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Replacement of Hazardous Chemicals Used in Engineering Plastics with Safe and Renewable Hydrogen-Bond Donor and Acceptor Solvent-Pair Mixtures
journal contribution
posted on 2015-08-03, 00:00 authored by Alif Duereh, Yoshiyuki Sato, Richard
Lee Smith, Hiroshi InomataMixtures of safe and renewable solvents
can replace hazardous solvents
presently being used in the manufacture of engineering plastics. In
this work, a methodology is proposed for identifying solvent-pair
mixtures for preparing polymer precursors, with poly(amic acid) (PAA)
being studied as an example. The methodology uses a chemical safety
index, Hansen solubility parameters and Kamlet–Taft solvatochromic
parameters of the pure and solvent-pair mixtures to identify hydrogen
bond acceptor (HBA)–hydrogen bond donor (HBD) solvent-pair
combinations. Ten replacement solvent-pairs for PAA syntheses identified
were cyclohexanone–methanol, cyclohexanone–ethanol,
cyclopentanone–methanol, cyclopentanone–ethanol, γ-butyrolactone–methanol,
γ-butyrolactone–ethanol, γ-butyrolactone–water,
γ-valerolactone–methanol, γ-valerolactone–ethanol,
and γ-valerolactone–water. Homogeneous PAA solutions
could be obtained from HBA–HBD solvent-pair mixtures when their
solubility parameters were within 21–29 MPa0.5 and
their Kamlet–Taft solvatochromic parameters were π* (>0.67)
and β (>0.67) for nonaqueous solutions and π* (>0.68)
and β (>0.59) for aqueous solutions. Replacement solvent-pairs,
γ-valerolactone–ethanol, γ-valerolactone–water,
and γ-butyrolactone–water gave homogeneous precursor
solutions that were comparable with commercial solutions prepared
with N-methyl-2-pyrrolidone. The proposed methodology
and reported solvatochromic parameters make it is possible to identify
other solvent-pair mixtures and new solvent-pairs for preparing polymer
precursor solutions used in engineering plastics.