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A novel strategy was developed to prepare a self-blowing poly(β-hydroxythioether) foam at room temperature by S-alkylation of 5-membered bis-cyclic carbonate using multifunctional thiol monomers. Two different thiol compounds, trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetrakis(3-mercaptopropanoic acid) were used for the decarboxylative s-alkylation reaction. The thiol compounds simultaneously act as crosslinking agents and generate carbon dioxide during the decarboxylative s-alkylation reaction. This enables foam preparation without an external blowing agent. The use of tetrathiol monomer improves thermal stability, provides flexibility to the foams, and induces an increase in the glass transition temperature (Tg) due to a higher degree of cross-linking. The apparent density of the foams decreases with the increase of the tetrathiol ratio. This novel solvent-free approach paves the way to design sustainable foams with modular properties using accessible components and additives, as well as provides an alternative to non-isocyanate polyurethane foams., The CNRST of Morocco acknowledged for funding this work from Projet Prioritaire (PPR1/2015/73)

Self-healing materials offer a potential solution to the problem of damage to fibre-reinforced plastics (FRPs) by allowing for the in-service repair of composite materials at a lower cost, in less time, and with improved mechanical properties compared to traditional repair methods. This study investigates for the first time the use of poly(methyl methacrylate) (PMMA) as a self-healing agent in FRPs and evaluates its effectiveness both when blended with the matrix and when applied as a coating to carbon fibres. The self-healing properties of the material are evaluated using double cantilever beam (DCB) tests for up to three healing cycles. The blending strategy does not impart a healing capacity to the FRP due to its discrete and confined morphology; meanwhile, coating the fibres with the PMMA results in healing efficiencies of up to 53% in terms of fracture toughness recovery. This efficiency remains constant, with a slight decrease over three subsequent healing cycles. It has been demonstrated that spray coating is a simple and scalable method of incorporating a thermoplastic agent into an FRP. This study also compares the healing efficiency of specimens with and without a transesterification catalyst and finds that the catalyst does not increase the healing efficiency, but it does improve the interlaminar properties of the material., This research was funded by the State Research Agency of Spain (AEI), under grant number PID2019-107501RB-I00/AEI/10.13039/501100011033

Metallic corrosion is an all-time dangerous and extremely expensive problem. Here, we present an autonomous self-healing polymer coating based on an epoxy resin and superabsorbent polymer (SAP) blend as an anticorrosion coating. Tailor-made coatings were manufactured by controlling the location of the SAP on the surface, middle, and bottom of the coating. The corrosion behavior and self-healing process of the coatings were analyzed at the macro, micro, and sub-micro scales using Electrochemical Impedance Spectroscopy (EIS). The SAP preferentially located at the bottom showed coating resistance values higher than 1 × 10 Ωcm over 10 days of immersion with 3-point defects. This configuration provided the best anticorrosion performance, preventing coating delamination, and protecting the metal from corrosion after surface damage, indicating better barrier properties. The SAP enabled local repair of the crack when in contact with water, minimizing the diffusion of oxygen and electroactive species, which are responsible for the corrosion of a metal., This research was funded by the Spanish Research Agency, grant numbers PID2019-107501RB-I00/AEI/10.13039/501100011033, and RYC-2017-22837. MPC acknowledges grant BES-2017-079899 funded by MCIN/AEI/10.13039/501100011033. VB would like to acknowledge financial support through the PID2019-104717RB-I00 project from the Spanish Ministry of Science and Innovation (MICI)

Poly(hydroxyurethanes) (PHUs) have been suggested as isocyanate-free, low-toxicity alternatives to polyurethanes (PUs). However, PHUs present low mechanical properties due to the presence of side reactions that limit the production of high-molar mass polymers. Here, we present the synthesis under mild conditions and atmospheric pressure of bi-cyclic carbonate monomer for the production of PHU nanocomposites with good physical properties. The kinetics of the bi-cyclic carbonate synthesis and its complete conversion to urethane were followed by FTIR. The addition of functionalized boron nitrate (f-BN) with sucrose crystals improved the thermal degradation temperature as well as the glass transition by approximately 20 °C and 10 °C, respectively. The storage modulus of PHU films gradually increases with the concentration of f-BN in the composite., This research is part of grant PID2020-119546RJ-I00 funded by MCIN/AEI/10.13039/501100011033

Self-healing rubbers have steadily been growing during the last decades. Various strategies have been studied to transform the vulcanized rubber into a reversible cross-linked network with multiple repair cycles. However, a detailed description on how the chemical constituents of a rubber formulation affect the healing properties of the vulcanizate is unknown and has not been reported until now. In this research, the individual effects of both the curing agent (sulfur and peroxide) and the activating complex (zinc oxide and stearic acid) have been assessed on the healing capability of a styrene-butadiene rubber (SBR) compound. The analysis of different healing conditions revealed that pristine materials should be subjected to the same thermal treatment as the healed samples to obtain scientifically sound values of the healing efficiency. Results also showed that each component affected the healing at different time scales, with the activating complex being responsible for the initial physical healing stage. Meanwhile, sulfur would act at later stages as dynamic healing moiety, enabling disulfide exchange reactions. In conclusion, the mechanical recovery of a rubber network can be potentially tailored depending on the relation between the chemical components of the rubber formulation., he authors acknowledge the State Research Agency of Spain (AEI) for a research contract (PID2019-107501RB-I00) and M. Hernández Santana for a Ramón y Cajal contract (RYC-2017-22837)

The use of hybrid fillers in rubbers can provide additional benefits to rubber foams compared to individual micro- or nano-scale particles due to an optimum packaging and synergic effects. The present work reports the development of vulcanized ethylene-propylene-diene-monomer nanocomposite hybrid foams filled with barium titanate and multiwall carbon nanotube (BT/MWCNT), prepared via a scalable protocol. The developed foams presented a high shear-thinning behavior, suggesting the formation of a 3D interconnected physical network of MWCNT within the polymer matrix. This network resulted in a notable improvement of the mechanical properties under tension and compression with increasing of MWCNT content. Also, the incorporation of MWCNT and BT enhanced thermal stability and thermal conductivity. Meanwhile, BT did not show any influence on the measured physical properties, due to the lack of interaction between BT and the EPDM matrix.

