Sunil,K Narayanankutty(OPA (Overseas Publishers Association), January 7, 1997)
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Abstract:
Cure characteristics of short polyester fiber-polyurethane composites with respect to
different bonding agents (MD resins) based on 4, 4' diphenylmethanediisocyanate (MDI)
and various diols like propyleneglycol (PG), polypropyleneglycol (PPG) and glycerol
(GL) were studied. Tmax. - Tmin. of composites having MD resin were found to be
higher than the composite without MD resin. Minimum torque and Tmax. - Tmin.,
scorch time and optimum cure time were increased with the increase of MDI equivalence.
Optimum ratio of MDI / -of in the resin was found to be within the range of
1-1.5. It was observed from the cure characteristics that for getting better adhesion
between short polyester fiber and the polyurethane matrix the best choice of MD resin
was one based on MDI and 1:1 equivalent mixture of polypropyleneglycol and glycerol.
Sreekumar, K; Elizabeth, Chirackal Varkey(Wiley, July 20, 2010)
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Abstract:
The toluene diisocyanate based optically
active chiral polyurethanes were synthesized according to
the symmetry conditions. The noncentrosymmetric (both
charge asymmetry and spatial asymmetry) environment
were attained by the incorporation of the chiral units
(diethyl-(2R,3R)(þ)-tartrate) and donor-acceptor building
blocks in the main chain which induce a helical conformation
in the macromolecular chain. A series of optically
active polyurethanes containing chiral linkages in the
polymer back bone have been synthesized by using
DBTDL catalyst by incorporating the amido diols which
were obtained by the aminolysis of e-caprolactone by
using the diamines, diaminoethane, diaminobutane, and
diaminohexane respectively. The effect of incorporation of
the chiral molecule diethyl-(2R,3R)(þ)-tartrate on the properties
of polyurethanes was studied by changing the chromophores
and also by varying the chiral-chromophore
composition. Various properties of polyurethanes were
investigated by UV, Fluorescence, TG/DTA, XRD, polarimetric
techniques, Kurtz-Perry powder techniques, etc.
Description:
Journal of Applied Polymer Science, Vol. 119, 111–119 (2011)
Sreekumar, K; Sudheesh Kumar, K(Taylor & Francis, June 1, 2007)
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Abstract:
Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl)
groups in the main chain were synthesized by polyaddition reactions of diols such
as bis(4-hydroxyphenylazo)-2,20-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo-
40-hydroxyphenylazo-2,20-dinitrodiphenylmethane and bis(4-hydroxy-3-
methylphenylazo)-2,20-dinitrodiphenylmethane with hexamethylene di-isocyanate
(HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate
(DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and
13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning
calorimetry (DSC) and gel permeation chromatography (GPC).
Description:
International Journal of Polymeric Materials, 58:160–166, 2009