The effect of fibre-interface and processing variables on the mechanical properties of glass-fibre filled nylon 6

Moulding compounds were produced from nylon 6 granules and eight different grades of E-glass fibre roving. The fibres were of 10–16 μm diameter and had been finished with sizes of different formulation which in three cases omitted the conventional silane coupling agent. Tensile test bars were produced from the compounds by injection moulding and these were tested in a standard ‘dry’ condition and also after boiling in water for 48 h to saturate the material. Impact tests were also carried out. The results show that under ‘dry’ conditions the absence of the silane may result in significant reductions in stiffness, strength, and also in ductility, but in one case the omission of the silane had little effect. In the ‘wet’ condition all materials showed significant degradation of properties and those without the coupling agent were by far the worst.

The reductions in stiffness and strength were not accompanied by corresponding increases in ductility, except in the extreme cases, on the contrary the poorly coupled materials were generally rather brittle. This trend was also reflected in the impact test results.