Rubber Filler Research Articles

Viability of Fillers in HTV Silicone Rubber in the AC and DC Inclined Plane Tests

The viability of fillers for inhibiting the dry-band arcing damage on high temperature vulcanized silicone rubber under the critical AC and the equivalent DC voltages of inclined plane test is investigated. Alumina tri-hydrate and ground silica are employed in the study as common fillers employed in silicone rubber formulation for outdoor high voltage insulation, and thermal analysis is applied in order to understand the protective mechanisms of the fillers. Filler volume effect plays a role in improving the erosion performance, and the dilution effect of water of hydration is shown advantageous for preventing progressive (directed) erosion. Dilution effect promoted with internal oxidation is found only notable at 50 wt% alumina tri-hydrate in this study. On the other hand, alumina tri-hydrate at 10 or 30 wt% may yield a porous residue, which is conducive to thermo-oxidation (combustion) and consequently erosion. The erosion suppression effects reported for the fillers in the composites employed in this study are found less viable under the equivalent DC as compared to the critical AC voltages of the inclined plane test. This study clarifies common perceptions about the viability of fillers in silicone rubber for AC and DC outdoor insulation applications.

Preparation of an eco‐friendly carbon–silicon dual‐phase rubber filler with humic acid and silica sol

AbstractA new type of carbon–silicon dual‐phase filler (CSDPF) was prepared from highly active and widely available humic acid and low‐cost silica sol as raw materials, which were further used for styrene butadiene rubber (SBR) by ball milling and carbonization methods. The effects of the silica sol content and the bis(3‐triethoxysilylpropyl) tetrasulfide (TESPT) on the structure and surface properties of the CSDPF were investigated systematically. Silica sol combined with humic acid in the carbon–silicon dual‐phase complexes in the form of SiOC, while the TESPT and carbon–silicon dual‐phase complexes were combined in the form of SiOSi in the CSDPF. As the content of silica sol increased in the dual‐phase complexes, the amount and particle size of silica on the surface of CSDPF increased. A certain amount of silica in the fabricated filler facilitated its subsequent modification and applications. Compared with CB/SBR (SBR filled with carbon black 660), the mechanical properties, thermal stability, wear resistance, and wet skid resistance of SBR filled with the CSDPF were significantly improved. This work provides a new strategy for developing CSDPF.

Influence of Carbon Black/Silica Hybrid Ratio on Properties of Passenger Car Tire Sidewall

Influence of carbon black (CB)/precipitated silica (SiO2) hybrid ratio on properties of a passenger car tire (PCT) sidewall based on natural rubber (NR) and butadiene rubber (BR) blend was investigated. Rubbers filled with various hybrid filler ratios at a constant loading of 50 phr were prepared and tested. The filler reinforcement efficiency in association with crucial properties of the tire sidewall were of interest. Results show the enhanced rubber–filler interaction with increasing SiO2 fraction leading to the improvement in many vulcanizate properties including hardness, tensile strength, tear strength and fatigue resistance, at the expense of cure efficiency and hysteretic behaviors (i.e., reduced heat build-up resistance and increased dynamic set). The results also suggest the improvement in tire sidewall performance of the NR/BR vulcanizates reinforced with CB/SiO2 hybrid filler, compared to that of the CB-filled vulcanizate.

Effect of Short Banana Fiber on Hardness and Tensile Properties of Natural Rubber Composites

Banana fiber (BF) was utilized as a reinforcing filler for natural rubber (NR). BF/NR composites containing banana fiber contents of 5, 10, and 15 parts per hundred parts of rubber (phr) were mixed on a two-roll mill machine. The hardness, tensile properties of BF/NR composites were studied. It was found that the hardness and moduli of BF/NR composites are higher than that of NR. Despite tensile strength and strain at break of BF/NR composite lower than NR. Moreover, hardness and moduli of BF/NR composites increased, while tensile strength and strain at break decreased with the increase in banana fiber content. Thus, banana fiber exhibited improvement in the stiffness significantly of NR composites

Preparation and characterization of Kaolinite supported lanthanum-hydroxide and its improvements for natural rubber composites

