High performance natural rubber/thermally reduced graphite oxide nanocomposites by latex technology

The latex technology is an innovative alternative for the preparation of composites of natural rubber (NR) and thermally reduced graphite oxide (TRGO). To achieve an improvement of material properties is indispensable to prepare stable suspensions of TRGO. In this work the influence of two surfactants, such as sodium dodecyl sulfate (SDS), as ionic, and Pluronic F 127 as non-ionic surfactant, on the dispersion of TRGO in NR latex and the mechanical and physical properties of the composites were studied. The results showed that the SDS surfactant is ideal for preparing latex NR/TRGO nanocomposite. An optimum dispersion of the nanoparticles in the polymer matrix was achieved in the presence of SDS, as reflected in a considerable improvement of the physical and mechanical properties of the material. Thus, the nanocomposites with 3 phr of TRGO exhibited an improvement of nearly 400% in the maximum strength and an electrical percolation threshold with values around 10-6 S/cm, above the static limit.Peer Reviewe

Electrical Properties of Poly(Monomethyl Itaconate)/Few-Layer Functionalized Graphene Oxide/Lithium Ion Nanocomposites

Poly(monomethyl itaconate) is outstanding because it is a glassy and dielectric polymer obtained from sustainable feedstock. Consequently, the study of the properties of its nanocomposites has gained importance. Herein, the electrical properties of nanocomposites based on poly(monomethyl itaconate) and functionalized few-layer graphene oxide (FGO) in the presence and absence of lithium ions (Li+) are studied. Not only did the electrical conductivities of the nanocomposites present values as high as 10−5 Scm−1, but also the dielectric permittivity of nanocomposites with (FGO) content lower than the percolation threshold was twice that of the pristine polymer, without presenting a drastic increase of the loss tangent. By contrast, nanocomposites containing Li+ ions presented significant increases of the permittivity with concomitant increases of the loss tangent. Moreover, it was determined that the presence of Li+ ions influenced the charge transport in the composites because of its ionic nature

Effect of the morphology of thermally reduced graphite oxide on the mechanical and electrical properties of natural rubber nanocomposites

Graphene materials often are obtained through thermal reduction of graphite oxide. This is due to the fact that other synthesis methods are more difficult and generally render lower yield. The structure and morphology of these graphene materials could affect their performance in different applications. Herein, thermally reduced graphite oxide (TRGO) was obtained from thermal reduction of graphite oxide prepared by using the methods reported by Brodie and Hummers. The oxidation method greatly affects the structure and morphology of the resulting TRGO. TRGO obtained by the Brodie's method generates a morphology comprised of rather exfoliated galleries while that obtained by the Hummers method presents randomly distributed sheets. The influence of structural differences on the dispersion of TRGOs in natural rubber latex (NR) and on the resulting mechanical and electrical properties of the TRGO/NR nanocomposites is studied. The TRGO prepared by the Brodie's method (TRGO-B) showed a more homogeneous dispersion in the polymer-matrix, rendering enhanced mechanical and electrical properties of their nanocomposites. TRGO-B/NR nanocomposites showed higher electrical conductivity, which is attributed to the formation of an electrically conducting filler network through the polymer-matrix. This is consequence of the morphology presented by TRGO produced by the Brodie's method.This research was supported by National Commission for Scientific and Technological Research (CONICYT)-Chile project FONDECYT 1131139, the Spanish Ministry of Science and Innovation (MICINN) e Spain, under Project MAT 2010-1874. Moreover, FA and MYP acknowledge additional support for their collaboration from CONACYT-Mexico, Project CIAM No 188089 and CONICYT-Chile, Project No 120003Peer Reviewe

Removal of surfactant from nanocomposites films based on thermally reduced graphene oxide and natural rubber

© The Author(s).Electrically conducting elastomer composites based on natural rubber and reduced graphene oxide (rGO) is reported. These composites were prepared by a latex method and an easy washing process. The latex method consists of the mixing of an aqueous suspension of rGO, stabilized by sodium dodecyl sulfate and pre-vulcanized natural rubber, followed by solvent casting. The percolation threshold of composites was estimated at 1.54 wt.% of rGO. The washing process allowed elimination of the surfactant completely from nanocomposites. The absence of surfactant in nanocomposites was demonstrated by Raman spectroscopy and dynamo-mechanical analysis. The surfactant-free nanocomposites showed improved mechanical and electrical properties.Miguel Lopez-Manchado thanks the support from MINECO (grant number MAT2016-81138-R).Peer reviewe

Influence of the NiII/MnIIratio on the physical properties of heterometallic Ni2xMn(2−2x)P2S6phases and potassium intercalates K0.8Ni2xMn(1.6−2x)P2S6·2H2O

