NR Compounds Research Articles

Utilization of Reactive Nitrogen Compounds for Nitrogen Circular Economy.

Nitrogen oxides (NOx) should be purified according to environmental regulations, being restricted increasingly year by year. A wide variety of denitration technologies, such as selective catalytic reduction (SCR) of NOx to nitrogen (N2) and NOx storage reduction (NSR) to N2 by injecting reducing agents like ammonia (NH3), has so far been developed practically. Sophisticated catalytic approaches are perhaps mandatory for the sustainability in energy including complete purification of NOx. As one of the solutions to overcome problems for environment and resource simultaneously, this concept article focuses on the utilization of reactive nitrogen (Nr) compounds, mainly NOx, for encouraging an opening to consider nitrogen circular economy. For the recycling of NOx via NH3, a challenging but rational catalytic technology can be proposed by an alternate switching the inlet gas between NOx containing oxidative gas and H2 containing reductive one without an operation to change the reaction temperature. Considering the reactivity of NOx higher than that of N2, this kind of NOx to NH3 (NTA) process is promising for synthesizing NH3, being valuable not only as fertilizer but also as fuel in near future.

Organic radicals stabilization in natural rubber: Discerning the influence of thermo-oxidation using chemically modified or unmodified lignin as antioxidant

We have implemented a lignin compatibilization strategy through silylation and elaborated NR compounds with lignin and silylated lignin. Then, the lignin’s contribution to the preservation of physico-mechanical properties and stability of the materials obtained against thermo-oxidation was studied. Thus, our work considered the indirect study of the antioxidant activity on NR compounds by determining the physico-mechanical properties before and after accelerated thermo-oxidative aging, which allowed us to determine that the increase in crosslinking density during the initial hours of accelerated aging was the main observed cause associated with a higher tensile strength retention rate (TSRR: 13.4 %) in NR compound with 5 phr of lignin (CL5) versus a TSRR: 4.7 % for the compound with 5 phr of silylated lignin (CL5Si1). On the other hand, the direct study of the antioxidant capacity by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) using oxygen atmosphere indicated greater thermal stability in NR compounds when lignin is not silylated. The maximum degradation temperature for the CL5 compound was 341.6 °C, while for the CL5Si1 compound it was 328.6 °C. The oxidation induction temperature (OITtemp) in the CL5 compound was 190.9 °C with a peak at 221.0 °C, while for CL5Si1 it was 170.3 °C with a peak at 194.1 °C, indicating again that unsilylated lignin is more suitable as an antioxidant. Finally, through Electron Paramagnetic Resonance (EPR), we determined that the radical quenching effect due to the presence of lignin was significant as the lignin content increases, with a reduction in radical presence close to 50 % compared to a reference compound without lignin.

Degradation during Mixing of Silica-Reinforced Natural Rubber Compounds.

The optimal mixing conditions for silica-filled NR compounds dictate the need to proceed at a high temperature, i.e., 150 °C, to achieve a sufficient degree of silanization. On the other hand, natural rubber is prone to degradation due to mechanical shear and thermal effects during mixing, particularly at long exposure times. The present work investigates NR rubber degradation during mixing in relation to prolonged silanization times. The Mooney viscosity and stress relaxation rates, bound rubber content, storage modulus (G'), and delta δ were investigated to indicate the changes in the elastic/viscous responses of NR molecules related to rubber degradation, molecular chain modifications, and premature crosslinking/interaction. In Gum NR (unfilled), an increase in the viscous response with increasing mixing times indicates a major chain scission that causes a decreased molecular weight and risen chain mobility. For silica-filled NR, an initial decrease in the Mooney viscosity with increasing silanization time is attributed to the chain scission first, but thereafter the effect of the degradation is counterbalanced by a sufficient silanization/coupling reaction which leads to leveling off of the viscous response. Finally, the higher viscous response due to degradation leads to the deterioration of the mechanical properties and rolling resistance performance of tire treads made from such silica-filled NR, particularly when the silanization time exceeds 495 s.

