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Polymers
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Rubber Materials: Processes, Structures and Applications
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Rubber Materials: Processes, Structures and Applications

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Networks".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 59162

Special Issue Editors

Dr. Juan Lopez Valentin

E-Mail Website
Guest Editor
CSIC, Inst Ciencia & Tecnol Polimeros, E-28006 Madrid, Spain
Interests: rubber materials; vulcanization; rubber elasticity; network structure and chain dynamics; rubber reinforcement; rubber nano-compounds; filler/rubber interactions; development of smart and functional rubber materials; rubber recycling; low field solid-state NMR applied to rubber science and technology
Dr. Rodrigo Navarro Crespo

E-Mail Website
Guest Editor
CSIC, Instituto de Ciencia y Tecnología de Polímeros, E-28006 Madrid, Spain
Interests: polyurethane materials; polymer synthesis and advanced characterization; rubber reinforcement; rubber nano-compounds; filler/rubber interactions; surface modifications; chemical recycling; self-healing materials; shape memory polymers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Rubbers are versatile, valuable and irreplaceable technological materials for multiple applications (from tire technology, automotive or aerospace industry to general rubber goods) because their unique elasticity, viscoelastic, mechanical and chemical properties. These properties are highly dependent on the used raw materials, applied processing and obtained structures which should be tailored in multiple time- and length-scales for developing high performance and more sustainable rubber materials for advanced applications. For these reasons, this special issue is focused on in the current state-of-the-art and future perspectives of the following aspects of rubber science and technology:

1.) Development of elastomeric materials with improved or new properties. This issue includes synthesis, modification and preparation of rubber and thermoplastic elastomer (block copolymers, polyurethanes, TPV and ionic elastomers) compounds, alternative suitable additives (e.g., use of raw materials from recycled waste or renewables resources) as well as novel and disruptive vulcanization and reinforcing systems that will improve the performance and sustainability of rubber materials.

2.) Rubber compounding and processing. Novel nano-fabrication, nano-processing and additive manufacturing approaches (e.g., 3-D printing) for rubber and thermoplastic elastomers are of special interest.

3.) Structure-property relationships in rubber materials. Better understanding of basic aspects of rubber science and technology such as vulcanization, reinforcement, wear resistance, fatigue, ageing, etc. should be addressed by obtaining new insights into structure and dynamics of rubber materials (e.g., using cutting-edge characterization approaches or novel analysis procedures).

4.) Smart and functional elastomers. Smart rubber materials with shape memory or self-healing properties, dielectric elastomers, rubber compounds with optical or magnetic properties are examples of functional soft materials that could open novel advanced applications for rubber compounds: sensors, actuators, microfluidic valves, artificial muscles, energy harvesting…

5.) Rubber recycling. Strategies of rubber recycling (reclaiming, devulcanization, pyrolysis, etc), especially for end-of-life tyres, should be evaluated in terms of selectivity and efficiency for expanding the use of these recycled materials as feedstock for high technology products in different industries.

Dr. Juan Lopez Valentin
Dr. Rodrigo Navarro
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Rubbers
  • Bio-elastomers
  • Polyurethanes
  • Vulcanization
  • Reinforcement
  • Nano-compounds
  • 3-D printing
  • Cutting-edge experiments
  • Functional elastomers
  • Recycling

Published Papers (16 papers)

