Jong-Yeop Lee

Styrene-butadiene-glycidyl methacrylate terpolymer/silica composites: dispersion of silica particles and dynamic mechanical properties

Styrene-butadiene-glycidyl methacrylate terpolymer (GMA-SBR) was synthesized by emulsion polymerization for the fuel efficient tire tread composite. The chemical structure of the GMA-SBR was analyzed using infrared spectroscopy, 1H NMR, gel permeation chromatography, and differential scanning calorimetry. The GMA-SBR/silica composite is the first instance introduced covalent bonds between silica filler and rubber molecules by in-chain modification of styrene-butadiene molecules. After compounding, the curing characteristics, the mechanical and dynamic mechanical properties of the composites were analyzed. The GMA-SBR/silica composite exhibited higher wear resistance of 32.9% and lower rolling resistance of 25.7% than the styrene-butadiene rubber 1721/silica composite. These results are due to the improvement of silica dispersion in the composite as the covalent bonding increased the filler–rubber interaction and the countervailing effects of less filler flocculation. The proposed approach assists in finding a solution to improve the performances of tires for fuel efficiency and the reduction of greenhouse gases from the vehicles.

Reduced filler flocculation in the silica-filled styrene–butadiene–glycidyl methacrylate terpolymer

This study presents a method to improve the dispersion of silica in rubber compounds using a styrene-butadiene-glycidyl methacrylate terpolymer (GMA-SBR) synthesized by cold emulsion polymerization. It has been demonstrated that silica particles in conventional rubbers tend to agglomerate during storage, as well as at the onset of vulcanization, because of their polarity. GMA-SBR can improve the compatibility with silica by the formation of covalent bonds between the epoxy groups of GMA-SBR and silanol groups on the silica surface. SBR 1721 and GMA-SBR silica-filled compounds were prepared without curatives by a kneader and a two-roll mill. After compounding, the reaction of the epoxy group, filler flocculation, and morphology of the compounds were analyzed using infrared spectroscopy, a rubber process analyzer, and transmission electron microscopy, respectively. In addition, the content of bound rubber in the compounds was determined by extracting the unbound rubber material with toluene. The GMA-SBR silica-filled compounds had a higher bound rubber content and exhibited significantly different filler flocculation and silica dispersion behaviors compared with the SBR 1721 silica-filled compounds.

Effect of styrene-butadiene rubber with different macrostructures and functional groups on the dispersion of silica in the compounds

In this study, the effects of high vinyl solution styrene-butadiene rubber (SSBR) containing different macrostructures and chain-end functional groups were investigated with respect to the dispersion of silica in the compounds. The microstructures and functional groups of three polymers were analyzed by using 1H nuclear magnetic resonance (NMR). According to the 1H NMR analysis, the star-shaped SSBR-E has a relatively higher numbers of ethoxy group in the polymer chain. All compounds showed good silica dispersion based on transmission electron microscopy (TEM) observation. According to analysis of the Payne effect, longer mixing times showed better dispersion of silica in the rubber compounds, and functional group differences in the SSBR also had an effect on the degree of silica dispersion that led to a decrease in storage modulus. In particular, the compound with star-shaped polymer containing ethoxy silyl groups showed the lowest storage modulus due to a higher number of functional groups compared to the other polymers. The abrasion resistance was closely related to the silica dispersion as well as the filler-rubber interaction. The abrasion loss decreased slightly when the mixing time was extended; however, this significantly decreased when the number of functional groups in the polymer chain was increased. Accordingly, the star-shaped polymer containing higher numbers of the functional group contributed to a better dispersion of silica in the compound. Mixing time was also considered as an important parameter to improve dispersion of silica and for reduction of silica flocculation in the rubber compounds.

The effect of accelerator contents on the vulcanizate structures of SSBR/silica vulcanizates

Abstract Physical properties of rubber compounds are affected by the filler–rubber interaction, filler dispersion in the rubber matrix, and cross-link structure formed during vulcanization. In particular, the cross-link structure is closely related to the physical properties of vulcanizates and has been analyzed using the swelling test and Flory-Rehner equation. However, the relationship between the structure and physical properties of vulcanizates cannot be explained by the cross-link density obtained using these methods. The cross-link density obtained from the swelling test is a complex result of the filler–rubber interaction occurring during the compounding as well as the chemical cross-link structure formed by sulfur during the vulcanization. Moreover, the rubber vulcanizates that use silica need to be separately analyzed for each factor as its physical properties are affected more by the filler–rubber interaction than by carbon black. Therefore, this study determines the factors that contribute to the total cross-link density of vulcanizates into chemical cross-link density and filler–rubber interaction via quantitative analysis using the swelling test results and Flory-Rehner and Kraus equations. The vulcanizates used for the analysis were carbon black-filled and silica-filled non-functionalized SSBR compounds with varying cure accelerator for each filler loading. Their chemical cross-link density was measured and the effect of the filler–rubber interactions on their mechanical and dynamic viscoelastic properties was investigated. Furthermore, the relationship between the structure and physical properties of rubber vulcanizates was elucidated.