Foam products are one of the largest markets for polyurethane (PU) and are heavily used in many sectors. However, current PU formulations use highly toxic and environmentally unfriendly production processes. Meanwhile, the increasing environmental concerns and regulations are intensifying the research into green and non-toxic products. In this study, we synthesized flexible polyurethane foam (PUF) using different weight percentages (0.025%, 0.05% and 0.1%) of a non-toxic bismuth catalyst. The bismuth-catalyzed foams presented a well evolved cellular structure with an open cell morphology. The properties of the bismuth-catalyzed flexible PUF, such as the mechanical, morphological, kinetic and thermal behaviors, were optimized and compared with a conventional tin-catalyzed PUF. The bismuth-catalyst revealed a higher isocyanate conversion efficiency than the stannous octoate catalyst. When comparing samples with similar densities, the bismuth-catalyzed foams present better mechanical behavior than the tin-catalyzed sample with similar thermal stability. The high solubility of bismuth triflate in water, together with its high Lewis acidity, have been shown to benefit the production of PU foams., This research was funded by the State Research Agency of Spain (AEI) through grant PID2019-107501RB-I00

Polyurethane foams (PUFs) are a significant group of polymeric foam materials. Thanks to their outstanding mechanical, chemical, and physical properties, they are implemented successfully in a wide range of applications. Conventionally, PUFs are obtained in polyaddition reactions between polyols, diisoycyanate, and water to get a CO foaming agent. The toxicity of isocyanate has attracted considerable attention from both scientists and industry professionals to explore cleaner synthesis routes for polyurethanes excluding the use of isocyanate. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines in the presence of an external blowing agent or by self-blowing appears to be the most promising route to substitute the conventional PUFs process and to produce isocyanate-free polyurethane foams (NIPUFs). Especially for polyhydroxyurethane foams (PHUFs), the use of a blowing agent is essential to regenerate the gas responsible for the creation of the cells that are the basis of the foam. In this review, we report on the use of different blowing agents, such as Poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons for the preparation of NIPUFs. Furthermore, the preparation of NIPUFs using the self-blowing technique to produce gas without external blowing agents is assessed. Finally, various biologically derived NIPUFs are presented, including self-blown NIPUFs and NIPUFs with an external blowing agent., This research is part of grant PID2020-119546RJ-I00 funded by MCIN/AEI/10.13039/501100011033.

The evolution of self-healing polymers has resulted in a myriad of healing designs that have given way to complex systems capable of supporting multiple cycles, among other features. This progression enables us to propose the implementation of a timeline that classifies self-healing polymers in generations based on the healing mechanism, and correlated with historical development. The first generation employed the encapsulation of external healing agents; the second one, based on intrinsic mechanisms, applied reversible chemistries; and the third generation was inspired by natural examples such as plants and human skin, in which the healing agent is embedded in vascular networks. Despite great efforts and, with a few exceptions, polymers with high healing efficiency and high mechanical performance are not common. To improve this situation, a combination of different mechanisms is currently emerging, giving birth to the fourth generation of self-healing materials. This article, focused on self-healing elastomers, provides a rigorous overview of this new generation, in which the combination of covalent bonds and non-covalent interactions provides an optimal balance between mechanical performance and repairability. The implementation of this concept leads to materials with real commercial potential in functional applications, such as coatings, sensors, actuators, controlled release of drugs, seals, gaskets, hoses, and even high-performance applications such as tires and railway components.

Natural rubber (NR)is one of Nature's most exceptional materials and is, therefore, widely used by industry, in particular by the tire industry. In spite of the interest in recycling vulcanized NR, there is no suitable way to do it and most of the tires are discarded in landfills. Here, we examine the use of a Diels-Alder reaction to obtain a NR fully and reversibly crosslinked and with self-repair capacity. NR was crosslinked via Diels-Alder (DA)reactions following a three-step procedure: i)NR was reacted with maleic anhydride; ii)furan moieties were then grafted to the maleated rubber; iii)pending furans were further crosslinked with a bismaleimide, resulting in a thermoreversible bridge which led to a crosslinked NR. The formation of the DA adduct was confirmed and the reversibility of the DA reaction was demonstrated through dynamic-mechanical analysis and rheological measurements. The self-healing capacity of the material was also evaluated; qualitatively, at different scales by scanning electron microscopy, optical profilometry and atomic force microscopy and; quantitatively, by tensile testing obtaining 80% of strength recovery at small deformations. We provide phenomenological explanations of the reversibility and healing performance of the DA reaction too. This research provides a framework to crosslink rubbers, yielding a straightforward strategy for both reusing and extending the lifetime of elastomeric goods., The authors acknowledge Dr. Nuria García (ICTP-CSIC), and Dr. Esther Rebollar and Dr. Tiberio Ezquerra (IEM-CSIC) for their support with optical profilometry and AFM measurements. M. Hernández Santana acknowledges the Ministry of Science, Innovation and Universities of Spain for a research contract (MAT2015-73392-JIN).

