Influence of SBR Type and Blend Ratio on Dynamic Mechanical Properties of SBR/SBR Biblend Composites

Sung-Seen Choi 한국고무학회 2024 엘라스토머 및 콤포지트 Vol.59 No.1

Solution styrene-butadiene rubber (S-SBR) is used to improve the wet grip and rolling resistance properties of tire treads. As blending of SBRs can improve the physical properties of tire treads, we investigated the effects of SBR type and blending ratio on the physical properties. Twelve SBR/SBR biblend composites were prepared using four SBRs with different microstructures. The glass transition temperature (Tg), tanδ at 0°C (wet grip predictor), and tanδ at 60°C (rolling resistance predictor) were obtained from dynamic mechanical analysis, and were compared to the expected values obtained from the results of single SBR samples. Most of the SBR/SBR biblend composites exhibited crosslink densities lower than the expected values. The tanδ values at 0°C and 60°C of the SBR/SBR blend composites deviated from the expected values, with many of the deviations being disadvantageous. Of the twelve composites, six samples had higher 0°C tanδ values than the corresponding expected values, and four exhibited superior wet grip properties to those of the SBR single samples. In addition, two of the twelve samples exhibited improved rolling resistance properties as compared with the single SBR samples. Finally, four samples exhibited lower Tg values than expected, and the Tg of one composite was lower than those of the single SBR samples.

Fragmentations and Proton Transfer Reactions of Product Ions Formed from Mono-, Di-, and Triethanolamines

Choi, Sung-Seen,So, Hun-Young Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.10

Fragmentations and proton transfer reactions of mono-, di-, and triethanolamines were studied using FTMS. It was found that the most abundant fragment ion was $[M-CH_2OH]^+$. The $[M-CH_2OH-H_2O]^+$ was observed in the mass spectra of diethanolamine and triethanolamine. By increasing the ion trapping time in the ICR cell, the $[M+H]^+$ and $[M+H-H_2O]^+$ ions were notably increased for all the samples while the $[M+H-2H_2O]^+$ was observed in the mass spectra of diethanolamine and triethanolamine. The proton transfer reactions between the fragment ions and neutral molecules occurred predominantly by increasing the ion trapping time. The rate constants for the proton transfer reactions were calculated from experimental results. The proton transfer reaction of $CHO^+$ was the fastest one, which is consistent with the heats of reaction. The rate constants for proton transfer reactions of triethanolamine were much slower than those of ethanolamine and diethanolamine because of the steric hindered structure of triethanolamine. The plausible structures of observed ions and heats of reaction for proton transfer were calculated with AM1 semiempirical method.

Thermal Aging Behaviors of Elemental Sulfur-Free Polyisoprene Vulcanizates

Choi, Sung-Seen,Han, Dong-Hun,Ko, Seung-Won,Lee, Hyung-Sik Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

Electron-Impact Ionization Mass Spectroscopic Studies of Acetylene and Mixed Acetylene-Ammonia Clusters as a Structure Probe

Sung Seen Choi,Kwang Woo Jung,Kyung Hoon Jung Korean Chemical Society 1992 Bulletin of the Korean Chemical Society Vol.13 No.5

Ion-molecule reactions of acetylene and mixed acetylene-ammonia cluster ions are studied using an electron impact time-of-flight mass spectrometer. The present results clearly demonstrate that $(C_2H_2)_n^+$ cluster ion distribution represents a distinct magic number of n=3. The mass spectroscopic evidence for the enhanced structural stabilities of $[C_6H_4{\cdot}(NH_3)_m]^+$ (m=0-8) ions is also found along with the detection of mixed cluster $[(C_2H_2)_n{\cdot}(NH_3)_m]^+$ ions, which gives insight into the feasible structure of solvated ions. This is rationalized on the basis of the structural stability for acetylene clusters and the dissociation dynamics of the complex ion under the presence of solvent molecules.

Influence of the Cure Systems on Long Time Thermal Aging Behaviors of NR Composites

Choi, Sung-Seen,Kim, Jong-Chul,Lee, Seung-Goo,Joo, Yong-L. The Polymer Society of Korea 2008 Macromolecular Research Vol.16 No.6

NR composites with different curing systems were aged thermally at 60, 70, 80, and $90^{\circ}C$ for 2-185 days in a convection oven, and the changes in the crosslink density were investigated as a function of the accelerated thermal aging. The overall crosslink densities increased with increasing aging time irrespective of the aging temperatures and curing systems. The changes in crosslink density were enhanced by increasing the aging temperature. The degree of the increased crosslink density was in the following order: "the conventional cure system > the semi-EV system > the EV system". For short term thermal aging, the change in crosslink density with the aging time was complicated, particularly for low temperature aging. The activation energies of the change in crosslink density with thermal aging using the conventional and semi-EV cure systems increased and then remained relatively constant with increasing aging time, whereas that of the specimen with an EV cure system tended to increase linearly. The experimental results were explained by the dissociation of the existing polysulfidic linkages and the formation of new cross links through the crosslinking-related chemicals remaining in the sample.

Chlorine Effect on Thermal Aging Behaviors of BR and CR Composites

Choi, Sung-Seen,Kim, Jong-Chul Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.9

Chloroprene is a chlorine substituent of 1,3-butadiene. Butadiene rubber (BR) and chloroprene rubber (CR) composites were thermally aged at 60, 70, 80, and $90^{\circ}C$ for 2 - 185 days in a convection oven and changes of the crosslink densities by the accelerated thermal aging were investigated. The crosslink densities increased as the aging time elapsed and as the aging temperature became higher. Degrees of the crosslink density changes of the BR composite were on the whole larger than those of the CR one except the short-term thermal aging at 60 and $70^{\circ}C$. The crosslink densities abnormally increased after themal aging at high temperatures for a long time. Activation energies for the crosslink density changes of the rubber composites tended to increase with increase of the aging time and the variation showed a local minimum. The activation energies of the CR composite were lower than those of the BR one. The experimental results were explained with a role of ligand of chlorine atom of CR in a zinc complex, steric hindrance by chlorine atom of CR, and oxidation of rubber chain.

