Triethoxysilylpropyl Tetrasulfide Research Articles

Improving the mechanical and abrasion properties of silica-reinforced styrene-butadiene rubber composites by optimizing the concentrations of compatibilizers

AbstractSilica (chemical formula SiO2) is a promising, more environmentally friendly alternative to carbon black (CB) used in the rubber industry as a filler. Although silica is already used in rubber products, it is not used as extensively as CB because the polar surface of silica cannot interact well with the apolar polymer molecules of the most frequently used rubbers. To solve this problem, experts have tried different grafting methods and several coupling agents for a stronger silica-elastomer connection. In this article, we used bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and polyethylene glycol (PEG) combined to improve the connection between the surface of silica and the apolar styrene-butadiene rubber (SBR) matrix. We examined mechanical and structural properties and found that adding 3 phr PEG and 4.5 phr TESPT to SBR is optimal for 60 phr silica content. This ratio of additives resulted in a 48% improvement in tensile strength. The positive effect of the coupling agents shows up in abrasion mass loss and tear strength as well.

Carbon Black Functionalized with Serinol Pyrrole to Replace Silica in Elastomeric Composites.

Elastomer composites for dynamic mechanical applications with a low dissipation of energy are of great importance in view of their application in tire compounds. In this work, furnace carbon black functionalized with 2-2,5-dimethyl-1H-pyrrol-1-yl-1,3-propanediol (SP) was used in place of silica in an elastomer composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. The traditional coupling agent used for silica was also used for the CB/SP adduct: 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT). The composite with the CB/SP + TESPT system revealed a lower Payne effect, higher dynamic rigidity, and lower hysteresis, compared to the composite with CB + TESPT, although the latter composite had a higher crosslinking density. The properties of the silica and the CB/SP + TESPT-based composites appear similar, though in the presence of slightly higher hysteresis and lower ultimate properties for the CB/SP-based composite. The use of CB in place of silica allows us to prepare lighter compounds and paves the way for the preparation of tire compounds with lower environmental impacts.

Effect of dispersants on the hydroxyapatite‐filled natural rubber biocomposites with enhanced functional properties

AbstractThe aim of this work was application of the hydroxyapatite (HAP) in various amounts by weight as a filler of natural rubber (NR) biocomposites. Innovatively, silanes, that is, (3‐aminopropyl)‐triethoxysilane (APTES) and bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPTS), surfactant, that is, cetyltrimethylammonium bromide (CTAB), and alkylimidazolium ionic liquids (ILs) with halide anions, that is, 1‐butyl‐3‐methylimidazolium chloride (BmiCl) and 1‐decyl‐3‐methylimidazolium bromide (DmiBr), were used to improve the dispersion of the HAP and curatives particles in the rubber matrix, and consequently the curing characteristics and properties of NR biocomposites. The influence of HAP and dispersants on the crosslink density, tensile properties, thermal stability, resistance to thermo‐oxidative aging, and ability to damp vibration of vulcanizates were investigated. It has been proven, that HAP can be efficiently used as a filler of NR biocomposites alternatively to commercial inactive or active fillers, for example, chalk, talc, or silica. The optimal HAP content is 30 phr. HAP did not detrimentally affect the curing characteristics of NR composites, crosslink density, and damping properties of the vulcanizates, while significantly raised their tensile strength, thermal stability, and resistance to thermo‐oxidative aging. Most importantly, CTAB and ILs considerably improved the dispersion of HAP and curatives particles in the NR matrix and consequently lowered the vulcanization temperature by approximately 25°C and enhanced by approximately 50% the crosslink density and tensile strength of the NR biocomposites.

Surface modification of commercial carbon black by silane coupling agents for improving dispersibility in rubber compounds