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13 pages, 3008 KiB  
Article
A Practical Approach for Uncertainty Management in Rubber Manufacturing Processes Using Physics-Informed Real-Time Models
by Ismael Viejo, Salvador Izquierdo, Ignacio Conde, Valentina Zambrano, Noelia Alcalá and Leticia A. Gracia
Polymers 2022, 14(10), 2049; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14102049 - 17 May 2022
Cited by 1 | Viewed by 1530
Abstract
Industrial manufacturing management can benefit from the use of modeling. For a correct representation of the manufacturing process and the subsequent management, the models must incorporate the effect of the uncertainty propagation throughout the stages considered. In this paper, the proposed methodology for [...] Read more.
Industrial manufacturing management can benefit from the use of modeling. For a correct representation of the manufacturing process and the subsequent management, the models must incorporate the effect of the uncertainty propagation throughout the stages considered. In this paper, the proposed methodology for uncertainty management uses a nonintrusive method that is based on building a deterministic physics-informed real-time model for the a posteriori computation of output uncertainties. This model is built using tensor factorization as the Model Order Reduction technique. It includes as model parameters: material properties, process operations, and those random and epistemic uncertainties of known variables. The resulting model is used off-line to identify sensitivities and therefore to unify uncertainty management across the material transformation process. This method is presented by its direct application to an automotive door seal manufactured by continuous co-extrusion of several rubbers and reinforcement (metal strip and glass fiber thread). Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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20 pages, 2932 KiB  
Article
Application of Sulfur and Peroxide Curing Systems for Cross-Linking of Rubber Composites Filled with Calcium Lignosulfonate
by Ján Kruželák, Klaudia Hložeková, Andrea Kvasničáková, Katarína Tomanová and Ivan Hudec
Polymers 2022, 14(9), 1921; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14091921 - 09 May 2022
Cited by 13 | Viewed by 2527
Abstract
Calcium lignosulfonate in different loadings was applied to the rubber matrix based on EPDM. A sulfur curing system, organic peroxide, and a combination of organic peroxide with two coagent types were used for cross-linking of rubber compounds. The work was focused on the [...] Read more.
Calcium lignosulfonate in different loadings was applied to the rubber matrix based on EPDM. A sulfur curing system, organic peroxide, and a combination of organic peroxide with two coagent types were used for cross-linking of rubber compounds. The work was focused on the investigation of filler content and curing system composition in the curing process, cross-link density, morphology, and physical–mechanical properties of composites. The achieved results demonstrated that the curing parameters of rubber compounds cured with the sulfur system were significantly different from those cured with peroxide systems. There was also an observed different influence of curing systems composition on cross link density, though in all cases, the degree of cross-linking showed a decreasing trend with increasing content of lignosulfonate. The tensile strength of the composites cured with sulfur system and organic peroxide was comparable, regardless of lignosulfonate loading. This points to the application of both curing systems in cross-linking of rubber compounds with biopolymer filler. However, the introduction of coagents in peroxide vulcanization led to the improvement of adhesion and compatibility between the rubber and the filler on the filler–rubber interface. This subsequently resulted in the improvement of the tensile characteristics of composites. The introduction of organic peroxide in combination with coagent seems to be a very simple and efficient way for the preparation of biopolymer-filled composites with applicable physical–mechanical properties. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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13 pages, 12457 KiB  
Article
High-Strength Heat-Elongated Thermoplastic Polyurethane Elastomer Consisting of a Stacked Domain Structure
by Mutsumi Takano, Koudai Takamatsu and Hiromu Saito
Polymers 2022, 14(7), 1470; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14071470 - 04 Apr 2022
Cited by 7 | Viewed by 1945
Abstract
We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain [...] Read more.
We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain recovery by heat elongation, i.e., the stress at break of a quenched TPU film was increased from 55 to 136 MPa by heat elongation at an elongation ratio of 300%. The results of small-angle X-ray scattering, DSC, and AFM observations revealed that: (1) anisotropically shaped HS domains were stacked at a nanometer scale and the longer direction of the HS domains was arranged perpendicular to the elongated direction due to the heat elongation, (2) the densification of the HS domains increased with increases in the elongation ratio without a significant increase in the crystallinity, and (3) the stacked domain structure remained during the stretching at 23 °C. Thus, the strengthening of the elongated TPU might be attributed to the densification of the HS domains in the stacked structure, which prevents the fracture of the HS domains during the stretching. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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18 pages, 3146 KiB  
Article
Shape-Memory Composites Based on Ionic Elastomers
by Antonio González-Jiménez, Pilar Bernal-Ortega, Fernando M. Salamanca and Juan L. Valentin