Forest–atmosphere exchange of reactive nitrogen in a remote region – Part II: Modeling annual budgets

Abstract. To monitor the effect of current nitrogen emissions and mitigation strategies, total (wet + dry) atmospheric nitrogen deposition to forests is commonly estimated using chemical transport models or canopy budget models in combination with throughfall measurements. Since flux measurements of reactive nitrogen (Nr) compounds are scarce, dry deposition process descriptions as well as the calculated flux estimates and annual budgets are subject to considerable uncertainties. In this study, we compared four different approaches to quantify annual dry deposition budgets of total reactive nitrogen (ΣNr) at a mixed forest site situated in the Bavarian Forest National Park, Germany. Dry deposition budgets were quantified based on (I) 2.5 years of eddy covariance flux measurements with the Total Reactive Atmospheric Nitrogen Converter (TRANC); (II) an in situ application of the bidirectional inferential flux model DEPAC (Deposition of Acidifying Compounds), here called DEPAC-1D; (III) a simulation with the chemical transport model LOTOS-EUROS (Long-Term Ozone Simulation – European Operational Smog) v2.0, using DEPAC as dry deposition module; and (IV) a canopy budget technique (CBT). Averaged annual ΣNr dry deposition estimates determined from TRANC measurements were 4.7 ± 0.2 and 4.3 ± 0.4 kg N ha−1 a−1, depending on the gap-filling approach. DEPAC-1D-modeled dry deposition, using concentrations and meteorological drivers measured at the site, was 5.8 ± 0.1 kg N ha−1 a−1. In comparison to TRANC fluxes, DEPAC-1D estimates were systematically higher during summer and in close agreement in winter. Modeled ΣNr deposition velocities (vd) of DEPAC-1D were found to increase with lower temperatures and higher relative humidity and in the presence of wet leaf surfaces, particularly from May to September. This observation was contrary to TRANC-observed fluxes. LOTOS-EUROS-modeled annual dry deposition was 6.5 ± 0.3 kg N ha−1 a−1 for the site-specific weighting of land-use classes within the site's grid cell. LOTOS-EUROS showed substantial discrepancies to measured ΣNr deposition during spring and autumn, which was related to an overestimation of ammonia (NH3) concentrations by a factor of 2 to 3 compared to measured values as a consequence of a mismatch between gridded input NH3 emissions and the site's actual (rather low) pollution climate. According to LOTOS-EUROS predictions, ammonia contributed most to modeled input ΣNr concentrations, whereas measurements showed NOx as the prevailing compound in ΣNr concentrations. Annual deposition estimates from measurements and modeling were in the range of minimum and maximum estimates determined from CBT being at 3.8 ± 0.5 and 6.7 ± 0.3 kg N ha−1 a−1, respectively. By adding locally measured wet-only deposition, we estimated an annual total nitrogen deposition input between 11.5 and 14.8 kg N ha−1 a−1, which is within the critical load ranges proposed for deciduous and coniferous forests.

From South Asia to the world: embracing the challenge of global sustainable nitrogen management

From South Asia to the world: embracing the challenge of global sustainable nitrogen management

Influence of the Order of Incorporation of Sulfur in the Mechanical Properties of Vulcanized Nr Compounds

The objective of this work was to evaluate the influence of the order of sulfur addition on the mechanical properties of vulcanized natural rubber compounds. The addition of sulfur was carried out by two methodologies: (I) sulfur was added at the beginning of the mastication process, and (II) sulfur was added at the end of the mixing process. The compounds were obtained in open cylinder, and vulcanized in a press at 150°C. The vulcanization parameters were determined by rheometry, where as the mechanical properties were evaluated by testing samples for their tensile strength, tear strength, resilience, and Shore-A hardness. The dimensional stability of the vulcanized samples was also evaluated experimentally, by comparing specimens not heat-treated to those submitted to 100°C for 4 hours. Comparing the results of method (I) to method (II), the results, indicate that the addition of sulfur at the beginning of the mastication process (method I) yielded increases of 20 and 11% in tensile strength and tear strength, respectively, followed by a 9% increase in hardness, and 6% in resilience, without significant losses in maximum elongation. The dimensional stability test showed a reduction of 75% in the contraction for the vulcanized samples which had sulfur addition at the beginning of the mastication process of the unvulcanized NR rubber.

