Properties of Vulcanized Polyisoprene Rubber Composites Filled with Opalized White Tuff and Precipitated Silica

Table 1

The chemical composition and physical properties of OWT and PSi.

The chemical composition (%)	OWT	PSi	The physical properties	OWT	PSi
SiO2	94.27	76	Specific weight (g/cm^3)	2.27	2
Al2O3	2.54	7	BET surface (m^2/g)	39.3	60
Fe2O3	0.57	—	pH	7	11.5
CaO	0.9	—	Density (kg/m^3)	370	140
MgO	Trace	—	Sieve residue (%)	0.15	—
Na2O	0.06	7
K2O	0.08	—