• Elastomers and Composites
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• v.44 no.2
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• pp.164-174
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• 2009

PA66/EPDM/PP-g-MA and PA66/EPDM-g-MA/PP-g-MA composites were manufactured by a modular intermeshing twin screw extruder for enhanced low temperature impact resistance with different content of PP-g-MA. The results showed that composite containing 90 wt% of PA66, 8 wt% of EPDM-g-MA, and 2 wt% of PP-g-MA has a optimum value in the thermal and mechanical properties. The characteristics of the composites were analyzed by TGA, DSC, and SEM. From above results, we established that the low interfacial strength and the impact resistance at low temperature shown in a pre-existing PP/EPDM composite were enhanced by grafting with compatibilizer such as maleic anhydride. These results show the possibility of local manufacturing process and cost down with optimum screw configuration for best mixing quality in the twin screw extruder.

• Elastomers and Composites
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• v.45 no.2
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• pp.112-121
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• 2010

In this study, styrene butadiene rubber(SBR)/organoclay nanocomposites were manufactured using the latex method with 3-aminopropyltriethoxysilane(APTES) as a modifier. The X-ray diffraction(XRD), transmission electron microscopy(TEM) images, Fourier transform infrared(FTIR) spectroscopy, swelling ratio and mechanical properties were measured in order to study the interaction between filler and rubber according to the mixing temperature in the internal mixer. In the case of SBR/APTES-MMT compounds, the dispersion of the silicates within the rubber matrix was enhanced, and thereby, the mechanical properties were improved. The characteristic bands of Si-O-C in APTES disappeared after hydrolysis reaction in the MMT-suspension solution and the peak of hydroxyl group was increased. Therefore the formation of chemical bonds between the hydroxyl group generated from APTES on the silicate surface and the ethoxy group of bis(triethoxysilylpropyl) tetrasulfide(TESPT) was possible. Consequently, the 300% modulus of SBR/APTES-MMT compounds was further improved in the case of using TESPT as a coupling agent. However, the silanization reaction between APTES and TESPT was not affected significantly according to the increase of mixing temperature in the internal mixer.

• Elastomers and Composites
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• v.44 no.4
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• pp.447-454
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• 2009

We synthesized polyester-diol containing Cloisite 30B which is exfoliated during the synthesis. First, esterification was conducted with excess adipic acids and two 2-hydroxyethyl groups of the tertiary ammonium tethered to Cloisite 30B silicate layer. Due to the small molecular size of adipic acid ($d{\approx}3.0\;{\AA}$, $L{\approx}9.3\;{\AA}$), it penetrated into the interlayer of Cloisite 30B, reacted with the 2-hydroxyethyl groups, and produced the tertiary ammonium that has the two ethyl-ester adipic acid groups, one methyl group, and one hydrogenated alkyl group. Through the esterification, the molecular size of the tertiary ammonium increased and as the result, the basal space of Cloisite 30B increased from $18.4\;{\AA}$ to more than $58.3\;{\AA}$. The produced ethyl-ester adipic acid and unreacted adipic acid reacted with excess diethylene glycol ([COOH]/[OH]${\approx}0.6$) to be polyester-diol. The COOH conversion calculated from the acid value of the reactant mixture was 94%. The number average molecular weight and PDI of the produced polyester-diol were 830 g/mol and 1.2, respectively.

• Elastomers and Composites
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• v.49 no.3
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• pp.181-190
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• 2014

Melt grafting of itaconic acid (IA) onto an ethylene-propylene-diene terpolymer (EPDM) with various organic peroxide initiators was performed. Finding the optimum mixing conditions and concentration of ingredients is critical for effective grafting and optimum properties of grafted materials. This study focused on the effects of mixing conditions (temperature and time), initiator type/concentration and monomer concentration on the grafting degree and efficiency, melt flow index, and gel content of EPDM-g-IA. The initiator, 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (T-101), appeared to meet for the best grafting degree (1.91%). The grafting degree increased markedly by increasing the amounts of monomer IA and initiator T-101. The grafting degree also increased by increasing mixing temperature and time. The optimum monomer and initiator concentrations and reaction temperature and time were found to be about 5wt%/0.05wt% and $160^{\circ}C$/15min, respectively. It was found that the physical properties of EPDM-g-IA were higher than those of the pristine EPDM.

