Weld lines behaviour in melt blended and in situ polymerised nylon 6 nanocomposites

Nylon 6 nanocomposites containing organically-modified montmorillonite made either by the melt blending or in-situ polymerised routes are investigated. Both nylon 6 nanocomposites are examined in X-ray diffraction and Transmission Electron Microscopy, to verify the level of intercalation / exfoliation of the organoclay layers in the nanocomposites. The materials are injected into tensile specimens either with single or double end-gated (with a weld line). Neat nylon 6 and single end-gated samples are used as a control, allowing comparison the performance of nylon 6 nanocomposites when weld line is present. The results show that the tensile strength and strain-to-failure of the neat nylon 6 exhibits little variation when comparing the single and double end-gated samples and thus no weld line behaviour is seen clearly. The melt blended nanocomposites show a greatly reduced in strain-to-failure for both single and double end-gated samples although the tensile modulus is increased significantly. In contrast, the in-situ polymerised nanocomposites show more ductile behaviour at single end-gated, compared to the double end-gated samples. Both nanocomposites show brittleness when the weld line is present. The fracture tensile surfaces are examined using Environmental Scanning Electron Microscopy and the results show that much larger micron-sized organoclay entities exist in the melt blended nanocomposites and that these, rather than nano-sized individual layers, cause the final behaviour. Whilst the dispersion is much finer for the in-situ polymerised than that of the melt blending nanocomposites.