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Advances in Functional Rubber and Elastomer Composites II
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Advances in Functional Rubber and Elastomer Composites II

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

Deadline for manuscript submissions: 31 December 2024 | Viewed by 17861

Special Issue Editors

Dr. Md Najib Alam

E-Mail Website
Guest Editor
School of Mechanical Engineering, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Korea
Interests: vulcanization; rubber nanocomposites; energy harvesting; sensors and actuators; magnetorheological elastomers
Special Issues, Collections and Topics in MDPI journals
Dr. Vineet Kumar

E-Mail Website
Guest Editor
School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea
Interests: rubber nanocomposites; graphene; carbon nanotube; mechanical properties of polymer nanocomposites; hybrid fillers; elastomers; magneto-rheological elastomers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Recently, research on functional rubber and elastomer-based materials has been expanding beyond their traditional mechanical applications. Elastomers possess high stretchability and low mechanical hysteresis, making them perfect for long-lasting dynamic applications. However, in many cases, rubber alone may not suffice. To render it useful for advanced applications, functional fillers can be employed. Rubber composites, tailored to specific functionalities, are now widely utilized in numerous advanced fields, including mechanical, thermal, electrical, and electronic applications. Particularly, rubber materials for energy harvesting and strain sensing are in the developmental stages, generating significant interest in energy devices for health monitoring and other technologies. Similarly, like other functional materials, rubber can find utility in various advanced engineering applications.

The aim of this Special Issue is to compile knowledge related to the fabrication, characterization, and properties of advanced functional rubber and elastomer composites for use in advanced mechanical, thermal, electrical, magnetic, and other stretchable applications. We also warmly welcome theoretical discussions and critical review papers pertaining to functional elastomers and their composites.

Dr. Md Najib Alam
Dr. Vineet Kumar
Guest Editors

Manuscript Submission Information

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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

  • advanced rubber composites
  • stretchable conductor
  • flexible electronics
  • sensors and actuators
  • magnetorheological elastomers
  • energy harvesting
  • functional fillers
  • phase change materials
  • functionalized elastomers
  • smart designing

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Published Papers (12 papers)