The nitrogen budget of laboratory-simulated western US wildfires during the FIREX 2016 Fire Lab study

Abstract. Reactive nitrogen (Nr, defined as all nitrogen-containing compounds except for N2 and N2O) is one of the most important classes of compounds emitted from wildfire, as Nr impacts both atmospheric oxidation processes and particle formation chemistry. In addition, several Nr compounds can contribute to health impacts from wildfires. Understanding the impacts of wildfire on the atmosphere requires a thorough description of Nr emissions. Total reactive nitrogen was measured by catalytic conversion to NO and detection by NO–O3 chemiluminescence together with individual Nr species during a series of laboratory fires of fuels characteristic of western US wildfires, conducted as part of the FIREX Fire Lab 2016 study. Data from 75 stack fires were analyzed to examine the systematics of nitrogen emissions. The measured Nr ∕ total-carbon ratios averaged 0.37 % for fuels characteristic of western North America, and these gas-phase emissions were compared with fuel and residue N∕C ratios and mass to estimate that a mean (±SD) of 0.68 (±0.14) of fuel nitrogen was emitted as N2 and N2O. The Nr detected as speciated individual compounds included the following: nitric oxide (NO), nitrogen dioxide (NO2), nitrous acid (HONO), isocyanic acid (HNCO), hydrogen cyanide (HCN), ammonia (NH3), and 44 nitrogen-containing volatile organic compounds (NVOCs). The sum of these measured individual Nr compounds averaged 84.8 (±9.8) % relative to the total Nr, and much of the 15.2 % “unaccounted” Nr is expected to be particle-bound species, not included in this analysis. A number of key species, e.g., HNCO, HCN, and HONO, were confirmed not to correlate with only flaming or with only smoldering combustion when using modified combustion efficiency, MCE=CO2/(CO+CO2), as a rough indicator. However, the systematic variations in the abundance of these species relative to other nitrogen-containing species were successfully modeled using positive matrix factorization (PMF). Three distinct factors were found for the emissions from combined coniferous fuels: a combustion factor (Comb-N) (800–1200 ∘C) with emissions of the inorganic compounds NO, NO2, and HONO, and a minor contribution from organic nitro compounds (R-NO2); a high-temperature pyrolysis factor (HT-N) (500–800 ∘C) with emissions of HNCO, HCN, and nitriles; and a low-temperature pyrolysis factor (LT-N) (<500 ∘C) with mostly ammonia and NVOCs. The temperature ranges specified are based on known combustion and pyrolysis chemistry considerations. The mix of emissions in the PMF factors from chaparral fuels (manzanita and chamise) had a slightly different composition: the Comb-N factor was also mostly NO, with small amounts of HNCO, HONO, and NH3; the HT-N factor was dominated by NO2 and had HONO, HCN, and HNCO; and the LT-N factor was mostly NH3 with a slight amount of NO contributing. In both cases, the Comb-N factor correlated best with CO2 emission, while the HT-N factors from coniferous fuels correlated closely with the high-temperature VOC factors recently reported by Sekimoto et al. (2018), and the LT-N had some correspondence to the LT-VOC factors. As a consequence, CO2 is recommended as a marker for combustion Nr emissions, HCN is recommended as a marker for HT-N emissions, and the family NH3 ∕ particle ammonium is recommended as a marker for LT-N emissions.