Kaolinite supported lanthanum-hydroxide was successfully prepared via a deposition method and used to improve the mechanical properties of natural rubber (NR) composite. A series of techniques including X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the samples. The XRD, FT-IR, and EDS results show that lanthanum-hydroxide was successfully loaded on the surface of Kao and may interact with the inner surface hydroxyls. The surface and edge of Kaolinite gradually become rougher, and the lamellar structure had defects due to the loading of lanthanum hydroxide. The resulting material had a uniform dispersion in the natural rubber composite. The scorch time (t10) and curing time (t90) of the filled NR composites decreased simultaneously relative to pure NR, and decreased when compared to that of raw Kao. The tear strength reached at 57.35 kN/m, which increased by 54% relative to that of pure NR. The thermal stability of the prepared composites improved with loading of lanthanum-hydroxide. The reinforcement of the mechanical properties of the filled NR composite is attributed to the fine dispersion of lamellar-like particles in a rubber matrix with restrictions on rubber chain motion via trapping rubber chains and improvements in the incorporation between rubber molecules and filler particles due to the complexation between the rare earth element on the surface of Kao and the double-bond in rubber chains.

Surface modification of rice husk–based carbon–silica dual‐phase filler by ethanol‐assisted milling and its reinforcing on natural rubber

AbstractSilica carbon black (SiCB) was used as a natural carbon–silica dual‐phase filler (CSDPF) containing both biochar and silica, which was obtained by pyrolysis of rice husks. The reinforcing performances of SiCB were limited by the large particle size and poor surface activity. In this work, the size and distribution of the SiCB particles were modified by ethanol‐assisted milling (S/E), and increase in oxygen‐containing groups enhanced the surface activity of SiCB and promoted the grafting of silane coupling agent (Si69). The filler–rubber interfacial interactions were enhanced when the Si69‐grafted SiCB (S/E‐X, X means the amount of Si69) was used as filler for natural rubber (NR). Compared with the SiCB‐filled NR (SiCB/NR), the S/E‐3‐filled NR (S/E‐3/NR) showed 44%, 19%, and 27% improvement in the tensile strength, tear strength, and stress at 300% strain, respectively, and the reinforcing properties have reached the level of commercial carbon black (N774). This study provides a novel way for surface modification of CSDPF and improves the application of rice husk–based materials in rubber composites.

Using the Lorenz–Park, Mooney–Rivlin, and dynamic mechanical analysis relationship on natural rubber/leather shavings composites

AbstractThe tanning industry generates millions of tons of waste every year, which can cause environmental damage as well as problems to human health. In this article, we analyzed the use of leather shavings (20 to 80 parts per hundred rubber) as fillers in Natural Rubber (NR) composites. For this purpose, the interfacial interaction of the filler was quantitatively evaluated based on the cross‐link density value calculated by the Flory–Rehner methodology using the Lorenz–Park equation (swelling). Then, the results of this evaluation were compared with those obtained by the Mooney–Rivlin method (by a stress–strain test). According to our findings, the tensile strength at rupture of the composites increased by 100%, that is, from 7.0 MPa (NR) to 14.0 MPa, when 80 phr of leather waste were incorporated. In addition, their final deformation decreased around 50% compared to pure gum (no filler). According to the Lorentz–Park equation, values over 0.7 indicate a strong interaction between the leather shavings and the NR matrix. Likewise, a dynamic mechanical analysis confirmed a strong interfacial interaction based on the B parameter. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to examine the morphology and chemical properties of the composites.

Research On the Effect of Reinforcing Filler on The Mechanical and Electrical Properties of Insulating Coated Silicone Rubber

This paper studies the silicone rubber insulation coating material used for the modification of overhead bare wires. The influence of two reinforcing fillers of silicone rubber on the density, mechanical properties and electrical properties of insulating coating materials was explored. Finally,25 copies of white carbon black were selected as a reinforcing filler to prepare a low-density, high-strength, and good insulating silicone insulating coating material.