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Research

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17 pages, 2821 KiB  
Article
On the Piezomagnetism of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields: Height Modulation in the Vicinity of an Operating Point by Time-Harmonic Fields
by Gašper Glavan, Inna A. Belyaeva and Mikhail Shamonin
Polymers 2024, 16(19), 2706; https://doi.org/10.3390/polym16192706 - 25 Sep 2024
Abstract
Soft magnetoactive elastomers (MAEs) are currently considered to be promising materials for actuators in soft robotics. Magnetically controlled actuators often operate in the vicinity of a bias point. Their dynamic properties can be characterized by the piezomagnetic strain coefficient, which is a ratio [...] Read more.
Soft magnetoactive elastomers (MAEs) are currently considered to be promising materials for actuators in soft robotics. Magnetically controlled actuators often operate in the vicinity of a bias point. Their dynamic properties can be characterized by the piezomagnetic strain coefficient, which is a ratio of the time-harmonic strain amplitude to the corresponding magnetic field strength. Herein, the dynamic strain response of a family of MAE cylinders to the time-harmonic (frequency of 0.1–2.5 Hz) magnetic fields of varying amplitude (12.5 kA/m–62.5 kA/m), superimposed on different bias magnetic fields (25–127 kA/m), is systematically investigated for the first time. Strain measurements are based on optical imaging with sub-pixel resolution. It is found that the dynamic strain response of MAEs is considerably different from that in conventional magnetostrictive polymer composites (MPCs), and it cannot be described by the effective piezomagnetic constant from the quasi-static measurements. The obtained maximum values of the piezomagnetic strain coefficient (∼102 nm/A) are one to two orders of magnitude higher than in conventional MPCs, but there is a significant phase lag (35–60°) in the magnetostrictive response with respect to an alternating magnetic field. The experimental dependencies of the characteristics of the alternating strain on the amplitude of the alternating field, bias field, oscillation frequency, and aspect ratio of cylinders are given for several representative examples. It is hypothesized that the main cause of observed peculiarities is the non-linear viscoelasticity of these composite materials. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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16 pages, 8399 KiB  
Article
The Hydrogen Bonding in the Hard Domains of the Siloxane Polyurea Copolymer Elastomers
by Ming Bao, Tianyu Liu, Ying Tao and Xiuyuan Ni
Polymers 2024, 16(17), 2438; https://doi.org/10.3390/polym16172438 - 28 Aug 2024
Viewed by 295
Abstract
For probing the structure–property relationships of the polyurea elastomers, we synthesize the siloxane polyurea copolymer elastomer by using two aminopropyl-terminated polysiloxane monomers with low and high number-average molecular weight (Mn), i.e., L-30D and H-130D. To study the influence of the [...] Read more.
For probing the structure–property relationships of the polyurea elastomers, we synthesize the siloxane polyurea copolymer elastomer by using two aminopropyl-terminated polysiloxane monomers with low and high number-average molecular weight (Mn), i.e., L-30D and H-130D. To study the influence of the copolymer structures on the film properties, these films are analyzed to obtain the tensile performance, UV-vis spectra, cross-sectional topographies, and glass transition temperature (Tg). The two synthetic thermoplastic elastomer films are characterized by transparency, ductility, and the Tg of the hard domains, depending on the reacting compositions. Furthermore, the film elasticity behavior is studied by the strain recovery and cyclic tensile test, and then, the linear fitting of the tensile data is used to describe the film elasticity based on the Mooney–Rivlin model. Moreover, the temperature-dependent infrared (IR) spectra during heating and cooling are conducted to study the strength and recovery rate of the hydrogen bonding, respectively, and their influence on the film performance is further analyzed; the calculated Mn of the hard segment chains is correlated to the macroscopic recovery rate of the hydrogen bonding. These results can add deep insight to the structure–property relationships of the siloxane polyurea copolymer. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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16 pages, 7629 KiB  
Article
The Effect of Rubber–Metal Interactions on the Mechanical, Magneto–Mechanical, and Electrical Properties of Iron, Aluminum, and Hybrid Filler-Based Styrene–Butadiene Rubber Composites
by Md Najib Alam, Vineet Kumar, Seok-U Jeong and Sang-Shin Park
Polymers 2024, 16(17), 2424; https://doi.org/10.3390/polym16172424 - 27 Aug 2024
Viewed by 345
Abstract
Multifunctional stretchable rubber composites are gaining attention due to their unique electrical, mechanical, and magnetic properties. However, their high production costs pose economic challenges. This study explores the use of cost-effective metal powders—iron, aluminum, and their 1:1 (vol/vol) hybrid filler—in styrene–butadiene rubber composites, [...] Read more.