Polymers 2022, 14(6), 1230; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14061230 - 18 Mar 2022
Cited by 5 | Viewed by 2259
Abstract
Shape-memory polymers tend to present rigid behavior at ambient temperature, being unable to deform in this state. To obtain soft shape-memory elastomers, composites based on a commercial rubber crosslinked by both ionic and covalent bonds were developed, as these materials do not lose [...] Read more.
Shape-memory polymers tend to present rigid behavior at ambient temperature, being unable to deform in this state. To obtain soft shape-memory elastomers, composites based on a commercial rubber crosslinked by both ionic and covalent bonds were developed, as these materials do not lose their elastomeric behavior below their transition (or activation) temperature (using ionic transition for such a purpose). The introduction of fillers, such as carbon black and multiwalled carbon nanotubes (MWCNTs), was studied and compared with the unfilled matrix. By adding contents above 10 phr of MWCNT, shape-memory properties were enhanced by 10%, achieving fixing and recovery ratios above 90% and a faster response. Moreover, by adding these fillers, the conductivity of the materials increased from ~10−11 to ~10−4 S·cm−1, allowing the possibility to activate the shape-memory effect with an electric current, based on the heating of the material by the Joule effect, achieving a fast and clean stimulus requiring only a current source of 50 V. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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24 pages, 1953 KiB  
Article
Rubber Material-Model Characterization for Coupled Thermo-Mechanical Vulcanization Foaming Processes
by Noelia Alcalá, Mariana Castrillón, Ismael Viejo, Salvador Izquierdo and Leticia A. Gracia
Polymers 2022, 14(6), 1101; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14061101 - 09 Mar 2022
Cited by 3 | Viewed by 2383
Abstract
A novel experimental methodology is developed for the characterization of the vulcanization and foaming processes of an ethylene propylene diene (EPDM) cellular rubber and for establishing the relationship of its physical and mechanical property evolution with vulcanization and foaming process temperature. To establish [...] Read more.
A novel experimental methodology is developed for the characterization of the vulcanization and foaming processes of an ethylene propylene diene (EPDM) cellular rubber and for establishing the relationship of its physical and mechanical property evolution with vulcanization and foaming process temperature. To establish this relationship, the vulcanization and foaming reaction kinetics and their coupling have been determined, as well as important parameters in the behaviour of the material, such as conductivity, specific heat capacity and coefficients of expansion and foaming. This aforementioned strategy allows the setting of a material model that can be implemented into finite-element (FE) codes to reproduce the material changes during the vulcanization and foaming processes. The material model developed reproduces with enough accuracy the coupling of chemical kinetics of vulcanization and foaming reactions. The results provided by the numerical material model fit a similar trend, and values with an accuracy of 90–99% to those observed in the experiments conducted for the determination of the cellular rubber expansion in function of the temperature. Moreover, the cellular rubber expansion values agree with the structural analysis of vulcanized and foamed samples at different isothermal temperatures and with the proportional loss of mechanical properties in the function of the vulcanization and foaming degree. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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26 pages, 1103 KiB  
Article
Crosslinked Elastomers: Structure–Property Relationships and Stress-Optical Law
by Paul Sotta, Pierre-Antoine Albouy, Mohammad Abou Taha, Benoit Moreaux and Caroline Fayolle
Polymers 2022, 14(1), 9; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14010009 - 21 Dec 2021
Cited by 5 | Viewed by 4297
Abstract
We present a combination of independent techniques in order to characterize crosslinked elastomers. We combine well-established macroscopic methods, such as rheological and mechanical experiments and equilibrium swelling measurements, a more advanced technique such as proton multiple-quantum NMR, and a new method to measure [...] Read more.
We present a combination of independent techniques in order to characterize crosslinked elastomers. We combine well-established macroscopic methods, such as rheological and mechanical experiments and equilibrium swelling measurements, a more advanced technique such as proton multiple-quantum NMR, and a new method to measure stress-induced segmental orientation by in situ tensile X-ray scattering. All of these techniques give access to the response of the elastomer network in relation to the crosslinking of the systems. Based on entropic elasticity theory, all these quantities are related to segmental orientation effects through the so-called stress-optical law. By means of the combination of these techniques, we investigate a set of unfilled sulfur-vulcanized styrene butadiene rubber elastomers with different levels of crosslinking. We validate that the results of all methods correlate very well. The relevance of this approach is that it can be applied in any elastomer materials, including materials representative of various industrial application, without prerequisite as regards, e.g., optical transparency or simplified formulation. Moreover, the approach may be used to study reinforcement effects in filled elastomers with nanoparticles. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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10 pages, 5788 KiB  
