Effect of graphene treated with cyclohexyl diamine by diazonium reaction on cure kinetics, mechanical, thermal, and physical properties of natural rubber/graphene nanocomposite foam

Abstract

The influence of functionalization of cyclohexyl diamine onto the graphene surface via diazonium reaction on the cure kinetics as well as morphology, mechanical, thermal and physical properties of natural rubber (NR)/graphene nanocomposite foam was investigated. The surface functionalization of graphene was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). Without an addition of blowing agent, the vulcanized NR composites containing cyclohexyl amine‐treated graphene showed not obvious different dispersion of graphene nanoplatelets than those containing untreated graphene as confirmed by transmission electron microscopy micrographs. Although the addition of untreated graphene could accelerate the sulfur vulcanization rate of NR nanocomposite foam due to the high thermal conductivity of graphene particle, and the remaining oxygen functional groups on the surface of graphene, the amines from cyclohexyl diamine on the treated graphene could react with carboxylic and epoxide group on the surface of graphene leading to a reduction of reactive oxygen functional groups on graphene surface and in turn slowed vulcanization rate. The fast vulcanization rate in untreated graphene system led to small bubble size in the NR nanocomposite foams. In contrast, the treated graphene system showed high tensile strength and low thermal expansion coefficient owing to low cell density. Finally, the defect on the graphene surface after functionalization was detected by Raman spectroscopy; this resulted in poor thermal conductivity for the treated graphene composite system. POLYM. COMPOS., 40:E1766–E1776, 2019. © 2018 Society of Plastics Engineers

Effect of carbon allotropes on foam formation, cure characteristics, mechanical and thermal properties of NRF/carbon composites

“…These affected the reduction of hardness and compression set due to the high amount of bubbles inside the rubber matrix and the large bubble size from coalescence between bubbles. 1,5 However, our research [8][9][10] used azodicarbonamide as a chemical blowing agent due to its low price with low processing temperature. The main factor that affects mechanical properties of natural rubber foam (NRF) composites is sulfur vulcanization reaction rate depending on the type and amount of accelerator, chemicals ingredient in sulfur vulcanization system and the effect of filler including filler type, amount of reinforcing filler and surface modification of reinforcing filler.…”

“…The main factor that affects mechanical properties of natural rubber foam (NRF) composites is sulfur vulcanization reaction rate depending on the type and amount of accelerator, chemicals ingredient in sulfur vulcanization system and the effect of filler including filler type, amount of reinforcing filler and surface modification of reinforcing filler. [8][9][10][11] The filler can be divided into two categories that are the filler of nonreinforcement and reinforcing filler. Some of the filler in rubber system is used to reduce cost thus it does not increase mechanical properties of the rubber matrix.…”

“…Thus, this research interested in the effect of carbon allotropes at 3 phr of carbon filler content on morphology, mechanical and thermal properties of natural rubber foam/carbon composites. This work explored the effect of carbon allotropes at 3 phr of carbon filler content because this content could be high enough for nanoparticle to improve properties of natural rubber foam/carbon composites from our previous research 10 and our preliminary results.…”

“…The main factor that affects mechanical properties of natural rubber foam (NRF) composites is sulfur vulcanization reaction rate depending on the type and amount of accelerator, chemicals ingredient in sulfur vulcanization system and the effect of filler including filler type, amount of reinforcing filler and surface modification of reinforcing filler. 8–11…”

“…Although, some works 10,11,18–21 studied on influence of carbon black and carbon nanoparticle on mechanical and thermal properties of rubber composites and our previous work 10 studied on the effect of graphene and surface treatement of graphene by cyclohexyl diamine, there was no research to compare the effect of carbon types or allotropes of carbon on rubber/carbon composite foam from the best of our knowledge. It was found from our previous study 10 that graphene treated with cyclohexyl diamine improved mechanical properties of NRF/functionalized graphene nanocomposites owing to the uniform of bubble diameter and low cell density in rubber matrix. The property of rubber/carbon composites could increase at high carbon filler content but the rubber foam/carbon composites could not be summarized with this knowledge because the rubber foam has other factors that should be concerned such as cure characteristics of sulfur vulcanization reaction and morphology of its product after processing.…”