The Role of Catalysts in Low-Gloss
Epoxy/Polyester Hybrid Powder Coatings
By John Schmidhauser
Cray Valley USA, LLC
Exton, Pennsylvania
USA
Presented at
the International Waterborne, High - Solids,
and Powder Coatings Symposium
Feb 21-23, 2001
Cray Valley USA, LLC • Oaklands Corporate Center
•
468 Thomas Jones Way, Suite 100
877-US1-CRAY (877-871-2729) •
5900 01/10
Web: www.crayvalley.com
•
Exton, PA 19341
Abstract
In this study, the crucial role played by catalysts in
the preparation of low-gloss hybrid powder coatings
using a reactive additive (styrene maleic anhydride
copolymer) is described. First, the reactions that
occur during the cure of epoxy/polyester hybrid
thermoset powder coatings are reviewed. DSC
measurements on model mixtures and fully
formulated powder paints revel relative reactivities
and the roles of catalysis on the various reaction
steps. The gloss properties of the coatings are found
to be closely tied to the presence of a catalyst.
Several approaches to preparing powder coating
formulations that exhibit fast cure kinetics, lowgloss appearance and excellent properties are
described.
use of certain reactive agents.
The choice of gloss control agent depends upon the
level of gloss reduction desired and the chemistry of
the powder coating. Fillers can give rough surfaces
due to the protrusion of the fillers from the surface
after baking, which disrupts reflected light. Waxes and
other incompatible ingredients tend to segregate on
the surface during baking, leaving circular voids or
forming a film on the surface. The 60° gloss reduction
of both fillers and waxes is limited to about 40. Blends
of powders of differing chemistries/reactivities, as well
as chemically reactive additives such as polycarboxylic
acids or their acid salts are used to achieve low and
matt finishes.
Low molecular weight styrene-maleic anhydride
(SMA®) resins are a family of anhydride and partial
ester functionalized copolymers which have been
widely used as gloss reducing additives in thermoset
epoxy powder coatings.2 Earlier studies suggest that
a two-stage reaction process leads to the textures
observed in low gloss epoxy powder coatings
containing SMA.1 In this mechanism, dicyandiamide
(Dicy), another epoxy curative traditionally added
to epoxy powder coatings, reacts at a different rate
than the SMA curing agent, leading to two structural
networks within the coating.1 In studies of a
similarly reactive low-gloss additive, Lee et al3
observed low gloss epoxy coatings during curing,
and saw that the coarse surface morphology formed
as the gel point of the coating was reached. After
gelation, the surface roughness remained fairly
constant even with further curing, although fine
structure continued to develop past the gel point.
This suggests that the low gloss texture is a
consequence of morphology develop-ment during
curing, and is not due to stress-induced texture
development during the cooling of the powder
coated surface.
Introduction
Gloss is a measure of the amount of light reflected
from a surface at a given angle, and is expressed as
a value between 0 and 100. Polished plate glass has
a value of about 100, and a completely nonreflective surface has a value of 0. Low gloss
coatings are typically measured as 60° gloss,
although the 85° gloss is also sometimes used. The
range of gloss readings are loosely divided into
several categories, as shown in Table 1.1
Table 1: Gloss Categories
1
Category
Gloss Reading (60°)
High
> 85
Standard
70 to 85
Semi
40 to 70
Low
15 to 40
Matt
< 15
The chemical and physical properties of most major
classes of powder coatings cure to give a level,
glossy surface. However, for aesthetic and
functional reasons it is often desirable to have a
powder coated surface with a low gloss or matt
finish. In such cases, gloss control may be achieved
through many different techniques, including the
addition of inorganic fillers or organic waxes, the
lending of powders of different reactivities or the
This study explores the use of SMA resins as gloss
reducing additives in the more complex epoxypolyester hybrid powder coating system. In these
formulations, the reactivities between three
components, the epoxy resin, the polyester and the
SMA anhydride and/or ester, must be balanced so
as to give the different curing rates which create the
3
low gloss morphology. The curing kinetics of the three
possible 2-component combinations are explored
first by DSC. Using these results, powder coating
formulations are prepared and analyzed. These
studies uncover the characteristics of the polyester resin
and the SMA resins necessary to obtain low gloss
epoxy/polyester hybrid powder coatings.
OH
CH CH2
CH3
O
H2C
O
Experimental
Materials
Epon 2002 (Shell Chemical) is a standard “Type 3”
Bisphenol A epoxy resin with EEW 675-760.
Albester 2240 (McWhorter Technologies) is a high
reactivity carboxyl-terminated 70/30 polyester resin
with an acid number range of 35-45 mg KOH/g and a
viscosity (at 200°C) of 6000-8000 mPa@s.
