Processability And Magnetic Properties Of Rubber Ferrite Composites Containing Barium Ferrite

Rubber ferrite composites (RFC) are magnetic polymer composites and have a variety of applications as flexible magnets, pressure=photo sensors, and microwave absorbers. The mouldability into complex shapes is one of the advantages of these magnetic elastomers. They have the potential of replacing the conventional ceramic materials, due to theire flexible nature. In the present study, the incorporation of pre-characterized hexagonal ferrites, namely barium ferrite (BaFe12O19), into natural rubber matrix is carried out according to a suitable recipe for various loadings of the filler. The processability of these compounds was determined by evaluating the cure characteristics: scorch time, cure time, and minimum and maximum torque. It has been found that the addition of magnetic fillers does not affect the processability of the composites, whereas the physical properties are modified. The magnetic properties of these composites containing various loadings of the magnetic filler were also investigated. The magnetic properties of RFC can be controlled by the addition of appropriate amount of the ferrite filler.

On the magnetic and dielectric properties of nickel–neoprene nanocomposites

Nickel nanocomposites were prepared by incorporating nickel nanoparticles in a neoprene matrix according to a specific recipe for various loadings of nickel particles. The dielectric properties of these composites were evaluated for different frequencies ranging from 100 kHz to 8MHz at different temperatures from 30 ◦C to 120 ◦C. The dielectric permittivity increases with increase of nickel concentration. Increase in temperature enhances the permittivity initially, till 40 ◦C and thereafter the permittivity decreases. The dielectric loss exhibits relaxation peaks and the peaks shift to lower frequencies with increase in volume fraction of the nickel nanoparticles in the matrix. The evaluation of magnetic and dielectric properties of these composites suggests that the dielectric permittivity can be tailored by an appropriate loading of the filler using semi-empirical equations and the magnetic properties vary according to simple mixture equations

Magnetic and processability studies of nitrile rubber vulcanisates containing barium ferrite and carbon black

Fine particles of barium ferrite (BaFe12O19) belonging to the M-type hexagonal ferrites were prepared by the conventional ceramic techniques. They were incorporated into a nitrile rubber matrix according to a specific recipe for various loadings to produce rubber ferrite composites (RFC). The percolation threshold is not reached for a maximum loading of 130 phr (parts per hundred rubber). Here in this paper, the magnetic properties and processability of the nitrile rubber based RFCs containing barium ferrite (BaF) and HAF carbon black is reported. The magnetic properties of the ceramic ferrite and these rubber ferrite composites were evaluated and it was found that the coercivity values of RFCs were less than that of the ceramic BaF, but remained constant with the loading of both the ferrite filler and carbon black. However, other properties like saturation magnetization and magnetic remanence increased with the loading of ferrite filler.

Cure Characteristics and Mechanical Properties of Rubber Ferrite Composites Based on Nano-Nickel Ferrites

Ultra fine nickel ferrite have been synthesized by the sol-gel method. By heat treating different portions of the prepared powder separately at different temperatures, nano-sized particles of nickel ferrite with varying particle sizes were obtained. These powders were characterised by the X-ray diffraction and then incorporated in the nitrile rubber matrix according to a specific recipe for various loadings. The cure characteristics and the mechanical properties of these rubber ferrite composites (RFCs) were evaluated. The effect of loading and the grain size of the filler on the cure characteristics and tensile properties were also evaluated. It is found that the grain size and porosity of the filler plays a vital role in determining the mechanical properties of the RFCs

Studies on the use of Nanokaolin, MWCNT and Graphene in NBR and SBR

The current research investigates the possibility of using unmodified and modified nanokaolin, multiwalled carbon nanotube (MWCNT) and graphene as fillers to impart enhancement in mechanical, thermal, and electrical properties to the elastomers. Taking advantage of latex blending method, nanoclay, MWCNT and graphene dispersions, prepared by ultra sound sonication are dispersed in polymer latices. The improvement in material properties indicated better interaction between filler and the polymer.MWCNT and graphene imparted electrical conductivity with simultaneous improvement in mechanical properties. Layered silicates prepared by microwave method also significantly improve the mechanical properties of the nanocomposites. The thesis entitled ‘Studies on the use of Nanokaolin, MWCNT and Graphene in NBR and SBR’ consists of ten chapters. The first chapter is a concise introduction of nanocomposites, nanofillers, elastomeric matrices and applications of polymer nanocomposites. The state-of-art research in elastomer based nanocomposites is also presented. At the end of this chapter the main objectives of the work are mentioned. Chapter 2 outlines the specifications of various materials used, details of experimental techniques employed for preparing and characterizing nanocomposites. Chapter3 includes characterization of the nanofillers, optimsation of cure time of latex based composites and the methods used for the preparation of latex based and dry rubber based nanocomposites. Chapter4 presents the reinforcing effect of the nanofillers in XNBR latex and the characterization of the nanocomposites. Chapter5 comprises the effect of nanofillers on the properties of SBR latex and their characterization Chapter 6 deals with the study of cure characteristics, mechanical and thermal properties and the characterization of NBR based nanocomposites. Chapter7 is the microwave studies of MWCNT and graphene filled elastomeric nanocomposites. Chapter 8 gives details of the preparation of layered silicates, their characterization and use in different elastomeric matrices. Chapter 9 is the study of mechanical properties of nanoclay incorporated nitrile gloves .Chapter 10 presents the summary and conclusions of the investigation.

