Effect of clay amounts on morphology and mechanical performances in multiscale PET composites

Abstract

This work presents an investigation of the properties of poly(ethylene terephthalate)/glass fibres/nanoclay multiscale composites. The aim is to demonstrate the effect of adding various clay amounts on the morphology and mechanical performance of multiscale PET composites. Multiscale composites were prepared by adding 0.5, 1.0, 3.0, and 5.0 wt% of Cloisite15A montmorillonite: Initially, a masterbatch of pure PET blended with 10 wt% of Cloisite15A was obtained in a co-rotating twin screw extruder. The multiscale composites were then blended, via mechanical mixing, and injection moulded by adding the masterbatch to the glass fibre reinforced matrix. The morphological and mechanical characterizations of all compounds are discussed. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the characteristic (001) peak of the nanocomposite obtained by extrusion (masterbatch) shifted to the lower angle region stating an intercalated structure. However, the subsequent injection moulding process changed the morphological structure of the multiscale nanocomposites reducing the basal distance mostly for small loadings of nanoclay. The addition of nanoclay to PET matrices increases the degree of crystallinity, the clay platelets possibly playing the role of nucleating agent, as revealed by DSC and FTIR. The time relaxation spectra broaden as seen by DMA, as the ratio of clay/polymer interfaces increases. The yield stress of composites with 0.5 and 1 wt% of C15A content are enhanced. For more than 3% of nanoclay, the yield stress decreases. The Young's modulus is increased when adding C15 nanoclay. Indeed, clay exfoliation was not attained, but the intercalated particle dispersion improved the stiffness properties of PET/glass fibres/nanoclay composites. © 2011 American Institute of Physics.