AbstractThe dispersion of a filler in a rubber matrix is a crucial parameter affecting the mechanical and dynamical properties of a rubber compound. It is the current issue of the rubber compounding industry because, most fillers are categorized as a mineral, while the rubber is an organic material. The surface modification of the filler has been accepted as an effective technique for the improvement of the abovementioned parameter. First, the surface premodification of commercial carbon black with a grade of N660 (CB) was implemented by four different oxidation methods. After that, among of used methods, the oxidation method using citric acid was selected to produce modified carbon black (CB‐Oxi) for further treatment. Subsequently, the coupling agent, Bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPT) was functionalized on the surface of CB‐Oxi to produce modified‐CB‐Oxi. Also, for comparison purposes, the TESPT functionalization was accomplished on untreated CB to form modified‐CB. The FTIR spectra of CB‐Oxi showed using the premodification method introduced the hydroxyl and carboxyl groups on the surface of CB. The correspondent spectra for modified‐CB‐Oxi confirmed the existence of silane groups on the surface of the carbon black. However, the mentioned silane groups were not observed on the surface of modified‐CB. The findings were strengthened by several characteristic techniques including, FESEM, XRD, EDS, CHNS elemental analysis, and RAMAN spectra. The FESEM graphs and elemental mapping showed homogeneous dispersion and uniform distribution of sulfur and silicon elements on the modified‐CB‐Oxi surface. According to RAMAN spectra, the disturbance in the structure of carbon black graphite was reduced after surface modification. modified‐CB‐Oxi is proposed as a potential substitute filler for current commercial carbon black in rubber compounding.

A FUNDAMENTAL STUDY ON CYCLIC TETRASULFIDE AS A SULFUR DONOR AND CO-AGENT FOR RUBBER CROSSLINKING

ABSTRACT Sulfur donors are used commonly in rubber crosslinking, usually in conjunction with elemental sulfur. In the crosslinking process, sulfur donors release in situ free sulfur. The difference between two sulfur donors, bis(triethoxysilylpropyl)-tetrasulfide (TESPT) and cyclic tetrasulfide (CTS), both of which contain at least one tetrasulfidic group in the molecule, is analyzed. Chemical model studies are deployed to assess the chemical reactivity of the two molecules. The difference in reactivity of the two sulfur donors was observed in chemical model studies in reaction with 2,3-dimethyl-2-butene, as followed by Raman spectroscopy, gas chromatography coupled with mass spectroscopy, and nuclear magnetic resonance analysis of the products of reaction. These studies represent a fundamental analysis and comparison between the two tetrasulfidic compounds, and the findings of these experiments can be extrapolated to crosslinking processes in rubber.

Highly selective adsorbents based on silica gel chemically modified with sulfur-containing groups of arched structure for preconcentration and determination of palladium(II) in products of processing of sulfide copper-nickel ore

Adsorbents based on silica gel chemically modified with arch structure 2-aminophenyl disulfide (DSS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TSS) groups have been synthesized. The proposed adsorbents quantitatively extracted (extraction ∼99 %) only palladium(II) among all platinum metals from solutions of 2 M HCl - pH 4. Quantitative extraction of Pd(II) was not interfered with 106-fold excesses of alkaline, alkaline-earth, 104-fold excesses of non-ferrous metals and iron, 102-103-fold excesses of other platinum metals. Pd(II) was eluted quantitatively (desorption ∼99 %) from the adsorbents surface with 5–10 % thiourea solutions and could be determined in the eluate by inductively coupled plasma optical emission spectrometry (ICP-OES). The adsorption capacity of DSS and TSS adsorbents was not changed after 5 adsorption-elution cycles. The limit of detection of palladium in the analyzed solution, calculated using the 3 s-criterion, was 0.1 μg/L for solid-phase extraction-inductively coupled plasma optical emission spectrometry (SPE-ICP-OES) method with a preconcentration factor of 50. Intensive yellow-orange color of the palladium surface complex was used in the development of express test-methods for its determination. SPE-ICP-OES and test methods were used in the determination of palladium in certified reference materials of sulfide copper-nickel ore and products of its technological processing.

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing.

Sulfite (SO32-) is considered a highly toxic anion for living organisms. Herein, we report the synthesis of copper immobilized over a 2D hexagonally ordered mesoporous silica material CuMS as an electrochemical and colorimetric dual-technique-based sensing platform for sulfite detection. The immobilization of copper on silica was achieved through the bis[3-(triethoxysilyl)propyl]tetrasulfide (TEPTS) ligand. Morphological and physical properties of the material were confirmed by several characterization techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 sorption, and X-ray photoelectron spectroscopy. The CuMS material retained mesoporosity with a narrow pore size distribution (D ≈ 5.4 nm) and a high Brunauer-Emmett-Teller surface area of 682 m2 g-1 after the immobilization of copper. The prepared catalyst shows promising electrocatalytic activity toward sulfite oxidation. A linear variation in the peak current was obtained for SO32- oxidation in the 0.2-15 mM range with a high sensitivity of 62.08 μA cm-2, under optimum experimental conditions. The limit of detection (LOD) was found to be 1.14 nM. CuMS also shows excellent activity toward colorimetric detection of sulfite anions with an LOD of 0.4 nM. The proposed sensor shows high selectivity toward the sulfite anion, even in the presence of common interferents. The detection of sulfite in white wine with excellent recovery demonstrates the practical applicability of this sensor.

