Hydrogenated butadiene-nitrile rubber elastomers: research of functional properties

The subject of the study were rubbers based on partially and fully hydrogenated nitrile-butadiene rubbers (HNBR) Therban АТ 5065 VP and Therban АТ 5005 VP, taken individually and in the ratios 80:20, 70:30, 60:40, 50:50 accordingly. The purpose of the work was to study the functional properties of rubbers based on HNBR of various degrees of unsaturation using modern methods of analysis. The degree of dispersion of the filler and the thermodynamic compatibility of polymer components in rubbers based on Therban АТ 5065 VP and Therban АТ 5005 VP mixtures are appreciated. Glass transition and decomposition temperatures, elastic modulus and mechanical loss tangent of HNBR-based and their combined compositions were identified. The microrelief of the surface of rubber samples based on HNBR, taken in different ratios, was investigated.

Functional Properties of Elastomers Based on Butadiene-Nitrile Rubbers

In this article Therban AT 5065 VP, Therban AT 5005 VP - HBNR elastomers of different unsaturation degrees and their combined compositions research results (using optical and atomic force microscopy, DSC, DMA) are described. With these results structure and functional properties operational data of nitrile elastomers was obtained with no need of durable tests under different temperatures. It was found out that filler dispersion rises from 61.8 to 90.5 % and decomposition temperature grows from 261.9 to 275.3 °C while Therban AT 5005 VP share is increased from 20 to 50 weight parts. It is shown that elastomers with rubber ratio of 50:50 within temperature range from minus 30 to plus 150 °C have the lowest elasticity coefficient (from 311 to 1.6 MPa) and mechanical loss tangent (0.20) at the end of the test.

Effect of activation of wollastonite surface by quaternary ammonium salts on the relaxation properties of PVC compositions modified by it

It is promising to use wollastonite as a modifier of plasticized polyvinyl chloride compositions. The main advantages of wollastonite are white colour and needle-shaped particles. To improve the compatibility of this filler with a polymer matrix, it is effective to activate the surface of this mineral by quaternary ammonium salts (QAS). Valuable information on molecular motion in modified compositions can be obtained by studying the relaxation processes using dynamic mechanical analysis. In the temperature dependences of the mechanical loss tangent of the PVC compositions in the region of transition from the glassy to highly elastic state, two maxima were observed. It has been established that for compositions modified with both natural and surface treated wollastonite, regardless of the chemical structure of QAS used to activate the polymer. This is probably due to the formation of a boundary layer in which molecular mobility is inhibited because of the interaction of the polymer with the filler. Thawing of segmental mobility in this boundary layer occurs at the higher temperatures than in the PVC matrix. The surface treatment of wollastonite by QAS somewhat shifts the described relaxation transitions to higher temperatures due to an increase in the efficiency of interaction of the components at the interface. The magnitude of the change in the temperature of the segmental mobility, both in the polymer matrix and in the boundary layer, increases with an increase in the degree of activity of the filler surface.

The Effect of the Functionalisation of Low-Dispersion Carbon Black of the OMCARB Series by Hydrogen Peroxide on the Properties of Filled Composites

The aim of this work was to produce a new filler for polymers in which a low surface activity is combined with a high degree of structure and functionalisation of the surface, which will bring the processing properties of filled rubber mixes closer to the properties of rubber mixes with channel carbon black. The oxidation of specimens of low-dispersion, highly structured carbon black of grade OMCARB S820 was carried out using aqueous solutions of hydrogen peroxide of different concentration. Using a combination of methods, including X-ray diffraction analysis (D8 Advance diffractometer; Bruker, Germany) and transmission electron microscopy (JEM 2100 electron microscope; JEOL, Japan), we assessed the physicochemical properties and the form and the number of oxygen-containing groups (carboxyl, phenolic, lactone) on the surface of a particle of oxidised S820 in comparison with carbon black K354 (produced by the Khazar Chemical Plant, Turkmenistan) and semi-active furnace black N550 (produced by Omsktekhuglerod). The rheological characteristics (MDR 3000 vibrorheometer and MV 3000 viscometer; MonTech, Germany) and the physicomechanical characteristics (tensometer; Shimadzu, Japan) of rubber mixes filled with these blacks and of rubber compounds based on natural rubber were determined. The dynamic properties of the rubber compounds and the glass transition temperatures were determined on a DMA 242D instrument (Netzsch, Germany). Comparative data on the temperature dependence of the mechanical loss tangent (tg δ)of the rubber compounds showed that at temperatures of −60 and +60°C the greatest differences are possessed by rubber compounds with K354. At intermediate temperatures, the tg δ values for rubber compounds with the different fillers are similar. The new carbon black was advantageous with respect to the strength properties and dynamic characteristics of the rubber compounds, retaining the unique properties of composites filled with channel black.

A Pilot Study on the Relationship between Mechanical and Electrical Loss Tangents of Glass Powder Reinforced Epoxy Composites Post-Cured in Microwaves

The mechanical and thermal properties of hollow glass powder reinforced epoxy resin composites have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the dielectric properties of the composites with a view to benefit the relevant industry. The relationship between the dielectric and thermal properties will also be studied and correlated. The original contributions of this paper are that samples post-cured in conventional ovens have higher electrical as well as mechanical loss tangent values than their counterparts cured in microwaves only. The storage modulus of all samples post-cured conventionally is higher than its counterpart. This is in line with the fact that they are softer material with lower glass transition temperatures. For all percentages by weight of glass powder, the glass transition temperature for the microwave cured sample was higher and the composite was stiffer; the opposite was true for the conventionally cured samples.

Extrinsic Resonance Effects in a Subresonant Mechanical Spectrometer

Extrinsic resonance effects observed in a low-frequency subresonant mechanical spectrometer are reported. High resolution of the mechanical spectrometer enables precise measurement of small values of the mechanical loss tangent ( tanϕ = 1- 2 × 10-4) and the apparent high values of the loss tangent detected for extrinsic resonance effects in the vicinity of the eigen frequencies of the spectrometer. Forced oscillations can be used as a ‘signal quality test’ to validate the quality of exponentially damped harmonic oscillations in the resonant mode.