The zero shear viscosity η0 of poly(vinyl
chloride) (PVC)/bis(2-ethylhexyl) phthalate (DOP)
pregels has been measured as a function of polymer concentration c as
well as molecular weight. It was
observed that the zero shear viscosity diverged as the gelling system
approached the gel point. The
establishment of the scaling law, η0 ∝
ε-γ, was examined where γ is the
scaling exponent and ε the relative
distance defined as (c
g −
c)/c
g. Here
c
g is the critical concentration for the
sol−gel transition. Two methods
were used to determine the scaling exponent γ. One is the direct
determination of γ using the c
g
obtained
by means of the frequency independence of loss tengent. The other
is called the Takigawa method that
determines simultaneously γ and c
g by
mathematically transforming the scaling law into
−η0
-1
(dη0
-1/dc)-1 =
(c
g − c)/γ. Good agreement
was obtained between the two methods. The scaling law,
η0 ∝ ε-γ,
was found to hold well for the PVC pregels, and the scaling exponent
γ was a constant (=1.5 ± 0.1) and
was independent of the PVC molecular weight. The results suggest
that the gelation rate defined as
−dη0/dε (=γη0/ε) is related to
PVC molecular weight, and at the same ε increases with decreasing
molecular
weight. The errors in determining the scaling exponent γ were
also discussed.
We have developed a novel technique to selectively block the V2 trigeminal nerve at FR. This novel FR approach may be a good alternative to the classical FO approach when an isolated V2 branch block is desired.
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