Study On Crystallization Kinetics And Crystal Morphology Of Polymerized Cyclic Butylene Terephthalate Oligomers

Cyclic butylene terephthalate oligomers(CBT)are a mixture of solids composed of different cyclic oligomers.CBT can be polymerized into the corresponding linear polymerized cyclic butylene terephthalate(pCBT)via entropically-driven ring-opening polymerization in the presence of suitable catalysts.The reaction time is very short.In the process of ring-opening polymerization of C BT,no reaction heat and by-products are generated,and rapid molding can be performed.One of the most important features of C BT is its very low water-like melt viscosity before polymerization.Compared with traditional high-viscosity thermoplastic resin,it can well impregnate fiber reinforcement,C BT resin has good compatibility with various reinforcing materials,fillers and polymer materials.CBT has become a promising ?green material? for the manufacture of recyclable thermoplastic composites and can be applied to almost all thermoplastic resin and thermosetting resin processing methods.The ring-opening polymerization of CBT,the crystallization kinetics of the polymerization products,the spherulite morphology,the brittleness mechanism,the preparation and application of composite materials,and other directions are all current research hotspots.At the same time,it also has theoretical guiding significance for actual production and processing.In this paper,the isothermal crystallization kinetics and crystal morphology of the polymerization product pCBT of C BT were studied in detail.1.Isothermal crystallization behavior of pCBT was studied by differential scanning calorimetry(DSC).The isothermal crystallization kinetics was analyzed using the Avrami equation.The isothermal crystallization kinetic parameters were fitted.The results show that during isothermal crystallization,The crystallization rate decreases as the crystallization temperature increases,and the crysta ls grow in heterogeneous nucleation.The fitting result is within reasonable error.2.The crystal morphology of pC BT was observed using polarized light microscopy(POM),atomic force microscopy(AFM),scanning electron microscopy(SEM),and confocal laser scanning microscopy(C LSM).A small amount of pCBT spherulites with an amber-like transparent three-dimensional(3D)morphology was first discovered.The amber-like 3D pC BT spherulites have ring-banded structures inside,and the inner ring-banded structures were derived from lamellae twisting.An irregularly curved edge-on oriented platelet may be a cross-section of the front end of the wafer.An irregularly curved edge-on oriented lamellae may be a cross-section of the front end of the wafer.The amber-like 3D pC BT spherulites have a lower melting point than the surrounding ordinary 2D pCBT spherulites.3.For the first time,some pCBT spherulites have been translated or rotated during the isothermal crystallization of pCBT thin films under confined condit ions,but not all the spherulites undergoing translation are accompanied by rotation.The translation or rotation of the pCBT spherulites is not only related to the locally inhomogeneous negative static pressure but also to the coexistence of the unwrapping region and the entangled region.