Rubber-filler Interaction Research Articles

High reactive sulphide chemically supported on silica surface to prepare functional nanoparticle

A solid-phase preparation method was applied to obtain a novel, green and effective functional nanoparticle, silica-supported sulfur monochloride (silica-s-S2Cl2), by the chemical reaction between chlorine atom and silicon hydroxyl on the silica surface. Through this chemical reaction, silica surface supported with high content of sulfur, and the functional nanoparticles can not only vulcanize the rubber instead of sulfur or other vulcanizing agent with high performance, but also improve the filler-rubber interaction as a modifier due to the improved modification effect. 29Si NMR, Raman spectroscopy, Element analysis and TGA confirm that the sulfur monochloride is chemically bonded on the silica surface. Cure properties measurement, morphology of filler dispersion, mechanical properties measurement, immobilized polymer layer and oxidation induction time increment together show that the novel vulcanizing agent silica-s-S2Cl2 instead of sulfur in rubber vulcanization gives rise to significant improvement in the crosslinking density and the interfacial adhesion between silica particles and the rubber matrix, which is on account of the promoted vulcanizing on the functional silica nanoparticles surface with the supported sulfur.

A Study of the Combined use of Carbon Black and Silica in Tyre Tread Formulations

A specially designed relaxometer was used to measure the stress relaxation under 30% elongation for tread rubber compounds based on a blend of three rubbers: natural rubber, neodymium butadiene rubber, and oil-extended styrene butadiene rubber. The rubber compounds were filled with carbon black and silica in different ratios: with 80 parts carbon black only, with 80 parts silica only, and with different ratios of carbon black and silica. The method proposed by Bartenev was used to calculate the relaxation specta. The maxima of the spectra at different relaxation times were assigned to different types of interaction: rubber-filler interaction, carbon black-carbon black interaction, silica-silica interaction, carbon black-silica interaction. New maxima were obtained for specimens containing roughly equal amounts of carbon black and silica. These results were compared with data obtained using transmission electron microscopy. The existence of three levels of structure of filled elastomers and the presence of ‘rigid’ rubber around filler particles are suggested.

Functionalized HNTs nanocluster vulcanized natural rubber with high filler-rubber interaction

A novel functional rubber vulcanizator, halloysite nanotubes (HNTs) supported sulfur monochloride (HNTs-s-S) is prepared by chemically bonding sulfur monochloride (S2Cl2) onto HNTs surface. Through this chemical reaction, high concentration of sulfur is supported onto HNTs inner and outer surface. Meanwhile, the functional nanotubes can not only vulcanize the rubber without sulfur and show the lower activation energy of vulcanization reaction, but also improve the filler-rubber interaction as a modifier due to the improved modification effect. Furthermore, the immobilized polymer layer and crosslinking density of rubber composites together indicate that this novel vulcanizing agent HNTs-s-S gives rise to significant improvement in the rubber-filler interfacial adhesion, which is on account of the promoted vulcanizing on the functional HNTs surface with the supported sulfur. After endowing the tubular nanofillers with vulcanized function, it may offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

EFFECTS OF SILANE COUPLING AGENTS ON STRUCTURE AND PROPERTIES OF SILICA-FILLED SILICONE RUBBER/STYRENE BUTADIENE RUBBER COMPOSITES

ABSTRACT Two silane coupling agents, bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) and vinyltriethoxysilane (A151), were selected to investigate their effects on structure and properties of silica-filled methyl vinyl silicone rubber (VMQ)/emulsion styrene butadiene rubber (ESBR) composites. The filler–rubber interactions were investigated via bound rubber content and solid-state 1H low-field nuclear magnetic resonance (NMR) spectroscopy, and the mass ratio of VMQ and ESBR in the rubber–filler gel was investigated by thermogravimetric analysis (TGA). The results revealed that VMQ showed a better compatibility with silica than ESBR. Compared with the A151 composite, the composite with Si69 showed the higher content of ESBR in rubber–filler gel, which resulted in the higher bound rubber content and the weaker Payne effect, and it also exhibited higher tensile strength, higher tear strength, better wear resistance, and lower hardness. However, the presence of Si69 reduced the crosslink efficiency of ESBR and completely inhibited the crosslinking of VMQ, which caused the composite to show higher tan δ value at 60 °C than the A151 composite.