Multifunctional stretchable rubber composites are gaining attention due to their unique electrical, mechanical, and magnetic properties. However, their high production costs pose economic challenges. This study explores the use of cost-effective metal powders—iron, aluminum, and their 1:1 (vol/vol) hybrid filler—in styrene–butadiene rubber composites, varying from 10 to 20 vol%. The effects of these metal particles on the mechanical, electrical, morphological, and swelling properties were investigated. Metal particles generally act as non-reinforcing fillers but can significantly enhance the mechanical modulus, electrical, and magnetic properties based on the filler structure and the filler–rubber interactions. Iron-based composites exhibit significant electrical conductivity and excellent magnetic properties. Aluminum enhances the modulus, while the combination yields average mechanical properties with added magnetic characteristics. Iron demonstrates higher reactivity with sulfur-based crosslinking ingredients, adversely affecting the rubber matrix’s crosslinks, as shown by swelling tests. This reactivity is attributed to iron’s transition metal characteristics. At 20 vol%, iron-filled composites display the highest magnetic anisotropic effect on toughness (~25%) under a magnetic field by permanent magnets and excellent electrical conductivity (1.5 × 10−2 S/m). While iron significantly boosts the electrical and magnetic properties, higher filler amounts degrade the mechanical properties. These composites are currently suitable for electrical and smart mechanical applications, but incorporating reinforcing fillers could enhance their robustness for broader applications. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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17 pages, 4688 KiB  
Article
Novel Reactive Polyhedral Oligomeric Silsesquioxane-Reinforced and Toughened Epoxy Resins for Advanced Composites
by Weibo Liu, Caiyun Wang, Yu Feng, Yongfeng Chen, Liqiang Wan, Farong Huang, Zuozhen Liu, Jianhua Qian and Weiping Liu
Polymers 2024, 16(13), 1877; https://doi.org/10.3390/polym16131877 - 1 Jul 2024
Cited by 1 | Viewed by 773
Abstract
Most toughening methods for epoxy resins are usually used at the expense of other properties. Some polyhedral oligomeric silsesquioxanes (POSSs) with both a rigid Si-O-Si structure and flexible organic chain segments could be expected to be effective toughening agents. In this study, three [...] Read more.
Most toughening methods for epoxy resins are usually used at the expense of other properties. Some polyhedral oligomeric silsesquioxanes (POSSs) with both a rigid Si-O-Si structure and flexible organic chain segments could be expected to be effective toughening agents. In this study, three reactive polyhedral oligomeric silsesquioxanes with a thiol group (OMPPS), a carboxyl group (OCOPS), and an epoxy group (OGCPS) were synthesized and characterized. They were utilized as modifiers to toughen 3-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline (AFG-90MH)/4,4′-methylenebis(2-ethylaniline) (MOEA) (epoxy resin) with different molar ratios to obtain hybrid resins named OMPPS-EP-i, OCOPS-EP-j, and OGCPS-EP-k. The effects of the amount of modifier added and the length of the organic chain on the cage structure on various properties of the hybrid resins were investigated. The results show that all three modifiers show good compatibility with the epoxy resin. The hybrid resins have a low viscosity at 45~85 °C and can be cured at a low temperature (110 °C). The cured hybrid resins display improved toughness. Typically, the critical stress intensity factor (KIC) and impact strength of OGCPS-EP-0.6-C are 2.54 MPa∙m−1/2 and 19.33 kJ∙m−2, respectively, which increased by 58.75% and 22.48% compared with the pristine epoxy resin, respectively. In addition, the glass transition temperature and flexural strength of the hybrid resins are basically unchanged. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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30 pages, 18328 KiB  
Article
Investigation of Macroscopic Mechanical Behavior of Magnetorheological Elastomers under Shear Deformation Using Microscale Representative Volume Element Approach
by Ilda Abdollahi and Ramin Sedaghati
Polymers 2024, 16(10), 1374; https://doi.org/10.3390/polym16101374 - 11 May 2024
Viewed by 920
Abstract
Magnetorheological elastomers (MREs) are a class of smart materials with rubber-like qualities, demonstrating revertible magnetic field-dependent viscoelastic properties, which makes them an ideal candidate for development of the next generation of adaptive vibration absorbers. This research study aims at the development of a [...] Read more.
Magnetorheological elastomers (MREs) are a class of smart materials with rubber-like qualities, demonstrating revertible magnetic field-dependent viscoelastic properties, which makes them an ideal candidate for development of the next generation of adaptive vibration absorbers. This research study aims at the development of a finite element model using microscale representative volume element (RVE) approach to predict the field-dependent shear behavior of MREs. MREs with different elastomeric matrices, including silicone rubber Ecoflex 30 and Ecoflex 50, and carbonyl iron particles (CIPs) have been considered as magnetic particles. The stress–strain characteristic of the pure silicon rubbers was evaluated experimentally to formulate the nonlinear Ogden strain energy function to describe hyper-elastic behavior of the rubbery matrix. The obtained mechanical and magnetic properties of the matrix and inclusions were integrated into COMSOL Multiphysics to develop the RVE for the MREs, in 2D and 3D configurations, with CIP volume fraction varying from 5% to 40%. Periodic boundary condition (PBC) was imposed on the RVE boundaries, while undergoing shear deformation subjected to magnetic flux densities of 0–0.4 T. Comparing the results from 2D and 3D modeling of isotropic MRE-RVE with the experimental results from the literature suggests that the 3D MRE-RVE can be effectively used to accurately predict the influence of varying factors including matrix type, volume fraction of magnetic particles, and applied magnetic field on the mechanical behavior of MREs. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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20 pages, 4078 KiB  
