Crystallization kinetics and morphology in miscible blends of two crystalline polymers

Miscibility, crystallization behavior and morphology of blends prepared fro m two crystalline polymers, poly(butylene succinate) (PBSU), and poly(vinyl idene chloride-co-vinyl chloride) [P(VDC-VC)] have been examined by polariz ed optical microscopy and differential scanning calorimetry. It is found th at PBSU is miscible with P(VDC-VC) since each blend showed a single glass t ransition temperature T-g. Spherulitic morphology and the melting behavior of the blends were strongly dependent upon the crystallization kinetics and some unique phenomena were found out: (i) in contrast to the other results reported so far. growth rate G of low-T-m component (PBSU) was decreased g reatly with increasing high-T-m component [P(VDC-VC)] content, (ii) for the PBSU/P(VDC-VC) (40:60) blend crystallized at 90 degrees C (i.e., the growt h rate of the two components was appproximately the same) so called interlo cked spherulites were formed, where PBSU spherulites grown through the inte rlamellar regions of P(VDC-VC) spherulites, (iii) for the blends crystalliz ed during fast cooling conditions from the melt (e.g., faster than 10 degre es C min(-1)), only one melting peak appeared corresponding to PBSU and no noticeable melting peaks of high-ir, component P(VDC-VC) were observed. Hen ce. it is seen that the crystallization behavior of high-T-m component is h eavily affected by the low-T-m component. Therefore, kinetic factors are th e most important one in controlling the crystallization behavior and the mo rphology of the crystalline/crystalline blends.