The aggregation structure regulation of lignin by chemical modification and its effect on the property of lignin/styrene–butadiene rubber composites

ABSTRACTThe aggregation structure of lignin in aqueous solution had an important effect on the dispersion of lignin and the properties of lignin/styrene–butadiene rubber (SBR) composites. This article revealed the relationship between aggregation structure and chemical structure of modified lignin. Unmodified lignin was amorphous; however, our results showed that aldehyde‐modified lignin was transformed into spherical aggregates, while propylene‐oxide‐modified lignin self‐aggregated into supramolecular domains. The relationships between aggregation structure, filler dispersion, filler–rubber interaction, and performance were also studied by investigating the microstructure, viscoelastic behavior, and mechanical properties of lignin/SBR composites. Meanwhile, a solution to improve the coprecipitation efficiency of lignin and SBR latex was proposed. In this article, epoxidized natural rubber (ENR) was also used as compatibilizer to improve the interfacial adhesion between polar lignin and nonpolar SBR. The results showed better lignin dispersion for the ENR‐containing rubber composites, as well as superior wet skid resistance and lower rolling resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45759.

Effect of organosilane agents on the vulcanizate structure and physical properties of silica-filled solution styrene butadiene rubber compounds

Physical properties of rubber compounds are affected by the filler-rubber interaction, filler dispersion in the rubber matrix, and crosslink structure formed during vulcanization. Organosilane agents are essentially used in silica-rubber compounds to inhibit the formation of silica agglomerates and increase the formation of silica-rubber networks. Generally, organosilane agents have an alkoxysilyl alkyl sulfide structure and are classified into silane coupling and covering agents depending upon the presence of sulfur. Coupling agents have a sulfur moiety and serve as a sulfur donor during the vulcanization process, thus increasing the formation of filler-rubber and chemical crosslink networks. On the other hand, covering agents promote the hydrophobation of silica surfaces, decreasing the adsorption loss of vulcanization additives, which increases the formation of chemical crosslink networks. This implies that organosilane agents can affect the vulcanizate structure, which causes a variation in the properties of silica compounds. Therefore, in this study, the effect of coupling (bis(3-triethoxysilylpropyl)disulfide (TESPD) and bis(3-triethoxysilylpropyl)tetrasulfide (TESPT)) agents and a covering (triethoxy(octyl)silane) agent on the vulcanizate structure and properties of silica compounds was investigated and compared. In the comparative study of coupling and covering agents, the influence of sulfur donors on the formation of vulcanizate structures was investigated. In the case of the coupling agents, the effect of sulfur rank on the vulcanizate structure and properties of silica-rubber compounds was quantitatively analyzed through various characterization techniques.

REINFORCEMENT OF NATURAL RUBBER BY SILICA/SILANE IN DEPENDENCE OF DIFFERENT AMINE TYPES

ABSTRACT Diphenyl guanidine (DPG) is the most commonly used secondary accelerator in silica-reinforced rubber compounds because of its additional positive effect on the silanization reaction and deactivation of free silanol groups that are left over after the silanization. However, because of health and safety concerns about the use of DPG, which decomposes to give highly toxic aniline during high processing temperature, safe alternatives are required. This work investigates the effect of various types of aliphatic amines having alkyl or cyclic structures and similar pKa (i.e., hexylamine [HEX], decylamine [DEC], octadecylamine [OCT], cyclohexylamine [CYC], dicyclohexylamine [DIC], and quinuclidine [QUI]) on the properties of silica-reinforced natural rubber (NR) compounds by taking the ones with DPG and without amine as references. When compared with the compound without amine, the use of all amine types reduces filler–filler interaction (i.e., the Payne effect) and enhances filler–rubber interaction, as indicated by bound rubber content and decreased heat capacity increment. The amines with alkyl chains can reduce the Payne effect and enhance cure rate to a greater extent compared with the amines with cyclic rings as a result of better accessibility toward the silica surface and a shielding effect because of less steric hindrance. The longer carbon tails on linear aliphatic amines ranging from HEX, DEC, to OCT lead to a lower Payne effect, lower heat capacity increment, higher bound rubber content, and higher modulus as well as tensile strength. Overall, the use of OCT provides silica-reinforced NR compounds with properties closest to the reference one with DPG and can act as a potential alternative for DPG.

