1) The document describes a study on the synthesis of waterborne polyurethanes (WPUs) using bio-based polyols from vegetable oils for coating applications. 2) Two commercially available bio-based polyols, a fully renewable fatty dimer polyol and a partially renewable amorphous polyester polyol, were functionalized with isophorone diisocyanate or dicyclohexylmethane-4,4'-diisocyanate in the presence of a ionic chain extender. 3) The functionalized polyols formed stable aqueous dispersions with particle sizes between 60-150 nm and zeta potentials less than -30 mV. Films of the WPUs

1. Copyright : photo © Denis Lecuyer
Synthesis of waterborne bio-based polyurethanes
for coating applications
Jevgenij Lazko, Loïc Poussard, Jérôme Mariage, Jean-Marie Raquez, Philippe Dubois
Materia Nova Research Center, Laboratory of Polymeric and Composite Materials (LPCM), Avenue Copernic 1, 7000 Mons, Belgium
Center of Innovation and Research in Materials & Polymers (CIRMAP), University of Mons (UMons), Place du Parc 23, 7000 Mons, Belgium
e-mail: jevgenij.lazko@materianova.be
Introduction
References
Functional Properties Characterization
0
1
2
3
4
5
0 500 1000 1500
Stress(MPa)
Strain (%)
P-H-0.5 P-H-1
V-H-0.5 V-H-1
V-I-0.5 V-I-1
0.0
0.5
1.0
0 5 10
5001000150020002500300035004000
Absorbance
Wavenumber (cm-1)
1480158016801780
1000110012001300
Priplast
P-H-0.5
P-H-1
Veopur
V-H-0.5
V-H-1
11.522.533.544.55
[ppm]
Priplast
P-H-0.5
P-H-1
Veopur
V-H-0.5
V-H-1
H
OO
O
O
N
H
O O
O
O
N
H
O
O
N
CO2
H
O
O
N
-
N
H+
b
a
d c e
bcde
a
Synthesis and Structural Analyses
Reference Mean diameter (nm) Zeta potential (mV)
V-H-0.5 83.4 ± 1.1 -45.8 ± 2.4
V-H-1 70.9 ± 0.9 -55.0 ± 3.8
V-I-0.5 103.3 ± 0.9 -45.7 ± 3.4
V-I-1 60.3 ± 0.9 -45.5 ± 1.2
P-H-0.5 149.2 ± 1.8 -51.3 ± 0.9
P-H-1 120.0 ± 0.2 -63.2 ± 3.0
P-I-0.5 142.4 ± 1.6 -45.3 ± 1.7
P-I-1 146.6 ± 1.0 -54.8 ± 2.3
Reference E (Mpa) σb (Mpa) εb (%) Shore D (%)
V-H-0.5 5.0 ± 0.2 4.2 ± 0.3 871 ± 81 8 ± 1
V-H-1 10.5 ± 2.3 6.9 ± 0.8 627 ± 49 24 ± 3
V-I-0.5 0.45 ± 0.03 0.23 ± 0.02 1496 ± 75 7 ± 1
V-I-1 0.65 ± 0.07 0.19 ± 0.04 721 ± 121 9 ± 1
P-H-0.5 35.7 ± 3.3 1.1 ± 0.2 48 ± 6 21 ± 2
P-H-1 99.0 ± 4.5 3.2 ± 0.6 15 ± 2 34 ± 1
Heterogeneous instable
biphasic medium
Homogeneous stable
aqueous dispersion
Reaction time
The restrictions on volatile organic compounds (VOC) in coatings led to major
technological progresses in the development of water-based formulations (1).
Waterborne polyurethanes (WPU), in particular, have gained increasing attention as
performant, non-toxic and environmentally friendly solutions (2,3). Moreover, both
the economic and environmental aspects of WPU could be improved replacing
petroleum based raw materials with renewable resources. Polyols extracted from
abundant and low cost vegetal oils issued from major agro-industrial crops,
represent precisely interesting bio-based alternatives (4,5).
In the present work, the focus was made on functionalization of two commercially
available bio-based polyols with similar low hydroxyl values: fully renewable fatty
dimer functionalized polyol Veopur (Vandeputte Oleochemicals) and partially
biobased amorphous polyester polyol Priplast (Croda).