Article
Carbon Black Functionalized with Serinol Pyrrole to Replace Silica in Elastomeric Composites
by Federica Magaletti, Martina Galbusera, Davide Gentile, Ulrich Giese, Vincenzina Barbera and Maurizio Galimberti
Polymers 2024, 16(9), 1214; https://doi.org/10.3390/polym16091214 - 26 Apr 2024
Cited by 1 | Viewed by 2407
Abstract
Elastomer composites for dynamic mechanical applications with a low dissipation of energy are of great importance in view of their application in tire compounds. In this work, furnace carbon black functionalized with 2-2,5-dimethyl-1H-pyrrol-1-yl-1,3-propanediol (SP) was used in place of silica in [...] Read more.
Elastomer composites for dynamic mechanical applications with a low dissipation of energy are of great importance in view of their application in tire compounds. In this work, furnace carbon black functionalized with 2-2,5-dimethyl-1H-pyrrol-1-yl-1,3-propanediol (SP) was used in place of silica in an elastomer composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. The traditional coupling agent used for silica was also used for the CB/SP adduct: 3,3′-bis(triethoxysilylpropyl)tetrasulfide (TESPT). The composite with the CB/SP + TESPT system revealed a lower Payne effect, higher dynamic rigidity, and lower hysteresis, compared to the composite with CB + TESPT, although the latter composite had a higher crosslinking density. The properties of the silica and the CB/SP + TESPT-based composites appear similar, though in the presence of slightly higher hysteresis and lower ultimate properties for the CB/SP-based composite. The use of CB in place of silica allows us to prepare lighter compounds and paves the way for the preparation of tire compounds with lower environmental impacts. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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16 pages, 2491 KiB  
Article
Enhancing Rubber Vulcanization Cure Kinetics: Lowering Vulcanization Temperature by Addition of MgO as Co-Cure Activator in ZnO-Based Cure Activator Systems
by Md Najib Alam, Vineet Kumar, Seok U Jeong and Sang-Shin Park
Polymers 2024, 16(7), 876; https://doi.org/10.3390/polym16070876 - 22 Mar 2024
Cited by 1 | Viewed by 1204
Abstract
Vulcanization is a chemical modification of rubber that requires a considerable amount of thermal energy. To save thermal energy, the kinetics of rubber vulcanization should be improved. In this article, the curing properties of rubber vulcanization are thoroughly investigated using the moving die [...] Read more.
Vulcanization is a chemical modification of rubber that requires a considerable amount of thermal energy. To save thermal energy, the kinetics of rubber vulcanization should be improved. In this article, the curing properties of rubber vulcanization are thoroughly investigated using the moving die rheometer (MDR) technique. To enhance the kinetics in different stages of ZnO-based sulfur vulcanization systems, small amounts of MgO were added. The results revealed that the small amount of 1 to 2 phr (per hundred grams of rubber) of MgO in the controlled 5 phr ZnO-based curing systems can significantly improve the curing kinetics. For example, the optimum curing time of 1 phr MgO added to the 5 phr ZnO-containing semi-efficient vulcanization system at different temperatures was more than half that of the controlled 5 phr ZnO-only compound. While maintaining a similar rate of vulcanization, the vulcanization temperature can be reduced by up to 20 °C by using MgO as a co-cure activator, which exhibits similar or better rheometric mechanical properties compared to the controlled compounds. With the addition of MgO as a co-cure activator, the vulcanization reactions become very fast, enabling vulcanization to be completed, even at the boiling point of water (100 °C) with an affordable curing time (<1 h). By reducing the vulcanization temperature, the scorch safety time can be enhanced in the ZnO/MgO-based binary cure activator-containing vulcanizates. Overall, MgO could be a potential candidate as a co-cure activator with ZnO for the vulcanization of rubber, offering better economical and eco-friendly methods. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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16 pages, 1823 KiB  
Article
Thermodynamic Parameters of Crosslinked Elastomers (BR, SBR and NBR) and Their Blends
by César Leyva-Porras, Iván A. Estrada-Moreno, Claudia I. Piñón-Balderrama, Sergio G. Flores-Gallardo and Alfredo Márquez-Lucero
Polymers 2024, 16(3), 351; https://doi.org/10.3390/polym16030351 - 28 Jan 2024
Cited by 1 | Viewed by 1597
Abstract
Herein, a methodology is employed based on the Flory–Rehner equation for estimating the Flory–Huggins interaction parameter (χ12*) of crosslinked elastomer blends. For this purpose, binary elastomer blends containing polybutadiene rubber (BR), styrene–butadiene rubber (SBR) and nitrile–butadiene rubber (NBR), were prepared in [...] Read more.
