Search

Fluoroelastomers (FKM) are used to manufacture seals and other rubber devices that can withstand harsh operating conditions, including aggressive media and extreme low and high temperatures. Even though nuclear magnetic resonance, Fourier-transform infrared spectroscopy (FTIR), and chromatographic techniques have been extensively used in the characterization of raw FKM molecules, the identification of cured compounds entails a characterization method that is able to overcome the complexity related to this kind of structure. In this sense, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy can outperform other characterization techniques because it does not require solubilization or any special preparation of the sample. In this study, 10 FKM compounds were produced in this study utilizing four commercial types of FKM and the fillers carbon black, barium sulfate, and iron oxide. All unfilled-FKM (as received) and their compounds were analyzed by ATR-FTIR with germanium crystal. Between 15 and 25 analyses were performed for all each FKM type sample and their respective compounds. All spectra were analyzed, and the bands were assigned. Findings regarding the interference of the fillers in the spectra were also reported. From relationships between the height of the spectral zones and the bands at 1397 and 1428 cm−1, it was possible to distinguish all sample compositions of FKM types 1, 2, 3, and 5. This study demonstrates that ATR-FTIR has the potential to be utilized as a technique to detect the type of FKM compounds, an important rubber used in harsh industrial applications. Replacing carbon with BaSO4 reduces the tensile at 50% strain of FKM types 1 and 2 composites. FKM types 3 and 5 composites filled with 30 phr of carbon black have a higher tensile at 50% strain than those of FKM type 1. [ABSTRACT FROM AUTHOR]

In this work, novel nanocomposite films based on babassu coconut mesocarp and zinc oxide nanoparticles (ZnO NPs), synthesized by a green route, were produced for application as food packaging films. The films were prepared using the casting method containing different contents of ZnO NPs (0 wt%, 0.1 wt%, 0.5 wt%, and 1.0 wt%). The films were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), instrumental color analysis, and optical properties. The water vapor permeability (WVP) and tensile strength of films were also determined. The antimicrobial activity of the films against cooked turkey ham samples contaminated with Staphylococcus aureus was investigated. The results showed that incorporating ZnO NPs into babassu mesocarp matrices influenced the structure of the biopolymer chains and the color of the films. The BM/ZnO-0.5 film (0.5 wt% ZnO NPs) showed better thermal, mechanical, and WVP properties. Furthermore, the synergistic effect of babassu mesocarp and ZnO NPs in the BM/ZnO-0.5 film improved the antimicrobial properties of the material, reducing the microbial count of S. aureus in cooked turkey ham samples stored under refrigeration for 7 days. Thus, the films produced in this study showed promising antimicrobial packaging materials for processed foods. [ABSTRACT FROM AUTHOR]

Copyright of Revista Foco (Interdisciplinary Studies Journal) is the property of Revista Foco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study produced and characterized composites based on nitrile rubber reinforced with rockwool fiber (RW) and carbon black (CB). Ten formulations with dual‐filler loading amounts ranging from 0 to 40 phr of CB and RW were designed using a simplex‐centroid mixture. The composites were assessed regarding their rheometric, rheological, mechanical, and thermal properties. The use of the RW in the dual‐filler system contributed to overall improvements in Shore A hardness, tear strength, modulus at 50%, and resilience, as well as reducing the Payne effect. Instead of using 40 phr of CB alone, a dual‐filler system comprising 20 phr of CB and 20 phr of RW lowers the Payne effect by around 60%, improves resilience by 35%, modulus at 50% strain by 8%, and the residual stress at equilibrium (σ∞/σ0) by 7%. On the other hand, the tensile strength is reduced by 23%. The optimum cure time, crosslink density, and maximum decomposition rate temperature were not affected by the rockwool's presence in the dual‐filler system. In general, the use of RW in combination with CB is advantageous mainly because it reduces compressive stress relaxation, which is an important property for sealing applications. Highlights: Dual‐filler systems based on carbon black (CB) and rockwool fiber (RW) offer advantages.RW‐rich dual‐filler systems reduce stress relaxation.RW‐rich dual‐filler systems reduce the Payne effect.CB‐rich dual‐filler systems increase tensile strength. [ABSTRACT FROM AUTHOR]