Modification of Polypropylene/High Density Polyethylene Blend Using Nanokaolinite Clay and E-Glass Fibre: Preparation, Characterization and Micromechanical Modelling

Upgrading two widely used standard plastics, polypropylene (PP) and high density polyethylene (HDPE), and generating a variety of useful engineering materials based on these blends have been the main objective of this study. Upgradation was effected by using nanomodifiers and/or fibrous modifiers. PP and HDPE were selected for modification due to their attractive inherent properties and wide spectrum of use. Blending is the engineered method of producing new materials with tailor made properties. It has the advantages of both the materials. PP has high tensile and flexural strength and the HDPE acts as an impact modifier in the resultant blend. Hence an optimized blend of PP and HDPE was selected as the matrix material for upgradation. Nanokaolinite clay and E-glass fibre were chosen for modifying PP/HDPE blend. As the first stage of the work, the mechanical, thermal, morphological, rheological, dynamic mechanical and crystallization characteristics of the polymer nanocomposites prepared with PP/HDPE blend and different surface modified nanokaolinite clay were analyzed. As the second stage of the work, the effect of simultaneous inclusion of nanokaolinite clay (both N100A and N100) and short glass fibres are investigated. The presence of nanofiller has increased the properties of hybrid composites to a greater extent than micro composites. As the last stage, micromechanical modeling of both nano and hybrid A composite is carried out to analyze the behavior of the composite under load bearing conditions. These theoretical analyses indicate that the polymer-nanoclay interfacial characteristics partially converge to a state of perfect interfacial bonding (Takayanagi model) with an iso-stress (Reuss IROM) response. In the case of hybrid composites the experimental data follows the trend of Halpin-Tsai model. This implies that matrix and filler experience varying amount of strain and interfacial adhesion between filler and matrix and also between the two fillers which play a vital role in determining the modulus of the hybrid composites.A significant observation from this study is that the requirement of higher fibre loading for efficient reinforcement of polymers can be substantially reduced by the presence of nanofiller together with much lower fibre content in the composite. Hybrid composites with both nanokaolinite clay and micron sized E-glass fibre as reinforcements in PP/HDPE matrix will generate a novel class of high performance, cost effective engineering material.

Revisión sistemática de la literatura: efecto de los rellenos inyectables en la región periorbitaria

Introducción: El conocimiento actual de la fisiopatología del envejecimiento periorbitario justifica la aplicación de materiales de relleno inyectables, dado que se enfocan en la restauración del volumen perdido en esta zona, convirtiéndose en una excelente alternativa a procedimientos quirúrgicos que remueven el tejido excedente. Sin embargo los efectos y la seguridad de esta naciente tendencia terapéutica aún no se sustentan en una sólida base científica. El objetivo de esta revisión es identificar el material de relleno inyectable más adecuado para el manejo de los defectos volumétricos estéticos de la región periorbitaria. Metodología: Se realizó una búsqueda exhaustiva de los artículos indexados publicados del 1º de enero de 2.000 al 30 de septiembre de 2.013, en diversas bases de datos electrónicas, se seleccionaron catorce publicaciones, se extrajo la información referente a datos demográficos, la intervención, el seguimiento y los desenlaces y se realizó un análisis de 14 estudios que cumplieron los criterios. Resultados: Todos los artículos incluidos poseían un bajo nivel de evidencia y del grado de recomendación. Todos los materiales de relleno se asociaron a altos niveles de satisfacción para el paciente, adecuada mejoría de la apariencia estética y similares efectos colaterales, el ácido hialurónico fue el material de relleno inyectable más utilizado en la región periorbitaria. Discusión: Los materiales de relleno inyectable mejoran los defectos volumétricos estéticos de la región periorbitaria pero es necesaria mayor evidencia para determinar el tipo relleno más apropiado para esta condición.

