Abstract
AbstractThe curing and cellular structure of natural rubber (NR)/silica composite foams were investigated. The presence of an activator in the rubber formulation significantly lowered the decomposition temperature of the azodicarbonamide foaming agent, which allowed foaming before NR curing. Therefore, two foam methods were designed: foaming initially at 90°C and then curing at 140°C, and foaming and curing simultaneously at 140°C. Two-step foaming generated a lower cell density and higher cell size. Incorporation of nano silica into NR increased the foam density, but decreased the cell size. The higher foaming temperature restricted the bubble growth because of a higher curing rate and inhibited cell coalescence.
Highlights
Available rubber foams are produced from ethylene propylene diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), natural rubber (NR), and polyurethane (PU)
It was stated that adding carbon black decreased the cell size and increased the cell density of NR foams [44,50]
In the two-step method, first foaming was conducted for 10 min at 90°C, and curing was performed at 140°C for 20 min using a hot oven
Summary
Nanomaterials have received widespread attention for numerous applications [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]. Several studies have been performed on the properties and performance of NR foams. A limited number of studies have been reported on the preparation of foams from solid NR. Najib et al investigated mechanical performance and sound absorption of NR foams [47]. The foams with smaller cell sizes displayed higher sound absorption performance. Similar work on these properties was performed by Harnnarongchai [48]. The impact of temperature and rubber type on the properties of NR foams was reported [49]. The impact of blowing agent content on cure characteristics and mechanical and morphological properties of NR foams was reported by Pechurai et al [51] who used
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