INFLUENCES OF STYRENE BUTADIENE RUBBER AND SILICA TYPES ON PERFORMANCE OF PASSENGER CAR RADIAL TIRE TREAD

ABSTRACTA performance comparison among three types of styrene butadiene rubber (SBR), that is, emulsion polymerized SBR (ESBR), solution polymerized SBR (SSBR), and functionalized solution polymerized SBR (F-SSBR), was of interest. Effect of silica type, that is, highly dispersible silica and conventional precipitated silica, was also investigated. It is found that SSBR demonstrates significantly better heat build-up, dynamic set, abrasion resistance, including wet grip (WG) with comparable fuel efficiency, as compared to ESBR. As expected, the best tire performance, that is, abrasion resistance, WG, and fuel efficiency, is found in F-SSBR vulcanizates, attributed mainly to the greatest improvement in magnitude of rubber–filler interaction and degree of filler dispersion. Results reveal that the reactive functional group, that is, propylaminedimethoxysilane, which is chemically anchored at chain ends of F-SSBR, plays a crucial role in tire performance. Unexpectedly, silica type does not significantly influence the degree of filler dispersion, including WG and fuel saving efficiency. Probably, the predominance of sufficiently long mixing time during the compound preparation step may be responsible, as compared to the effect of silica characteristics.

Reactive supramolecular filler for elastomer reinforcement

A reactive amphiphile, SA1, which comprises a mercaptodecyl oleophilic tail and a β-alanine oleophobic moiety, has been introduced to serve as the building block for supramolecular filler. At least a fraction of SA1 reacts in situ during mechanically mixing and vulcanization with SBR via thiol-ene reaction. Some oxidative dimerization also concomitantly occurs to give DSA1. The chemical coupling between SA1 and SBR results in drastically improved filler domain dispersion. Short fibrous crystalline domains, which are likely composed of SA1, SA1 grafted to SBR, and DSA1, less than 10 nm in width and a few tens to one hundred nanometers in length are observed by TEM. The filler domains are evenly distributed in the SBR. In contrast, the simple filler PA1 forms large irregular aggregates on the length scale of hundreds of nanometers. The improved filler dispersion and filler-rubber interaction allow effective energy dissipation and result in significantly improved mechanical properties.A solution-mixing method proves feasible for mixing SA1 and SBR and actually has resulted in better mechanical properties than the mechanical mixing method. Since the conventional mechanical mixing method for rubber compounding is highly energy-intensive, avoidance of the mechanical mixing method is another practical advantage for the novel strategy of supramolecular reinforcement.

Urushiol-derived non-silane coupling agent

Sulfur was chemically incorporated into urushiol in one step to afford an oligomeric sulfurized urushiol (SU). About 53% of the linkages between urushiol monomer units are cleavable multi-sulfidic bonds. Surface modification of silica with SU can be achieved either in a suspension before rubber compounding or in situ during rubber compounding. SU performs better when added in situ into the rubber compound than when used to pre-modify silica. Mooney viscosity and Payne effect studies of the uncured rubber compounds show that SU is as effective as TESPT to promote filler dispersion during mixing. The increased bound rubber content and suppressed filler flocculation demonstrate that SU does indeed generate covalent filler-rubber interactions during mixing in contrast to our previously reported hydrogenated urushiol, which only act as a covering agent. However, SU is less effective than TESPT as a coupling agent. The dynamic mechanical properties of the SU-containing vulcanizate are intermediate between the TESPT-containing standard and the hydrogenated urushiol-containing standard. When SU is used to replace 50% TESPT, mechanical and dynamic mechanical properties of the two vulcanizates are essentially identical. Noteworthy is that the reaction between SU and silica during rubber compounding produces water instead of ethanol, which the reaction of silica and TESPT produces, as a volatile organic compound.