Silanization of functionalized PET fabric to improve PET-nitrile rubber (NBR) adhesion; effects of functionalization type and silane concentration

Surface modification could increase affinity of PET fibers to polymer matrix by changing the interfacial physical interactions to covalent bonds. In this research, surface modification of a superfine polyethylene terephthalate (PET) fabric was performed by bis(triethoxysilylpropyl)tetrasulfide (TESPT). The surface grafting was performed at different silane concentrations (i.e. 1, 5 and 10X). Before silanization, the fabrics were functionalized using photochemical method (i.e. irradiation of UV light in presence of glutaric acid peroxide (GAP)) and also hydrolysis by Sodium hydroxide (NaOH). Due to functionalization, carboxyl and hydroxyl groups were formed on the PET surface that made it ready to condense with hydrolyzed silane molecules. The fabrics were characterized using FTIR, TGA, FE-SEM, XPS analysis for evaluation of grafting performances. XPS analysis confirmed the presence of new peaks of Si and S after surface modification with TESPT. Comparing the results of TESPT-grafted functionalized PETs, it was found that the silane grafting content on PET surface is dependent not only to the silane concentration but also to the functionalization method. Finally, the influences of silane grafting on the functionalized PET fabrics to NBR adhesion were evaluated using H-pull and T-peel tests. The results showed that silane grafted-carboxylated PET fabric illustrated more adhesion to NBR than silane grafted-hydroxylated PET (i.e. 33 and 12% improvement in the pullout strength and T-peel adhesion, respectively).

Talc modification with bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT)-based coating to improve the mechanical characteristics of silicone rubber

Rubber is a main material of prosthetic foot products. A local product of Indonesian prosthetic foot is available in the market. However, the quality of the product need to be improved. Several material formulations have been made to make prosthetic foot more elastic, strong, and affordable. An optimization formula of talc powder reinforced silicone rubber has been carried out in the previous study. However, the bonding between talc powder and silicone rubber is weak. In the present study, the talc powder is coated with a bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) in order to obtain strong bond between talc powder and silicone rubber. Mechanical characterizations were conducted to compare the composites with and without TESPT coating. The characterization include tensile and hardness tests. The tribometer tests are also conducted to compare both composites, it evaluates the value of friction and wear mass of the composites. The results show that the composites using coated talc powder can reduce wear and friction force. The friction and wear of composites containing coated talc powder is better than the local products. The hardness of the composites containing coated talc powder increases compared to those without coating. While the use of coated talc powder reduces the tensile strength and elongation at break.

Effect of Silica Nanoparticles and Modified Silica Nanoparticles on the Mechanical and Swelling Properties of EPDM/SBR Blend Nanocomposites

The influences of nanosilica and modified nanosilica on cure, compression set, mechanical and swelling characteristics are studied in blends of ethylene-propylene-diene monomer (EPDM)/styrene-butadiene rubber (SBR). In EPDM/SBR composites, the nanosilica made from rice husk ash (RHA) was utilised as a reinforcing nanofiller. The interaction between the nanosilica and the EPDM/SBR matrix at the interface is crucial for the production of rubber composites. This study uses bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and polyoxyethylene (20) sorbitan monolaurate (TWEEN-20) as a silica modifier, with the ratio of TESPT to TWEEN-20 maintained at 2:1. The cure and mechanical characteristics, compression set, abrasion and swelling resistance increased with the incorporation of nanosilica and modified nanosilica. By interacting at the interface between silica nanoparticles and the EPDM/SBR rubber matrix, TESPT with the TWEEN-20 modifier exhibits a considerable effect on cure characteristics, mechanical qualities, and swelling resistance.

Potential Utilization of Ground Eggshells as a Biofiller for Natural Rubber Biocomposites.