Effect of Vulcanization Processes on Properties of Natural Rubber/Cellulose Composites

The effect of vulcanization processes and surface treatment of cellulose were investigated on tensile strength, degradation temperature, and morphological properties of cellulose/natural rubber composites. Cellulose was surface-treated with Si-69 silane coupling agent and used as reinforcing filler in natural rubber (NR). Different vulcanization processes including electron beam irradiation (EB-Cured) and sulphur vulcanization (S-Cured) were used to crosslink NR. The incorporation of both untreated and treated cellulose at various concentrations (5, 10, 15 and 20 phr) into NR was found to significantly improve the tensile strength and modulus. Notably, with addition of treated cellulose in NR, the tensile strength and modulus were considerably higher than that of the untreated cellulose for all curing system. SEM morphological analysis revealed a well dispersion of cellulose particles in NR matrix. Addition of cellulose slightly decreased the onset of degradation temperature of NR, however, the degradable temperature was found to be unchanged. The curing systems had shown an impact on tensile property of NR. S-Cured NR exhibited highest modulus of 2.23 MPa comparing to the EB-Cured NR (1.69 MPa) for the same amount of cellulose (20 phr), due to a stronger crosslink network. However, the curing system had no significant impact on degradation temperature of NR.

Study of the rheological properties of the highly-filled paste-like fuel composition based on oligomeric rubber and dispersed fillers

We present the results of creation of paste-like fuel compositions with a high degree of filling (up to 90 wt.%) and investigation of their rheological properties. The developed composition contained the following components: a polymer matrix (type SNBR-N butadiene rubber) and a mixture of inorganic fillers (preliminarily surface-modified highly disperse potassium chloride, that was microencapsulated by using oligomeric products of polyehtyleneterepthalate glycerolize, and highly dispersed aluminum powder. A surface-active compound (oligomeric polioxypropylene glycol) and plasticizers of different natures were used as additional components, which were introduced in order to increase the degree of filling of the resulting paste-like compositions while maintaining a low level of their viscosity. The dynamic viscosity of the compositions was evaluated in the range of the shear stresses of 1 to 30 kPa and the temperatures of 293 to 323 K by using a rotary viscometer (cone–plane system). The viscosity of the composition which is a mixture of saturated and unsaturated methyl ester fatty acids at the maximum degree of filling (90 wt.%) was at the level of viscosity of the individual binder.

Toughening and enhancing thermostability of vitrimer rubber via adding heterocyclic aramid

Vitrimers instead of traditional materials is deemed as an effective way to solve the problem of material recycling. However, because of the reversible nature of dynamic covalent bonds, it is a challenge to improve the thermostability of vitrimers. Herein, we present a facile strategy by adding a small quantity of heterocyclic aramid to epoxidized natural rubber to simultaneously reinforce the mechanical properties and thermostability of dynamically cross-linked rubber. The improved comprehensive performances of vitrimer rubber resulted from the hydrogen bonds and covalent cross-linking bonds formed between epoxidized natural rubber and heterocyclic aramid fillers.

Effects of silicon carbide as a heat conductive filler in butyl rubber for bladder tire curing applications

Rubber composites are widely used in tires and their related applications. In the present study, butyl rubber/carbon black/silicon carbide (α-SiC) composites were prepared by melt blending. They are used in tire curing applications for utilization of silicon carbide for the development of heat conductive bladder. The effect of α-SiC micro particle loading on resin curing characteristics, tensile properties (normal and aged), hardness, tear strength and morphology were studies. We also investigated its effect on the thermal transport properties of carbon black filled butyl rubber such as its heat conductivity, heat diffusivity, and specific heat capacity. A heat transfer mathematical modeling and computer simulation were conducted using ABAQUS finite element software to simulate the effect of bladder composite heat diffusivity increment on temperature-time dependency for different points of a tire during curing process. The results showed an average increase of 72% in the thermal conductivity, an average increment of 45% in heat capacity, and an average increment of 13% in heat diffusivity coefficient of carbon black filled composite in the presence of 18 phr (part per hundred of rubber) of α-SiC, without significant loss of mechanical properties. Further addition of α-SiC to 28 phr while decreasing mechanical properties did not have a further improving effect on the composite thermal conductivity and its thermal diffusivity coefficients. The tire curing simulation results revealed that it is possible to reduce the steam pressure inside of curing bladder from 22 to 20 bar (9%) in the presence of 18 phr α-SiC in bladder formula.

Effect of the Epoxide Contents of Liquid Isoprene Rubber as a Processing Aid on the Properties of Silica-Filled Natural Rubber Compounds.

