Effects of foaming agents and eggshell calcium carbonate (CaCO3) Filler on natural rubber foam physical-Thermal-mechanical properties

Egg and egg derivative consumptions produce a great amount of daily waste. eggshell is one source of calcium carbonate (caco3) source known as calcite and it is a stable polymorph at ambient conditions and was chosen here as a filler for the sponge rubber production. the main composition of eggshell is more than 96 wt% calcium carbonate along with other inorganic substances. commercial and eggshell calcium carbonates (caco33) were utilised as fillers of the fabricated natural rubber composites. the calcium carbonate benefits were to increase the mechanical,thermal,and physical properties of the natural rubber matrix as ca2+ and co3 2- ions from the calcium carbonates provided a bridge bonding or interface interaction within the natural rubber matrices. sponge rubber was prepared by the sulphur vulcanisation of natural rubber using two foaming agents,sodium bicarbonate (nahco3) and n,ń-dinitrosopenta methylene tetramine (dnpt) to generate open and closed cell structures. the best natural rubber foams were obtained by crosslinking natural rubber with nahco3 as the foaming agent due to being odourless and non-toxic. dnpt generated toxic gases which had a fish-like characteristic odour. with 60 phr of either commercial or eggshell calcium carbonate (caco3),the obtained natural rubber foams possessed light weight and with low bulk density values of 0.4066 and 0.4308 g/cm3,relative foam density values of 0.1123 and 0.1338,fast curing times of 13.36 and 37.60 min,good compression sets of 32.60 and 31.50%,small and uniform open and closed pores,high specific heat of 25.19 kj/kg.k,and high thermal conductivity values of 0.069 and 0.074 w/m.k,respectively. the sem results of the sponge rubber samples with the eggshell caco3 showed more uniform cell structures than the commercial caco3. they are thus potentially useful as heat sinks in certain electronic systems or devices.