CRYSTALLIZATION PHENOMENA IN BACTERIAL POLY[(R)-3-HYDROXYBUTYRATE] .2. EMBRITTLEMENT AND REJUVENATION

Poly[(R)-3-hydroxybutyrate] (PHB) is a bacterial storage polymer, curr ently receiving much attention because of its potential as a biodegrad able plastic. A major drawback of PHB is its intrinsic brittleness. Al though as-moulded PHB shows ductile behaviour, upon storage at ambient temperature a detrimental ageing process seriously embrittles the mat erial and restricts its application possibilities. This remarkable emb rittlement is delineated in the present study and could be attributed to progressive crystallization. Strikingly, we found that by using a s imple annealing treatment PHB can be rejuvenated while subsequent agei ng is prevented to a large extent. This observation might considerably enlarge the applicability of PHB.