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Investigating non-linear viscoelastic behaviour of PVC–green coconut fibres composites through Fourier transform rheometry

Abstract Composites of polyvinyl chloride and green coconut fibres were investigated by Fourier transform rheometry, a new dynamic test technique that resolves the complex dynamic response of materials submitted to harmonic strain into their main and harmonic components. It was observed that the preparation method of composites had a major effect on their linear and non-linear viscoelastic response; essentially dry blending plus extrusion does not lead to a homogeneous material; in contrast dry blending plus mixing is the recommended technique, because full PVC plasticization is then achieved. One of the most important rheological characteristics of PVC–GCF composites is the progressive disappearance of the linear viscoelastic behaviour as fibres content increases. An easy extrapolation technique was used to extract 'linear modulus' data from FT results, which led to the conclusion that the reinforcing effect of GC fibres is probably of hydrodynamic origin with little, if any, interfacial interaction between the polymer matrix and the fibres. Results gathered from non-linear viscoelastic properties, as obtained through FT rheometry, support this conclusion.