Dielectric elastomers have been regarded as truly artificial muscles for their electro-mechanical (EM) actuation performance. However, they require large driving voltages to present adequate actuation strains. The main pursued route to solve it has been the development of elastomeric composites with high dielectric permittivity. Unfortunately, such approach reinforces the matrix and has a detrimental effect on the EM actuation and the dielectric breakdown strength. Here, we study a complementary strategy to improve the dielectric permittivity without increasing its stiffness. We analyze the effect of thermoplastic PU elastomer on the actuation response of a thermoplastic dielectric elastomer, such as poly(styrene-ethylene-butadiene-styrene). The addition of 10 wt% PU resulted in an improved EM actuation without reducing its dielectric breakdown strength. This result was ascribed to the interaction of the urethane hard segments of the PU and the styrene moieties of the SEBS. The results revealed that DEAs can be developed through a simple blending procedure, where a proper selection of the polymer systems is key for their actuation performance., This research was supported by National Commission for Scientific and Technological Research, Chile, under Postdoctoral fellowship Nº 3170104 granted to H. Aguilar-Bolados. RV acknowledges financial support from Consejo Superior de Investigaciones Cientificas, Spain through grant project number 201660I032

New bio-thermoplastic elastomer composites with self-healing capacities based on epoxidized natural rubber and polycaprolactone blends reinforced with alginates were developed. This group of salts act as natural reinforcing fillers, increasing the tensile strength of the unfilled rubber from 5.6 MPa to 11.5 MPa without affecting the elongation at break (~1000% strain). In addition, the presence of ionic interactions and hydrogen bonds between the components provides the material with a thermally assisted self-healing capacity, as it is able to restore its catastrophic damages and recover diverse mechanical properties up to ~100%. With the results of this research, an important and definitive step is planned toward the circularity of elastomeric materials., This research was funded by the State Research Agency of Spain (AEI), grant numbers PID2019-107501RB-I00/AEI/10.13039/501100011033 and RYC-2017-2283, and the Spanish National Research Council, grant numbers LINKA20325 and PIE-202060E183.

The management of end-of-life tires (ELTs) is one of the main environmental issues that society faces nowadays. Recycling of ELTs appears as one feasible option for tackling the problem, although their incorporation as ground tire rubber (GTR) in other rubber matrices is limited due to poor compatibility. In this research, we report a successful combination of a cryo-grinding process with a chemical treatment for modifying the surface of GTR. Various cryo-grinding protocols were studied until a particle size of 100–150 µm was achieved. Chemical treatments with different acids were also analyzed, resulting in the optimal modification with sulfuric acid (H2SO4). Modified GTR was added to a styrene-butadiene rubber (SBR) matrix. The incorporation of 10 phr of this filler resulted in a composite with improved mechanical performance, with increments of 115% and 761% in tensile strength and elongation at break, respectively. These results validate the use of a recycled material from tire waste as sustainable filler in rubber composites.

The dichotomy between mechanical performance and repairability is a well-known fact in the self-healing field. One alternative to overcome this trade-off is the inclusion of reinforcing fillers. In this research, hybrid reinforced self-healing styrene-butadiene rubber (SBR) composites are developed by combining mechano-chemically modified ground tire rubber (mGTR) with carbon black (CB). The SBR matrix is systematically analyzed by means of dynamic mechanical analysis and broadband dielectric spectroscopy. The SBR composite reinforced with 20 phr mGTR and 20 phr CB maintains the healing efficiency of the unfilled SBR (80%) and improves its tensile strength by 300%, balancing perfectly well both properties. The healing efficiency is determined at different damage levels. The damage at the microscopic scale is easier to recover and does not depend on the presence of fillers, while the recovery at the macroscopic level clearly relies on the addition of filler, with more demanding healing conditions., This work was supported by the State Research Agency of Spain (AEI) [grant numbers PID2019-107501RB-I00, RYC-2017-22837]; the Spanish National Research Council (CSIC) [grant number PIE-202060E183]; and the Community of Madrid [grant number PEJ 2019-AI/IND-14635].

Thermoplastic resins are likely to replace thermoset resins in wind blade manufacturing, as their similar structural properties together with their recyclability would enable the reuse of the raw materials in other composites at the end of life. This paper presents the manufacturing, testing and recycling process of a 1 m thermoplastic composite wind turbine blade compared to a similar thermoset blade. The results showed that the static and centrifugal performance of the two blades were similar, but the thermoplastic composite blade had a lower deflection compared to the epoxy blade. The different components of the thermoplastic blade were recovered by immersion in a suitable solvent for their possible reuse in the manufacture of a new wind turbine blade. Thus, this study provides an example of the use of circular economy principles in a strategic renewable sector, wind energy, validating the use of a new thermoplastic resin in the design and recycling of wind turbine blades, without changing their current manufacturing process.

Composite coatings are used in order to reduce the friction and protect contacting surfaces against wear with good adhesive to substrate. The present study deals with two sizes of solid particles used in composite coatings. As received graphite G1, the mean size is 20µm and the crushed one, obtained by ball mill, is 10µm. The resulting tribological behavior and micromechanical properties were discussed and compared. As expected, the smaller the particle size the greater reduction in the coefficient of the friction and wear rate. The experimental findings show that adding 5 wt% of crushed graphite provide similar COF than when introducing 10 wt% of as received graphite. Coatings scratch behavior is affected by the size and percentage of fillers inside the polyester matrix. In fact, the scratch resistance is observed with polyester coatings filled at 5 wt% G2 and 10 wt% G1.

