Authors:T. Watanabe, G. Zhang, H. Yoshida, and T. Kawai
The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated
by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free
energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular
level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth
rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation
with the size between few nm to less than 80 nm.
The crystallization dynamics of Nylon 66/Nylon 6
blends, the crystalline/crystalline polymer blends, was analyzed by DSC under
isothermal conditions. The crystal growth rate (G)
and the nucleation rate (N) depended on
both the degree of supercooling (ΔT)
and the blend mass fraction (ϕ). The ΔT
values obtained at the fixed G, which corresponded
to the chemical potential difference of molecules between liquid and crystal
states, and the surface free energy parameters evaluated from G
and N depended on ϕ for blends. The
results suggested that Nylon 66/Nylon 6 blends with ϕN66≥0.80
or ϕN66≤0.15 are miscible.
Authors:H. Yoshida, G. Zhang, T. Kitamura, and T. Kawai
The mixing state of poly(vinylidene fluoride) (PVDF) and two amorphous polymers,poly(methyl methacrylate) (PMMA) and poly(isopropyl
methacrylate) (PiPMA) were investigated from the viewpoint of crystallization dynamics using simultaneous DSC-FTIR method.
The crystallization rate (R*) and the growth rate of trans-gauche-trans-gauche’ (TGTG’) conformation (Rc*) depended on both the blend content (ϕ) and the crystallization temperature for PVDF/PMMA. The temperature and ϕ dependency
of R* and Rc* were almost the same for PVDF/PMMA. However, R* and Rc* depended scarcely on f for PVDF/PiPMA, and the temperature dependency of R* differed from that of Rc* for PVDF/PiPMA. These results showed that PVDF and PMMA were miscible on molecular level, and that PVDF/PiPMA was immiscible
and the concentration fluctuation existed in the PVDF-rich phase.
Conformational formation and crystallization dynamics of miscible PVDF/at-PMMA and PVDF/iso-PMMA polymer blends from the molten
state were studied by the simultaneous DSC/FT-IR measurement. Formation of TGTG' conformation occurred before starting crystallization
exothermic peak in the PMMA content (ΦPMMA) range from 0 to 0.4 for both blends. The formation rate of TGTG' conformation, crystal growth rate and surface free energy
of PVDF crystal in blends depended linearly on ΦPMMA for PVDF/at-PMMA, however, those rates for PVDF/iso-PMMA slightly influenced by ΦPMMA. These results suggested that the former was miscible blend in molecular level, however, the latter was a miscible blend
with large concentration fluctuation or a partially segregated system.
The concept of crystallization dynamics method evaluating the miscibility of binary blend system including crystalline component
was proposed. Three characteristic rates, nucleation, crystal growth rates (N*, G*) and growth rate of conformation (Gc*) were used to evaluate the miscibility of PVDF/at-PMMA and PVDF/iso-PMMA by the simultaneous DSC-FTIR. N*, G* and Gc* depended remarkably on both temperature and blend fraction (ϕPMMA) for PVDF/at-PMMA system, which indicated the miscible system. PVDF/iso-PMMA showed small ϕPMMA dependency of N*, G* and Gc*, was estimated the immiscible system. The ΔT/Tm0 values, corresponding to Gibbs energy required to attend the constant G* and Gc*, evaluated from G* and Gc* showed the good linear relationships with different slope. The experimental results suggested that the concentration fluctuation
existed in PVDF/iso-PMMA system.