Thermal destruction of carbon black network structure in natural rubber vulcanizate

Abstract

To investigate thermal destruction and rearrangement of the carbon black (CB) network consisting of CB aggregates in rubbery matrix, the proper heat-treatment temperature without thermal decomposition of rubber matrix were examined by using differential scanning calorimetry, dynamic mechanical measurements, and thermal expansion measurements. 383 K was chosen as the heat-treatment temperature under vacuum. The volume resistivity (q v ) of 50 phr CB-filled natural rubber vulcanizate (CB-50) increased rapidly up to a heat-treatment time of 24 h and it decreased by further heat-treatment time, whereas the q v of CB-80 remained almost constant without depending on heating time. Three-dimensional electron microscope (3D-TEM) observations revealed that after the heat-treatment for 75 h, the average lengths of the crosslinked and the branched chains and the crosslinked points density (D cross ) of the CB network decreased, whereas the branched points density (D branch ) increased with decrease of D cross . After the heat-treatment, their fractions (F cross 0 s) of crosslinked chains decreased, whereas their fractions (F branch 0 s) of the branched ones increased. Especially, F branch of CB-50 became larger than that of CB-80, while the decrease of F cross of CB-50 was almost the same as that of CB-80 by the heat-treatment. And, F cross and F branch of the heat-treated CB-50 were the same compositions (F cross and F branch ¼ ca. 0.7 and ca. 0.3, respectively) as those of the heat-treated CB-80. It is suggested that the CB network of CB-80 is more thermal stable than that of CB-50. These results directly indicate that CB network is broken and is rearranged by a heat-treatment.

Structural changes in the carbon black network in carbon‐black‐filled styrene‐butadiene rubber samples cured with a two‐step process

“…Meanwhile, on the basis of q v measurements and 3D TEM observations, Kato et al14 reported that the CB net in CB‐filled crosslinked NR was destroyed when the heat treatment conditions were set to minimize the occurrence of thermal oxidative degradation. It was found that the crosslinked chains of the CB net were broken by the heat treatment process and that the number of branched chains increased.…”

Biochar from waste agriculture as reinforcement filer for styrene/butadiene rubber

“…Since as the surface area of CB increases, the rubber composite exhibited higher Young's moduli, lower tensile strength, and elongation at the break. Kato et al [ 21 ] found that thermal treatment of CB influences the structure and surface area of CB which affects the properties of CB filled rubber composites. Jovanović et al [ 22 ] studied the content of CB effects on the mechanical properties of the NBR/EPDM rubber blend.…”

Influence of annealing time on linear rheology and morphology of silica filled polyisoprene rubber and ethylene‐propylene rubber

“…Compounding rubber and filler usually rises temperature of compounds due to the friction during mixing and sometimes, the compounds are thermally treated at high temperatures for modifying the physical mechanical properties . Thermal‐treatment influences the performance of rubber compounds intricately while the exact mechanisms remain ambiguous.…”