Silica‐filled NR compounds prepared by dry and wet masterbatches with different mixing times

AbstractSilica‐filled NR compounds are prepared by mixing rubber with organic‐networked silica and additives such as curatives, processing and coupling agents, and stabilizer in a dried state (dry‐mixed NR, DNR) and mixing a silica‐NR wet masterbatch prepared in liquid phase with the additives (wet‐mixed NR, WNR). The effects of mixing method and time of DNR and WNR compounds on their cure, process, tensile, and dynamic properties are investigated. The mixing of DNR crushes silica aggregates to smaller ones, but also forms occasionally large ones, while the mixing of WNR produces small aggregates without forming larger ones because silica aggregates are already covered with rubber. The high silica dispersion, suppressed silica aggregation, low Payne effect, and low‐loss modulus of the WNR compounds prepared by mixing for a sufficient time result in their low viscosity, high scorch safety, and low rolling resistance without sacrificing other rubber properties.

A review of measurements of air-surface exchange of reactive nitrogen in natural ecosystems across North America

This review summarizes the state of the science of measurements of dry deposition of reactive nitrogen (Nr) compounds in North America, beginning with current understanding of the importance of dry deposition at the U.S. continental scale followed by a review of micrometeorological flux measurement methods. Measurements of Nr air-surface exchange in natural ecosystems of North America are then summarized, focusing on the U.S. and Canada. Drawing on this synthesis, research needed to address the incompleteness of dry deposition budgets, more fully characterize temporal and geographical variability of fluxes, and better understand air-surface exchange processes is identified.Our assessment points to several data and knowledge gaps that must be addressed to advance dry deposition budgets and air-surface exchange modeling for North American ecosystems. For example, recent studies of particulate (NO3−) and gaseous (NOx, HONO, peroxy nitrates) oxidized N fluxes challenge the fundamental framework of unidirectional flux from the atmosphere to the surface employed in most deposition models. Measurements in forest ecosystems document the importance of in-canopy chemical processes in regulating the net flux between the atmosphere and biosphere, which can result in net loss from the canopy. These results emphasize the need for studies to quantify within- and near-canopy sources and sinks of the full suite of components of the Nr chemical system under study (e.g., NOy or HNO3-NH3-NH4NO3). With respect to specific ecosystems and geographical locations, additional flux measurements are needed particularly in agricultural regions (NH3), coastal zones (NO3− and organic N), and arid ecosystems and along urban to rural gradients (NO2). Measurements that investigate non-stomatal exchange processes (e.g., deposition to wet surfaces) and the biogeochemical drivers of bidirectional exchange (e.g., NH3) are considered high priority. Establishment of long-term sites for process level measurements of reactive chemical fluxes should be viewed as a high priority long-term endeavor of the atmospheric chemistry and ecological communities.

Silanization Efficiency of Silica/Silane in Dependence of Amines in Natural Rubber-based Tire Compounds

Silica-silane technology for low rolling resistance tire compounds requires efficient bridging between the silica surface and rubber molecules through silanization and coupling reactions. The presence of diphenylguanidine (DPG) as secondary vulcanization accelerator is also needed to catalyze the silanization reaction between the alkoxy groups of silane coupling agents and the silanol groups on the silica surface. However, DPG can liberate toxic aniline under high mixing temperatures and therefore safer alternatives are required. This study investigates the influence of amines with different structures, i.e. hexylamine (HEX), octadecylamine (OCT), cyclohexylamine (CYC) and dicyclohexylamine (DIC) on the primary silanization reaction rate constant in a model system, and on interfacial compatibility of practical silica-reinforced NR compounds. Compared to the system without, the amines clearly increase the reaction rate constant for which linear aliphatic amines work better than cyclic ones. This is due to better accessibility of the amines towards the silica surface, in agreement with the values of Payne effect as observed in the rubber compounds, except for the OCT case. The lowest Payne effect of the OCT-containing rubber compound is attributed to the additional shielding effect obtained from the long alkyl-chain that leads to more hydrophobicity, resulting in good physical interaction between silica and rubber. The presence of all amines improves the cure properties in which the linear aliphatic amines give shorter cure times than the cyclic aliphatic ones. As a result of good interfacial compatibility, the OCT-containing compound which shows lowest filler-filler interaction gives good mechanical properties that are closest to the reference compound with DPG.

