Influence of Carbon Black and Silica Fillers with Different Concentrations on Dielectric Relaxation in Nitrile Butadiene Rubber Investigated by Impedance Spectroscopy

In neat nitrile butadiene rubber (NBR), three relaxation processes were identified by impedance spectroscopy: α and α′ processes and the conduction contribution. We investigated the effects of different carbon black (CB) and silica fillers with varying filler content on the dielectric relaxations in NBR by employing a modified dispersion analysis program that deconvolutes the corresponding processes. The central frequency for the α′ process with increasing high abrasion furnace (HAF) CB filler was gradually upshifted at room temperature, while the addition of silica led to a gradual downshift of the center frequency. The activation energy behavior for the α′ process was different from that for the central frequency. The use of HAF CB led to a rapid increase in DC conductivity, resulting from percolation. The activation energy for the DC conductivity of NBRs with HAF CB decreased with increasing filler, which is consistent with that reported in different groups.

Pengaruh Oleamida Terhadap Karakteristik Pematangan Karet Alam Terisi Silika

The purpose of this study was as a feasibility study of the utilization of oleamide as a new additive for natural rubber (NR) filled with silica using the semi-efficient vulcanization system. Silica fillers used as much as 30 parts per hundred parts rubber (phr). Oleamide was obtained from the synthesis of oleic acid with urea. Oleamide was inserted into the silica filled NR compounds with the varied composition of 0.0 phr; 2.0 phr; 4.0 phr; 6.0 phr, and 8.0 phr. The influence of oleamide on the curing characteristic of the silica filled NR compounds was observed. It was obtained that the oleamide functions as a curative and also a plasticizer. The greater the levels of oleamide added, the shorter the scorch time and optimum curing time were. Oleamide also decreased the minimum torque with addition up to 8.0 phr. The greater the levels of oleamide was, the lower the minimum torque was. Oleamide also increased the maximum torque and torque difference of the silica-filled NR composites at the addition of 2.0 phr. The 2.0 phr was the optimum composition of the oleamide.

Effects of polymorphic form and particle size of SiO2 fillers on the properties of SiO2–PEEK composites

The effects of polymorphic form and particle size of SiO2 fillers on the dielectric, mechanical and thermal properties of SiO2–Polyetheretherketone (SiO2–PEEK) composites were investigated in this paper. Strong low frequency (<10Hz) Debye-like dielectric dispersions could be observed for all samples. The dielectric permittivity at high frequencies of the composite exhibits little morphology or particle size-sensitive characteristics of the SiO2 fillers. All the composites obtained in this case demonstrate the dielectric permittivities of [Formula: see text] at high frequencies. The crystalline [Formula: see text]-cristobalite filled composite exhibits lower dielectric loss and mechanical strength, but larger thermal expansion coefficient and thermal conductivity, compared with the similar particle sized amorphous SiO2 filled one. The crystalline [Formula: see text]-quartz filled composite demonstrates the lowest mechanical strength and highest dielectric loss. An increase in particle size of the spherical fused silica fillers decreases the dielectric loss, while increases the thermal conductivity of the composite. The flexural strength of the composite reaches the maximum value of 113 MPa when the particle size of spherical SiO2 filler is [Formula: see text]m. Particle packing by combining optimal amounts of differently sized spherical fused silica fillers leads to a substantial improvement of mechanical strength (153MPa) coupled with reasonable dielectric and thermal properties due to the synergic effect (dielectric permittivity ([Formula: see text] = 3.35, dielectric loss (tan[Formula: see text] @10 GHz, thermal conductivity ([Formula: see text] = 0.74 W/m*k ([Formula: see text]C), coefficient of thermal expansion ([Formula: see text]C and relative density ([Formula: see text]) = 99.72%).

A Novel Framework to Study the Role of Ground and Fumed Silica Fillers in Suppressing DC Erosion of Silicone Rubber Outdoor Insulation

This paper investigates the effect of ground and fumed silica fillers on suppressing DC erosion in silicone rubber. Fumed silica and ground silica fillers are incorporated in silicone rubber at different loading levels and comparatively analyzed in this study. Outcomes of the +DC inclined plane tracking erosion test indicate a better erosion performance for the fumed silica filled composite despite having a lower thermal conductivity compared to the ground silica composite. Results of the simultaneous thermogravimetric and thermal differential analyses are correlated with inclined plane tracking erosion test outcomes suggesting that fumed silica suppresses depolymerization and promotes radical based crosslinking in silicone rubber. This finding is evident as higher residue is obtained with the fumed silica filler despite being filled at a significantly lower loading level compared to ground silica. The surface residue morphology obtained, and the roughness determined for the tested samples of the composites in the dry-arc resistance test indicate the formation of a coherent residue with the fumed silica filled composite. Such coherent residue could act as a barrier to shield the unaffected material underneath the damaged surface during dry-band arcing, thereby preventing progressive erosion. The outcomes of this study suggest a significant role for fumed silica promoting more interactions with silicone rubber to suppress DC erosion compared to ground silica fillers.

Evaluation of Mechanical and Tribological properties of Biowaste and Biowaste Based Silica Particulate Epoxy Composites

This paper reports the mechanical-erosion wear properties of extracted silica from Biowaste (rice husk) and pure rice husk-filled epoxy composites. A comparison is made on the influence of dispersed silica and rice husk particles on the properties of the epoxy composites. The composites are fabricated by hand lay-up process. The specimens are tested as per the ASTM standards for three different filler loadings of each silica and rice husk separately (2,4 and 6wt%). It is perceived that with the increase in the rice husk filler loading in epoxy, there is a decline in tensile, flexural, and erosion wear properties. It is also evident that, with the increase in silica content until 6%, the tensile and flexural strength have displayed consistent enhancement. Alongside, erosion results confirm that the properties of the pure epoxy had exhibited transition from semi-brittle to ductile nature due to the addition of silica fillers.