Preparation of Halloysite Nanotubes–Silica Hybrid Supported Vulcanization Accelerator for Enhancing Interfacial and Mechanical Strength of Rubber Composites

To enhance the interfacial interaction between rubber and hybrid nanofiller (HS) consisting of halloysite nanotubes and silica, and simultaneously prevent migration and volatilization of rubber additives, commercial vulcanization accelerator N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was chemically grafted onto HS to obtain a functionalized nanofiller (HS-s-CZ). It was found that the grafted CZ molecules within an inorganic host structure have better efficiency to accelerate cross-linking reaction than free CZ molecules. In addition, HS-s-CZ could be evenly dispersed into styrene butadiene rubber (SBR) with further improved filler–rubber interaction compared with that between HS and SBR. Consequently, SBR/HS-s-CZ composites exhibited greater mechanical strength than SBR/HS composites containing equivalent accelerator component, showing 45% increase in tensile strength when the filler content was 40 phr. Potentially, this work offers a new design strategy for the surface modification of nanofiller and preparation of high-efficiency rubber additives, which may represent a new path for preparing high-performance elastomer composites.

Reinforcing mechanism of a novel hydrophilic nano-carbon black in natural rubber latex

ABSTRACTNovel water-dispersible carbon nanoparticles (PNASS-CBs) were produced by radical polymerization of sodium 4-styrenesulfonate (NASS) on the surface of carbon black (CB) in the solid state. Scanning electron microscopy (SEM) and the Payne effect results showed that the modified CBs were less likely to form particle networks and thus dispersed better in the natural rubber (NR) matrix, with an average size of 90 nm that was much less than that of the aggregated pristine CBs. We propose that the appropriate modification of CBs mitigates filler-filler interaction and enhances the filler-rubber interaction, which can also be proved by the higher bound rubber contents of the NRL/PNASS-CB composites. When a NRL/PNASS-CB composite is subjected to an outside force, e.g. tensile, more physically absorbed rubber chains (bound rubber) slip and self-adjust their absorbed spots on the CBs’ surface (stress redistribution) in order to jointly share the applied stress. This has a positive effect on the resistance to damage of the rubber molecular chains. Therefore, the addition of the hydrophilic CBs in NR latex leads to significant improvements in the mechanical properties of the NRL/PNASS-CB composites.

Incorporation of nanoclay into field latex to develop nanoclay filled dry rubber compounds

Two types of nanoclay filled dry rubber compounds were prepared by incorporating sodium montmorillonite (MMT) into natural rubber (NR) at latex stage. Nanoclay filled rubber sheets prepared by acid co-coagulation (ACC) and acid free co-coagulation (AFCC) rubber production methods were milled and compounded to develop nanoclay filled dry rubber compounds. The MMT loading was varied from 0 to 20 phr. Both the above methods are not used as filler incorporation methods in dry rubber industry. AFCC rubber vulcanisates, compared to ACC rubber vulcanisates showed improved mechanical properties mainly due to increased crosslink density associated with the presence of natural accelerators and nano-scale dispersion obtained under acid free environment. The AFCC method is proposed as a new route in filler incorporation, which shows the best mechanical properties at a MMT loading of 8 phr. At higher MMT loadings, due to the formation of aggregated clay structures associated with filler-filler interactions, tensile strength and elongation at break decreased. Modulus and hardness increased with the increase of MMT loading, while tear strength remained unchanged. XDR deffractograms and SEM images revealed that the AFCC rubber at optimum loading has partially exfoliated clay structures with fine phase morphology. DSC analysis revealed that no significant rubber-filler interactions are formed in the rubber vulcanisates.