Application of fractional time derivatives in modeling the finite deformation viscoelastic behavior of carbon-black filled NR and SBR

Mechanical behavior of elastomers includes nonlinear and time dependent phenomena such as creep and relaxation where due to low stiffness, these materials usually undergo large deformations. The classical approaches of viscoelasticity,i.e. differential constitutive models and hereditary integrals have been widely used to model the viscoelastic behavior of these materials even at finite deformations. However, from the viewpoint of computational analysis, the integral based methods are often time and memory consuming and the differential methods usually need a large number of material parameters whose identification is a real challenge. A potential solution is to introduce fractional order derivatives instead of regular differential operators in the standard spring-dashpot mechanical models which remarkably reduces the number of required material parameters. In the present paper, relaxation behavior of NR and SBR is investigated in finite strains. Due to the remarkable effects of filler particles and deformation rate on the mechanical properties of elastomers, compounds of each material with different amounts of filler content are investigated at two strain rates. A main interest is to examine efficiency of the fractional derivative models in modeling the finite deformation relaxation behavior of elastomers with different filler contents. The other goal is to investigate the effect of loading rate on the obtained model parameters. It is observed that, the fractional Maxwell chain is able to well fit the stress relaxation response of all compounds with only three parameters. Analyzing the obtained parameters and the experimental data, it is concluded that, order of the associated Maxwell element is not much affected with the filler content. Seemingly, it depends on the matrix material and more noticeably on the deformation rate. Moreover, as much as the deformation rate, the associated relaxation time is low. Decrease of the relaxation time with the deformation rate is more evident for compounds of SBR compared with NR compounds.

Effects of Cashew Nut Shell Liquid and Its Decarboxylated Form on the Properties of Natural Rubber

Effects of addition of raw cashew nut shell liquid (CNSL) or its decarboxylated form (D-CNSL or cardanol) on curing characteristics, physical properties and temperature scanned stress relaxation were investigated. The study revealed that the CNSL containing high anacardic acid concentration acts as an acid activator and strongly affects curing behavior of NR compounds. The effective curing rate and curing efficiency, i.e., torque difference, crosslink density, and activation energy for curing, clearly increased with 2–5 phr of CNSL. Furthermore, physical properties and thermal stability also improved. However, when the acidity was removed by forming D-CNSL, the effects were totally different from those of the CNSL. The D-CNSL behaves like a plasticizer improving chain flexibility and might show dilution effects if used at a high content in the compound formulation. These effects are clearly seen in decreased curing rate and curing efficiency, together with slight losses of tensile properties, tear strength, and thermal stability, with D-CNSL addition.

Mixing and Comparative Properties of NR Compounds Filled with Different Types of Reinforcing Fillers

Mixing behaviors of the compounds filled with different reinforcing fillers were studied in correlation with compound and vulcanizate properties. Four filler systems were used including: 1) silica plus small amount of silane coupling agent; 2) carbon black; 3) pre-modified silica; and 4) silica+silane-carbon black mixed one. The results have shown that silica provides longer optimum cure time and shorter cure rate than carbon black due to accelerator adsorption on silica surface. In addition, owing to highly polar nature on silica surface the silica-based compounds show rather high viscosity, attributed to stronger filler-filler interaction as can be confirmed by Payne effect and reinforcement index. However, the commercial surface treatment or pre-modified form of silica shows superior properties than in-situ modification of silica by silane during mixing, while it gives comparable properties to carbon black-based compound. Tensile properties of vulcanizates show a good correlation with the basic properties of their compounds.