The paper and pulp industry produces lignin as a byproduct, which could be a bio‐based reinforcing filler for rubber. Carboxylated nitrile rubber (XNBR) contains carboxyl groups that form ionic bonds with zinc oxide, potentially increasing compatibility with lignin, compared to usual nonpolar rubbers. This study employed the traditional mixing method, two‐roll mill, to incorporate hardwood Kraft lignin without chemical or physical modification as a reinforcing filler in commercial XNBR. A mixture design of experiments was used to explore the effect on rubber/lignin interaction of the carboxyl group content (from 1% to 7% in blends of XNBR) and the amount of lignin (from 0 to 40 phr). Adding 40 phr of lignin increased stress at 100% in XNBR 7% from 1.7 to 6.3 MPa. In XNBR 1%, the increase was from 1.2 to 1.9 MPa. Lignin showed better interaction and dispersion with XNBR 7%, determined from response surface of G′ at high deformations and SEM, respectively. Loss of thermal transition in DMA indicates interaction through ionic groups. These results show that the presence of carboxyl groups enhances the rubber/lignin interaction. This research open possibilities of compatibilization of lignin, offering guidance for future studies and technologies involving lignin in technical applications. Highlights: Lignin dispersion increased as the carboxyl group content increased to 7% (w/w).Stress at 100% elongation increased 370% with 40 phr of lignin and 7% carboxyl.Rubber/lignin interaction as per G′ increased with carboxyl groups.Loss of thermal transition suggests lignin/carboxy/zinc oxide interaction.Lignin can be used as a reinforcing filler in nitrile carboxylated rubber. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) is the most widely used activator in the rubber industry; however, there is growing concern about its use as it can become toxic to the environment, particularly in aquatic systems. This study describes the synthesis of magnesium oxide (MgO) assisted by the Alpinia zerumbet extract, which is then used as an activator in the replacement of ZnO to vulcanize nitrile rubber (NBR) containing 33% and 45% acrylonitrile (ACN). The t90 for NBR‐33% and NBR‐45% are 20 and 15 min, respectively. This indicates a reduction of 5 min in t90 with an increase in ACN. In comparison, ZnO‐activated NBR compounds exhibit the opposite trend, with t90 increasing from 10 for NBR‐33% to 19 min for NBR‐45%. Furthermore, the decrease in activation energy (Ea) with the increase in conversion for 33%‐MgO and 45%‐MgO indicates that vulcanization with MgO is a complex process. This behavior is comparable to that of 45%‐ZnO, but not for 33%‐ZnO because its Ea remains oscillating at 80–90 kJ mol−1 in the entire conversion range. The crosslink densities of 33%‐MgO and 45%‐MgO are 5.87 and 4.78 mol cm−3, respectively. These values are slightly higher than those for 33%‐ZnO (5.77 mol cm−3) and 45%‐ZnO (4.38 mol cm−3). [ABSTRACT FROM AUTHOR]