• Elastomers and Composites
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• v.48 no.3
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• pp.225-231
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• 2013

In this study, we observed the effect of carboxylated SBR latex and zinc oxide on styrene-butadiene-styrene( SBS) composites for improving abrasion and debris. SBS composite, which added only silica, showed poor mechanical properties, NBS abrasion, and debris, caused by strong filler-filler interaction of silica. In case of adding carboxylated SBR latex, mechanical properties, NBS abrasion and debris of SBS composite were improved. Because of carboxyl group of carboxylated SBR latex interacted with silanol group of silica. Both carboxylated SBR latex and zinc oxide were added, SBS composite showed highest mechanical properties, NBS abrasion, and debris by forming ion cluster between carboxylated SBR latex and zinc oxide. By FT-IR analysis, ion clusters were confirmed that observed zinc carboxylated group stretch peak at $1550{\sim}1650cm^{-1}$ range. SBS composite, SC-4, showed excellent mechanical properties ; tensile strength $156kgf/cm^2$, elongation 936%, tear strength 59.4kgf/cm ; and excellent abrasion characteristics ; NBS abrasion 338%. Also, debris of SC-4 was minimized and showed wave-shape in fracture surface.

• Elastomers and Composites
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• v.48 no.3
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• pp.216-220
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• 2013

The phase separation in Wood Flour-Polymer Composite (WPC) was investigated and the reasons for change in mechanical properties with the content of wood flour were explored. The wood flour-polypropylene composite samples with different wood flour contents were prepared. From differential scanning calorimetry (DSC) thermograms of WPC samples, the trend of crystallinity and melting temperature ($T_m$) were analyzed. The crystallinity and melting temperature increased and then decreased as the content of wood flour increased. From these results, it was confirmed that at the low wood flour content the wood flours were dispersed into the polypropylene matrix but at the high wood flour content, the phase separation between polymer and wood flour phases appeared. The tensile strength of WPC samples was continuously decreased with the increase of wood flour content. At a low wood flour content, the low interfacial bonding and the decrease in crystallinity were the main reasons for the decrease in tensile strength with the increase of wood flour content. At a high wood flour content, the decrease in tensile strength resulted from the interfacial defects between the polymer and wood flour phases. The impact strength of the WPC sample showed the maximum behavior with the content of wood flour. At a low wood flour content, the impact strength was enhanced owing to the decrease in brittleness, which results from the decrease in crystallinity. At a high wood flour content, however, the impact strength decreased due to phase separation.

• Elastomers and Composites
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• v.48 no.3
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• pp.201-208
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• 2013

In this study, effect of different amounts of sulfur and vulcanization accelerators in the acrylonitrile styrene-butadiene rubber (AN-SBR)/silica compounds on the properties of tire tread compound were studied. As a result, cure rate and degree of cross-linking of the compounds were increased due to enhanced cross-linking reactivity by the increased amounts of sulfur and vulcanization accelerators. Also, abrasion resistance and the mechanical properties such as hardness and modulus of the compounds were improved by enhanced degree of cross-linking of the compounds. For the dynamic properties, tan ${\delta}$ value at $0^{\circ}C$ was increased due to the increase of glass transition temperature ($T_g$) by enhanced degree of cross-linking of the compound, and tan ${\delta}$ value at $60^{\circ}C$ was decreased. Initial cure time ($t_1$) showed the linear relationship with tan ${\delta}$ value at $60^{\circ}C$. This result is attributed that reduced initial cure time ($t_1$) of compounds by applying increased amount of curatives can form cross-linking in early stage of vulcanization that may suppress development of filler network. This result is verified by observation on the surface of annealed compounds using AFM (atomic force microscopy). Consequently, decreased initial cure time is considered a very important parameter to reduce tan ${\delta}$ at $60^{\circ}C$ through reduced re-agglomeration of silica particles.