Synthesis of Ionic Elastomer Based on Styrene-Butadiene Rubber Containing Methacrylic Acid

R&BD Center, Kumho Petrochemical, Daejeon, 305-348, Korea(Received December 17, 2012, Revised December 24, 2012, Accepted December 28, 2012)요 약：본 연구에서는 저온유화중합을 통해 벤질메타아크릴레이트 (benzyl methacrylate, BzMA) 를 third mono-mer 로 사용하여 styrene-butadiene-benzyl methacrylate copolymer (BzMA-SBR) 를 합성하였다. 수산화나트륨 (NaOH) 을 이용하여 가수분해반응을 통해 BzMA 의 벤질 그룹을 deprotection 시켜 carboxylated styrene butadiene rubber (XSBR) 로 만든 후, Na-XSBR 아이오노머를 제조하였다. 중합 시 BzMA 의 투입량을 달리하여 XSBR 의 카르복실기 (carboxyl group) 함량을 다양하게 조절하였다. FTIR (ATR),

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

Abstract 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.

Effect of the amounts of glycidyl methacrylate on the mechanical and dynamic properties of styrene–butadiene–glycidyl methacrylate terpolymer/silica composites

Abstract GMA-SBRs with GMA contents in the range of 0.06–0.71 wt.% were synthesized and used to evaluate the properties of the silica composites for fuel-efficient tires. The chemical structures of the GMA-SBRs were analyzed using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (1H NMR), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). GMA-SBRs can enhance filler–rubber interaction through covalent bond formation between the silica filler and rubber molecules. After compounding, the cure characteristics and mechanical and dynamic properties of the GMA-SBR silica-filled composites were analyzed. The mechanical properties, including the Mooney viscosity, bound rubber, swelling ratio, and moduli, exhibited obvious differences with increasing GMA content. However, the optimum content of GMA in the GMA-SBR, in terms of dynamic properties such as the Payne effect which represents the change in dynamic modulus against the strain to determine the extent of filler flocculation and tan δ at 60 °C representing tire rolling resistance, was ~0.6 wt.%. These results are due to improved silica dispersion, resulting from increased covalent bond formation between GMA-SBR and the silica surface. This approach assists in the determination of functional group contents in functionalized emulsion styrene–butadiene rubber for fuel-efficient tires, leading to a decrease in vehicular greenhouse gas emission.

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

Abstract 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.

Effect of the functional group of silanes on the modification of silica surface and the physical properties of solution styrene-butadiene rubber/silica composites

ABSTRACT Silica compounds were prepared using non-functionalized solution styrene-butadiene rubber (SSBR) to investigate effect of the functional group of silanes on the silica modification and properties of SSBR/silica compounds. Bis-[3-(triethoxysilyl)propyl]disulfide (TESPD), 3-mercaptopropyltriethoxysilane (MPTES), 3-aminopropyltriethoxysilane (APTES), vinyltriethoxysilane (VTES), and 3-chloropropyltriethoxysilane (CPTES) were used as silane agents. Bound rubber contents and vulcanizate structures were analyzed, and physical properties, cure characteristics and viscoelasticities were evaluated. MPTES and TESPD have chemically reactive functional groups with rubber chain. Particulary, as thiol group is more reactive than disulfide, the filler–rubber interaction is outstanding when applying MPTES. The bound rubber content of the MPTES applied compound was 30% higher. Vulcanizate structure analysis exhibited that the filler–rubber interaction of the MPTES applied compound is more than twice as high. As amino group of APTES can form hydrogen bonds with other amino or silanol groups on silica surface, strong filler–filler interaction which leads to easy agglomeration and accelerator adsorption, resulting in flocculation and marching. VTES cannot hydrophobize silica surface owing to its short carbon chain. Therefore, the compounds that apply APTES or VTES had high Payne effect, indicating poor silica dispersion. CPTES has polar functional group but behaves as covering agent because of its weak interaction with rubber.