1) 50 wt% MEK, 70°C, 5h
2) Addition of water
3) MEK removal
Water dispersions of ionic hard segment functionalized polyurethanes
HO OH
CO2
- +
HNEt3
NCOOCNHO OH ++
Tests were made with two aliphatic diisocyanates
(diNCO): isophorone diisocyanate (IPDI) and
dicyclohexylmethane-4,4-diisocyanate (H12MDI). The
DMPTEA salt, prepared by reacting triethylamine (TEA)
and dimethylolpropionic acid (DMPA), was selected to be
introduced as ionic chain extender. Reaction kinetics was
followed by Fourier transform infrared (FTIR) with a
progressive disappearing of the absorption peak of the
NCO groups (2700 cm-1), whose consumption stabilized
at 70 % after 5 hours. The reaction medium was then
dispersed in water, and the residual MEK removed at
40°C in a rotary evaporator. The final solid content of
water dispersion was 20 wt%.
Mechanical properties characterisations showed that
WPU formulations especially based on fully renewable
polyol Veopur and H12MDI could be considered as
particularly promising materials for sustainable coatings.
An appropriate choice of hard segment content might be
used to meet specific requirements for various
applications and supports (wood, metal, walls).
The introduction of hydrophilic segments
progressively brought amphiphilic properties
to WPU, whose evolution can be easily
followed during the reaction. Homogeneous
and stable water dispersions, with the zeta
potential clearly under -30 mV and the
average particle size between 60 and 150
nm, were eventually obtained after 300
minutes reaction time.
Casted WPU films were suitable for mechanical properties characterizations by tensile and hardness tests. For the whole set of studied polyols
and diisocyanates, the results showed that a higher hard segment content induced a higher rigidity noted with Young modulus values and Shore
D hardness. Moreover, stress-strain experiments revealed the polyol nature incidence, since formulations based on Priplast exhibited brittle
behaviour with rubbery break compared to formulations based on Veopur which may be considered as elastomeric.
According to 1H NMR analyses, the WPU hard
segment content was highlighted by the increasing
intensity of peaks corresponding to urethane
moieties. Furthermore, the absence of the peaks at
3.5-3.6 ppm, assigned to CH2 in α position of the end-
terminated hydroxyl function, indicated their full
conversion into urethane segments.
FTIR bands specific to urethane moieties in the final
materials can be attributed to N-H stretching vibration
(3340 cm-1), NH-CO stretching (1545 cm-1), C-O-C(O)
stretching (1250 cm-1), their absorbances being
directly proportional to the hard segment content.
Conclusion & Prospects
(1) K.-L. Noble, Waterborne polyurethanes, Progress in Organic Coatings 32 (1997) 131–136. (2) C. Fang et al., Synthesis and characterization of low crystalline waterborne polyurethane for potential application in water-based ink binder, Progress in
Organic Coatings 77 (2014) 61–71. (3) J. Li et al., Structure, properties and application of a novel low-glossed waterborne polyurethane, Applied Surface Science 307 (2014) 255-262. (4) M. Desroches et al., From vegetable oils to polyurethanes: Synthetic
routes to polyols and main industrial products. Polymer Reviews 52 (2012) 38-79. (5) C. Fu et al., A fully bio-based waterborne polyurethane dispersion from vegetable oils: From synthesis of precursors by thiol-ene reaction to study of final material,
Progress in Organic Coatings 77 (2014) 53–60.
Waterborne & bio-based
Polyurethanes for Coatings
Renewable resources
Polyols from vegetal oils
Reference Polyol diNCO Polyol / DMPTA /diNCO (mol) HS (wt%)
V-H-0.5 Veopur H12MDI 1 / 0.5 / 1.65 21.7
V-H-1 Veopur H12MDI 1 / 1 / 2.20 28.2
V-I-0.5 Veopur IPDI 1 / 0.5 / 1.65 19.3
V-I-1 Veopur IPDI 1 / 1 / 2.2 25.6
P-H-0.5 Priplast H12MDI 1 / 0.5 / 1.65 20.8
P-H-1 Priplast H12MDI 1 / 1 / 2.20 27.2
P-I-0.5 Priplast IPDI 1 / 0.5 / 1.65 18.6
P-I-1 Priplast IPDI 1 / 1 / 2.20 24.7
WPU compositions and theoretical hard segment mass fraction