a common and economical method to improve the mechanical properties in the rubber industry. To [...] Read more.
The sustainable material—thermoplastic potato starch (TPS)—was blended with modified natural rubber–epoxidized natural rubber (ENR). The poor mechanical properties of the ENR/TPS blends limited the application. Sulfur vulcanization is a common and economical method to improve the mechanical properties in the rubber industry. To fully understand the relationship between vulcanization systems and ENR/TPS blends and the sustainability of the developed material, the effects of a vulcanization accelerator (N-cyclohexylbenzothiazole-2-sulphenamide (CBS), 2-mercaptobenzothiazole (MBT), N-tert-butylbenzothiazole-2-sulphenamide (TBBS)) and a system type (conventional vulcanization (CV), semi-efficient vulcanization (SEV) and efficient vulcanization (EV)) on curing characteristics, mechanical and thermal properties, water absorption and biodegradability were systematically evaluated. The results indicate that vulcanization significantly improves the mechanical properties of ENR/TPS blends. The performance optimization of the CBS-CV vulcanization system is the best for improving the mechanical properties and reducing the water absorption. The CBS-CV curing system makes ENR/TPS less biodegradable (12–56% of mass loss) than other accelerators and systems. TBBS-CV makes the material more biodegradable (18–66% of mass loss). The low rubber content enables the rapid biodegradation of the vulcanized blend. This has implications for research on sustainable materials. The material can be applied for eco-friendly packaging and agricultural films, etc. The investigation on performance by using common accelerators and systems provides ideas for industries and research. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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24 pages, 13938 KiB  
Article
Fly Ash from Lignite Combustion as a Filler for Rubber Mixes—Part II: Chemical Valorisation of Fly Ash
by Wojciech Orczykowski, Dariusz M. Bieliński, Rafał Anyszka, Tomasz Gozdek, Katarzyna Klajn, Grzegorz Celichowski, Zbigniew Pędzich and Agnieszka Wojteczko
Materials 2022, 15(17), 5979; https://doi.org/10.3390/ma15175979 - 29 Aug 2022
Cited by 4 | Viewed by 1631
Abstract
Fly ash (FA) fractions with a particle size of 63 µm < FA < 250 µm obtained by sieve fractionation were used as a partial carbon black (CB) replacement in a rubber mixture based on styrene-butadiene rubber (SBR). In order to improve the [...] Read more.
Fly ash (FA) fractions with a particle size of 63 µm < FA < 250 µm obtained by sieve fractionation were used as a partial carbon black (CB) replacement in a rubber mixture based on styrene-butadiene rubber (SBR). In order to improve the interactions at the interface between rubber and fractionated ash, at the stage of preparing the rubber mixtures, two different vinyl silanes were added to the system: Vinyltrimethoxysilane (U-611) or Vinyl-tris (2-methoxy-ethoxy) silane (LUVOMAXX VTMOEO DL50), silane with epoxy groups: 3-(glycidoxypropyl)trimethoxysilane (U-50) or sulfur functionalized silanes: containing sulfide bridges: Bis(triethoxysilylpropyl)polysulfide silane (Si-266) or mercapto groups: Mercaptopropyltrimethoxysilane (Dynaslan MTMO). The conducted research confirmed the effectiveness of silanization with selected functional silanes, from the point of view of improving the processing and operational properties of vulcanizates, in which CB is partially replaced with the finest fractions of fly ash. The silanization generally increased the interaction at the rubber–ash interface, while improving the degree of filler dispersion in the rubber mixture. The results of TGA and FTIR analyses confirmed the presence of silanes chemically bonded to the surface of fly ash particles. SEM tests and determination of the bound rubber (BdR) content show that the introduction of the silanes to the mixture increases the degree of ash dispersion (DI) and the Payne effect, which is the greatest when mercaptosilane was used for modification. The highest increase in torque, which was recorded in the case of rubber mixtures containing sulfur silanes and silane with epoxy groups, may be due to their participation in the vulcanization process, which is confirmed by the results of vulcametric studies. The lowest values of mechanical strength, elongation at break, and the highest hardness of vulcanizates obtained in this case may be the result of the over-crosslinking of the rubber. The addition of sulfur-containing silanes significantly slowed down the vulcanization process, which is particularly visible (up to three times extension of the t90 parameter, compared to mixtures without silane) in the case of Si-266. The addition of silanes, except for Si-266 (with a polysulfide fragment), generally improved the abrasion resistance of vulcanizates. The Dynaslan MTMO silane (with mercapto groups) performs best in this respect. Proper selection of silane for the finest fraction of fly ash in the rubber mixtures tested allows for an increase in the mechanical strength of their vulcanizates from 9.1 to 17 MPa, elongation at break from 290 to 500%, hardness from 68 to 74 °ShA, and reduction in abrasion from 171 to 147 mm3. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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24 pages, 7560 KiB  
Article
Fly Ash from Lignite Combustion as a Filler for Rubber Mixes. Part I: Physical Valorization of Fly Ash
by Wojciech Orczykowski, Dariusz M. Bieliński, Rafał Anyszka and Zbigniew Pędzich
Materials 2022, 15(14), 4869; https://doi.org/10.3390/ma15144869 - 13 Jul 2022
Cited by 6 | Viewed by 2285
Abstract
The potential use of fly ash (FA) originating from lignite combustion at the Belchatow Power Plant (Poland) as filler for rubber mixes was evaluated. Samples of fly ash collected from heaps created in different years were compared according to their chemical and phase [...] Read more.
The potential use of fly ash (FA) originating from lignite combustion at the Belchatow Power Plant (Poland) as filler for rubber mixes was evaluated. Samples of fly ash collected from heaps created in different years were compared according to their chemical and phase composition, particle size distribution, and morphology. The sieve fractionation of fly ash results in size fractions of different chemical structures, phase compositions, and morphologies, reflected in changes to their specific surface area, surface energy, and activity in rubber mixes. Fractionation turned out to be more effective than grinding from the point of view of using ash as a filler for rubber mixes, because it results in higher specific surface area (SSA) and chemical composition differentiation. Carbon black can be replaced by up to 40% by weight with the fly ash fraction (FFA) of dimensions below 125 µm, without any significant deterioration in the mechanical properties of styrene butadiene rubber (SBR) vulcanizates filled with 50 phr of active carbon black (N 220). Despite the larger fly ash fraction of grain dimensions in the range between 125 and 250 µm presenting the highest specific surface area, the particle size adversely affects its strengthening effect in rubber. Taking into account all the tests performed, ranging from morphology, Payne effect and bound rubber, to mechanical and abrasion tests, the highest potential effectivity is presented by a sample containing 30 phr of N 220 and 20 phr of FFA of grain sizes from 63 to 125 µm. The obtained results indicate that fractionation seems to be an effective physical method of fly ash valorization. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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