The influence of 0.5, 0.75, and 1 wt.% of graphene oxide (GrO) in nanocomposite coating on scratch behavior and tribological performance was analyzed. Graphite was oxidized using the Marcano and Tour method to obtain graphite oxide, which is thermally exfoliated at 700°C getting graphene oxide. The transformation of graphite to graphene oxide was evaluated via Raman spectroscopy and X-ray diffraction. Effects of graphene oxide content on the friction and wear behavior of polyester composite coatings were evaluated under dry sliding conditions. Experimental findings showed that the addition of 0.5 wt.% GrO was effective in reducing the friction coefficient of polyester coating. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with 1 wt.% GrO has better antiwear ability compared to those filled with 0.5 and 0.75 wt.% GrO. From the scratch analyses, we deduced that coating scratch behavior was highly affected by the amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance were observed in the case of polyester coatings filled with the lower amount of GrO, namely 0.5 wt.%.

Herein, a study is presented, addressed to understand the influence of the terbium (III) species contained in a thermoplastic polyurethane (TPU) matrix. The studied terbium (III) species were terbium (III) nitrate, Tb(NO)·5HO, and a terbium (III) complex, [TbL (NO)](NO) (HO), where L is a macrocyclic ligand derived from 2,6-pyridinedicarboxyaldehyde and ethylenediamine. SEM-EDXS showed that in both films the terbium (III) species were homogeneously distributed in the polymer matrix. The film doped with the nitrate salt displayed different physical properties, in comparison to the pristine TPU and the film containing the terbium (III) complex. Both TPU/Tb films, exhibiting a green color emission, with a G/B ratio being temperature independent. By comparison of the emission of both films containing terbium (III) species, the TPU/Tb complex film presented a more intense luminescence due to the antenna effect. TPU doped with the nitrate salt showed weak emission, indicating the lack of sensitizing groups., H.A.B. and P.F. thank to the projects ANID FONDECYT Iniciación 11200437 and ANID FONDECYT Iniciación 11200919, respectively, for the financial support. E.S., A.V. and D.V. thank Financiamiento Basal, AFB 180001 Project (CEDENNA). E.S., A.V., D.V. and P.F. acknowledge financial support from FONDECYT 1200033 Project. The authors also acknowledge the support from Brazilian agencies, CNPq and FAPEG and the State Research Agency of Spain (AEI) for a research contract (PID2019-107501RB-I00)

The combination of vulcanizing agents is an adequate strategy to develop multiple networks that consolidate the best of different systems. In this research, sulfur (S), and zinc oxide (ZnO) were combined as vulcanizing agents in a matrix of carboxylated nitrile rubber (XNBR). The resulting dual network improved the abrasion resistance of up to ~15% compared to a pure ionically crosslinked network, and up to ~115% compared to a pure sulfur-based covalent network. Addition-ally, the already good chemical resistance of XNBR in non-polar fluids, such as toluene and gasoline, was further improved with a reduction of up to ~26% of the solvent uptake. A comprehensive study of the molecular dynamics was performed by means of broadband dielectric spectroscopy (BDS) to complete the existing knowledge on dual networks in XNBR. Such analysis showed that the synergistic behavior that prevails over purely ionic vulcanization networks is related to the restricted motions of rubber chain segments, as well as of the trapped chains within the ionic clusters that converts the vulcanizate into a stiffer and less solvent-penetrable material, improving abrasion resistance and chemical resistance, respectively. This combined network strategy will enable the production of elastomeric materials with improved performance and properties on demand., This research was funded by the State Research Agency of Spain (AEI), Grant No. PID2019-107501RB-I00 and RYC-2017-22837; the Spanish National Research Council, Grant No. PIE-202060E183; the Community of Madrid, Grant No. PEJ-2019-AI/IND-1635 and the Ministry of Economy, Industry and Competitiveness, Grant No. PEJ2018-002334-A

The present study investigates the mechanical and tribological properties of an epoxy matrix filled with different graphitic particles deposited on an aluminum substrate by the electrostatic spray technique. Three different particles added to the epoxy matrix were the received graphite, the crushed graphite obtained by crushing the natural flake graphite particles using a ball mill, and graphite oxide obtained by oxidation treatment. Nanoindentation tests were conducted on the different coatings in order to evaluate the surface hardness and the contact elastic modulus. The effect of the oxidation treatment and the loading content on the tribological behavior of the above composites were also evaluated under dry-friction conditions. As expected, the smaller the particle size, the greater the reduction in the dynamic friction. The experimental findings showed that adding 5 wt % of crushed graphite (10 µm) provided a similar dynamic friction as the addition of 10 wt % of received graphite (20 µm). The epoxy filled with received graphite showed a lower wear rate than that filled with graphite oxide and crushed graphite. Moreover, both hardness and elastic modulus increased in the case of the epoxy filled with graphite oxide and crushed graphite.