The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPTS), were used to increase the activity of ground eggshells in the elastomer matrix and to ameliorate the cure characteristics and properties of NR biocomposites. The influence of ground eggshells, CTAB, ILs, and silanes on the crosslink density, mechanical properties, and thermal stability of NR vulcanizates and their resistance to prolonged thermo-oxidation were explored. The amount of eggshells affected the curing characteristics and crosslink density of the rubber composites and therefore their tensile properties. Vulcanizates filled with eggshells demonstrated higher crosslink density than the unfilled sample by approximately 30%, whereas CTAB and ILs increased the crosslink density by 40-60% compared to the benchmark. Owing to the enhanced crosslink density and uniform dispersion of ground eggshells, vulcanizates containing CTAB and ILs exhibited tensile strength improved by approximately 20% compared to those without these additives. Moreover, the hardness of these vulcanizates was increased by 35-42%. Application of both the biofiller and the tested additives did not significantly affect the thermal stability of cured NR compared to the unfilled benchmark. Most importantly, the eggshell-filled vulcanizates showed improved resistance to thermo-oxidative aging compared to the unfilled NR.

Eco-friendly Silane-Based Coating for Mitigation of Carbon Steel Corrosion in Marine Environments.

Losses from corrosion contribute roughly 3-5% of the gross domestic product of developed nations, and among the many methods used to avoid corrosion, using silane-based coatings is seen to be of the biggest importance due to their low toxicity and superior adhesive qualities. It is essential to develop an anti-corrosion coating that is efficient, economical, and eco-friendly. The corrosion resistance and durability of various silane-based coatings such as 1,2-bis(triethoxysilyl)ethane (BTSE), bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), and vinyltrimethylsilane (VTES) for carbon steel 1018 substrates were investigated in a high-salinity environment (4.5 wt % NaCl). The corrosion resistance performance was evaluated via potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. Results revealed that the TESPT film (pH ≈ 7) has the best corrosion resistance performance on the carbon steel surface in the aggressive chloride environment, that is, 99.6%. The high corrosion resistance of the TESPT film is due to the hydrophobic nature of this silane, which leads to the formation of a stable and dense film. These results were supported by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses.

Effect of TESPT on viscoelastic and mechanical properties with the morphology of SSBR/BR hybrid nanocomposites

AbstractIn this study, the various properties of hybrid nanocomposite based on solution styrene butadiene rubber (SSBR)/butadiene rubber (BR) have been investigated. For this purpose, SSBR/BR rubber blend with nano‐silica and carbon black (CB) in constant filler content (60 phr) with and without Bis (triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent was fabricated. The various properties, including curing behavior, morphology, dynamic–mechanical, and dissipation characteristics, were studied. For this objective, rheometry, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), tensile test, and Dynamic mechanical thermal analysis (DMTA) were used. The results of rheometry illustrated that the addition of nano‐silica increased the optimum cure time (t90) and declined the cure rate index (CRI). However, the addition of surface‐modified silica improved the t90 and CRI. Replacing nano‐silica with CB also reduced the scorch and optimum cure time. TEM and SEM micrographs showed the good dispersion state of nano‐silica in the SSBR/BR/nano‐silica/TESPT matrix. According to the mechanical test data, including tensile, hardness, and abrasion, the addition of hybrid filler containing 40 phr modified nano‐silica and 20 phr CB improved properties. The results of DMTA illustrated the appropriate compatibility between blend phases, also an increase in the glass transition temperature (Tg) and storage modulus (E′) for the samples containing higher amounts of CB. Considering the importance of the damping factor at temperatures of −20, 0, and 60°C, which is related to ice grip, wet grip, and rolling resistance, respectively, the TSi40CB20 sample showed the essential properties of the magic triangle better than other samples. Dissipative properties also revealed that by increasing the filler content and replacing nano‐silica with CB, the dissipation of the compound increases significantly. According to the results, the optimum amount of nano‐silica and CB in the SSBR/BR/TESPT was 40 and 20 phr, respectively.

Preparation and Characterization of Acrylonitrile Butadiene Rubber Reinforced with Bio-Hydroxyapatite from Fish Scale.

