The preparation and mechanical properties of natural rubber latex foam (NRLF) using calcium carbonate (CaCO3) or combinations of CaCO3 and crumb rubber (CRM) as fillers were investigated. The CaCO3 contents were varied as 10, 20, and 30 phr. The ratios of CaCO3/CRM at 0.5/1.0, 0.75/0.75 and 1.0/0.5 were used. The experimental findings were that CaCO3 was well dispersed and blended with the natural rubber latex. The density of the NRLF increased with the increase in CaCO3 content. The foam containing less than 20 phr of CaCO3 showed higher tensile strength and elongation at the break than natural rubber latex foam without CaCO3. The percentage of compression set and depression of NRLF increased with increasing CaCO3 content. When the mixture of CaCO3 and CRM was used as a filler in NRLF, it was found that both CaCO3 and CRM were well dispersed and mixed with natural rubber latex. The NRLF containing the mixture of CaCO3 and CRM was more flexible than the foam containing only CaCO3. Furthermore, the NRLF with CaCO3 and CRM at the ratio of0.75/0.75 showed more uniform bubble shape and higher density than foam with other CaCO3/CRM ratios. The tensile strength of the foam decreased with decreasing CRM content, while the percentage of depression was low when the proportion of the CRM was reduced. Furthermore, the foam containing CaCO3/CRM ratio of 0.75/0.75 showed the lowest compression set.
Keywords: calcium carbonate; crumb rubber; natural rubber; natural rubber latex foams
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E-mail: suwat.r@rmutsv.ac.th