Substituent Effect on Fragmentations and Ion-Molecule Reactions of Ionized Alkyn Alcohols

Choi, Sung-Seen,So, Hun-Young,Kim, Beom-Tae Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.4

The fragmentation patterns and ion-molecule reactions of two alkyn alcohols, 2-propyn-1-ol (HC≡$CCH_2$OH) and 2-methyl-3-butyn-2-ol (HC≡CC($CH_3)_2$OH), were investigated using Fourier transform mass spectrometry (FTMS). The most abundant fragment ions formed from the molecular ions were [M-H]$^+$ for 2-propyn-1-ol and [M-$CH_3]^+$ for 2-methyl-3-butyn-2-ol. The dehydrated ion, [M-$H_2O]^+$ was formed only from 2-propyn-1-ol in which $\alpha$ -hydrogen atoms were available for $\alpha,\;\alpha$ -elimination reaction. The protonated molecules were dissociated into [M+H-$H_2O]^+$ and [M+H-$C_2H_2]^+$ through dehydration and deacetylenylation processes. The formations of [M+H-$H_2O]^+$ and [M+H-$C_2H_2]^+$ from 2-methyl-3-butyn-2-ol were more favorable than those from 2-propyn-1-ol due to stabilization by two methyl groups at $\alpha$ -carbon. Ion-neutral complexes formed at long ion trapping time gave dehydrated and/or deacetylenylated ion products by further dissociation.

Influence of Alkyl Chain Length on Fragmentations and Ion-Molecule Reactions of Ionized c-C₆H₁₁-(CH₂)_nCO₂H

Choi, Sung-Seen,So, Hun-Young Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

Fragmentations and ion-molecule reactions of ionized cyclohexane propionic acid and cyclohexane butyric acid were studied using FTMS and theoretical calculations. The difference in bond dissociation depending on the aliphatic chain length was investigated and mechanisms for the possible rearrangements depending on the aliphatic carbon length were suggested. The most abundant fragment ion of the ionized cyclohexane propionic acid was c-$C_6H_{11}CH_2\;^+$ formed from the molecular ion by the direct C-C bond cleavage, while that of the ionized cyclohexane butyric acid was c-$C_6H_9C(OH)=OH^+$ formed by rearrangement of the molecular ion from the acid to diol form and loss of propyl radical. Stabilities of the radical and distonic ions of $C_nH_{2n}O^{+\bullet}$ formed from the molecular ion were compared. Protonated molecules were dissociated into smaller ions by losing one or two water molecules. The $[nM + H]^+$, $[nM + H - H_2O]^+$, and $[nM + H - 2H_2O]^+$ with n = 2 and 3 were generated by solvation with the neutral molecules in the ICR cell at long ion trapping time.

Fragmentations and Proton Transfer Reactions of Product Ions Formed from Mono-, Di-, and Triethanolamines

Sung-Seen Choi*,소헌영 대한화학회 2004 Bulletin of the Korean Chemical Society Vol.25 No.10

Fragmentations and proton transfer reactions of mono-, di-, and triethanolamines were studied using FTMS. It was found that the most abundant fragment ion was [M−CH2OH]+. The [M−CH2OH−H2O]+ was observed in the mass spectra of diethanolamine and triethanolamine. By increasing the ion trapping time in the ICR cell, the [M+H]+ and [M+H−H2O]+ ions were notably increased for all the samples while the [M+H−2H2O]+ was observed in the mass spectra of diethanolamine and triethanolamine. The proton transfer reactions between the fragment ions and neutral molecules occurred predominantly by increasing the ion trapping time. The rate constants for the proton transfer reactions were calculated from experimental results. The proton transfer reaction of CHO+ was the fastest one, which is consistent with the heats of reaction. The rate constants for proton transfer reactions of triethanolamine were much slower than those of ethanolamine and diethanolamine because of the steric hindered structure of triethanolamine. The plausible structures of observed ions and heats of reaction for proton transfer were calculated with AM1 semiempirical method.

Substituent Effect on Fragmentations and Ion-Molecule Reactions of Ionized Alkyn Alcohols

Sung-Seen Choi*,소헌영,Beom-Tae Kim 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.4

The fragmentation patterns and ion-molecule reactions of two alkyn alcohols, 2-propyn-1-ol (HCºCCH2OH) and 2-methyl-3-butyn-2-ol (HCºCC(CH3)2OH), were investigated using Fourier transform mass spectrometry (FTMS). The most abundant fragment ions formed from the molecular ions were [M-H]+ for 2-propyn-1-ol and [M-CH3]+ for 2-methyl-3-butyn-2-ol. The dehydrated ion, [M-H2O]+ was formed only from 2-propyn-1-ol in which  -hydrogen atoms were available for  , -elimination reaction. The protonated molecules were dissociated into [M+H-H2O]+ and [M+H-C2H2]+ through dehydration and deacetylenylation processes. The formations of [M+H-H2O]+ and [M+H-C2H2]+ from 2-methyl-3-butyn-2-ol were more favorable than those from 2-propyn-1-ol due to stabilization by two methyl groups at  -carbon. Ion-neutral complexes formed at long ion trapping time gave dehydrated and/or deacetylenylated ion products by further dissociation.