SYNERGISTIC MAGNETORHEOLOGICAL NR–NBR ELASTOMER BLEND WITH ELECTROLYTIC IRON PARTICLES

ABSTRACT This article presents the development of a new kind of magnetorheological elastomer blend made with natural rubber, acrylonitrile–butadiene rubber (NR-NBR), and electrolytic iron particles through solution mixing. The compressive stress and elastic modulus of the composites in the isotropic and anisotropic states of the filler were studied. A unique study of the filler distribution and filler orientation mechanism was proposed from the compressive properties and scanning electron microscopy. A strong improvement in the elastic modulus of the NR–NBR blend from isotropic to anisotropic change was achieved as compared with NR and NBR in single-rubber composites. The filler content in the anisotropic magnetorheological elastomers was optimized by measuring the field-dependent elastic modulus in the presence of an externally applied magnetic field. The blend rubber composites showed better sensitivity in the presence of a magnetic field than the NR and NBR composites did. The improvement might be due to the better filler orientation and strong adhesion of filler particles by the NR phase in the blend matrix. The new elastomer blends may have applications in active dampers, vibrational absorption, and automotive bushings.

Effect of Fabrication Method on Tensile Behaviour of Polysiloxane (POS) Filled Rice Husk Silica (RHA SiO2) Composites

The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO2) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO2 addition but strength decreased at 12wt% due to agglomeration of RHA SiO2. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO2 as filler. The surface morphology of CO composites had showed that the most of RHA SiO2 were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO2 to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Changes in Electrical Conductance of Polymer Composites Melts Due to Carbon Nanofiller Particles Migration

In this work, the results of investigation of the effect of polymer composite melts electrical conductance increase with time are presented. The conductance time dependencies were obtained for composites based on polypropylene filled with carbon nanoparticles of different types. The dependencies were analyzed to demonstrate the possibility of correlation of the conductance kinetics with different composite parameters, such as the filler geometry. Additional studies were carried out, such as electron microscopy study, conductance measurements after consecutive surface layer removal, and composite melt conductance measurements using a three-electrode scheme. The results showed that the increased electrical conductance of the composite materials can be attributed to the formation of an enriched with the filler particles surface layer, which happens during the stay of the composite in a melt state. Analysis of the experimental data, along with the results of numerical modeling, allowed to suggest a possible filler distribution transformation scheme. The physical premises behind the investigated effect are discussed.

MODIFICATION OF MIXTURES BASED ON ETHYLENEPROPYLENE RUBBER AND SILICON ACID FILLER

The aim of the work was to study the effect of bis-(triethoxysilylpropyl)-tetrasulfide (TESPT) mixed with carbon black N330 in a ratio of 1:1, as a technical product OFS 6945 on the structure and properties of rubber mixtures and rubbers based on ethylene propylene rubber of the brand Vistalon 2504N and silica filler (KKN) of the brand Rosil-175, taken at a dosage of 30 wt. h. per 100 wt.h. rubber. The content of TESPT was 0.035, 0.050 and 0.070 mmol / 100 g of rubber. A group of vulcanizing agents included sulphur, thiuram, captax, zinc oxide and technical stearin. Rubber mixtures were prepared on rollers Lb 320 160/160. Organosilane was injected into rubber at the same time as Rosil-175. The homogeneity of the filler distribution in the finished mixtures was evaluated based on the results of testing samples on the RPA-2000 vibrorheometer. Vulcanization characteristics were determined using an MDR-2000 device. The structure of mixtures and rubbers was studied by the method of equal swelling of samples in toluene. It is shown that with the increasing content of TESPT, the proportion of bound rubber in a three-component mixture of the rubber – filler – organosilane increases due to the formation of interfacial connections. The uniformity of distribution of silica fillers in rubber matrix also increases. Workability of the mixtures on roller equipment improves. The rate of cross-linking in the core period and the degree of cross-linking of macromolecules at the same time curing increase as well. As a result, the elastic-strength properties of rubbers determined in the static test mode are improved, the best complex of which is provided with an organosilane content of 0.050 mmol/100 g of rubber.

THz Spectroscopy as a Versatile Tool for Filler Distribution Diagnostics in Polymer Nanocomposites

Polymer composites containing nanocarbon fillers are under intensive investigation worldwide due to their remarkable electromagnetic properties distinguished not only by components as such, but the distribution and interaction of the fillers inside the polymer matrix. The theory herein reveals that a particular effect connected with the homogeneity of a composite manifests itself in the terahertz range. Transmission time-domain terahertz spectroscopy was applied to the investigation of nanocomposites obtained by co-extrusion of PLA polymer with additions of graphene nanoplatelets and multi-walled carbon nanotubes. The THz peak of permittivity’s imaginary part predicted by the applied model was experimentally shown for GNP-containing composites both below and above the percolation threshold. The physical nature of the peak was explained by the impact on filler particles excluded from the percolation network due to the peculiarities of filler distribution. Terahertz spectroscopy as a versatile instrument of filler distribution diagnostics is discussed.