This work reports the synthesis of poly (monomethyl itaconate) grafted multi-layer graphene oxide (PMMI-g-GO) by atom transfer radical polymerization using activators regenerated by electron transfer (ARGET-ATRP). PMMI-g-GO presents outstanding properties, such as a high electrical conductivity (5.04 S m), low number of stacked graphene layers (6) and I/I ratio of 2.05 estimated from Raman spectrum, which indicates the high quality of PMMI-g-GO as a graphenic material. In addition, polymer brushes based on PMMI represent a new green alternative for the development of polymer composite materials, since the monomer used for their production is obtained from a renewable source. Interestingly, the PMMI-g-GO nanomaterial is also capable of storing Li ions without the need of using electron conductive additives that are usually employed in the electrode's composition of conventional lithium ion batteries., his research was supported by the Chilean Agency for Research and Development (ANID) under Postdoctoral fellowship FONDECYT N◦3170104 granted to H. Aguilar-Bolados. H. Aguilar-Bolados also ac-knowledges to ANID the financial support under the grant FONDECYT project N◦1200437. M Yazdani-Pedram, R. Quijada and H. Aguilar- Bolados acknowledge financial support from ANID through grant FONDECYT projects N◦1191566 and 1191642. R. Verdejo and M. A. Lopez-Manchado acknowledge the financial support from the MICI (grant number MAT2016-81138-R). Javier Carretero Gonz ́alez ac-knowledges the Ramon y Cajal Fellow (RYC-2015-17722) from the MICI. The authors also thank Alejandro May-Pat for performing the AFM analysis. F. Avil ́es acknowledges the CONACYT infrastructure project N◦268595 for acquiring the AFM.

© 2020 by the authors., Composite materials of poly(3,4-ethylenedioxythiophene) (PEDOT)/activated carbon (AC) were prepared by ‘in-situ’ polymerization and subsequently deposited by spray-coating onto a flexible electrolyte prepared in our laboratories. Two activated carbons were tested: a commercial activated carbon and a lab-made activated carbon from brewer’s spent grain (BSG). The porous and spongy structure of the composite increased the specific surface area, which helps to enhance the energy storage density. This procedure to develop conductive composite materials using AC prepared from biowaste has the potential to be implemented for the preparation of polymer-based conductive inks for further applications as electrodes in pseudocapacitors., Francisco González and Mario Hoyos are grateful to CONACYT-SENER for the scholarship granted (CVU559770/Registro 297710).

© 2020 by the authors., The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene–propylene–diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28–45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability, This research was funded by MICIU, grant number MAT2016-81138-R.

Self-healing polymers typically face an enforced trade-off between repairability and mechanical properties, with a high degree of self-healing being achieved mainly by materials having low mechanical strength and stiffness. This study focuses on the development of SBR compounds that can combine together self-healing properties with the use of ground tire rubber (GTR) as alternative sustainable filler. The self-healing efficiency of GTR filled SBR compounds is compared to conventional carbon black filled compounds. The influence of the vulcanization system and the addition of silane-based coupling agents are also assessed. Results show that SBR compounds vulcanized by means of a semi-efficient sulfur based system recover around 50% of their mechanical strength, being the self-healing response related to the presence of disulfide bonds. Contrary to carbon black compounds, GTR samples present similar healing efficiency to the unfilled SBR samples, improving mechanical properties in 50%. Moreover, the coupling agent enhances even more (up to 80%) the mechanical strength of the SBR-GTR compounds without adversely affecting the healing efficiency. These results can thus be seen as a starting model material for developing new sustainable applications economically and environmentally convenient with good mechanical properties as well as healing ability., M. Hernández acknowledges the Ministry of Economics and Competitiveness of Spain for a research contract (MAT2015-73392- JIN). The authors also acknowledge Signus for providing the ground tire rubber and C. Chirico (Carlos III University, Madrid) for the particle size distribution measurements

Graphene materials (GMs) are deeply studied as nanoreinforcements of polymer matrices, especially for epoxy matrices. Here, we analyze the effect of GMs on the transport properties of a poly(bisphenol A-co-epichlorohydrin) resin. In particular, we focus on the effect of the morphology, chemical composition and structure of different GMs obtained by varying the reduction temperature of the thermal/exfoliation treatment of graphite oxide synthesized by a modified Hummers method. The dispersion degree of the GMs was studied by microscopy techniques, showing a strong dependence on the specific surface area and chemical composition of the graphene material. The transport properties imposed different requirements on GMs. The thermal conductivity benefited from a high aromatic restoration. Meanwhile, the electrical conductivity required the right balance of filler/matrix interaction and aromatic restoration., The authors gratefully acknowledge the financial support of the MINECO, Spain, through the project MAT2013-48107-C3. R. Sánchez- Hidalgo thanks to MINECO, Spain for the Predoctoral grant BES-2014- 070802.

The mechanical properties, electrical conductivity and piezoresistive response of thermosetting polymer nanocomposites comprising carbon nanotubes (CNTs, one-dimensional topology, 1D), few-layer thermally reduced graphene oxide (FLG, two-dimensional topology, 2D), cubic-shaped few-layer graphene shells (CGSs, three-dimensional topology, 3D), and hybrid combinations of them (1D-2D and 1D-3D) are investigated. It is observed that the most electro-conductive materials are formed when CGSs, CNTs or a hybrid combination of both are used, likely because of the lower defect density of CGSs and the higher aspect ratio of CNTs. The mechanical properties and piezoresistive sensitivity are higher for composites comprising CNTs or a 1D-2D hybrid combination of CNTs and FLGs. While the increased mechanical properties for these two groups of composites are attributed to the higher aspect ratio/lateral size, higher number of dangling bonds and functionalities, and higher specific surface area (for the case of FLGs) of their fillers, the increased piezoresistive sensitivity is explained in terms of their higher excluded volume within the composite., This work was supported by CONACYT grant number 220513 under the direction of Dr. FA. Support of the infrastructure (Raman-AFM equipment) acquired through CONACYT project No. 268595 is also appreciated. MALM thanks support from the MINECO project MAT2016-81138-R. MHR thanks the National Science Foundation China (NSFC Project 51672181), the National Science Center (Poland) for the financial support within the frame of the Opus program (Grant agreement 2015/19/B/ST5/03399). The authors thank Santiago Duarte (CICY) for SEM imaging, Martín Baas and Dr. Daniela Pacheco from the CICY’s Energy department for the BET measurements. Technical assistance of Dr. Jesús Kú for sample preparation and testing at CICY is appreciated