Article
Reinforcement Mechanism of Carbon Black-Filled Rubber Nanocomposite as Revealed by Atomic Force Microscopy Nanomechanics
by Xiaobin Liang, Makiko Ito and Ken Nakajima
Polymers 2021, 13(22), 3922; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13223922 - 12 Nov 2021
Cited by 11 | Viewed by 2873
Abstract
In this study, atomic force microscopy (AFM) nanomechanics were used to visualize the nanoscale stress distribution in carbon black (CB)-reinforced isoprene rubber (IR) vulcanizates at different elongations and quantitatively evaluate their volume fractions for the first time. The stress concentrations in the protofibrous [...] Read more.
In this study, atomic force microscopy (AFM) nanomechanics were used to visualize the nanoscale stress distribution in carbon black (CB)-reinforced isoprene rubber (IR) vulcanizates at different elongations and quantitatively evaluate their volume fractions for the first time. The stress concentrations in the protofibrous structure (stress chains) that formed around the CB filler in CB-reinforced IR vulcanizates were directly observed at the nanoscale. The relationship between the local nanoscale stress distribution and macroscopic tensile properties was revealed based on the microscopic stress distribution and microscopic spatial structure. This study can help us gain insight into the microscopic reinforcement mechanism of carbon black-containing rubber composites. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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19 pages, 9924 KiB  
Article
Radiation Graft-Copolymerization of Ultrafine Fully Vulcanized Powdered Natural Rubber: Effects of Styrene and Acrylonitrile Contents on Thermal Stability
by Niratchaporn Rimdusit, Chanchira Jubsilp, Phattarin Mora, Kasinee Hemvichian, Tran Thi Thuy, Panagiotis Karagiannidis and Sarawut Rimdusit
Polymers 2021, 13(19), 3447; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13193447 - 08 Oct 2021
Cited by 12 | Viewed by 2861
Abstract
Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation [...] Read more.
Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation of the graft copolymers in the presence of di-trimethylolpropane tetra-acrylate (DTMPTA) as a crosslinking agent and, subsequently, a fast spray drying process. The effects of St or AN monomer contents and the radiation doses on the chemical structure, thermal stability, and physical properties of the graft copolymers and UFPNRs were investigated. The results showed that solvent resistance and grafting efficiency of DPNR-g-PS and DPNR-g-PAN were enhanced with increasing monomer content. SEM morphology of the UFPNRs showed separated and much less agglomerated particles with an average size about 6 μm. Therefore, it is possible that the developed UFPNRs grafted copolymers with good solvent resistance and rather high thermal stability can be used easily as toughening modifiers for polymers and their composites. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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18 pages, 7254 KiB  
Article
Novel Crosslinking System for Poly-Chloroprene Rubber to Enable Recyclability and Introduce Self-Healing
by Anureet Kaur, Julien E. Gautrot, Gabriel Cavalli, Douglas Watson, Alan Bickley, Keizo Akutagawa and James J. C. Busfield
Polymers 2021, 13(19), 3347; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13193347 - 29 Sep 2021
Cited by 2 | Viewed by 3699
Abstract
The introduction of dynamic bonds capable of mediating self-healing in a fully cross-linked polychloroprene network can only occur if the reversible moieties are carried by the cross-linker itself or within the main polymer backbone. Conventional cross-linking is not suitable for such a purpose. [...] Read more.
The introduction of dynamic bonds capable of mediating self-healing in a fully cross-linked polychloroprene network can only occur if the reversible moieties are carried by the cross-linker itself or within the main polymer backbone. Conventional cross-linking is not suitable for such a purpose. In the present work, a method to develop a self-healable and recyclable polychloroprene rubber is presented. Dynamic disulfide bonds are introduced as part of the structure of a crosslinker (liquid polysulfide polymer, Thiokol LP3) coupled to the polymer backbone via thermally initiated thiol-ene reaction. The curing and kinetic parameters were determined by isothermal differential scanning calorimetry and by moving die rheometer analysis; tensile testing was carried to compare the tensile strength of cured compound, healed compounds and recycled compounds, while chemical analysis was conducted by surface X-ray Photoelectron Spectroscopy. Three formulations with increasing concentrations of Thiokol LP-3 were studied (2, 4, 6 phr), reaching a maximum ultimate tensile strength of 22.4 MPa and ultimate tensile strain of 16.2 with 2 phr of Thiokol LP-3, 11.7 MPa and 10.7 strain with 4 phr and 5.6 MPa and 7.3 strain with 6 phr. The best healing efficiencies were obtained after 24 h of healing at 80 °C, increasing with the concentration of Thiokol LP-3, reaching maximum values of 4.5% 4.4% 13.4% with 2 phr, 4 phr and 6 phr, respectively, while the highest recycling efficiency was obtained with 4 phr of Thiokol LP-3, reaching 11.2%. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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17 pages, 2554 KiB  
Article
Enhancement of EPDM Crosslinked Elastic Properties by Association of Both Covalent and Ionic Networks
by Chloé Larrue, Véronique Bounor-Legaré and Philippe Cassagnau
Polymers 2021, 13(18), 3161; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13183161 - 18 Sep 2021
Cited by 1 | Viewed by 1952
Abstract
The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak [...] Read more.
