Calcium silicate (CaSiO_3) as alternative ionic coagulantand solid lubricant for ceramic molds in natural rubber latex film preparation

摘要

Calcium silicate gel (CaSiO_3) is a synthesized, ionic coagulant and solid lubricant prepared by the sol-gel process. Calcium silicate is an oxide compound used as an ionic coagulant in coatings on prototypic, standard molds before those molds are dipped into concentrated natural rubber latex in the latex film-production process. The advantages of coating the CaSiO_3 gel, made from eggshells, on a ceramic mold surface are low water treatment, less-acid rising step, and a longer life of the standard molds. Synthesized CaSiO_3 has good physical properties: a specific surface area of 107 m~2/g, a small pore diameter of 14.91 nm, and a fine, average particle size of 20.76 lm, suitable for coating on standard or other ceramic molds. The concentrated latex film products obtained are thin and clear, with a smooth surfaces; they provide ease of mold release and have high tensile strength. The interfacial interaction γSL, between a prototype standard mold and the CaSiO_3 gel, as an ionic coagulant is stronger than the γSL between a prototype standard mold and calcium nitrate gel is because of the electrostatic charges of CaSiO_3 (Ca~(2+), Si~(4+), and O~(2-)) on the mold surface.