This work aims to enhance the mechanical properties, oil resistance, and thermal properties of acrylonitrile butadiene rubber (NBR) by using the Nile tilapia fish scales as a filler and using bis(triethoxysilylpropyl)tetrasulfide (TESPT) as a coupling agent (CA). The prepared fish scale particles (FSp) are B-type hydroxyapatite and the particle shape is rod-like. The filled NBR with FSp at 10 phr increased tensile strength up to 180% (4.56 ± 0.48 MPa), reduced oil absorption up to 155%, and increased the decomposition temperature up to 4 °C, relative to the unfilled NBR. The addition of CA into filled NBR with FSp at 10 phr increased tensile strength up to 123% (5.62 ± 0.42 MPa) and percentage of elongation at break up to 122% relative to the filled NBR with FSp at 10 phr. This work demonstrated that the prepared FSp from the Nile tilapia fish scales can be used as a reinforcement filler to enhance the NBR properties for use in many high-performance applications.

Increase in Properties and Self-Healing Ability of Conductive Butyl Rubber/Epoxidized Natural Rubber Composites by Using Bis(triethoxysilylpropyl)tetrasulfide Coupling Agent.

Flexible self-healing composite was fabricated based on blending the bromobutyl rubber (BIIR) and epoxide natural rubber (ENR) filled with hybrid fillers of carbon nanotubes (CNT) and carbon black (CB). To achieve self-recoverability, modification of BIIR was carried out through butyl imidazole (IM), and the healing capability was then activated by the addition of bis(triethoxysilylpropyl)tetrasulfide (TESPT), which resulted in good dispersion of CNT/CB in BIIR/ENR blends. The silanization of TESPT and CNT/CB hybrid filler surfaces was confirmed by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Adding CNT/CB and incorporating TESPT into the composites effectively improved the curing and mechanical properties of the blends in terms of estimated crosslink density and tensile modulus. Further, the self-healing propagation rate was enhanced by the thermal conductivity of fillers and the ion-dipole intermolecular forces between the rubber chains, leading to the highest abrasion resistance and electrical conductivity. Using an environmentally friendly process, the recyclability of the self-healing composites was improved by the re-compression of the samples. With this, the constant conductivity relating to the rearrangement of the CNT/CB network is examined related to the usability of the composites at 0 and 60 °C. The conductive composites filled with a TESPT silane coupling agent present an opportunity for vehicle tires and other self-repairing applications.

Effect of Alumina Modified by Silane on the Mechanical, Swelling and Dielectric Properties of Al2O3/EPDM/SBR Blend Composites

Rubber blending has been widely used to improve various properties in finished rubber products. The purpose of this paper is to investigate the effect of filler size, type, concentration, and surface treatment on the mechanical, swelling, dielectric, and morphology properties of ethylene propylene diene rubber (EPDM)/styrene-butadiene rubber (SBR) rubber blend nanocomposites filled with alumina (Al2O3) nanoparticles. Bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) was used as a silane coupling agent. Rubber blend nanocomposites containing Al2O3 nanoparticles were compared to carbon black (CB). The results indicate that the nanocomposites prepared, in particular with the TESPT, had better properties than the composites without the TESPT. Mechanical properties of the CB-filled EPDM/SBR rubber blend were noticeably improved, indicating CB's inherent reinforcing potential. We found that rubber nanocomposites' crosslink density and filler–rubber interaction increase, and the swelling coefficient decreases with increasing filler content. The dielectric properties of the nanocomposites showed a significant enhancement with fillers. SEM images showed that the CB sample had a higher distribution than Al2O3 due to good interaction and dispersion. This study's experimental data will help design and manufacture outdoor insulators.

Viable Properties of Natural Rubber/Halloysite Nanotubes Composites Affected by Various Silanes.

Natural rubber (NR) is incompatible with hydrophilic additives like halloysite nanotubes (HNT) due to their different polarity. The silane coupling agent is the ideal component to include in such a compound to solve this problem. Many types of silane are available for polymer composites depending on their functionalities. This work aimed to tune it to the composite based on NR and HNT. Four different silanes, namely Bis[3- (Triethoxysilyl)Propyl]Tetrasulfide (TESPT), 3-Aminopropyl triethoxysilane (APTES), N-[3-(Trimethoxysilyl)Propyl] Ethylenediamine (AEAPTMS), and Vinyltrimethoxysilane (VTMS) were used. Here, the mechanical properties were used to assess the properties, paying close attention to how their reinforcement influenced their crystallization behavior after stretching. It was revealed that adding silane coupling agents greatly improved the composites' modulus, tensile strength, and tear strength. From the overall findings, AEAPTMS was viable for NR/HNT composites. This was in direct agreement with the interactions between NR and HNT that silanes had encouraged. The findings from stress-strain curves describing the crystallization of the composites are in good agreement with the findings from synchrotron wide-angle X-ray scattering (WAXS). The corresponding silanes have substantially aided the strain-induced crystallization (SIC) of composites.