The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak elasticity recovery of such a physical network after a long period of compression, the combination of both physical and chemical networks was studied. In that frame, an ethylene-propylene-diene terpolymer grafted with maleic anhydride (EPDM-g-MA) was crosslinked with metal salts and/or dicumyl peroxide (DCP). Thus, the influence of these two types of crosslinking networks and their combination were studied in detail in terms of compression set. The second part of this work was focused on the influence of different metallic salts (KOH, ZnAc2) and the sensitivity to the water of the physical crosslinking network. Finally, the combination of ionic and covalent network allowed combining the processability and better mechanical properties in terms of recovery elasticity. KAc proved to be the best ionic candidate to avoid water degradation of the ionic network and then to preserve the elasticity recovery properties under aging. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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21 pages, 6913 KiB  
Article
Mechanical, Thermal, Electrical Characteristics and EMI Absorption Shielding Effectiveness of Rubber Composites Based on Ferrite and Carbon Fillers
by Ján Kruželák, Andrea Kvasničáková, Klaudia Hložeková, Roderik Plavec, Rastislav Dosoudil, Marek Gořalík, Jarmila Vilčáková and Ivan Hudec
Polymers 2021, 13(17), 2937; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13172937 - 31 Aug 2021
Cited by 8 | Viewed by 2254
Abstract
In this work, rubber composites were fabricated by incorporation of manganese-zinc ferrite alone and in combination with carbon-based fillers into acrylonitrile-butadiene rubber. Electromagnetic parameters and electromagnetic interference (EMI) absorption shielding effectiveness of composite materials were examined in the frequency range 1 MHz–3 GHz. [...] Read more.
In this work, rubber composites were fabricated by incorporation of manganese-zinc ferrite alone and in combination with carbon-based fillers into acrylonitrile-butadiene rubber. Electromagnetic parameters and electromagnetic interference (EMI) absorption shielding effectiveness of composite materials were examined in the frequency range 1 MHz–3 GHz. The influence of ferrite and fillers combination on thermal characteristics and mechanical properties of composites was investigated as well. The results revealed that ferrite imparts absorption shielding efficiency to the composites in tested frequency range. The absorption shielding effectiveness and absorption maxima of ferrite filled composites shifted to lower frequencies with increasing content of magnetic filler. The combination of carbon black and ferrite also resulted in the fabrication of efficient EMI shields. However, the EMI absorption shielding effectiveness was lower, which can be ascribed to higher electrical conductivity and higher permittivity of those materials. The highest conductivity and permittivity of composites filled with combination of carbon nanotubes and ferrite was responsible for the lowest absorption shielding effectiveness within the examined frequency range. The results also demonstrated that combination of ferrite with carbon-based fillers resulted in the enhancement of thermal conductivity and improvement of mechanical properties. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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25 pages, 5669 KiB  
Article
Analysis on Microstructure–Property Linkages of Filled Rubber Using Machine Learning and Molecular Dynamics Simulations
by Takashi Kojima, Takashi Washio, Satoshi Hara, Masataka Koishi and Naoya Amino
Polymers 2021, 13(16), 2683; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13162683 - 11 Aug 2021
Cited by 3 | Viewed by 2479
Abstract
A better understanding of the microstructure–property relationship can be achieved by sampling and analyzing a microstructure leading to a desired material property. During the simulation of filled rubber, this approach includes extracting common aggregates from a complex filler morphology consisting of hundreds of [...] Read more.
A better understanding of the microstructure–property relationship can be achieved by sampling and analyzing a microstructure leading to a desired material property. During the simulation of filled rubber, this approach includes extracting common aggregates from a complex filler morphology consisting of hundreds of filler particles. However, a method for extracting a core structure that determines the rubber mechanical properties has not been established yet. In this study, we analyzed complex filler morphologies that generated extremely high stress using two machine learning techniques. First, filler morphology was quantified by persistent homology and then vectorized using persistence image as the input data. After that, a binary classification model involving logistic regression analysis was developed by training a dataset consisting of the vectorized morphology and stress-based class. The filler aggregates contributing to the desired mechanical properties were extracted based on the trained regression coefficients. Second, a convolutional neural network was employed to establish a classification model by training a dataset containing the imaged filler morphology and class. The aggregates strongly contributing to stress generation were extracted by a kernel. The aggregates extracted by both models were compared, and their shapes and distributions producing high stress levels were discussed. Finally, we confirmed the effects of the extracted aggregates on the mechanical property, namely the validity of the proposed method for extracting stress-contributing fillers, by performing coarse-grained molecular dynamics simulations. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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16 pages, 2972 KiB  
Article
