The melting, crystallization and dynamic mechanical behaviour of blend
s of bacterially produced poly[D(-)-3-hydroxybutyrate] (PHB) and poly[
D(-)-3-hydroxyvalerate] (PHV) have been investigated. Results showed t
hat melt-pressed PHB-PHV blends contained phase-separated domains in t
he melt which subsequently crystallized as PHB and PHV type spherulite
s respectively. The two melting regions detected by DTA related to sep
arate melting of PHB and PHV crystallites, which were almost unaffecte
d by the blend composition. The mechanical behaviour of a random copol
ymer of PHB/HV was compared with that of a blend of almost the same co
mposition, and found to be markedly different.