Effect of phase separation on spherulitic growth rate of PP/EPR in‐reactor alloys

Abstract

In this work, the effect of phase separation on the spherulitic growth rate of a polypropylene/ethylene-propylene random (PP/EPR) copolymer in-reactor alloy was investigated. The PP/EPR in-reactor alloy was either directly quenched from homogeneous melt to crystallization temperature or held at various temperatures for phase separation prior to crystallization. It is found that at lower crystallization temperatures previous phase separation in the melt retards the crystallization rate. The higher the phase separation rate, the smaller the spherulitic growth rate. This can be attributed to faster crystallization rate than the rate of secondary phase separation. The composition of the PP-rich phase and corresponding depression of the equilibrium melting temperature of PP vary with phase separation temperature. On the other hand, at higher crystallization temperature, previous phase separation in the melt has little effect on the spherulitic growth rate because secondary phase separation can take place prior to crystallization. The transition temperature from regime II to regime III also shifts to lower temperature as the phase separation temperature increases.

Effect of phase separation on overall isothermal crystallization kinetics of PP/EPR in‐reactor alloys

“…This is exactly what we observed in our previous work and can be explained in terms of the phase diagram (Figure 6). 62 Because of the faster crystallization rate at lower crystallization temperatures, the secondary phase separation, which is the phase separation occurring at T c following the phase separation at T s , is avoided. In such a situation, the PP‐rich phase starts crystallization from the composition at the phase separation temperature, instead of the composition at the crystallization temperature.…”

“…So far, although there are some studies on crystallization kinetics of PP/EPR in‐reactor alloys,59–61 the effect of phase separation is seldom considered in this type of in‐reactor alloy. In our previous work, we reported the effect of phase separation in the melt on the linear spherulitic growth rate ( G ) of a PP/EPR in‐reactor alloy prepared by MSSP process 62. We found that higher phase separation temperature ( T s ) led to a smaller G at lower crystallization temperatures ( T c ), but phase separation had no significant effect on G at higher T c s. This result was interpreted based on the phase diagram.…”

Improvements in spinodal alloys from past to present

“…Numerous papers were published on the spinodal decomposition of the polymers [129][130][131][132][133] using a number of experimental techniques such as scanning electron microscopy, energy dispersive-X analysis, small-angle neutron scattering (SANS) and polarized optical microscopy with a hot stage and digital camera.…”

Effect of annealing‐induced interfacial demixing on crystallization of PEO confined in coaxial electrospun nanofibers

“…The effect of annealing temperature on crystallization behavior of PEO/PAN coaxial electrospun fibers can be interpreted in terms of the composition of the PEO‐rich phase formed in demixing process. It is clearly that the PEO/PAN mixture exhibits an upper critical solution temperature‐type phase diagram, since demixing occurs while lowering the temperature . Figure shows the schematic phase diagram at the PEO/PAN interface in the coaxial electrospun fibers.…”