Miscibility in cyclic poly(butylene terephthalate) and styrene maleimide blends prepared by solid‐dispersion and in situ polymerization of cyclic butylene terephthalate oligomers within styrene maleimide

Blends of cyclic butylene terephthalate oligomers (CBT) and styrene maleimide (SMI) were prepared by a solid dispersion technique in various compositions ranging from 90 to 10 wt % of CBT. In situ polymerization of the oligomers in the blend at 190°C produced a blend of cyclic poly(butylene terephthalate) (c‐PBT) and SMI. The blends were characterized by a variety of techniques including differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). It was found that the presence of 30 wt % and above of SMI impeded the crystallization of c‐PBT to such an extent that crystallization could not be detected under the conditions of the DSC experiment. The blend system exhibited a single composition‐dependent glass transition temperature ( T g ), which indicated the presence of miscibility. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012