Temporal characteristics of atmospheric ammonia and nitrogen dioxide over China based on emission data, satellite observations and atmospheric transport modeling since 1980

Abstract. China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen (Nr). Atmospheric ammonia (NH3) and nitrogen dioxide (NO2) are the most important precursors for Nr compounds (including N2O5, HNO3, HONO and particulate NO3− and NH4+) in the atmosphere. Understanding the changes in NH3 and NO2 has important implications for the regulation of anthropogenic Nr emissions and is a requirement for assessing the consequence of environmental impacts. We conducted the temporal trend analysis of atmospheric NH3 and NO2 on a national scale since 1980 based on emission data (during 1980–2010), satellite observation (for NH3 since 2008 and for NO2 since 2005) and atmospheric chemistry transport modeling (during 2008–2015).Based on the emission data, during 1980–2010, significant continuous increasing trends in both NH3 and NOx were observed in REAS (Regional Emission inventory in Asia, for NH3 0.17 and for NOx 0.16 kg N ha−1 yr−2) and EDGAR (Emissions Database for Global Atmospheric Research, for NH3 0.24 and for NOx 0.17 kg N ha−1 yr−2) over China. Based on the satellite data and atmospheric chemistry transport model (CTM) MOZART-4 (Model for Ozone and Related chemical Tracers, version 4), the NO2 columns over China increased significantly from 2005 to 2011 and then decreased significantly from 2011 to 2015; the satellite-retrieved NH3 columns from 2008 to 2014 increased at a rate of 2.37 % yr−1. The decrease in NO2 columns since 2011 may result from more stringent strategies taken to control NOx emissions during the 12th Five Year Plan, while no control policy has focused on NH3 emissions. Our findings provided an overall insight into the temporal trends of both NO2 and NH3 since 1980 based on emission data, satellite observations and atmospheric transport modeling. These findings can provide a scientific background for policy makers that are attempting to control atmospheric pollution in China. Moreover, the multiple datasets used in this study have implications for estimating long-term Nr deposition datasets to assess its impact on soil, forest, water and greenhouse balance.

INVESTIGATION OF THE VULCANIZATION CHARACTERISTICS OF NATURAL RUBBER COAGULATED BY MICROORGANISMS

ABSTRACTThe network variations of NR during the vulcanization process were investigated by 1H chemical shift by liquid-state 1H-NMR spectroscopy. NR latexes coagulated by microorganisms (NR-m) or acid (NR-a) were contrasted. The influences of coagulation on the structures, vulcanization characteristics, and mechanical properties of NR were analyzed. The results show that the cross-link density (XLD) and mass percentage of cross-link network [A(Mc)] increased with the increment of the vulcanization time, whereas the mass percentage of bangling free ends of the hydrocarbon and small molecules [A(T2)], the longitudinal relaxation time (T1), the transverse relaxation time (T2), and the molecular mass of inter–cross-link chains (Mc) decreased with the prolonging of vulcanization time for both NR-m and NR-a. Although NR-m exhibits shorter scorch times and optimum cure time, it shows higher maximum torque and minimum torque than that of NR-a. It is obvious that the higher XLD and A(Mc), the lower the A(T2), T1, T2, and Mc values of NR-m, resulting in higher stress, tensile strength, and tear strength of NR compounds.

Hydrogen Ion Role on the Reduction of Poly-(Neutral Red)