Herein, a methodology is employed based on the Flory–Rehner equation for estimating the Flory–Huggins interaction parameter (χ12*) of crosslinked elastomer blends. For this purpose, binary elastomer blends containing polybutadiene rubber (BR), styrene–butadiene rubber (SBR) and nitrile–butadiene rubber (NBR), were prepared in a mixing chamber at a temperature below the activation of the crosslinking agent. Swelling tests with benzene were employed to determine the crosslinked fraction, finding that after 20 min of thermal annealing, the BR and NBR were almost completely crosslinked, while the SBR only reached 60%. Additionally, the BR-SBR blend increased by 2–3 times its volume than its pure components; this could be explained based on the crosslink density. From the mechanical tests, a negative deviation from the rule of mixtures was observed, which suggested that the crosslinking was preferably carried out in the phases and not at the interface. Furthermore, tensile tests and swelling fraction (ϕsw) results were employed to determine the average molecular weight between two crosslinking points (Mc), and subsequently χ12*. Calculated χ12* values were slightly higher than those reported in the literature. The calculated thermodynamic parameters for the blends showed positive ΔGmix values and endothermic behavior, suggesting their immiscible nature. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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22 pages, 16713 KiB  
Article
Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets
by Veerapat Kitsawat, Saranrat Siri and Muenduen Phisalaphong
Polymers 2024, 16(2), 288; https://doi.org/10.3390/polym16020288 - 20 Jan 2024
Cited by 2 | Viewed by 1883
Abstract
Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated [...] Read more.
Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young’s modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10−4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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22 pages, 5219 KiB  
Article
Improved Heat Dissipation of NR/SBR-Based Tire Tread Compounds via Hybrid Fillers of Multi-Walled Carbon Nanotube and Carbon Black
by Mehmet Kodal, Nazlı Yazıcı Çakır, Rumeysa Yıldırım, Nursel Karakaya and Güralp Özkoç
Polymers 2023, 15(23), 4503; https://doi.org/10.3390/polym15234503 - 23 Nov 2023
Cited by 2 | Viewed by 1891
Abstract
The development of thermally conductive rubber nanocomposites for heat management poses a formidable challenge in numerous applications, notably within the realm of tire technology. Notably, rubber materials are characterized by their inherently low thermal conductivity. Consequently, it becomes imperative to incorporate diverse conductive [...] Read more.
The development of thermally conductive rubber nanocomposites for heat management poses a formidable challenge in numerous applications, notably within the realm of tire technology. Notably, rubber materials are characterized by their inherently low thermal conductivity. Consequently, it becomes imperative to incorporate diverse conductive fillers to mitigate the propensity for heat build-up. Multi-walled carbon nanotubes (MWCNTs), as reinforcement agents within the tire tread compounds, have gained considerable attention owing to their extraordinary attributes. The attainment of high-performance rubber nanocomposites hinges significantly on the uniform distribution of MWCNT. This study presents the influence of MWCNTs on the performance of carbon black (CB)-reinforced natural rubber (NR)/styrene butadiene rubber (SBR) tire compounds prepared via high shear melt mixing. Morphological analysis showed a good distribution of MWCNTs in the NR/SBR/CB compound. The vulcanization parameters, such as the maximum and minimum torque, cross-linking density, hardness, abrasion resistance, tensile strength, and Young modulus, exhibited a progressive improvement with the addition of MWCNT. Remarkably, adding MWCNT into CB improved the heat conductivity of the NR/SBR/CB compounds, hence decreasing the heat build-up. A percolation mode was also proposed for the hybrid carbon fillers based on the data obtained. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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15 pages, 3917 KiB  
Article
Enhanced Low-Density Silicone Foams Blown by Water–Hydroxyl Blends
by Ingrid Rebane, Karl Jakob Levin, Uno Mäeorg, Urmas Johanson, Peeter Piirimägi, Tauri Tätte and Tarmo Tamm
Polymers 2023, 15(22), 4425; https://doi.org/10.3390/polym15224425 - 16 Nov 2023
Viewed by 1482
Abstract
Water, alcohols, diols, and glycerol are low-cost blowing agents that can be used to create the desired silicone foam structures. Although their combined use can be beneficial, it remains unclear how it affects the physical properties of the resulting materials. We conducted a [...] Read more.
Water, alcohols, diols, and glycerol are low-cost blowing agents that can be used to create the desired silicone foam structures. Although their combined use can be beneficial, it remains unclear how it affects the physical properties of the resulting materials. We conducted a comparative study of these hydroxyl-bearing blowing agents in fumed silica- and mica-filled polymer composite systems for simultaneous blowing and crosslinking to obtain a low-density, uniform porosity and superior mechanical properties. The foams were optimized for a uniform open-pore structure with densities ranging from 75 to 150 kg‧m−3. Varying the diol chain length (Cn) from one to seven carbons can alter the foam density and structure, thereby enhancing the foam tensile strength while maintaining a low density. Replacing 10 mol% of water with 1,4-butanediol decreased the density by 26%, while increasing the specific strength by 5%. By combining glycerol and water blowing, the resulting foams exhibited a 30% lower apparent density than their water-blown analogs. The results further showed that Cn > 4 alkane chain diols had an odd–even effect on the apparent density and cell wall thickness. All foamable compositions had viscosities of approximately 7000 cSt and curing times below 2 min, allowing for quick dispensing and sufficient time for the foam to cure in semi-industrial volumes. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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Review

