Rheological behaviour of titanate coated mica‐filled polypropylene

Titanate coupling agents have been used for the surface modification of mica to improve the viscoelastic behaviour of mica‐filled polypropylene. Four titanate coupling agents, neoalkoxy tri(dioctylpyrophosphato) titanate (CA1), neoalkoxy trineodecanoyl titanate (CA2), bisacetylacetonatodistearato titanate (CA3), and bisacetylacetonatodipalmitato titanate (CA4), were used in the present investigation. Mica powder (10 μm, particle size) was coated with these coupling agents in varying concentrations (0.5‐10% based on the weight of the filler), and then blended with stabilised polypropylene powder of 10 melt flow index (MFI). The mica‐filled (10‐50 wt%) polypropylene samples were extruded and used in the granular form for studying the viscoelastic behaviour. The melt viscosity of titanate coated mica‐PP samples decreases irrespective of the nature of the coupling agent used. The activation energy of melt rheology is independent of the mica content. The die swell increases with the use of titanate coupling agent. Compatibility of mica and polypropylene has also been studied with the help of a scanning electron microscope.