• Elastomers and Composites
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• v.40 no.3
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• pp.166-173
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• 2005

Effect of thermal aging on the weight loss and water absorption of epoxy adhesives was investigated in the presence of three types of different hardeners, such as D-230, G-5022, and HN-2200. Thermal and mechanical properties of the cured epoxy resins were also studied througth the glass transition temperature and shear adhesion strength measurements. Weight losses of DGEBA/D-230 and DGEBA/HN- 2200 systems were not varied. However, the weight of DGEBA/G-5022 system was significantly decreased with increasing the thermal aging time. The water absorption of the specimens was increased as the thermal aging time increased except that using G-5022. DEGBA/HN-2200 system showed higher $T_g$ value than those of other systems, due to the formation of the fine three-dimensional network structure containing aliphatic ring. Shear adhesion strength of all systems was increased with increasing the thermal aging tine, which is attributed to increased degree of cure and fine three-dimensional network structure formation. And $T_g$ values and shear adhesion strength of all specimens exposed to water was decreased as the immersion time increased.

• Elastomers and Composites
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• v.40 no.3
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• pp.188-195
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• 2005

Chemical and physical changes and the contents of functional groups in the carbon black surface after the ozone treatment was investigated using elemental analysis, pH, tint strength, DBP, $N_2SA$, IA, and acid-base reaction. As the treatment time was increased, surface structure, particle size and surface area of carbon black did not change, while surface oxygen contents increased, and pH decreased and then saturated after $1{\sim}2$ hour. The contents of carboxylic, lactone, hydroxyl, and carbonyl groups were analyzed with four bases such as $NaHCO_3,\;Na_2CO_3,\;NaOH$, and $NaOC_2H_5$. Before oxidation, the carbonyl group was dominantly present on the surface, but by increasing the treatment time, the contents of the carboxylic and carbonyl groups increased to a saturated level after $1{\sim}2$ hour. Before and after the oxidation, the lactone and hydroxyl groups were nearly absent. These results showed that the reaction mechanism of carbon black and ozone is similar to that of ethylene and ozone. Weight of oxidized carbon black was increased after treating AIBN, while free radical was slightly decreased by ESR analysis. When carbon black was treated with organic compounds containing mercapto- groups, the results of ESR showed that free radical peak intensity was almost diminished compared to original carbon black.

• Elastomers and Composites
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• v.46 no.3
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• pp.237-244
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• 2011

Five natural rubber (NR) composites with different reinforcing systems of unfilled, carbon black, carbon black with silane coupling agent, silica, and silica with silane coupling agent were thermally aged and change of the crosslink densities by the accelerated thermal aging was investigated. The crosslink densities on the whole increased as the aging time elapsed irrespective of the reinforcing systems. The crosslink density changes became noticeable by increasing the aging temperature. For carbon black-filled composites, the silane coupling agent made the crosslink density change to be increased. For silica-filled composites, however, the silane coupling agent made the crosslink density increment reduced at 60 and $70^{\circ}C$ and it hardly affect the degree of the crosslink density change at 80 and $90^{\circ}C$. The activation energies for the crosslink density changes of the carbon black-filled samples increased continuously in a logarithmic fashion, whereas that of the silica-filled one showed a quasi-steady state ranges at aging times of 30-150 days. The activation energy of the unfilled sample increased exponentially with the aging time. The experimental results were explained with sulfur donation from the silane coupling agent, surface modification of the filler by the silane coupling agent, adsorption of curative residues on the silica surface, and release of the adsorbed curative residues.