Aprovechamiento integral del Cannabis sativa como material de refuerzo/carga del polipropileno

En este trabajo se ha estudiado el potencial tanto los filamentos de cáñamo como de la cañamiza como refuerzo/carga del polipropileno. La modificación de estos materiales se realiza para lograr una mayor compatibilidad con la matriz polimérica. Se evaluaron las propiedades mecánicas de las resistencias a tracción e impacto, de los materiales compuestos reforzados tanto de filamento como de cañamiza. Los filamentos de cáñamo poseen suficiente capacidad de refuerzo en los materiales compuestos basado en polipropileno debido a sus propiedades intrínsecas, siendo una buena alternativa como material de refuerzo. Así, la adición de MAPP (polipropileno modificado con anhídrido maleico) conduce a materiales compuestos con unas resistencias a tracción de hasta el 70% de las que se obtienen con compuestos de PP reforzados con fibra de vidrio. Mientras que la cañamiza ha actuado como una carga en la matriz, incrementado significativamente la rigidez de los materiales compuestos.

Inplante erabilerako polimero erradio-opakoen lorpena eta ezaugarritzea

[EU]Biomedikuntzan gero eta material polimeriko gehiago aplikatzen dira. Metalezko inplanteekin alderatuz, ekoizterako orduan azkarragoak eta merkeagoak baitira beste hainbat ezaugarriren artean. Baina onurak ekartzearekin batera, erradio-opakotasun eza ere badakar. Eta ezaugarri hau gabe, inplantearen jarraipena behin giza gorputzean ezarrita dagoenean ezinezkoa da, X izpiekin ezin baita ikusi. Beraz, arazo horri aurre egiteko, proiektu honetan matrize polimerikoari kargak gehitzea proposatzen da. Lortutako material konposatuak, polimeroak soilik dituen ezaugarriak berdintzea edo hobetzea espero da. Hau da, erradio-opakotasuna lortzeaz gain, propietate mekanikoak behintzat mantentzea espero da. Giza gorputzean aplikatzen diren inplanteetarako erabiliko den material konposatu bat lortzea duenez helburu proiektu honek, matrizea polimero biobataragarria eta biodegradagarria izango da. Biodegradagarria izanik, inplantea kanporatzeko bigarren ebakuntza bat ekiditen da. Zehazki, poli(D-laktida) (PDLA) polimeroa matrize moduan eta karga moduan bismuto oxidoa (Bi2O3) erabiliko dira, medikuntza arloko inplanteetan erabili izan ohi dira eta.

Language processing with dynamic fields

We construct a mapping from complex recursive linguistic data structures to spherical wave functions using Smolensky's filler/role bindings and tensor product representations. Syntactic language processing is then described by the transient evolution of these spherical patterns whose amplitudes are governed by nonlinear order parameter equations. Implications of the model in terms of brain wave dynamics are indicated.

Optimal protection of stabilised dry live bacteria from bile toxicity in oral dosage forms by bile acid adsorbent resins

We previously found that dried live bacteria of a vaccine strain can be temporarily sensitive to bile acids and suggested that Bile Adsorbing Resins (BAR) can be used in oral vaccine tablets to protect dried bacteria from intestinal bile. Here, we report a quantitative analysis of the ability of BAR to exclude the dye bromophenol blue from penetrating into matrix tablets and also sections of hard capsule shells. Based on this quantitative analysis, we made a fully optimised formulation, comprising 25% w/w of cholestyramine in Vcaps™ HPMC capsules. This gave effectively 100% protection of viability from 4% bile, with 4200-fold more live bacteria recovered from this formulation compared to unprotected dry bacteria. From the image analysis, we found that the filler material or compaction force used had no measurable effect on dye exclusion but did affect the rate of tablet hydration. Increasing the mass fraction of BAR gave more exclusion of dye up to 25% w/w, after which a plateau was reached and no further dye exclusion was seen. More effective dye exclusion was seen with smaller particle sizes (i.e. cholestyramine) and when the BAR was thoroughly dried and disaggregated. Similar results were found when imaging dye penetration into capsule sections or tablets. The predictions of the dye penetration study were tested using capsules filled with dried attenuated Salmonella vaccine plus different BAR types, and the expected protection from bile was found, validating the imaging study. Surprisingly, depending on the capsule shell material, some protection was given by the capsule alone without adding BAR, with Vcaps™ HPMC capsules providing up to 174-fold protection against 1% bile; faster releasing Vcaps Plus™ HPMC capsules and Coni Snap™ gelatin capsules gave less protection.

