Effect of ageing and annealing on the mechanical behaviour and biodegradability of a poly(3‐hydroxybutyrate) and poly(ethylene‐ co ‐methyl‐acrylate‐ co ‐glycidyl‐methacrylate)blend

Poly(3‐hydroxybutyrate) ( PHB ) undergoes an ageing process that contributes to its remarkable fragility. Blending it with an elastomer is a possibility to increase toughness. In this work, the mechanical properties of a 70/30 wt% blend of PHB and poly(ethylene‐ co ‐methyl‐acrylate‐ co ‐glycidyl‐methacrylate) were studied over time. The phenomenon of ageing affected the blend, which lost its ductility and became fragile days after its processing. Differential scanning calorimetry and small angle X‐ray scattering analyses showed that this drop in mechanical properties was due to changes in the crystalline structure of the matrix. Annealing reduced fragility, increased toughness and prevented a re‐ageing of the blend. Biodegradation in soil was also more intense for annealed samples.