In this study, we examined the feasibility of using epoxidized liquid isoprene rubber (E-LqIR) as a processing aid for truck and bus radial (TBR) tire treads and investigated the effects of the epoxide content on the wear resistance, fuel efficiency, and resistance to extraction of the E-LqIRs. The results confirmed that, compared to the treated distillate aromatic extract (TDAE) oil, the E-LqIRs could enhance the filler–rubber interactions and reduce the oil migration. However, the consumption of sulfur by the E-LqIRs resulted in a lower crosslink density compared to that of the TDAE oil, and the higher epoxide content decreased the wear resistance and fuel efficiency because of the increased glass-transition temperature (Tg). In contrast, the E-LqIR with a low epoxide content of 6 mol% had no significant effect on the Tg of the final compound and resulted in superior wear resistance and fuel efficiency, compared to those shown by TDAE oil, because of the higher filler–rubber interactions.

Investigation on the mechanical and tribological properties of polyethylene wax/silicone rubber composites

As an auxiliary agent for rubber processing, polyethylene wax can be used to enhance the diffusion of filler in rubber, improve the extrusion speed of rubber compound and facilitate rubber demoulding, which has good development potential in the field of rubber processing and manufacturing. At present, there is no research on the optimum amount of polyethylene wax in silicone rubber. Therefore, in this paper, we studied the influence of different amount of polyethylene wax on the mechanical and friction properties of silicone rubber. Firstly, silicone rubber composites with different polyethylene wax content were prepared by mechanical mixing and hot pressing. Then, the mechanical properties and friction and wear properties of silicone rubber composites were tested by tensile testing machine and multifunctional comprehensive tester for surface properties of materials. Finally, combined with a series of characterization methods, such as three-dimensional (3D) morphology, scanning electron microscopy (SEM), microscopic observation and energy dispersive X-ray spectroscopy (EDS), the mechanism of polyethylene wax in silicone rubber was studied. The results show that the best addition amount of polyethylene wax in silicone rubber is 0.25 phr, and the friction coefficient of polyethylene wax/silicone rubber composite is the lowest and most stable, and the wear amount is the least. In the process of friction, polyethylene wax can be separated from silicone rubber matrix and distributed on the surface of wear marks, playing a better role in lubrication and wear reduction.

Properties of Natural Rubber with Molasses Carbon Powder Activated Using Microwave Radiation as a Filler

In this research, the preparation of carbon powder from molasses, a by-product of the sugar production process or agricultural wastes, was studied as filler in natural rubber. The carbon powder from molasses or molasses black (MB) was subsequently activated using 1:4 by weight (MB: KOH) using heating energy from microwave radiation and comparing with the electrically heating furnace. The result showed the surface area and total pore volume of MB activated by microwave radiation (MB KOH Wave) are clearly enhanced comparable with those activated using an electrically heating furnace. All of KOHactivated MB were used as filler in NR in the amount of 10 phr. It was found that MB KOH Wave filled NR obviously shows the improvement in cure characteristic, tensile properties, tear strength and swelling resistance of NR vulcanizate and is close with that of filled with carbon black (CB).

Influences of purification and surface treatment of sugarcane bagasse ash on mechanical properties of natural rubber composites

AbstractAttempts to use bagasse ash (BA) as a filler in natural rubber (NR) have been made. Acidolysis/alkaline extraction method was used to purify BA. The purified BA (PBA) was subsequently characterized by various techniques such as X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and so forth. After the purification, PBA had a lower particle size and a higher specific surface area. XRD results showed that silica was the main composition of PBA while FTIR results revealed the existence of hydroxyl groups on the PBA surface. The reinforcement magnitude of PBA in NR was subsequently evaluated both without and with the addition of surface modifying agents, namely, bis‐3‐triethoxysilylpropyl tetrasulfide (TESPT) and epoxidized natural rubber (ENR). Due to its large particle size, PBA acted as a semi‐reinforcing filler for NR, that is, the small increases of hardness, modulus and tensile strength were observed in the presence of PBA. As TESPT and ENR could improve the extent of rubber‐filler interaction, mechanical properties of the NR vulcanizates filled with PBA‐TESPT and PBA‐ENR were slightly higher than those of the PBA‐filled NR vulcanizate. For instance, tensile strength exhibited approximately 22% increase after the surface treatment. In this study, both PBA‐TESPT and PBA‐ENR showed comparable degree of reinforcement.

Common Origin of Filler Network Related Contributions to Reinforcement and Dissipation in Rubber Composites.

