Characterization and processing of blends of polyethylene terephthalate with several liquid crystalline polymers

Abstract

Blends of an engineering thermoplastic, poly(ethylene terephthalate) (PET), and two liquid crystalline polymers (LCPs) viz., copolyesters of PET and parahydrox‐ybenzoic acid (PHB) in 40/60 mole percent (LCP60) and in 20/80 mole percent (LCP80) were prepared. A blend of LCP60 and LCP80 in 50/50 weight percent (LCP60‐80) was blended with PET. Both flat films and rods were extruded and their properties examined. The morphology of the films investigated using Scanning Electron Microscopy (SEM) revealed that the LCP phase remained as dispersed droplets in the PET matrix. In spite of the lack of fibrillation in these films, the mechanical properties were enhanced to some extent with a maximum at 10 weight percent of the LCP phase. However, in the case of the rods thin fibrils of the LCP phase of the order of 1 μm in diameter were observed provided the composition of the LCP was 20 weight percent or greater. This success In achieving fibrillation is through to be due to the extensional flow fields present at the entrance of the capillary die and the fact that a short L/D ratio die was used. Differential Scanning Calorimetry (DSC) thermograms of the extruded films indicated that the LCP phase may act as a nucleating agent for the crystallization of PET. Rheology of the blends revealed that the complex viscosity of the blends is not much different from that of pure PET. This is attributed to the partial miscibility of the two components. Based on the DSC results and residence times in the extruder, it is concluded that no significant transesterification reactions appear to have: taken place in the blends. The rheology is studied further with respect to the cooling behavior of the pure components and factors important to the fibrillation of the LCP phase and the formation of in‐situ reinforced composites are discussed.

Thermodynamics Properties and Isothermal Crystallization Kinetics of Carbon Black/Poly(ethylene terephthalate) Composites

“…It is clear that the addition of CB nanoparticles largely accelerates crystallization from the t 1/2 values of neat PET and CB/PET composites in Table 3. It is reported that the crystallization rate increases by the addition of polymeric nucleating agents [18][19][20][21][22][23][24][25][26][27]. The results in the present work also indicate that CB nanoparticles may be an ideal nucleating agent for PET crystallization processing.…”

Poly(ethylene Terephtalate)-Containing Polymer Liquid Crystals and Their Blends

“…We note that the process of forming an elongated thermotropic PLC fibrous structure in-situ depends on factors such as the relative composition, the interfacial tension, the viscosity ratio, and the flow field involved in the processing procedure [23]. We note that the process of forming an elongated thermotropic PLC fibrous structure in-situ depends on factors such as the relative composition, the interfacial tension, the viscosity ratio, and the flow field involved in the processing procedure [23].…”

Polymer Blends

“…The resulting ''molecular composite'' can be regarded as a material in which the rigid crystalline polymers are reinforced at a molecular level. Liquid crystalline polymer blends have been reported for PC [129], [130]; PEI [129]; PP [131]; PBT [132]; PPE -PS [133]; ABS [134]; PSU [135]; PETP [136], [137]; and PA 6 [138]. These blends can be processed by conventional techniques such as extrusion, injection molding, and fiber spinning.…”