A very simple method of reductive amination, based on the Leuckart reaction, is reported. This method enables not only the reduction of graphite oxide but also results in reduced graphene oxide functionalized with amine groups, where the amination degree is 3.2 at. % as determined by XPS. The dominant nitrogen functional group was primary amine, but pyridines and lactam groups were also observed. It was found that the amino-functionalized reduced graphene oxide is a semi-metallic material because of the lack of band gap, unlike the graphite oxide that presented a band gap of 2.16 eV., This research was supported by the National Commission for Scientific and Technological Research (CONICYT), Chile, under Postdoctoral Fellowship No. 3170104 granted to H.A.-B.; the Vice Presidency of Research and Development (VID), Universidad de Chile, Chile, under Project Enlaces 2017 granted to M.Y.-P.; and the Spanish Ministry of Science and Innovation (MICINN), Spain, under Project MAT2013-48107-C3.

© 2020 by the authors., The technological demands imposed on dielectrics and electrical insulation materials are being increasing with the transition from traditional to smart grids. Epoxy resin/conductive polymer (CP) blends with high dielectric permittivity have been prepared by means of a straightforward methodology. Poly(3,4-ethylenedioxythiophene) (PEDOT) and polyaniline (PANI), doped with p-tosylate and ammonium peroxide sulfate (APS), respectively, were synthesized and blended with an epoxy matrix. The addition of 3 wt % of PEDOT and PANI results in permittivity values of 68.9 and 9.5, respectively at 0.1 Hz—1300 and 111 times higher than pure resin. Hence, PEDOT is more effective than PANI at improving the permittivity of the epoxy resin. Moreover, the material retains the electrical insulation of the resin and exhibits a slight increase in thermal conductivity., This research was funded by MINECO, grant number MAT2016-81138-R.

Nitrile rubber is considered the workhorse of the automotive rubber industry, thanks to its chemical resistance and mechanical performance. However, applications such as hoses, seals or gaskets are prone to damage, limiting their lifetime. In this work, carboxylated nitrile rubber (XNBR) was ionically crosslinked with zinc oxide (ZnO), forming ionic domains grouped into ionic clusters. These clusters have the advantage of being reversible under the application of an external stimulus such as temperature, conferring the material a certain self-healing capability and enabling a lifecycle extension. Ground tire rubber selectively modified by grafting of poly(acrylic acid) (gGTR), was added to XNBR-ZnO compounds with the aim of improving the healing properties of the rubber matrix. The incorporation of acid groups contributed to the formation of additional ionic clusters during the crosslinking process, resulting in a notorious increase in healing efficiency from 15% for the XNBR-ZnO to 70% for the XNBR-ZnO-gGTR compound. Chemical and mechanical resistance were also evaluated, showing that the addition of a waste material like gGTR keeps mechanical strength suitable for many applications; meanwhile, it does not deteriorate its resistance to aliphatic solvents such as motor oil and gasoline. These promising results open the path for developing sustainable rubber products with extended lifetime and applicable within the automotive industry., The authors acknowledge the Ministry of Science, Innovation and Universities of Spain for a research contract (PID2019-107501RB-I00) and M. Hernández Santana for a Ramón y Cajal contract (RYC-2017- 22837). S. Utrera-Barrios acknowledges the Spanish National Research Council (CSIC) for a predoctoral contract (PIE-202060E183). Reyes Verdugo Manzanares acknowledges the Community of Madrid for a research assistant contract (PEJ-2019-AI/IND-1635). All the authors also acknowledge Arlanxeo and Signus Ecovalor for kindly providing the XNBR and ground tire rubber, respectivel

The first example of the usefulness of titanium (IV) butoxide, as initiators for open air in-situ intercalative polymerization of ε-caprolactone (ε-CL) in the presence of organoclay is herein reported. The bionanocomposites based on poly(ε-caprolactone) (PCL) were prepared by in-situ Ring Opening Polymerization (ROP) of ε-caprolactone in the presence of different organomodified montmorillonite clay (ODA-MMT) loading (1, 3 and wt%). Structural, thermal and mechanical characterizations of the resulting bionanocomposites were investigated. The presence of the nanoclay increased PCL crystallinity, melting temperature and thermal stability, whereas some decrease in T was observed. TEM analyses confirmed the good dispersion of ODA-MMT with 1 and 3 wt% content into the PCL polymer as already asserted by XRD diffraction. Finally, the Young's modulus of the PCL nanocomposites was higher compared to the neat PCL, while a decrease of stress and strain at break for materials with different filler content was observed., Financial support for cooperative research came from the Hassan II Academy of Science and Technology of Morocco/CSIC-Spain (Project AH11STC-nano 2011 – 2012 and 2010MA003), the MESRSFC and CNRST of Morocco (PPR program), and the bilateral scientific committee programs of collaboration between Morocco and Tunisia (n 17/TM/20), and the Spanish Ministry of Science and Innovation (MICINN) through the project MAT2016-81138-R.

