S. Haseebuddin et al., APPLICABILITY OF THE WLF EQUATION TO POLYURETHANE POLYOLS AND FILM PROPERTIES OF THEIR RESINS, Progress in organic coatings, 30(1-2), 1997, pp. 25-30
Citations number
20
Categorie Soggetti
Chemistry Applied","Materials Science, Coatings & Films
The need to reduce solvent content of coatings in compliance to air po
llution and other Statutory Regulations has led to major efforts to de
velop high solids coatings. The reduction in molecular weight helps to
achieve application viscosity by an increase in free volume. Various
polyurethane polyols have been synthesised by reacting the diols with
polyisocyanates. The molecular weight and polydispersity indexes of th
ese polyols have been determined by gel permeation chromatography (GPC
). The viscosity of 50% polyol solutions in various solvents has been
determined at different temperatures. The temperature dependence on vi
scosity of solution of these polyols has been determined by the Willia
ms, Landel and Ferry (WLF) equation. The non-linear regression analysi
s has been solved by using Levenberg Marquardt's algorithm. It is foun
d that non-linear regression analysis gives high correlation coefficie
nts and very low overall residual errors. The variation in the values
of constants A and B for each WLF equation in the polyol solution indi
cates that these constants are system dependent. The values of constan
ts A and B obtained for polyurethane polyols in a particular solvent h
ave been used to calculate the values of glass transition temperature
of the oligomer solution (T-gs) at different concentrations. The value
s of T-gs are found to vary with concentration. As the concentration o
f polymer increases there is an increase in the T-gs value. The tensil
e properties and resistance to scratch of resins prepared using these
polyols and butylated melamine formaldehyde are better than those of c
onventional resins. The VOC content of these coating formulations is l
ower than the value prescribed by the Environmental Protection Agency
(EPA). (C) 1997 Elsevier Science S.A.