In this work, the stability of oil-in-water emulsions (O/W) of patauá (Oenocarpus bataua) and pracaxi (Pentaclethra macroloba) oils, both from Amazon rainforest, was investigated. Low-energy emulsification methods were used, such as Emulsion Inversion Point (EIP) and Phase Inversion Temperature (PIT), both based on the minimal interfacial surface, combined with optimized Hydrophilic-Lipophilic Balance (HLB). Phase inversion was determined by electrical conductivity measurements. The surfactants used were Span® 80, Tween® 20, Tween® 60, and Tween® 80. Surfactant mixtures of Span® 80 + Tween® 80 were the best samples prepared. The composition of the most stable samples was 80.00 wt% aqueous phase, 15.00 wt% nonionic surfactants, and 5.00 wt% oil phase (patauá or pracaxi oil). The samples with the best kinetic results were those prepared with the required HLB and PIT values of 12.86 and 84.05 °C, for patauá oil, and of 9.61 and 79.50 °C for pracaxi oil. The kinetic stability of the oil emulsions was characterized by creaming index (CI), by evolution over time of the droplet size, viscosity, and electric conductivity. The results showed that: (1) the droplet size distribution influenced electric conductivity; (2) the relative amount of surfactants Tween® and Span® used is more important to determine the physicochemical and interfacial properties of the emulsion than the oil identity itself; (3) it is crucial to pay attention to the influence of air bubbles—involuntarily inserted into the mixture during the emulsification process—in the physicochemical properties of the system. These conclusions can be extended to other oil-in-water emulsions. [ABSTRACT FROM AUTHOR]

Copyright of Configurações is the property of Centro de Investigacao em Ciencias Sociais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de Direitos Fundamentais & Democracia is the property of Revista de Direitos Fundamentais & Democracia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study reports the reinforcement degree investigation of two types of rockwool fibers (F1 and F2), in nitrile rubber composites. The micro-computed tomography (micro-CT) 3D images showed that both fibers were well-dispersed in the NBR matrix, without a preferential orientation. The micro-CT analysis also allowed quantifying volume fraction, inter-fiber distance, and aspect ratio. Those morphometric parameters were used for supporting the composites rheological behavior assessment. Changes in the elastic modulus and phase angle followed the same trend of the inter-fiber distance values, regardless the type of fiber. Both volume fraction and aspect ratio data from the micro-CT analysis were used to predict theoretical values of elastic modulus using the Guth-Gold and modified Guth-Gold equations, and the results obtained were compared to the rheological experimental data. This analysis was helpful to better understand the rockwool fibers reinforcement degree differences in the production of the nitrile rubber composites. [ABSTRACT FROM AUTHOR]

Persimmon is among the fruits with a significant postharvest loss over the last few years. Thus, it is important to investigate new technical feasibilities to obtain products with higher added value from this fruit. In this study persimmon puree films (Diospyros kaki L.) incorporated with glycerol and pectin by casting technique were formulated using a Plackett–Burman design and characterized. The puree showed high carbohydrate content (175.70 g/kg). In descending order, fructose, glucose, and maltohexaose were the sugars found in persimmon. All the independent variables studied—puree concentration, pectin, glycerol, and temperature—statistically influenced the tensile strength (0.75–1.30 MPa), elongation at break (17.69–26.02%), and Young's modulus (3.34–10.94 MPa) of the films. Water solubility ranged from 68.80% to 80.86%, which were very similar to other films based on puree fruit in the literature. Samples presented high vapor permeability (5.77–6.63 × 10−6 g/h/m/Pa) when compared to biodegradable films. Scanning electron microscopy showed smooth surfaces and good plasticizer dispersion. The colorimetric coordinates indicated the films are reddish and yellowish, giving them an orange‐ish visual aspect. The films exhibited antimicrobial activity, especially against Escherichia coli and Staphylococcus aureus. These results indicate that the developed films might be a good candidate for antimicrobial food packaging improving food quality and safety. Practical Application: The production of fruit‐film packaging with functional and biodegradable characteristics might reduce postharvest loss of fruit and have the potential to develop active food packaging. In this sense, this study is in line with precepts of the circular economy, once it takes advantage of exceeded resources that would be discarded by generating biodegradable films which can be used as edible packaging. Furthermore, given the antimicrobial potential of the films developed, they might be applied as active packaging to improve food safety and extend shelf life. [ABSTRACT FROM AUTHOR]

