CRYSTALLIZATION PHENOMENA IN BACTERIAL POLY[(R)-3-HYDROXYBUTYRATE] .3. TOUGHENING VIA TEXTURE CHANGES

Poly[(R)-3-hydroxybutyrate] (PHB) is a bacterial storage polyester tha t is genuinely biodegradable, but its brittleness hampers its wide app licability as a biodegradable plastic. Most attempts to improve the me chanical properties of PHB have focused on incorporating comonomers, b ut at the expense of production costs. Strikingly, it appeared possibl e to toughen PHB homopolymer using a simple annealing treatment. The p resent study attributes this remarkable phenomenon to a change in the lamellar morphology, which reduces the amorphous-crystalline interface area and thus the constraint imposed on the amorphous chains by the c rystals. This elevates the relaxation strength of the amorphous region s, giving rise to the favourable fracture behaviour.