Plant Based Poly-functional Hindered Phenol Derivative as an Alternative for Silane in Cis-Polyisoprene and its Functionalized Derivative Systems Containing Nano-sized Particulates

The present work provides extensive insight into the newly developed sustainable bio-resin (terpene) functionalized Natural Rubber (NR). Structural elucidation of the functionalized NR was established by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR) respectively. This study demonstrates the effect of Bio-Resin Functionalized NR (BR-NR)/Epoxidized Natural rubber (ENR) blends combined with four different specific surface areas of highly dispersible silica (HDS). The primary aim of these analyses is the description of the interfacial area on the HDS surface involved in physical form (Micro pearl and Granule) and synergistic rubber-filler interaction mechanism for the superior reinforcement. Improved state of HDS dispersion has been achieved in absence of conventional toxic processing oil, silane coupling agent and normal zinc oxide. Remarkable improvement in overall properties corroborated with various meticulous characterization including cure characteristics, bound rubber content, Mullins effect and physico-mechanical properties etc. An augmented rubber-filler interaction is also supported by micro computed tomography morphology study. Dynamic mechanical analysis shows an ultra-low rolling resistance coupled with high traction and advanced elastic response of the greener macromolecules. More decisively, the macromolecule system toned up sparingly in the presence of the bio-resin. Newly developed BR-NR together with ENR 25 and their significant contribution to the improvements of properties are schematically explained.

PERFORMANCE COMPARISON OF VARIOUS SURFACE MODIFYING AGENTS ON PROPERTIES OF SILICA-FILLED CHLOROPRENE RUBBER

ABSTRACTInfluence of the surface modifying agents (SMAs) polyethylene glycol (PEG), 3-aminopropyl triethoxysilane (APTES), and bis-(3-triethoxysilylpropyl)tetrasulfide (TESPT) on properties of silica-filled chloroprene rubber (CR) was investigated. Results reveal that the presence of SMAs greatly improves mechanical and dynamic properties of the silica-filled CR because of the reduced filler–filler interaction and improved rubber–filler interaction as evidenced by the Payne effect and bound rubber content results, respectively. When compared at the same SMA dosage, TESPT gives the best overall vulcanizate properties. This effect is attributed to high coupling efficiency of TESPT and its ability to donate sulfur atoms during vulcanization, leading to the improved filler dispersion, rubber–filler interaction, and cross-link density. APTES gives high coupling efficiency, but because of the lack of sulfur atoms, its performance is slightly inferior to that of TESPT. In contrast, PEG can only reduce filler–filler interaction, with no significant impact on rubber–filler interaction and cross-link density; therefore, PEG provides lower property improvement.

Investigation of Structural, Morphological, and Dynamic Mechanical Properties of Unvulcanized PDMS/Silica Compound

Abstract In this study, the interaction between the silica filler and polydimethylsiloxanes (PDMS) was investigated from the aspects of the bound rubber and morphological characterization. With special attention to the dynamic properties, the dynamic test was conducted by dynamic shear rheometer. The results show that the modified filler disperses uniformly within the PDMS matrix without aggregation and connects closely with the matrix compared to that of the unmodified fillers. Surface modification of the filler increases the bound-rubber content. The increase in silica loading leads to an increase in the silica–silica interaction and a decrease in filler–rubber interaction, which results in the aggregation of fillers and the increase of the bound-rubber content. It was apparent that storage modulus, loss modulus, and tanδ of unvulcanized PDMS/filler compounds filled with treated silica filler were lower than that of the untreated silica system. Moreover, the tanδ decreases with increasing silica loading.

Influence of partial substitution for CB with MWNTs on performance of CB‐filled NR composites

The effects of substituting carbon black (CB) with multiwall carbon nanotubes (MWNTs) on the structure and properties of natural rubber (NR)/CB composites is explored. Compared with NR/CB composites, NR/MWNTs/CB presents better filler dispersity and dynamic properties of the MWNT up to a certain concentration, as confirmed by scanning electron microscope, dynamic mechanical analyser and rubber processing analyser. Sample with 1 phr MWNTs shows obviously the highest tensile strength, 28.60 MPa, and almost the lowest heat build-up, only 9.6°C, and it is attributed to that not only large cross-link density and better filler dispersity but also high effective elasticity and large filler–rubber interaction. However, when the concentration is much higher, MWNTs tend to aggregate and lead to the poor efficiency to enhance the dynamic properties of rubber composites or even deteriorate the properties.