Polylactide (PLA) is an eco-friendly biodegradable thermoplastic with excellent processability, demanding less energy to be produced compared to the petroleum-based polymers. However, PLA has drawbacks that impose some restrictions of uses use such as poor toughness property. Blending PLA with other polymers is a more practical and economic way to improve its toughness. The present study assessed the effect of the addition of the pre-crosslinked powdered nitrile rubber (NBR) containing calcium carbonate (CaCO3) and extruder screw rotation on the mechanical, rheological, morphological and thermal properties of polylactide (PLA) by using a Central Composite Rotatable Design (CCRD) analysis, which provides statistical support for the experimental data. The results showed that NBR/CaCO3 can be used as toughness modifier for PLA. This property improved due to the increase in energy expended to deform the material and generate cracks, as showed in the impact and morphological analyzes. Despite this improvement, the presence of CaCO3 caused a slight decline in the thermal resistance of the composites. The influence of rubber (NBR/CaCO3) content in PLA matrix on rheological properties, such as elongation viscosity, melt strength and drawability was also investigated. The results showed that the composition PLA/NBR/CaCO3 with higher NBR/CaCO3 content can be used in thermoforming applications. [ABSTRACT FROM AUTHOR]

This study aimed at evaluating the coupling effect of silane Si69 bis(triethoxysilylpropyl)tetrasulfide in metakaolin (MK) in automobile tire tread compounds based on a styrene–butadiene rubber/butadiene rubber blend. A reference compound of a typical tread recipe, filled with silica and carbon black, was used as a reference due to the acknowledged effect of TESPT in silica incorporation in elastomers. A silica sample without silane was also prepared. Silica was then completely substituted by MK, producing two samples, with and without silane. The samples were tested for crosslink density, rheometry, and morphology, and the vulcanization reaction parameters were determined and evaluated. Silane improved the interaction between MK and the polymer matrix, evidenced by the increase in crosslink density and vulcanization reaction rate, the same effect silane causes on silica-filled composites. Morphology also revealed that silane increased MK dispersion and adhesion to rubber. On the other hand, MK seems not to be as reinforcing as silica, considering that maximum torque is related to the stiffness of the material, with MK exhibiting lower values for this parameter. [ABSTRACT FROM AUTHOR]

The increasing growth of cities has caused disorders in urban space and has made difficult the free displacement of people with deficiency. Good urban mobility is relevant for identity, life experience and opportunity for all. However, frequently there are hindrances for people with deficiency and thus a limitation to their rights, especially their inclusion rights. Current paper discusses and demonstrates that free urban mobility of people with deficiency is an efficacious strategy to promote inclusion rights. The paper involves a bibliographic and documental research coupled to a theoretical and doctrinal approach. [ABSTRACT FROM AUTHOR]

Carbon black and high performance silica have been widely employed as binary system filler in tire tread formulations. This study evaluated the total and partial substitution of silica by metakaolin (MK) on the properties of tread rubber composites. Dynamic mechanical thermal analysis and abrasion tests were conducted as typical assessments of tire tread performance: rolling resistance (fuel consumption), wet traction (safety), and abrasion (durability). Further the energy spent by the equipment during the processing of formulations was also analyzed, as well as rheological and mechanical properties. A significant reduction of rolling resistance was obtained with 75% and 100% of silica substitution by MK, which could lead to lower heat buildup in tire tread applications, without showing negative effects on wet traction, although abrasion showed undesired results. The substitution of silica by MK also lowered energy demanded for processing. No major changes were observed in vulcanization parameters and mechanical properties, which is interesting considering the fact that MK is nonreinforce filler. [ABSTRACT FROM AUTHOR]

iPP/Talc composites were produced, with different methods of filler addition in iPP matrix. Two different grades of Talc were used for comparison. The tensile tests results showed that talc particles promoted an improvement in composite rigidity, indicating the reinforcing effect of the talc particles in the iPP matrix. However, PP/talc-based composites that were prepared from a masterbatch and with talc grade with smaller particle size showed a better efficiency on dispersion/distribution of particle filler on the thermoplastic matrix, resulting in an improvement in Young’s modulus property, even with higher filler contents. SEM analyses evaluated the composite morphologies and different mathematical models were used as a tool on prediction of mechanical behaviour of the materials. It was observed that the results of Young’s modulus of the composites can be adjusted by different models, depending on the talc characteristics and the mixing procedure used. [ABSTRACT FROM AUTHOR]

