Segregation morphology of poly(3-hydroxybutyrate)/poly(vinyl acetate) and poly(3-hydroxybutyrate-co-10% 3-hydroxyvalerate)/poly(vinyl acetate) blends as studied via small angle X-ray scattering

Segregation morphology of poly(3-hydroxybutyrate) (PHB)/poly(vinyl acetate) (PVAc) and poly(3-hydroxybutyrate-co-10% 3-hydroxyvalerate) (P(HB-co-10% HV)/PVAc blends crystallized at 70 degrees C have been investigated by means of small angle X-ray scattering (SAXS). Morphological parameters including the crystal thickness (l(c)) and the amorphous layer thickness (l(a)) were deduced from the one-dimensional correlation function (gamma(z)). Blending with PVAc thickened the PHB crystals but not the P(HB-co-10% HV) crystals. On the basis of the composition variation of l(a), and the volume fraction of lamellar stacks (phi(s)) revealed that PHB/PVAc blends created the interlamellar segregation morphology when the weight fraction of PVAc (w(PVAc)) <= 0.2 and the interlamellar and interfibrillar segregation coexisted when w(PVA) > 0.2, while P(HB-co-10% HV)/PVAc blends yielded the interfibrillar segregation morphology at all blend compositions. For both PHB/PVAc and P(HB-co-10% HV)/PVAc blends, the distance of PVAc segregation was promoted by increasing PVAc composition and the distance of PVAc segregation in P(HB-co-10% HV)PVAc blends was greater than in PHB/PVAc at a given PVAc composition. The crystal growth rate played a key role in controlling the segregation of PVAc. (c) 2005 Elsevier Ltd. All rights reserved.