The weathering resistance of quaternary High-density polyethylene (HDPE) composites: Effects of weld lines, formulation and degradation on tensile properties

In this work, the effects of weld lines, additives and the degree of QUV weathering on the tensile behavior of a range of high-density polyethylene composites with calcium carbonate, stabilizers and a carbon black/SEBS masterbatch are studied. The degree of weathering is characterized using FTIR-derived carbonyl, double-bond and carbonate indexes based on curve fitting, to allow for the fairer comparison of specimens with and without calcium carbonate. Weld-line specimens exhibited more rapid degradation than that seen in the reference specimens, while the exposed surfaces of the specimens degraded more quickly than the unexposed surfaces. ISO G154 Cycle 1 and Cycle 6 weathering protocols were compared. The additives were found to be effective at decreasing oxidative degradation, albeit with reduced effects at higher loadings and in mixed systems. These findings were mirrored in the mechanical properties of the specimens, with the modified specimens even exhibiting broadly improved properties with increasing aging. Elongation at break was most sensitive to weathering, with increasing degradation with increasing weathering across almost all specimens.