Neutral Red (3-amino-7-dimethylamino-2-methylphenazine, abbreviated as NR) is a heterocyclic compound belonging to the phenazine family. Like its close relative Azure A, NR has been subject of much ongoing research [1] due to its biochemical (as dye for staining in histology) and chemical (as a pH indicator) relevance. Among other relevant functions, NR can be used as DNA-revealing dye by optical and electrochemical methods [2], for the evaluation of natural and synthetic biomaterials [3, 4], development of optical sensors [5], mediator of electro transfer in organic and bio-electrochemistry [6]. The first polymer of such a family, poly(thionine) was obtained by Albery et al. [7] and, since then, a whole lot of research has been devoted to polymer derivatives of NR and phenazine-like compounds. Their potential applications span from photogalvanic cells [8], batteries [9], bio-sensing [10], electrochromic systems [11], sensor of pH [12] and biosensors metal/PNR [13]. Indeed, the presence of the counter-anion A- becomes important. When no small anions (i.e. Cl-) are present, the electro-catalysis is favoured at basic pH. On the other hand, H2 is discharged at acidic pH, because the big counter-anions present in the Britton-Robinson buffer cannot pass through the polymer matrix. In other words, the proposed mechanisms above can be summarized as follows: PNR + 2e- + 2H+ ⇆ PNRH2 PNRH2 + 2 e- + 2 H+ ⇆ PNRH2 + H2 In order to retrieve reliable information about such redox processes and be able to tell “which is which”, derivative voltoabsorptometry was carried out on PNR films over the 2.18 to 8.95 pH range. Such an analytical method is a very useful tool in that UV-Vis absorptions are monitored as a function of a specific potential range. This, in turn, allows telling apart different contributions to the same redox peak(s) that may come from different phenomena. dA/dt changes against potential. During cycling of PNR at acidic pH, the most prominent changes were detected at 4 wavelengths: 418 nm, 587 nm, 745 nm, and 925 nm. In here, the current intensities and dA/dt are plotted against the potential window. The reduction-oxidation processes of the central ring on the NR molecule [14] absorbs at 418 and 578 nm, whereas the redox activity of the inter-monomer bond causes absorption at 745 and 925 nm. It can be inferred that, at acidic pH, the central ring is protonated and its reduction is easier (i.e. a lower potential is required); as the pH increases, the amount of protonated PNR decreases and its reduction becomes more difficult (i.e. the potential shifts to more negative values) till it becomes impossible or highly unlikely/not detectable. REFERENCES [1] R. Osborne. M. A. Perkins, Food Chem. Toxicol. 32 (1994) 133-142. [2] A. C. Allison, I. A. Magnus, M. R. Young, Nature 209 (1966) 874-878. [3] X. Zhong, J. Chen, B. Liu, Y. Xu, Y. Luang, J. Solid State Electrochem. 11 (2007) 463–468. [4] M. E. Ghica, C. M. A. Brett, Electroanalysis 18 (2006) 748 – 756. [5] G. Broncová, T. V. Shishkanova, P. Matejka, R. Volf, V. Král, Anal. Chim. Acta 511 (2004) 197–205. [6] M. M. Barsan, J. Klincar, M. Batic, C. M.A. Brett, Talanta 71 (2007) 1893–1900. [7] B. S. B. Salomi, C. K. Mitra, Biosens. Bioelectron. 22 (2007) 1825–1829. [8] J. C. Lamanna, K. A. McCracken, Anal. Biochem. 142 (1984) 117-125. [9] H. Heli, S. Z. Bathaie, M. F. Mousavi, Electrochim. Acta 51 (2005) 1108–1116. [10] G. Zhang, S. Shuang, C. Dong, D. Liu, M. M.F. Choi. J. Photoch. Photobio. B 74 (2004) 127–134. [11] Y. Ni, S. Dua, S. Kokot, Anal. Chim. Acta 584 (2007) 19–27. [12] D. Benito, J.J. García-Jareño, J. Navarro-Laboulais, F. Vicente, J. Electroanal. Chem. 446 (1998) 47. [13] J. Agrisuelas, J.J. Garcia-Jareño, P. Rivas, J.M. Rodriguez-Mellado, F. Vicente, Electrochim. Acta. 171 (2015) 165–175. [14] J. Agrisuelas, J.J. García-Jareño, D. Gimenez-Romero, F. Vicente, Electrochim. Acta. 55 (2010) 6128–6135. ACKNOWLEDGEMENTS Part of this work was supported by FEDER-CICyT CTQ2015-71794-R. Figure 1