In 2018, the Federal Constitution of Brazil completes thirty years of its promulgation. During this interval, many transformations have been observed in different branches of knowledge. Among them, a phenomenon that draws international attention, especially in Brazil, is the aging of the population, constituting one of the most significant events that have modified Brazilian social reality. Aging refers to the issue of a greater number of elderly people, but it also has a connection with the dimensional diversity and with elderly people living increasingly more. In this sense, the legislation has been struggling to establish standards to guarantee the rights of such group of people; but the public policies that accomplish these rights are still not enough, demanding the effective social commitment of all entities involved in planning, projects, programs and activities. In this work, the phenomenon of aging will have as its discussion two fundamental aspects: the legislative and the social. The methodology used will be the bibliographical and documentary research and the systematization of knowledge, under deductive reasoning, will have a theoretical-doctrinal approach. [ABSTRACT FROM AUTHOR]

Rice husk (RH) residue was submitted to a sequence of experimental procedures, specifically to investigate the reaction time influence of NaOH pretreatment on the extraction of silica, hemicellulose, and lignin components. In order to follow the extraction of each non-cellulosic components of rice husk, techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy were performed on untreated RH and samples collected from the NaOH reaction media at several different reaction times, as well as the sample after alkaline-peroxide treatment. Under the process parameters used in the present study, the results showed that a great part of hemicellulose and silica contents was removed during the first 30 min of reaction time in NaOH pretreatment. Although there is evidence that NaOH pretreatment also removed some lignin content, the complete delignification process was more effective just after alkaline-peroxide reaction, which produced material rich in type I cellulose. [ABSTRACT FROM AUTHOR]

Riparian zones represent ecotones between terrestrial and aquatic ecosystems and are of utmost importance to biodiversity and ecosystem functions. Modelling/mapping of these valuable and fragile areas is needed for improved ecosystem management, based on an accounting of changes and on monitoring of their functioning over time. In Europe, the main legislative driver behind this goal is the European Commission's Biodiversity Strategy to 2020, on the one hand aiming at halting biodiversity loss, on the other hand enhancing ecosystem services by 2020, and restoring them as far as is feasible. A model, based on Earth Observation data, including Digital Elevation Models, hydrological, soil, land cover/land use data, and vegetation indices is employed in a multi-modular and stratified approach, based on fuzzy logic and object based image analysis, to delineate potential, observed and actual riparian zones. The approach is designed in an open modular way, allowing future modifications and repeatability. The results represent a first step of a future monitoring and assessment campaign for European riparian zones and their implications on biodiversity and on ecosystem functions and services. Considering the complexity and the enormous extent of the area, covering 39 European countries, including Turkey, the level of detail is unprecedented. Depending on the accounting modus, 0.95%-1.19% of the study area can be attributed as actual riparian area (considering Strahler's stream orders 3-8, based on the Copernicus EU-Hydro dataset), corresponding to 55,558-69,128 km2. Similarly, depending on the accounting approach, the potential riparian zones cover an area about 3-5 times larger. Land cover/land use in detected riparian areas was mainly of semi-natural characteristics, while the potential riparian areas are predominately covered by agriculture, followed by semi-natural and urban areas. [ABSTRACT FROM AUTHOR]