A comparative study focusing on the visco–elastic properties of two series of carbon black filled composites with natural rubber (NR) and its blends with butadiene rubber (NR-BR) as matrices is reported. Strain sweeps at different temperatures are performed. Filler network-related contributions to reinforcement () are quantified by the classical Kraus equation while a modified Kraus equation is used to quantify different contributions to dissipation (, ). Results indicate that the filler network is visco-elastic in nature and that it is causing a major part of the composite dissipation at small and intermediate strain amplitudes. The temperature dependence of filler network-related reinforcement and dissipation contributions is found to depend significantly on the rubber matrix composition. We propose that this is due to differences in the chemical composition of the glassy rubber bridges connecting filler particles since the filler network topology is seemingly not significantly influenced by the rubber matrix for a given filler content. The underlying physical picture explains effects in both dissipation and reinforcement. It predicts that these glassy rubber bridges will soften sequentially at temperatures much higher than the bulk of the corresponding rubber. This is hypothetically due to rubber–filler interactions at interfaces resulting in an increased packing density in the glassy rubber related to the reduction of free volume. From a general perspective, this study provides deeper insights towards the molecular origin of reinforcement and dissipation in rubber composites.

Preparation and characterization of non‐vulcanized natural rubber‐based cocoa pod husk composites

AbstractSeveral ingredients are often introduced into rubber matrices during the production of natural rubber (NR) based articles, essentially to modify and improve upon the properties of the final products as well as to reduce their costs. In this study, composites of natural rubber and cocoa pod husk were prepared by solution casting and tested for their rheological and thermal properties in order to ascertain the suitability of the latter as a substitute for standard fillers in the NR industry. An increase in the level of substitution significantly reduced the rheological properties of the composites in the linear viscoelastic region but had no significant effects on their thermal stability, glass transition temperature and on the α‐relaxation of the NR composites except at the highest level of substitution (25%). However, α‐relaxation and rheological shift factors were always temperature‐dependent and had a direct influence on their electrical conductivity with no permanent chemical bonds formed or broken during preparation of the composites. Hence, untreated cocoa pod husk could serve as non‐reinforcing filler for raw natural rubber.

Hybrid Silica-Based Fillers in Nanocomposites: Influence of Isotropic/Isotropic and Isotropic/Anisotropic Fillers on Mechanical Properties of Styrene-Butadiene (SBR)-Based Rubber.

The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer–silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene (PBD) rubber matrix. Precipitated Highly Dispersed Silica (HDS) nanoparticles (10 nm) have been associated with spherical Stöber silica nanoparticles (250 nm) and anisotropic nano-Sepiolite. By imaging filler at nano scale through Scanning Transmission Electron Microscopy, we have shown that anisotropic fillers align only in presence of a critical amount of HDS. The dynamic mechanical analysis of rubber compounds confirms that this alignment leads to a stiffer nanocomposite when compared to Sepiolite alone. On the contrary, spherical 250 nm nanoparticles inhibit percolation network and reduce the nanocomposite stiffness.

Study on the Use of CTAB-Treated Illite as an Alternative Filler for Natural Rubber

Fillers are indispensable for rubber composites. Carbon black as an efficient reinforcing filler is most widely used in the rubber industry. However, the utilization of nonrenewable feedstock, energy consumption, and footprint for making carbon black lead to the seeking of alternative substitutes for carbon black, which is of great significance. Here in this work, the possibility of illite, a most common mineral in sedimentary rocks, as an alternative filler for natural rubber (NR) is determined. It is found that pristine illite slows the curing rate and decreases the cross-linking density of NR, which results in the inferior performance of NR. This is associated with the weak filler–rubber interaction, which is a vital factor in deciding the performance of rubber composites. Therefore, illite has been modified using hexadecyl trimethyl ammonium bromide (CTAB), a commonly used cation surfactant, for improving the filler–rubber interaction. The thus obtained C-illite is confirmed to be efficient for (i) enhancing the illite–NR interaction, (ii) improving the dispersion of illite in the NR matrix, and (iii) accelerating the curing process of NR with increased cross-linking density. All of these lead to significantly improved mechanical properties and wear resistance of the C-illite/NR composites, e.g., a 71.88% increase of the modulus at 300% strain compared to the pure NR and a 23.79% reduction of the DIN abrasion volume compared to the NR filled with 40 phr pristine illite. This illustrates the high possibility of CTAB-modified illite with an optimal particle size as a promising alternative filler of carbon black for reinforcing rubbers.