Insight into Mechanical Properties and Strain-induced Crystallisation of Epoxidized Natural Rubber Filled with Various Silanized Halloysite Nanotubes

Natural rubber (NR) and halloysite nanotube (HNT) composites are known to perform poorly due to polarity differences between the two components. As such, many extant studies have attempted to increase their compatibility. Therefore, this study introduced epoxidized natural rubber (ENR) together with silane coupling agents into the composite to ensure rubber-filler interactions. Four different silanes namely bis-[(triethoxysilyl)propyl] disulphide (TESPD), bis[(triethoxysilyl)propyl] tetrasulfide (TESPT), triethoxyvinylsilane (VTEO), and 3-mercaptopropyl-di(tridecan-1-oxy-13-penta(ethyleneoxide)) ethoxysilane (VPSi-363) were used. Fourier-transform infrared (FTIR) spectroscopy of the composite confirmed the formation of hydrogen bonds between the silane as the peak of Si-O shifted to higher wavenumbers; i.e., 1080 cm-1 to 1042 cm-1. Silane was also found to improve the tensile strength, modulus and tear strength regardless of functionality. This was further supported by the findings of the Payne effect. As for strain-induced crystallisation (SIC), the stress-strain curves agreed well with the development of crystallinity observed during synchrotron wide-angle X-ray scattering analysis.

Reinforcement of surface-modified cellulose nanofibrils extracted from Napier grass stem in natural rubber composites

Cellulose nanofibrils (CNFs) were prepared from Napier grass stems via alkalization, bleaching and sulfuric acid hydrolysis treatments and subsequently characterized by various techniques. Transmission electron microscopy (TEM) confirmed that CNFs with average diameter of 15 nm were successfully obtained in the diluted suspension. However, after freeze drying, CNFs aggregated and formed large fibrillar bundles. X-ray diffraction (XRD) results revealed that CNFs exhibited Cellulose I structure with crystallinity index of 74 %. Results from Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirmed the complete removal of noncellulosic compounds after the alkali and bleaching treatments. Surface treatment of CNFs by Bis-(triethoxysilyl-propyl) tetrasulfide (TESPT) was also carried out. Both untreated and TESPT-treated CNFs were added into natural rubber (NR) at various loadings (0–10 phr) to investigate their reinforcements. Regardless of the filler type, modulus and hardness of the NR composites increased continuously with increasing filler loading. Tensile strength increased with increasing filler loading up to 5 phr before leveling off. At any given filler loading, TESPT-treated CNFs exhibited greater reinforcement than untreated CNFs due to the improved rubber-filler interaction and the enhanced crosslink density. The results show the potential use of the TESPT-treated CNFs in rubber reinforcement.

Synergistic Effect by Polyethylene Glycol as Interfacial Modifier in Silane-Modified Silica-Reinforced Composites.

The viscoelastic behavior and reinforcement mechanism of polyethylene glycol (PEG) as an interfacial modifier in green tire tread composites were investigated in this study. The results show a clear positive effect on overall performance, and it significantly improved all the parameters of the “magic triangle” properties, the abrasion resistance, wet grip and ice traction, as well as the tire rolling resistance, simultaneously. For the preparation of the compounds, two mixing steps were used, as PEG 4000 was added on the second stage in order to avoid the competing reaction between silica/PEG and silanization. Fourier transform infrared spectroscopy (FTIR) confirmed that PEG could cover the silanol groups on the silica surface, resulting in the shortening of cure times and facilitating an increase of productivity. At low content of PEG, the strength was enhanced by the improvement of silica dispersion and the slippage of PEG chains, which are chemically and physically adsorbed on silica surface, but the use of excess PEG uncombined with silica in the compound, i.e., 5 phr, increases the possibility to shield the disulfide bonds of bis(3-(triethoxysilyl)-propyl) tetrasulfide (TESPT), and, thus, the properties were deteriorated. A constrained polymer model was proposed to explain the constrained chains of PEG in the silica-loaded composites on the basis of these results. An optimum PEG content is necessary for moderately strong matrix–filler interaction and, hence, for the enhancement in the mechanical properties.