Colloidal properties of precipitated calcium carbonate dispersion and its effect on prevulcanised natural rubber latex rheology and film tensile properties

In this work, the interaction between PCC in NR latex and physical properties of the resulting films were studied. PCC dispersion was first prepared and its colloidal properties together with the colloidal properties of prevulcanised natural rubber (PV-NR) latex were investigated using particle size analysis, zeta potential and rheology. PCC dispersion and PV-NR latex were then mixed together and their interaction was followed by rheology. Next, the dipped films were prepared and the resulting film thickness and tensile properties were determined. PCC dispersion showed an average particle size of 4.2 µm with a wide particle distribution whereas PV-NR latex showed an average particle size of 0.74 µm with a much narrower particle distribution. Viscoelastic studies showed PCC dispersion to be an elastic material whereas PV-NR latex was observed to be a viscous material. Mixing of the two materials produced a change in the rheological behaviour. Up to 30 phr PCC loading, flow studies revealed the mixtures to behave as Bingham materials but above that, the mixtures behaved as Herschel–Bulkley materials. Viscoelastic measurements showed that the initially viscous PV-NR latex became more elastic with increasing PCC loading. A shift from dominant viscous to dominant elastic behaviour was observed with the addition of 80 phr PCC in the latex. Thickness and tensile stress of the dipped films increased with increasing PCC loading. However, both tensile strength (TS) and elongation at break (EB) of the films reduced with increasing PCC loading. Ageing caused reduction in tensile stress but EB and TS increased. The increase in TS was, however, only observed to occur up to 15 phr PCC loading.