Thermal Characteristics, Kinetics and Thermodynamics of Thermal Degradation Reaction, and Hydrophobicity of Corn Starch Affected by Chemical and Physical Modifications

A Comprehensive Study on the Effect of Highly Thermally Conductive Fillers on Improving the Properties of SBR/BR-Filled Nano-Silicon Nitride

The effect of silicon nitride (Si3N4) as a thermally conductive material on the mechanical, microstructural, and physical properties as well as kinetics of the curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) was investigated in this work. The results showed an improvement in tensile, hardness, and compression features of the composite due to the presence of Si3N4. The properties were enhanced with the filler loading content; somehow, the composite including Si3N4 = 6 parts per hundred (phr) had the most significant performance, an increase of ∼15 and 20% in the maximum strain and toughness of the composite, respectively, an increase of almost 7% in the hardness, and an ∼13% reduction in the compression set. Also, the filler led to an increase in the crosslink density (calculated via the Flory-Rehner equation using swelling test) by 7.12 × 10-5 mol/g, proving the increment of the covalent bonds between the polymer chains during the curing reaction. The kinetic consideration revealed a reduction in the scorch and optimum curing times by ∼40 and ∼25%, respectively. In order to describe the kinetics of curing reaction of SBR/BR-Si3N4, an autocatalytic model based on the Kamal-Sourour model was applied on the rheometry results. The calculated kinetic parameters indicated that the thermally conductive Si3N4 accelerated the curing reaction by ∼40%, particularly at Si3N4 = 6 phr. After 6 phr of Si3N4, agglomeration of the filler particles decreased its performance.

Catalytic effect of high thermal conductive SiC on the kinetics and thermodynamics of vulcanization reaction of SBR/BR-filled nano-SiC

Nano-silicon carbide (SiC) as a high thermal conductive material with an intrinsic thermal conductivity of ~ 490 W/m K was used to improve the cure characteristics, kinetics, and thermodynamics of curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds. The considerations were carried out by non-isothermal differential scanning calorimetry (DSC). Results revealed that the presence of SiC shifted the peak and end temperatures of the curing peak to lower temperatures. The calculated activation energy of the curing reaction based on the Kissinger approach showed a descent from 409.8 to 93.8 kJ/mol by adding SiC from 0 to 7.5 phr (part per hundred rubber). Moreover, the obtained Gibbs free energy variation and equilibrium constant of the curing reaction proved that the reaction was absolutely forced and irreversible, which can be increasingly characterized as a one-way process. According to the results, SiC accelerated the curing reaction because of the increment of heat transfer into the compound. This phenomenon caused the increment of enthalpy variation of the vulcanization reaction, particularly at the SiC content of 5 phr. The achieved kinetic parameters via fitting an autocatalytic model based on the Sestàk-Berggren model by the Màlek method to describe the kinetics of the curing reaction indicated that the SiC filler had a catalytic effect on the curing reaction of SBR/BR-SiC, particularly after 2.5 phr of the filler.