Rheology and thermal properties of liquid crystalline copolyester and poly(ethylene 2,6‐naphthalate) blends

Abstract

Blends of a poly(ethylene 2,6‐naphthalate) (PEN) and a liquid crystalline copolyester (LCP), poly(benzoate‐naphthoate) were prepared in a twin‐screw extruder. Specimens for thermal properties were investigated by means of an instron capillary rheometer (ICR) and scanning electron microscopy (SEM). The blend viscosity showed a minimum at 10 wt% of LCP and increased with increasing LCP content above 10 wt% of LCP. Above 50% of LCP and at higher shear rate, phase inversion occured and the blend morphology was fibrous and similar to pure LCP. The ultimate fibrillar structure of LCP phase appeared to be closely related to the extrusion temperature. By employing a suitable deformation history, the LCP phase may be elongated and oriented such that a microfibrillar morphology can be retained in the solid state. Thermal properties of the LCP/PEN blends were studied using DSC and a Rheovibron viscoelastomer. These blends were shown to be incompatible in the entire range of the LCP content. For the blends, the Tg and Tm were unchanged. The half time of crystallization for the LCP/PEN blends decreased with increasing LCP content. Therefore, the LCP acted as a nucleating agent for the crystallization of PEN. The dimensional and thermal stability of the blends were increased with increasing LCP content. In studies of dynamic mechanical properties, the storage modulus (E′) was improved with increasing LCP content and synergistic effects were observed at 70 wt% of LCP content. The storage modulus for the LCP/PEN 70/30 blend is twice that of PEN matrix and exceeded pure LCP.

Effects of chemical reactions on the properties of polycarbonate/liquid crystalline polymer blends

“…The minimum viscosity in the incompatible blend systems suggests the presence of microstructure of the LCP, which is consistent with results of other researchers. [22][23][24] To investigate the effects of chemical reactions on the rheological properties, the storage modulus (GЈ) and loss modulus (GЉ) of PC90/LCP10 blends were measured at 250°C and shown in Figure 11. The moduli of reactive blends at 290°C are too low to measure.…”

Rheological and physical properties ofin situ composite based on liquid crystalline polymer and poly(ethylene 2,6-naphthalate) blends

“…The tan ␦ versus temperature curve of PEN/LCP blends exhibits two distinct peaks, typically characteristic of an immiscible two-phase system. 26,27 The high T g (at ϳ154°C) comes from the PEN-rich phase, whereas the low one (at ϳ99°C) is due to the LCP (PHB80/PET20)-rich phase, respectively. This peak is related to the motion of PET segments in the PHB-rich phase; similar results were reported by Benson and Lewis.…”

“…It can be considered only as a measure of the amount of crystalline phase, and not necessarily a description and regularity of the lamellas. 27 The cold crystallization temperatures as a function of LCP content for PEN/LCP blends are shown in Figure 5. The PEN had a cold crystallization temperature peak at 201.72°C with a heat of cold crystallization of 40.04 J/g.…”

Polymer blends of poly(ethylene‐2,6‐naphthalate) with polystyrene compatibilized by styrene‐glycidyl methacrylate copolymers. I. Rheology, morphology, and mechanical properties

“…The most familiar subject is the PEN/PET blending system, in which the reactive processing,3 miscibility,4–6 phase behavior,7 and dynamic mechanical properties8 were studied in detail. On the other hand, blends of PEN with polyester‐type liquid crystalline polymer (LCP),9, 10 polycarbonate,11 poly(butylene terephthalate) (PBT),12 and poly(butylene‐2,6‐naphthalate) (PBN)13 were also reported. Except for polyesters, studies on PEN blends with other commodity polymers are relatively few.…”