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32 pages, 8733 KiB  
Review
Research Progress of Natural Rubber Wet Mixing Technology
by Qinghan Zhao, Fangyan Niu, Junyu Liu and Haishan Yin
Polymers 2024, 16(13), 1899; https://doi.org/10.3390/polym16131899 - 2 Jul 2024
Viewed by 925
Abstract
The performance of natural rubber (NR), a naturally occurring and sustainable material, can be greatly enhanced by adding different fillers to the NR matrix. The homogeneous dispersion of fillers in the NR matrix is a key factor in their ability to reinforce. As [...] Read more.
The performance of natural rubber (NR), a naturally occurring and sustainable material, can be greatly enhanced by adding different fillers to the NR matrix. The homogeneous dispersion of fillers in the NR matrix is a key factor in their ability to reinforce. As a novel method, wet mixing technology may effectively provide good filler dispersion in the NR matrix while overcoming the drawbacks of conventional dry mixing. This study examines the literature on wet mixing fillers, such as graphene, carbon nanotubes, silica, carbon black, and others, to prepare natural rubber composites. It also focuses on the wet preparation techniques and key characteristics of these fillers. Furthermore, the mechanism of filler reinforcement is also examined. To give guidance for the future development of wet mixing technology, this study also highlights the shortcomings of the current system and the urgent need to address them. Full article
(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)
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