O CH2
CH3
CH3
O
O
O CH2
CH3
x
Bisphenol A Epoxy Resin
Albester 2250 (McWhorter Technologies) is an
uncatalyzed version of Albester 2240. Crylcoat 7401
(UCB Chemical) is a high reactivity carboxylfunctionalized 70/30 polyester resin with an acid
number range of 32-40 mg KOH/g and a melt viscosity
(at 160°C) of 25-42 Pa@s. Crylcoat 7402 (UCB
Chemical) is the uncatalyzed version of Crylcoat 7401.
Resiflow P-67 (Estron Chemical) is a flow-control
agent. Huberbrite #1 (J. M. Huber) is a grade of
powdered barium sulfate suitable for use in powder
coatings.
SMA 3000 (Cray Valley Company) is a low molecular
weight copolymer of styrene and maleic anhydride in
a 3:1 ratio, available in powder (P) and ultrafine
powder (UFP) grades, with an acid number of 265305. SMA 10840 (Cray Valley Company) is a
copolymer of styrene and maleic anhydride
esterified about 65% with iso-octanol, having an
acid number of about 240.
O
[
C H C H2
3
O
CH
CH
C
C
]10
O
C
[
CH
O
O
C H2
1.2
O
C
O
C
C
OR O H
SMA 10840 ( R = iso-octyl)
SMA 3000
4
] 10
C H C H 0.35 C H C H 0.65
O
DSC Studies
Resin mixtures for DSC analysis were dry blended by
grinding in a coffee mill for 5 minutes. The powders
were analyzed on a TA Instruments DSC 2920
instrument, using a heating profile of 10 °C/ min.
became softer with a visible change in appearance.
‘Softened’ indicates more severe swelling, where a
significant amount of the coating came off onto the
cotton ball.
Chemistry Of Polyester-Epoxy Hybrid
Formulations
Polyester-epoxy hybrid powder coatings contain
both epoxy resins and carboxyl-terminated polyester
resins, and may also contain a catalyst to drive the
curing reactions. Polyester producers market “high
reactivity”, “active” or “low temperature curing”
polyester resins which have been admixed with
catalysts during production.4 These catalysts are
intended to speed the cure rate or to lower the cure
temperature of high-gloss hybrid coatings. In this
study they are investigated to find if they aide in
the cure of gloss reducing additives.
Powder Coating Formulations
All formulations are given in phr (parts-per-hundred
resin), where the mass of “resin” (epoxy + polyester)
totals 100 and all other ingredients are given as a
fraction of this mass. Formulations were prepared
on a 1 kg scale, with pre-mixing via a “bag-shake”,
where the ingredients were simply shaken together
in a bag. After pre-mixing, the blend was passed
through a lab-scale 50mm twin-screw APV
extruder. Unless stated otherwise, all formulations
were prepared under high-shear conditions, at 400
rpm with a rear-zone temperature of 175°F and a
front-zone temperature of 100°F. After cooling, the
resin blends were ground in a hammermill and
passed through a 140 mesh (105 mm) screen. Test
panels were sprayed using an electrostatic spraygun to a dry film thickness of 2.0 ± 0.2 mils and
cured in an oven at 350, 375 or 400°F for 10
minutes, at 375°F for 10 minutes or at 300°F for
20 minutes.
To understand the effect of catalyst addition on low
gloss hybrid formulations, we chose to concentrate
on two SMA Resins (SMA 3000 and 10840), one
epoxy resin (Epon 2002) and two families of 70/30
carboxyl-terminated polyester resins (Albester
2240/2250 from McWhorter and Crylcoat 7401/
7402 from UCB). These polyester resins are
catalyzed and uncatalyzed versions of the same
materials, allowing us to examine the use of precatalyzed polyesters, to add external catalysts to
uncatalyzed formulations, and to perform control
experiments.
Physical Testing
Panels were evaluated for 60° gloss, forward impact
resistance, reverse impact resistance, crosshatch
adhesion and solvent resistance. Gloss values were
measured using a BYK Micro-Gloss 60° meter with
a statistics feature; all reported values are the
average of ten readings. Impact resistance was
measured using a Gardner impact tester and
reported values are the highest level of impact at
which the coatings showed no cracking. Solvent
resistance was evaluated by rubbing a cotton ball
soaked in methyl ethyl ketone (MEK) back and forth
over the surface 50 times. After drying, the coating
was inspected for any changes in appearance. A
‘pass’ rating indicates no visible change, while a
‘fail’ indicates that the film was completely removed.
