Atmospheric plasma activation and plasma coating with 3-aminopropyltriethoxysilane (APTES) were used to investigate the effect of a modified interface on the creep behaviour of flax fibre reinforced polyoxymethylene composite. The wetting parameters and the interfacial shear strength indicate that using air-based plasma activation is superior to plasma coating with APTES when improvement of interface and mechanical properties are concerned. Hygrothermal creep tests within the linear viscoelastic region reveal that the creep resistance of air plasma treated composites is significantly enhanced, evidenced by reduced instantaneous strain and slower viscoelastic flow when compared to the untreated composites. However, creep rupture (run to failure) tests demonstrate that the air plasma treatment extends the creep lifespan only under standard conditions (50 % RH and 23 °C). Under severe conditions (85 % RH and 23 °C), plasma-treated composites exhibit a somewhat shorter lifespan, possibly because some damage induced by the plasma treatment is exacerbated at high humidity.
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