Copyright of Revista Jurídica (0103-3506) is the property of Revista Juridica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The vulcanization process of rubber compounds comprises multiple chemical reactions and the investigation of this process can be carried out using several techniques. This paper aims at investigating the influence of acrylonitrile content (28, 33 and 45%) and the presence of a carboxyl group in the vulcanization process of nitrile rubber. A methodology that uses rheometric parameters to determinate the cure rate constant ( k) and activation energy (E) was conducted. The results showed that there was a decrease in cure rate constant with increasing of acrylonitrile content in the rubber, for a given vulcanization temperature. Furthermore, a higher value of activation energy was obtained for the 33% of acrylonitrile compound. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nursing UFPE / Revista de Enfermagem UFPE is the property of Revista de Enfermagem UFPE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Políticas Culturais em Revista is the property of Politicas Culturais em Revista and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the obstruction and reinforcement of permeable rocks (pores and or fractures), materials to combat loss of circulation (LCMs) are commonly used in the drilling fluid. LCMs, when forming bridges, support and seal rocks, with the objective of preventing drilling fluid from reaching the reservoir. In this study, drilling fluid formulations were developed using full four-level factorial design (DOE), with a central point (4 ^ 2 + 3) in order to evaluate the effect of drilling fluid components on their rheological properties and in the loss of circulation. The tested fluids were prepared using carboxymethylcellulose polymer (CMC), bentonite (BT) as a thickener, and the materials used to combat loss of circulation were used with diatomaceous earth (DE) and hydrogel (HG). The density and pH of all fluids were adjusted to approximately ≈1.14 g/cm−3 and 8.5, respectively, being named F(CMC)BT-DE-HG. The filtration experiments were performed in a HTHP (high temperature, high pressure) filtration cell and the fracture was sealed in a physical simulator, called Fracture Flow Simulator (SEF). The rheological data were adjusted using the Herschel Bulkley model. The incorporation of LCMs in the drilling fluid improved the rheological properties. The results indicated that the investigated factors CMC, BT and HG had the main effects in combating the loss of circulation in the fracture and filtration phases. Diatomaceous earth was not significant in filtration and fracture tests. Finally, based on rheological tests, it can be inferred that the interaction of HG*CMC and BT*CMC is highly significant in combating loss of circulation. The fluid with lower DE level showed superior performance, as it sealed the fracture in 1 min of testing and a low volume of filtrate was observed in the test. • The hydrogel can be used as a good viscosifier because it increases the gel strength of the aqueous suspension. • Plugging the fractures is the main way to deal with lost circulation. • Non-expansion of bentonite did not modify its rheological properties in the drilling fluid. • A concentration criterion of LCMs was developed based on laboratory and statistical investigations. • CMC polymer is important in formulation and has had major effects on fluid rheology, acting alone or interacting with LCMs. [ABSTRACT FROM AUTHOR]

Several papers describe the treatment of calcium carbonate (CaCO3) with stearic acid acting as a surface modifier, in order to avoid particle coalescence and, at the same time, enhancing filler hydrophobic properties. However, there is still a lack of data relating the efficiency of a traditional modifier used, stearic acid, in the synthesis of CaCO3 nanofiller with other modifiers in terms of inhibition of the agglomeration process during the synthesis. Thus, the present work evaluates the stability of CaCO3 nanoparticles obtained by a carbonation reaction, considering the contents of the crystallization inhibitor (trisodium phosphate-Na3PO4) and the surface modifier (myristic acid) applied. In order to achieve an efficient carbonation process, a bubbling system was used. The results showed that higher surface modifier and crystallization inhibitor contents lead to a narrower particle size distribution and a lower particle size. Comparing the CaCO3 nanoparticles coated with myristic acid (CaCO3-MA) and with stearic acid (CaCO3-SA), it was observed that CaCO3-MA has a higher thermal stability and a lower particle size in relation to CaCO3-SA. Besides this, a more spherical geometry was achieved for CaCO3-MA nanoparticles due to the bubbling system applied during the carbonation reaction. [ABSTRACT FROM AUTHOR]