Dynamic viscoelasticity and molecular orientation in uniaxially drawn PC/PET blends

Abstract

The dependence of dynamic viscoelasticity on molecular orientation of the hot-drawn polycarbonate (PC)/poly(ethylene terephthalate) blends was studied experimentally. The oriented states of samples were investigated by wide-angle X-ray diffraction and quantified by Hermans' factor. The viscoelasticity was probed by dynamic mechanical analysis. For the fitting curves of dynamic modulus versus orientation, the PC-rich blends with different compositions had an opposite concavity and convexity compared with the neat PC. The difference revealed the influence of molecular mobility on orientation and viscoelasticity. The assumption on the phase morphological change from sea-island to local sandwich-like structure in blends was proposed and used to interpret the variation of slope of fitting curves. The relationship between orientation and viscoelasticity was observed in PC-rich blends, which can help understand the mechanism of molecular orientation and develop the constitutive relations for simulation.

Mechanical behavior and molecular orientation of polycarbonate plates prepared by press‐induced deformation

“…In reality, a certain dynamic relationship between the storage modulus and internal orientation state of PC was similar to a positively correlated rule of e-index. 12 The incremental storage modulus indicated the improved level of molecular orientation, which was verified in Figure 11, where Hermans' factor was greatly increased after compression at 20 C-120 C compared with the untreated sample. Thus, the essential identity in patterns of variability between storage modulus and elastic modulus was observed.…”

“…Figures 11(a)–(d) illustrate that an average orientation of samples compressed at 120°C exhibited near upon 0.06, which indicated a relatively high level of orientation degree in pure PC 18 . Figures 11(e)–(h) reflect that the Hermans' factor did not exceed 0.018 at high press temperatures or untreated situation 12,18 . Thus, highly oriented PC plates were formed at 20°C–120°C.…”

“…18 Figures 11 (e)-(h) reflect that the Hermans' factor did not exceed 0.018 at high press temperatures or untreated situation. 12,18 Thus, highly oriented PC plates were formed at 20 C-120 C. Regular arrangement from short-range to long-range order of molecular segments, with reduction of internal defects, improved the impact strength and elastic modulus. Meanwhile, the variation of arranged patterns in greatly oriented segments reflected the continuous enhancement of tensile strength as press temperature increased from 20 C to 120 C. In contrast with the condition of a relatively lower press temperature, a slight decline of these indexes at 120 C was ascribed to the slight decrease in orientation degree.…”

“…9 The resultant orientation is related to its strain rate and deformation degree. 5,[10][11][12] Essentially, relative studies should be extended to specific strain strengthening applications on the basis of these theoretical analyses.…”

“…Segments compulsively move at a temperature far below T g when a sufficient external force is applied due to a wide range of response temperature of these chains 9 . The resultant orientation is related to its strain rate and deformation degree 5,10–12 . Essentially, relative studies should be extended to specific strain strengthening applications on the basis of these theoretical analyses.…”