Antecedent priming at trace positions in children's sentence processing

The present study examines whether children reactivate a moved constituent at its gap position and how children's more limited working memory span affects the way they process filler-gap dependencies. 46 5-7 year-old children and 54 adult controls participated in a cross-modal picture priming experiment and underwent a standardized working memory test. The results revealed a statistically significant interaction between the participants' working memory span and antecedent reactivation: High-span children (n = 19) and high-span adults (n = 22) showed evidence of antecedent priming at the gap site, while for low-span children and adults, there was no such effect. The antecedent priming effect in the high-span participants indicates that in both children and adults, dislocated arguments access their antecedents at gap positions. The absence of an antecedent reactivation effect in the low-span participants could mean that these participants required more time to integrate the dislocated constituent and reactivated the filler later during the sentence.

On-line processing of wh-questions in children with G-SLI and typically developing children

Background: The computational grammatical complexity ( CGC) hypothesis claims that children with G(rammatical)-specific language impairment ( SLI) have a domain-specific deficit in the computational system affecting syntactic dependencies involving 'movement'. One type of such syntactic dependencies is filler-gap dependencies. In contrast, the Generalized Slowing Hypothesis claims that SLI children have a domain-general deficit affecting processing speed and capacity. Aims: To test contrasting accounts of SLI we investigate processing of syntactic (filler-gap) dependencies in wh-questions. Methods & Procedures: Fourteen 10; 2 - 17; 2 G-SLI children, 14 age- matched and 17 vocabulary-matched controls were studied using the cross- modal picturepriming paradigm. Outcomes & Results: G-SLI children's processing speed was significantly slower than the age controls, but not younger vocabulary controls. The G- SLI children and vocabulary controls did not differ on memory span. However, the typically developing and G-SLI children showed a qualitatively different processing pattern. The age and vocabulary controls showed priming at the gap, indicating that they process wh-questions through syntactic filler-gap dependencies. In contrast, G-SLI children showed priming only at the verb. Conclusions: The findings indicate that G-SLI children fail to establish reliably a syntactic filler- gap dependency and instead interpret wh-questions via lexical thematic information. These data challenge the Generalized Slowing Hypothesis account, but support the CGC hypothesis, according to which G-SLI children have a particular deficit in the computational system affecting syntactic dependencies involving 'movement'. As effective remediation often depends on aetiological insight, the discovery of the nature of the syntactic deficit, along side a possible compensatory use of semantics to facilitate sentence processing, can be used to direct therapy. However, the therapeutic strategy to be used, and whether such similar strengths and weaknesses within the language system are found in other SLI subgroups are empirical issues that warrant further research.

Incremental processing in head-final child language: online comprehension of relative clauses in Turkish-speaking children and adults

The present study investigates the parsing of pre-nominal relative clauses (RCs) in children for the first time with a realtime methodology that reveals moment-to-moment processing patterns as the sentence unfolds. A self-paced listening experiment with Turkish-speaking children (aged 5–8) and adults showed that both groups display a sign of processing cost both in subject and object RCs at different points through the flow of the utterance when integrating the cues that are uninformative (i.e., ambiguous in function) and that are structurally and probabilistically unexpected. Both groups show a processing facilitation as soon as the morphosyntactic dependencies are completed and parse the unbounded dependencies rapidly using the morphosyntactic cues rather than waiting for the clause-final filler. These findings show that five-year-old children show similar patterns to adults in processing the morphosyntactic cues incrementally and in forming expectations about the rest of the utterance on the basis of the probabilistic model of their language.

Thermal and structural properties of commercial dental resins light-cured with blue emitting diodes (LEDs)

We have investigated the thermal and structural properties of different commercial dental resins: Filtek(TM) Z-350, Grandio(A (R)), Tetric Ceram(A (R)), and TPH Spectrum(A (R)). The purpose of the present study was to evaluate quantitatively the photo-polymerization behavior and the effect of filler contents on the kinetic cures of the dental resins by using Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. We have successfully obtained the low and high glass transition T (g) values of the dental composite resins from DSC curves. It was also observed a good agreement between the both T (g) values, activation energies from thermal degradation, and the degree of conversion obtained for all samples. The results have shown that Tetric Ceram(A (R)) dental resin presented the higher T (g) values, activation energy of 215 +/- A 6 KJ mol(-1), and the higher degree of conversion (63%) when compared to the other resins studied herein.