Silane grafted natural rubber and its compatibilization effect on silica-reinforced rubber tire compounds

Natural Rubber (NR) grafted with 3-octanoylthio-1-propyltriethoxysilane (NXT) was prepared by melt mixing using 1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane as initiator at 140 °C with NXT contents of 10 and 20 parts per hundred rubber [phr] and initiator 0.1 phr. The silane grafted on NR molecules was confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR) and scanning electron icroscopy/energy dispersive X-ray spectroscopy (SEM-EDX). Based on1H-NMR, the use of 10 and 20 phr (parts per hundred resin) of silane resulted in grafted NXT onto NR of 0.66 and 1.32 mol%, respectively, or a grafting efficiency of approx.38%. The use of NXT-grafted NR as compatibilizer in silica-filled NR compounds, to give a total amount of NXT in both grafted and non-grafted forms in the range of 0.8-6.1 wt% relative to the silica, decreases the Mooney viscosity and Payne effect of the compounds, improves filler-rubber interaction, and significantly increases the tensile properties of the silica-filled NR-compounds compared to the non-compatibilized one. At the same silane-content, the use of silane-grafted NR gives slightly better properties than the straight use of the same silane. With sulfur compensation, the use of NXT-grafted-NR with about 6 wt% NXT relative to the silica gives technical properties that reach the levels obtained for straight use of bis-(3-triethoxysilyl-propyl) tetrasulfide (TESPT) at 8.6 wt% relative to the silica.

Influence of the silanes on the crosslink density and crosslink structure of silica-filled solution styrene butadiene rubber compounds

The effects of three silane coupling agents, triethoxy(octyl)silane (TEOS), bis[3-(triethoxysilyl)propyl]disulfide (TESPD), and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) on the filler-rubber interaction, crosslink density and crosslink structure of the silica-filled solution styrene butadiene rubber (SSBR) vulcanizates were studied. High dispersion silica, 7000GR, was used as the filler, and the loading range was varied from 0 to 60 phr. Crosslink density was measured by the swelling method. Experimental results showed that Kraus plot can be applicable to the silica-filled SSBR vulcanizates to separate filler-rubber interaction from the measured swelling data. Filler-rubber interaction increased by increasing sulfur rank in the silane as TEOS < Silica without silanes < TESPD < TESPT. Sulfurless silane, i.e. TEOS, only worked as a covering agent for hydrophobating silica surface. Silica without silane show high filler-rubber interaction than TEOS system because chain-end functionalized SSBR was used in this study. Unfilled system showed similar amounts of poly, di, and mono-sulfidic crosslinks. On the contrary to this, all of the silica-filled vulcanizates showed high mono-sulfide contents due to longer cure time.

Development of highly reinforced acrylonitrile butadiene rubber composites via controlled loading of sol-gel titania

Remarkable improvement in mechanical properties of acrylonitrile butadiene rubber (NBR) composites is achieved by incorporating nano-titania that is synthesised in solution of the raw rubber using titanium n-butoxide (TNB) as the titania precursor. This is achieved by designed and controlled incorporation of titania that resulted in very good dispersion of titania of nanometric dimension in rubber matrix and enhanced rubber-filler interaction. This sol-gel transformation is carried out under optimised reaction condition. Surface modification of titania by a silane coupling agent (bis-(3-triethoxysilylpropyl)-tetrasulfide, TESPT) causes further improvement in filler dispersion and composite properties when added in the reactive sol-gel system during in situ titania generation rather than it's external addition in the titania filled NBR during mixing and compounding. Thorough characterisation of the composites are done that encompasses a wide range of studies on thermal, morphological, mechanical, dielectric, dynamic mechanical, rheological and antifungal properties. The results are analysed on a comparative basis to investigate the effect of in situ incorporation and in situ surface modification of titania on the composite properties.