Common Origin of Filler Network Related Contributions to Reinforcement and Dissipation in Rubber Composites
by Sriharish Malebennur Nagaraja, Sven Henning, Sybill Ilisch and Mario Beiner
Polymers 2021, 13(15), 2534; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13152534 - 31 Jul 2021
Cited by 3 | Viewed by 1976
Abstract
A comparative study focusing on the visco–elastic properties of two series of carbon black filled composites with natural rubber (NR) and its blends with butadiene rubber (NR-BR) as matrices is reported. Strain sweeps at different temperatures are performed. Filler network-related contributions to reinforcement [...] Read more.
A comparative study focusing on the visco–elastic properties of two series of carbon black filled composites with natural rubber (NR) and its blends with butadiene rubber (NR-BR) as matrices is reported. Strain sweeps at different temperatures are performed. Filler network-related contributions to reinforcement (ΔG′) are quantified by the classical Kraus equation while a modified Kraus equation is used to quantify different contributions to dissipation (ΔGD″, ΔGF″). Results indicate that the filler network is visco-elastic in nature and that it is causing a major part of the composite dissipation at small and intermediate strain amplitudes. The temperature dependence of filler network-related reinforcement and dissipation contributions is found to depend significantly on the rubber matrix composition. We propose that this is due to differences in the chemical composition of the glassy rubber bridges connecting filler particles since the filler network topology is seemingly not significantly influenced by the rubber matrix for a given filler content. The underlying physical picture explains effects in both dissipation and reinforcement. It predicts that these glassy rubber bridges will soften sequentially at temperatures much higher than the bulk Tg of the corresponding rubber. This is hypothetically due to rubber–filler interactions at interfaces resulting in an increased packing density in the glassy rubber related to the reduction of free volume. From a general perspective, this study provides deeper insights towards the molecular origin of reinforcement and dissipation in rubber composites. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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20 pages, 1354 KiB  
Article
Numerical Approach for the Assessment of Micro-Textured Walls Effects on Rubber Injection Moulding
by María García-Camprubí, Carmen Alfaro-Isac, Belén Hernández-Gascón, José Ramón Valdés and Salvador Izquierdo
Polymers 2021, 13(11), 1739; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13111739 - 26 May 2021
Cited by 6 | Viewed by 2087
Abstract
Micro-surface texturing of elastomeric seals is a validated method to improve the friction and wear characteristics of the seals. In this study, the injection process of high-viscosity elastomeric materials in moulds with wall microprotusions is evaluated. To this end, a novel CFD methodology [...] Read more.
Micro-surface texturing of elastomeric seals is a validated method to improve the friction and wear characteristics of the seals. In this study, the injection process of high-viscosity elastomeric materials in moulds with wall microprotusions is evaluated. To this end, a novel CFD methodology is developed and implemented in OpenFOAM to address rubber flow behaviour at both microscale and macroscale. The first approach allows analyzing the flow perturbation induced by a particular surface texture and generate results to calculate an equivalent wall shear stress that is introduced into the macroscale case through reduced order modelling. The methodology is applied to simulate rubber injection in textured moulds in an academic case (straight pipe) and a real case (D-ring seal mould). In both cases, it is shown that textured walls do not increase the injection pressure and therefore the manufacturing process is not adversely affected. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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12 pages, 9880 KiB  
Article
New Vegetable Oils with Different Fatty Acids on Natural Rubber Composite Properties
by Siwarote Boonrasri, Pongdhorn Sae-Oui, Alissara Reungsang and Pornchai Rachtanapun
Polymers 2021, 13(7), 1108; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13071108 - 31 Mar 2021
Cited by 13 | Viewed by 2880
Abstract
Owing to the toxicity of polycyclic aromatic (PCA) oils, much attention has been paid to the replacement of PCA oils by other nontoxic oils. This paper reports comparative study of the effects of new vegetable oils, i.e., Moringa oil (MO) and Niger oil [...] Read more.
Owing to the toxicity of polycyclic aromatic (PCA) oils, much attention has been paid to the replacement of PCA oils by other nontoxic oils. This paper reports comparative study of the effects of new vegetable oils, i.e., Moringa oil (MO) and Niger oil (NO), on rheological, physical and dynamic properties of silica–filled natural rubber composite (NRC), in comparison with petroleum–based naphthenic oil (NTO). The results reveal that MO and NO exhibit higher thermal stability and better processability than NTO. Cure characteristics of the rubber compounds are not significantly affected by the oil type. It is also found that the NRCs containing MO or NO have better tensile strength and lower dynamic energy loss than the NRCs containing NTO. This may be because both MO and NO improve filler dispersion to a greater extent than NTO as supported by storage modulus and scanning electron microscopy results. Consequently, the present study suggests that MO and NO could be used as the alternative non–toxic oils for NRC without any loss of the properties evaluated. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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Review

