Chemistry Reference
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and 9.5 (cal/cm
3
)
1/2
. A manufacturer wishes to make solutions of this
copolymer in Varsol No. 2 (a nonaromatic hydrocarbon distillate,
7.6,
poorly hydrogen-bonded). Suggest another relatively low-cost solvent that
could be added to the Varsol to increase its solvent power for the copoly-
mer and calculate the composition of this mixed solvent.
(b) Would you expect this copolymer to form stable mixtures with poly
ethylene? Why or why not?
δ
5
5-5 Calculate the composition by volume of a blend of n-hexane, t-butanol,
and dioctyl phthalate that would have the same solvent properties as tetra-
hydrofuran. (Use
Table 5.4
and match
δ
H
values.)
5-6 The introduction of a minor proportion of an immiscible second poly-
mer reduces the viscosity and elastic character of a polymer melt at the
processing rates used in normal commercial fabrication operations
[19]
.
It is necessary, also, that there be good adhesion between the dissimilar
zones in the solid blend to obtain finished articles with good mechanical
strength.
Suggest polymeric additives that could be used in this connection to
modify the processing behavior of
(a) polyethylene melts.
(b) styrene
δ
P
and
butadiene rubber (SBR).
5-7 Note: (This problem is for illustrative purposes only. Methyl isobutyl
ketone fumes have been reported to be hazardous.) A common solvent
mixture for commercial nitrocellulose consists of the following:
Diluent (toluene) 50 parts by volume
“Latent” solvent (1-butanol) 13 parts by volume
“Active” solvent (mixture) 37 parts by volume
The “active” solvent mixture includes:
Methyl ethyl ketone (fast evaporation rate) 32%
Methyl isobutyl ketone (medium evaporation rate) 54%
Diethylene glycol monomethyl ether (slow evaporation rate) 14
From these data estimate whether tetrahydrofuran would be a solvent
for this nitrocellulose polymer. Use
Table 5.3
.
5-8 Consider a hypothetical binary blend composed of linear polymers A and
B with DP
A
5
1000 and DP
B
5
500. The Hildebrand solubility parameters
of the polymers are
δ
A
52
0.001 T
10.0 and
δ
B
52
0.0008 T
10.2,
1
1
is in (cal/cm
3
)
1/2
and T is in K. The reference vol-
ume for the blend has a functional form of V
0
5
respectively, where
δ
20
0.015 T. Here, V
0
is
1
in cm
3
/mol while T is in K. Note that
the universal gas constant
R
1.987 cal/mol K.
(a) Determine
5
χ
critical
for the blend;
