Critical phenomena and viscosity of macromolecular solutions, blends and melts

The coexistence curve of polymer solution (polystyrene/methylcyclohexane, PS/MCH) and polymer blend (polystyrene/poly-o-chlorostyrene, PS/POCS), as well as the viscosity of polymer melts (an alternating copolymer of ethylene/tetrafluoroethylene, PETFE and polytetrafluoroethylene, PTFE) are studied by a newly developed centrifuge which can act as an instrument to measure the volumes of coexisting phases or the velocity of a ball moving under centrifugal acceleration in the presence of gravity. The latter function is termed as a centrifuge ball viscometer(CBV). In addition to the CBV, synchrotron small angle X-ray scattering (SAXS) has also been incorporated to investigate the critical phenomena.; With the centrifuge, the formation of the boundary between the concentrated phase and the dilute phase could be achieved more quickly after phase separation. The volume of the concentrated phase and that of the dilute phase could be measured directly by means of a travelling microscope which can measure the distance to {dollar}pm1mu{dollar}m. This apparatus also permits us to determine the diameter of the coexistence curve. The extended universal coexistence (COEX) curve fits the PS/MCH solution data extremely well and the X value of the COEX curve can be extended from 0.3 to 0.5 where X is equal to {dollar}epsilonrm Nsp{lcub}0.31{rcub}{dollar} with {dollar}epsilon{dollar} (=(T{dollar}sb{lcub}c{rcub}{dollar}-T)/T{dollar}sb{lcub}c{rcub}{dollar}) being the reduced temperature and N the number of polymer segments. Very precise coexistence curves for a PS/POCS blend with and without a plasticizer DBP (di-n-butylphthalate) were determined for the first time. The PS/POCS blend has {dollar}betasimeq0.33{dollar} and 0.5 with 22.6 wt% DBP and without DBP, respectively.; At very low shear rates ({dollar}dot gammato0{dollar}), the polymer melt behaves like Newtonian fluid with the viscosity being independent of shear rate. The differences in polymer molecular weight (MW), molecular weight distribution (MWD) and activation energy (E{dollar}sb{lcub}rm a{rcub}{dollar}) can be related to the corresponding rheological behaviors. The viscosity of PETFE copolymer and of PTFE polymer has been determined by using the CBV. The fluoro polymer melt viscosity as a function of temperature and molecular weight was explored systematically. A single master curve could be used to describe viscosity behavior of the polymer melt over a range of molecular weight and of temperature. The most exciting accomplishment of the CBV is that a viscosity value of {dollar}sim{dollar}10{dollar}sp{10}{dollar} Pa{dollar}cdot{dollar}s of one commercial PTFE sample measured in a sealed sample chamber at 380{dollar}spcirc{dollar}C has been achieved.