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28 pages, 7637 KiB  
Review
Nature of Carbon Black Reinforcement of Rubber: Perspective on the Original Polymer Nanocomposite
by Christopher G. Robertson and Ned J. Hardman
Polymers 2021, 13(4), 538; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13040538 - 12 Feb 2021
Cited by 110 | Viewed by 16919
Abstract
Adding carbon black (CB) particles to elastomeric polymers is essential to the successful industrial use of rubber in many applications, and the mechanical reinforcing effect of CB in rubber has been studied for nearly 100 years. Despite these many decades of investigations, the [...] Read more.
Adding carbon black (CB) particles to elastomeric polymers is essential to the successful industrial use of rubber in many applications, and the mechanical reinforcing effect of CB in rubber has been studied for nearly 100 years. Despite these many decades of investigations, the origin of stiffness enhancement of elastomers from incorporating nanometer-scale CB particles is still debated. It is not universally accepted whether the interactions between polymer chains and CB surfaces are purely physical adsorption or whether some polymer–particle chemical bonds are also introduced in the process of mixing and curing the CB-filled rubber compounds. We review key experimental observations of rubber reinforced with CB, including the finding that heat treatment of CB can greatly reduce the filler reinforcement effect in rubber. The details of the particle morphology and surface chemistry are described to give insights into the nature of the CB–elastomer interfaces. This is followed by a discussion of rubber processing effects, the influence of CB on crosslinking, and various chemical modification approaches that have been employed to improve polymer–filler interactions and reinforcement. Finally, we contrast various models that have been proposed for rationalizing the CB reinforcement of elastomers. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
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