© 2020 by the authors., Itaconic acid (IA) is an organic acid produced by the fermentation of sugars with aspergillus. It has been identified as one of the top 12 building-block chemicals. Here, we report the use of IA as a possible substitute to petroleum-based compatibilizers in polymer composite. We applied this study to thermoplastic elastomers based on styrene copolymers, since they are commonly used in blends and composites. Poly(styrene-b-ethylene-butylene-b-styrene) (SEBS) was grafted with 2.6 wt.% of itaconic acid (SEBS-g-IA) prepared by a reactive melt-mixing process, and was subsequently used to prepare composites filled with BaTiO3.). IA was successfully grafted as demonstrated by FTIR and XRD. SEBS-g-IA composites presented better mechanical properties, achieving an increase of Young modulus up to 80% compared with the neat polymer. This was ascribed to better dispersion and compatibility with the filler. Additionally, SEBS-g-IA showed increased dielectric permittivity, i.e., showed increased polarity, which indicates that it could potentially be used as a modifier for specialized polymers., This research was supported by National Commission for Scientific and Technological Research (CONICYT), Chile, under Postdoctoral fellowship FONDECYT N° 3,170,104 granted to H. Aguilar-Bolados. R. Quijada, H Aguilar-Bolados and M ¡ Yazdani-Pedram acknowledge the financial support from CONICYT (FONDECYT N° 1191642). R. Verdejo and M. A. Lopez-¡ Manchado acknowledge the financial support from the MINECO (grant number MAT2016-81138-R).

The electrical, mechanical and piezoresistive responses of vinyl ester nanocomposites made of two types of multilayer graphene sheets (GSs) and multiwall carbon nanotube hybrid fillers at different relative concentrations is presented. Two types of GSs are used in order to evaluate the role of their physicochemical properties. The best mechanical properties were achieved with hybrids at 75% relative concentration of GSs. Collaborative effects were also observed in the electrical conductivity of the hybrids at this relative concentration. The flexural piezoresistive response yielded low sensitivity (with both, positive and negative gage factors) at the compression side of the flexural coupon. On the contrary, the tensile side of the coupon always presented positive resistance changes and significantly higher piezoresistive sensitivity. The highest piezoresistive sensitivity was found for hybrid materials with 75% relative concentration of GSs, using the graphenic sheets with larger lateral dimensions and higher structural quality (lower Raman I/I ratio)., This work was sponsored by CONACYT project No. 2262. CS Acknowledges CONACYT scholarship 240300 for his Doctoral studies. Support of the infrastructure acquired through CONACYT project No. 268595 (CICY) as well as the LANNBIO facilities at CINVESTAV-M�erida under the supervision of Dr. Patricia Quintana are kindly acknowledged. Raquel Verdejo and Miguel Angel Lopez Manchado acknowledge the Ministry of Science, Innovation and Universities in Spain for project MAT2016-81138-R. Technical assistance of Dr. Alejandro May Pat is highly appreciated. Authors also wish to acknowledge assistance of Jorge Ocampo Bello for his dedicated contribution with the electrical instrumentation, as well as that of Santiago Duarte Aranda and Rossana Faride Vargas Coronado for SEM. Technical assistance of Jos�e M. Baas Lopez for BET measurements as well as facilities provided by Dr. Daniela Pacheco for using the adsorption isotherm equipment acquired through the SENER-CONACYT energetic sustainability project No. 254667 is also appreciated.

The development of self-healing rubbers is currently under investigation as a strategy to promote their reuse and, hence, reduce their waste. However, autonomous, multicycle self-healing rubbers with good mechanical properties have so far proven difficult to achieve. Here, mechanically robust composites based on epoxidized natural rubber (ENR) and thermally reduced graphene oxide (TRGO) were successfully designed and prepared with a high healing efficiency of up to 85% at room temperature without applying external stimuli. The incorporation of TRGO not only improves the mechanical performance in more than 100% in relation to pristine ENR but also promotes the hydrogen bonding interactions with the rubber. This leads to a homogenous dispersion of TRGO within the ENR matrix, which further increases its self-healing capability., The authors acknowledge the Ministry of Science, Innovation and Universities of Spain for a research contract (MAT2015- 73392-JIN) and M. Hernández Santana for a Ramón y Cajal contract (RYC-2017-22837).

Elastomers have found myriad uses in our everyday life and, as technology improves, their applications have encountered ever more extreme conditions in which elastomer nanocomposites have already proved their value. However, there are countless jobs where solid rubbers are often unable to perform effectively. For these, foamed rubbers are selected because of their excellent strength-to-weight ratio, impact, and sound absorbing capabilities, among others. This chapter reviews progress to date in the development of elastomeric nanocomposites foams. In particular, we focus our attention on ethylene-propylene-diene terpolymer (EPDM) and silicone foams since they provide an overview of foaming processes, and they are both used in extreme environmental conditions.

Nowadays, the different types of nano-carbons such as carbon nanotubes, graphene and nano-diamond are considered as revolutionary materials, since they present outstanding electrical, thermal and mechanical properties. The expansion of the knowledge related to their syntheses and their unique properties has favored important advances in the development of new type of elastomer composites. Elastomer composites with enhanced electrical and thermal properties are possible to obtain by using low amounts of these nano-carbon based materials as filler in elastomer matrices. On the other hand, the wide range of commercially available rubbers and thermoplastic elastomers provides a number of possibilities in order to obtain tailor-made elastomeric materials. Herein, concise information concerning the preparation methods, properties and application of elastomer composites filled with nano-carbon based materials is presented. The role of nano-carbon based materials in the transport properties of resulting elastomer composites is emphasized, which is attributed to the formation of a percolation network of filler through the elastomeric matrix. Likewise, the influence of the viscoelastic properties and the behavior of elastomers in presence of oil and organic solvents on sensing properties of electrically conducting elastomer composites filled with nano-carbon based materials is discussed.