International audienceBimetallic Ni2xMn2−2xP2S6phases, where 2X= 0.4 (Ni0.4), 0.8 (Ni0.8) and 1.2 (Ni1.2), were synthesized by a microwave assisted method, starting from the corresponding potassium intercalates K0.8Mn1.6P2S6·2H2O, K0.8Ni0.4Mn1.2P2S6·2H2O, and K0.8Ni0.8Mn0.8P2S6·2H2O. The magnetic, optical, and electrical properties were recorded, in order to visualize the influence of the secondary nickel(ii) ions on the physical properties of the pristine Mn2P2S6phase. Both dc susceptibility and EPR data show that the antiferromagnetic interactions are attenuated in the layers of the bimetallic phases, while the critical temperature remains constant (ca.80 K) for all the bimetallic phases, similar to that of Mn2P2S6. Conversely, the absorption edge of the solid state UV-visible spectra shifted to lower energies as the percentage of nickel(ii) increased, tending to that of the band gap value of the pristine Ni2P2S6phase. Moreover, the electric conductivity ofNi0.4was similar to that of the pristine Mn2P2S6phase, while that ofNi0.8andNi1.2approached the values of the electric conductivity of the pristine Ni2P2S6phase. On the other hand, the potassium intercalates K0.8Mn1.6P2S6·2H2O and K0.8Ni0.4Mn1.2P2S6·2H2O showed magnetization at 16 K, the latter being much weaker as compared to the first. The detrimental effect of the secondary nickel(ii) ions in the layers of the bimetallic phases became evident for K0.8Ni0.8Mn0.8P2S6·2H2O, where the magnetization at low temperatures was not observed. The absorption edge shifted to higher energy values for K0.8Mn1.6P2S6·2H2O and K0.8Ni0.4Mn1.2P2S6·2H2O, as compared to Mn2P2S6andNi0.4, respectively, but the value remained close to that of Ni2P2S6for K0.8Ni0.8Mn0.8P2S6·2H2O. InNi0.8andNi0.4, the electrical conductivity at low frequencies stems from polarization processes such as Maxwell/Wagner/Sillars electrode polarization. Moreover, an additional polarization process is observed in the intercalates because K+ions in the interlayer act as charge transport carriers. Consequently, the interacalates present higher electrical conductivity compared with the pristine Mn2P2S6phase, by a factor ofca.102 © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

Influence of the morphology of carbon nanostructures on the piezoresistivity of hybrid natural rubber nanocomposites

Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.compositesb.2016.10.057The electrical and piezoresistive response of hybrid nanocomposites comprising a combination of few-layer thermally reduced graphite oxide (TRGO) and multiwall carbon nanotubes (MWCNTs) mixed with natural rubber is reported. The influence of the structure and morphology of the TRGO, and MWCNTs on the electrical and piezoresistive response of these nanocomposites is examined. All composites showed a different nonlinear piezoresistive behavior depending on the nanostructure (or combination) used. The hybrid combination of 2 wt.% TRGOs and 2 wt.% MWCNTs increased the electrical conductivity of the polymer 13 orders of magnitude, change that was not possible to achieve by using only TRGOs. This outcome can be attributed to the formation of a highly interconnected percolation network, and indicates that the morphology of the nanostructure plays a paramount role in the electrical and piezoresistive behavior of the nanocomposite. Platelet-type carbon nanostructures of the graphene family used as fillers for polymer composites may not outperform the electrical behavior of rod-type ones such as MWCNTs, but a tailored combination of both may be beneficial for the development of piezoresistive-based sensors.This research was supported by National Commission for Scientific and Technological Research (CONICYT), Chile projects FONDECYT 1131139, CIAM No. 1200013 and the Spanish Ministry of Science and Innovation (MICINN) e Spain, under project MAT2013- 48107-C3. FA and AM acknowledge support from projects CONACYT No. 220513 and CIAM No. 188089 for their contribution.Peer Reviewe

Electro-mechanical actuation performance of SEBS/PU blends

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 201660I032Peer Reviewe

Physical properties of new ordered bimetallic phases MCdPS (M = Zn, Ni, Co, Mn)

International audienceFour bimetallic phases of the thiophosphate family have been synthesized by the cationic exchange reaction using a freshly prepared K0.5Cd0.75PS3 precursor phase and methanolic solutions of nitrates of the divalent cations Zn II , Ni II , Co II , and Mn II. All the materials were characterized by FTIR, PXRD, SEM-EDXS and (in the case of the diamagnetic compounds) by solid state NMR. For the K0.5Cd0.75PS3 precursor, the X-ray powder diffraction data suggest a modification of the structure, while solid state NMR results confirm that this phase possesses an ordered arrangement of Cd vacancies. The cationic exchange reaction achieves a complete removal of potassium ions (no potassium detected by SEM-EDXS) and re-occupation of the vacancies by divalent cations. Therefore, the obtained compounds have an average composition of M0.25Cd0.75PS3 (M = Zn II , Ni II , Co II , Mn II) and possess an ordered distribution of the substituent cations. Even with the paramagnetic substitution level of 25%, antiferromagnetic behaviour is present in the phases with Mn II , Co II and Ni II , as evidenced by dc susceptibility and in the case of the Mn II substituted phase by EPR. The cooperative magnetic interactions confirm the conclusion that the paramagnetic ions adopt an ordered arrangement. The analysis by broad band impedance spectroscopy allows to attribute the conductivity in these materials to charge movements in the layers due to the difference in electronegativity of the metal ions. Zn0.25Cd0.75PS3 is the phase that shows the highest conductivity values. Finally, the band gap energies of the bimetallic phases tend to be lower than those of the single-metal phases, probably due to an overlap of the band structures

Effect of terbium(III) species on the structure and physical properties of polyurethane (TPU)

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)Peer reviewe