Effects of nematic polymer liquid crystal on crystallization and structure of PET/Vectra blends

We investigate the effects of a nematic liquid crystalline polymer, Vectra A, on the structure and properties of its blends with a semicrystalline polymer, poly(ethylene terephthalate),PET. PET/Vectra blend composition ranged from 100/0 to 60/40. Real-time, in situ studies ofisothermal and non-isothermal melt crystallizations of these blends were conducted usingsimultaneous wide and small angle X-ray scattering (WAXS and SAXS), differentialscanning calorimetry (DSC), and quantitative polarizing optical microscopy. All techniquesconfirm that the addition of Vectra nematic liquid crystal delays the onset of crystallization,and affects the degree of crystallinity and structural parameters such as Bragg long period,lamellar thickness and linear stack crystallinity. SAXS results indicate that some of theVectra component penetrates into the interlamellar regions of the crystal stacks. Vectrainterrupts the entangled polymer network making it more difficult for lamellar crystals tonucleate. Slower nucleation and growth result in increased perfection of the PET crystalsgrown isothermally, but reduces the crystallization temperature of PET crystals grownnon-isothermally causing these crystals to be less perfect.