REDUCED ETHANOL EMISSIONS BY A COMBINATION OF EPOXIDIZED NATURAL RUBBER AND SILANE COUPLING AGENT FOR SILICA-REINFORCED NATURAL RUBBER-BASED TIRE TREADS

ABSTRACT In an attempt to reduce the high volatile organic compound (ethanol) emissions from silica-reinforced NR compounds, this work aimed to, at least partially, replace the use of large quantities of silane coupling agent bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT). The use of 7.5 phr of epoxidized natural rubber (ENR-51) as compatibilizer between NR and silica enhances the properties, which can be further improved by half or even lower amounts than required with TESPT alone. The properties obtained with TESPT are nearly matched, except for steric limitations imposed upon the ENR molecules to cap the silanol groups on the silica surface to the same extent as TESPT can do. Furthermore, TESPT donates reactive elemental sulfur to the compound during vulcanization, which needs to be compensated for in use with ENR.

Influence of silane coupling agent on bound rubber formation of NR/SBR blend compounds reinforced with carbon black

Influence of silane coupling agent [bis-(3-(triethoxysilyl)-propyl)-tetrasulfide, TESPT] on bound rubber formation of carbon black-filled NR/SBR blend compounds was investigated. Bound rubber formation of carbon black-filled NR compounds with and without TESPT was also examined. Bound rubber contents of the NR/SBR blend compounds were less than those of the single NR compounds. Secondary layer bound rubber content of the NR/SBR compound containing TESPT was greater than that of the compound without TESPT, whereas formation of the primary layer bound rubber was not nearly affected by TESPT. For the single NR compounds, both the primary and secondary layer bound rubber contents of the compound containing TESPT were greater than those of the compound without TESPT. TESPT enhances the bound rubber formation by making sulfur crosslinks between NR chains in the compound. The secondary layer bound rubber contents of the NR/SBR blend compounds were lower than the primary layer ones, while for the single NR compounds the secondary layer bound rubber contents were greater than the primary layer ones. Rubber ratios of NR and SBR of bound rubbers of the NR/SBR blend compounds were determined using thermogravimetric analysis (TGA). The NR/SBR rubber ratio of the secondary layer bound rubber was much greater than that of the primary layer one.

The Effects of Reactive Nitrogen (Nr) Compounds on the Acidification in Soil and Water Environment Ecosystems and the Mitigation Strategy

산업 및 기술의 발달과 인간 활동의 증가로 인해 자연적인 질소 순환의 균형이 무너지고 다량의 질소가 대기, 토양 및 물 환경 생태계에 과잉으로 존재하게 되었다. 이로 인한 과잉의 반응성 질소화합물이 토양과 물 환경생태계에 영향을 미치고 있는 것을 국내외 문헌과 사례 조사를 통해 확인하고 유역생태계에서 질소화합물로 인한 토양 및 물 환경 생태계의 산성화 영향 감소방안을 제시하였다. 반응성 질소는 대기, 토양 및 물의 여러 매체를 이동하면서 다른 유형으로 전환될 수 있으며 유형 간 상호작용이 일어나기도 한다. 효과적인 질소관리 방안으로 반응성질소 배출원의 다양성 및 유형에 따른 배출량을 규제하는 정책과, 반응성 질소화합물로 인한 토양 및 물 환경생태계의 환경적 피해 (산성화)를 조사 및 평가 (모니터링 및 안전성 지표 적용)하고 복원하는 전략 (예, 화학적 복원 연구 및 개발)이 필요하다.

Insight into vulcanization mechanism of novel binary accelerators for natural rubber

A novel TU derivative, N-phenyl-N′-(γ-triethoxysilane)-propyl thiourea (STU), is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl isothiocyanate fragment still remains in the NR/STU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.