Summary The epoxy composite hollow microspheres (ECHM) was prepared by single emulsion technique. Porofor Toluenesulfonyl hydrazide (TSH) 75 was used as blowing agent. Carbon black was used as filler for polyamide‐epoxy adduct matrix, which was reverted ratio of 1:2 epoxy to polyamide. The epoxy mixture (internal phase) was dropped and stirred into a heated corn oil (external phase) to form spherical droplets. These epoxy droplets underwent two simultaneous mechanisms of curing and foaming and became hollow microspheres. As expected, higher TSH content produced lower density of ECHM because of more expansion in ECHM. This fact was also evident from the size of hollow microspheres observed by using scanning electron microscope. In addition, high TSH content of 16 phr induced higher thermal properties of ECHM compared to those of ECHM using 8 phr and 12 phr TSH.
Summary Carbon black‐filled epoxy porous (CBEP) was fabricated by using single emulsion technique. Mixture of epoxy, polyamide hardener, sodium bicarbonate (as blowing agent) and carbon black (as conductive filler) was dropped into a heated corn oil at 160 °C (containing free of polyunsaturated fatty acids). The epoxy‐oil system was stirred at 1000 rpm for 1 hour. Because of the immiscibility of epoxy mixture and corn oil, droplets of epoxy mixture were formed. Initial epoxy droplets were broken into small droplets due to the applied shear (from stirring). Receiving heat from oil phase, the decomposition of sodium bicarbonate and the curing reaction of epoxy and polyamide occurred simultaneously so CBEP was formed. It was found that sodium bicarbonate exhibited a significant effect on the morphology, thermal and conductivity properties of CBEP. Increase of sodium bicarbonate's content from 4 phr to 12 phr could produce larger epoxy particle size in CBEP. However, CBEP using 20 phr of sodium bicarbonate's content had the lowest particle size. The content of 20 phr could induce an early and strong decomposition reaction in the initial epoxy droplets, which broke them into smaller size; hence the smaller particle size was obtained after curing. This fact was evident from the result of bulk density, where higher sodium bicarbonate content induced lower bulk density of CBEP. Furthermore, CBEP using higher sodium bicarbonate content also exhibited better electrical conductivity.
Process temperature greatly affects the decomposition behavior of a blowing agent, and changes the structure of the porous epoxy. This paper investigates the effect of processing temperature on the decomposition rate and volume of decomposing gases from ammonium bicarbonate as well as the properties of porous epoxy micro-bead through a single epoxy droplet. A single epoxy droplet (epoxy-polyamide-ammonium bicarbonate) was dropped into the corn oil heated at the temperatures of 80°C, 90°C and 100°C. This study found that by controlling the processing temperature, an epoxy foam bulk (80°C) or a number of porous epoxy micro-beads were fabricated (90°C and 100°C). Higher total volume of gas was generated which was 1142.86 cm 3 /g at 100°C, with lower viscosity of epoxy. Therefore, the initial epoxy droplet of 10:6 ratio burst into smaller micro-beads with dominant sizes in the range of 251-500 μm and porosity of 30%. From the perspective of epoxy polyamide ratios, the 10:10 ratio has porous epoxy micro-beads slightly larger than that of 10:6 ratio. This induced a decrease in porosity and an increase in specific gravity of micro-beads of 10:10 ratio.
This paper explored the effects of ammonium bicarbonate and different ratios of epoxy to polyamide on the formation of porous epoxy micro-beads through a single epoxy droplet. A single drop of a mixture, consisting of epoxy, polyamide, and ammonium bicarbonate, was dropped into heated corn oil at a temperature of 100 °C. An epoxy droplet was formed due to the immiscibility of the epoxy mixture and corn oil. The ammonium bicarbonate within this droplet underwent a decomposition reaction, while the epoxy and polyamide underwent a curing reaction, to form porous epoxy micro-beads. The result showed that the higher ammonium bicarbonate content in the porous, epoxy micro-beads increased the decomposition rate up to 11.52 × 10−3 cm3/s. In addition, a higher total volume of gas was generated when a higher ammonium bicarbonate content was decomposed. This led to the formation of porous epoxy micro-beads with a smaller particle size, lower specific gravity, and better thermal stability. At an epoxy to polyamide ratio of 10:6, many smaller micro-beads, with particle sizes ranging from 201 to 400 μm, were obtained at an ammonium bicarbonate content of 10 phr. Moreover, the porous epoxy micro-beads with open pores were shown to have a low specific gravity of about 0.93 and high thermal stability at a high ammonium bicarbonate content. Based on the findings, it was concluded that porous epoxy micro-beads were successfully produced using a single epoxy droplet in heated corn oil, where their shape and particle size depended on the content of ammonium bicarbonate and the ratio of epoxy to polyamide used.
Conductive composite requires a well dispersion of conductive filler, which is this difficult to be achieved low content of filler for high density conductive filler. This work investigates the effect of carbon black and graphite on the morphology and conductive properties of conductive epoxy micro-porous. The conductive epoxy micro-porous was prepared by using single emulsion technique. It involved the drop of epoxy-hardener-blowing agent-conductive filler mixture into corn oil at 160 °C and followed by the leaching process to remove excess corn oil. Results show the addition of conductive filler in epoxy matrix lead to increases porous structure in epoxy micro-porous. Carbon black filled epoxy micro-porous possessed smaller particles compared to graphite filled epoxy micro-porous. For skeleton density and total pore, both of the value increase with filler loading due to packing sphere effect. However, the skeleton density for carbon black filled epoxy micro-porous is higher compared to graphite filled epoxy micro-porous. For electrical conductivity, graphite filled micro-porous was higher than that of carbon black filled epoxy micro-porous.
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