© The Author(s)., Owing to their high strength and stiffness, thermal and environmental stability, lower shrinkage, and water resistance, epoxy resins have been the preferred matrix for the development of syntactic foams using hollow glass microspheres. Although these foams are exploited in multiple applications, one of their issues is the possibility of breakage of the glass hollow microspheres during processing. Here, we present a straightforward and single-step foaming protocol using expandable polymeric microspheres based on the well-established compression molding process. We demonstrate the viability of the protocol producing two sets of nanocomposite foams filled with carbon-based nanoparticles with improved transport properties., The authors gratefully acknowledge the financial support of MINECO, through the project MAT2016-81138-R.

Conventional carbon fiber-reinforced plastics (CFRP) have extensively been used as structural elements in a myriad of sectors due to their superior mechanical properties, low weight and ease of processing. However, the relatively weak compression and interlaminar properties of these composites limit their applications. Interest is, therefore, growing in the development of hierarchical or multiscale composites, in which, a nanoscale filler reinforcement is utilized to alleviate the existing limitations associated with the matrix-dominated properties. In this work, the fabrication and characterization of hierarchical composites are analyzed through the inclusion of graphene to conventional CFRP by vacuum-assisted resin infusion molding., This research was funded by the Spanish Ministerio de Economía y Competitividad (MINECO), grant number MAT2016-81138-R, We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Multifunctional elastomer nanocomposites have been applied in several high-tech fields. The design of materials with tailored properties capable of tuning their performance is a topical challenge. Here, we demonstrate that it is possible to modulate the mechanical and transport properties of silicone rubber nanocomposites by controlling the structure, chemical composition and morphology of the graphene material. Intrinsic graphene properties, such as remaining oxygen groups, specific surface area, and aspect ratio, among others, have a profound effect on the final properties of the nanocomposite. Thus, the thermal conductivity benefits from larger filler size and high aromatic restoration. Whereas mechanical properties and electrical conductivity require a proper balance between filler/polymer matrix interaction and a partial aromatic restoration., This research was funded by MINECO, grant number MAT2016-81138-R. R.S. thanks to MINECO for the Predoctoral grant BES-2014-070802, We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Self-healing polymers are currently receiving widespread attention as a strategy to extend the product's lifetime. Thermosetting polymers, particularly epoxies, are the most studied materials due to their uses as coatings, adhesives, or structural elements, among others. Scarcely noticed studies have reported the inherent healing capacity in arrested cracks of unmodified epoxy resins. Here, we present that healing can also occur in non-arrested cracks and its mechanism is a combination of an already described physical phenomenon and a chemical phenomenon, due to the formation of reversible hydrogen bonds. Here, we exemplify the need for fixing a set of standard testing conditions and propose they require complete and non-arrested cracks to do so.

To overcome the limitation of traditional photoluminescent materials, a cost-effective photoluminescence polymer was synthesized by a simple and one-step technique using benzyl alcohol as the starting material and aqueous sulfuric acid as the catalyst. The synthesized photoluminescent polymer showed photoluminescence properties independent of the excitation wavelength together with high thermal stability and excellent mechanical properties. The synthesized photoluminescent polymer was incorporated into different polymers viz. thermoplastic as well as thermoset polymers by melt and solution processes, respectively, to achieve photoluminescent polymer blends. The thermal, mechanical, and photoluminescent properties of the fabricated blends were improved or remained almost the same with the photoluminescence polymer contents, strongly proving that the photoluminescent polymer was well dispersed in the polymeric matrix. The potential applications of the photoluminescence polymer blends were investigated for 3D printing and a fluorescent ink. The study paves a way for the development of photoluminescent materials for various applications., ST thanks the Ministry of Science, Innovation and Universities of Spain for a Juan de la Cierva contract (FCJI-2017-34621).

Carbon nanofibres (CNFs) and graphite flake microparticles were added to thermoplastic polystyrene polymer with the aim of making new conductive blends suitable for 3D-printing. Various polymer/carbon blends were evaluated for suitability as printable, electroactive material. An electrically conducting polystyrene composite was developed and used with commercially available polystyrene (HIPS) to manufacture electrodes suitable for electrochemical experiments. Electrodes were produced and evaluated for cyclic voltammetry of aqueous 1, 1’-ferrocenedimethanol and differential pulse voltammetry detection of aqueous Pb2+ via anodic stripping. A polystyrene/CNF/graphite (80/10/10 wt%) composite provides good conductivity and a stable electrochemical interface with well-defined active geometric surface area. The printed electrodes form a stable interface to the polystyrene shell, give good signal to background voltammetric responses, and are reusable after polishing.

Hybrid ethylene-propylene-diene-monomer (EPDM) nanocomposite foams were produced via compression molding with enhanced electromagnetic wave absorption efficiency. The hybrid filler, consisting of 20 phr ferroelectric barium titanate (BT) and various loading fractions of multi-wall carbon nanotubes (MWCNTs), synergistically increased the electromagnetic (EM) wave absorption characteristics of the EPDM foam. Accordingly, while the EPDM foam filled with 20 phr BT was transparent to the EM wave within the frequency range of 8.2&ndash, 12.4 GHz (X-band), the hybrid EPDM nanocomposite foam loaded with 20 phr BT and 10 phr MWCNTs presented a total shielding effectiveness (SE) of ~22.3 dB compared to ~16.0 dB of the MWCNTs (10 phr). This synergistic effect is suggested to be due to the segregation of MWCNT networks within the cellular structure of EPDM, resulting in enhanced electrical conductivity, and also high dielectric permittivity of the foam imparted by the BT particles. Moreover, the total SE of the BT/MWCNTs loaded foam samples remained almost unchanged when subjected to repeated bending due to the elastic recovery behavior of the crosslinked EPDM foamed nanocomposites.