A rating of ‘slight softening’ was given when the coating
Individual reaction steps in the curing of the epoxy/
polyester/SMA formulations are illustrated in Figure
1. The initial reaction between SMA 3000 and the
epoxy resin involves the reaction between anhydride
and alcohol functionality (A), between SMA 10840
and epoxy resin involves epoxy and acid
functionality (B), between polyester resin and epoxy
involves acid and epoxy functionality (C) and
between epoxy resin and the product of reaction A
involves epoxy and acid functionality (D).5 It is these
reactions which are first investigated by DSC.
5
Figure 1. Idealized reactions involved in curing of epoxy resin/polyester resin/SMA resin formulations.
A.
O
O
O
OH
CH
+
O
O
CO2H
SMA
B.
O
+
HO2C
CO2R
O
CO2R
O
SMA Ester
OH
C.
O
CO2
CO2H
+
Polyester
D.
O
+
O
HO
O
O
CO2H
O
O
OH
O
at 10°C/min. The curing onset temperature (To) and
temperature of the maximum exotherm (Tmax) were
measured for each sample (see Figure 2 for a typical
trace). This onset temperature data is compiled in Table
2.
DSC Curing Studies Of Epoxy/Polyester/SMA
Formulations
Differential scanning calorimetry (DSC) is a
powerful tool for studying the kinetics of curing
reactions.6 A variety of kinetic data may be garnered
from DSC traces acquired in isothermal or dynamic
mode, including the enthalpy of curing, the length
of time to cure at specific temperatures, the
temperatures at which curing begins or exhibits a
maximum in the curing exotherm under specific
heating rates, and the extent of cure at certain
conditions. When similar systems are examined
under identical heating rates, the temperature at
which curing begins can be utilized as a comparative
measure of cure rates. Powder coating or other
crosslinking formulations that cure at lower
temperatures on the DSC will probably be found
to cure more quickly or at lower temperatures under
application conditions.
Figure 2. Typical DSC trace of epoxy/polyester/SMA
resin formulation showing To and Tmax.
0.1
0.0
-0.1
194.70°C
-0.2
132.59°C
Tmax
-0.3
To
Samples of the mixtures of two of the three resin
components (catalyzed and un-catalyzed) and fully
formulated hybrid powders were analyzed via DSC
-0.4
o Up
6
0
50
100
150
Temperature (°C)
200
250
300
Universal V2.6D TA Instruments
Table 2. Onset temperatures of resin reactions determined by DCS.
Composition
SMA 3000 + Albester 2250
EPON 2002 + Albester 2250
SMA 3000 + EPON 2002
SMA 10840 + Albester 2250
EPON 2002 + Albester 2250
SMA 10840 + EPON 2002
SMA 3000 + Albester 2250 + EPON 2002
SMA 10840 + Albester 2250 + EPON 2002
* 0.5 Wt. % Tetrabutylphosphonium bromide added.
No Catalyst
>210
193
>210
>210
193
180
195
190
These DSC studies indicate that all reactions are slow
in the absence of an esterification catalyst, although
the reactions of the carboxylic acid functionalized SMA
resin (10840) occur at a lower temperature compared
to reactions of the anhydride functionalized SMA resin
(3000). The catalyst has the most pronounced effect
on the reaction between the SMA resins and the epoxy
resin. Based on these results we looked at powder
coating formulations based on pre-catalyzed polyester
resins.
Tg Onset (°C)
With Catalyst*
>210
147
175
>210
147
148
149
146
containing catalysts. Pre-catalyzed formulations
containing SMA 3000P are outlined in Table 3. All
formulations were prepared as outlined in Section
2.
The results from formulations H1-H4 are
summarized in Table 4. All coatings were found to
exhibit poorer solvent resistance than comparable
epoxy formulations, which is typical of hybrids in
general, probably due to a lower crosslink density.
Curing at 400°F or higher is recommended, as
higher glosses and reduced physical properties are
obtained at lower curing temperatures. It appears
that these high temperatures are required to allow
curing to be as complete as possible. The lowest
glosses were obtained using the Crylcoat resin with
10 parts of SMA 3000.
SMA 3000 Hybrid Formulations with
Pre-Catalyzed Polyesters
Two families of carboxyl-terminated polyester resins
were chosen for this study: Crylcoat 7401 and 7402;
and Albester 2240 and 2250. All resins are of the
70/30-type, with Crylcoat 7401 and Albester 2240
Table 3: Formulations - Hybrids containing SMA 3000 and Pre-catalyzed Polyesters
Material
H1
H2
H3
H4
Epon 2002
50
50
50
50
Crylcoat 7401
50
50
50
Albester 2240
50
SMA 3000P
5
10
20
10
Carbon Black
2.0
2.0
2.0
2.0
Resiflow P-67
1.2
1.2
1.2
1.2
Barium sulfate
40
40
40
40
Benzoin
0.5
0.5
0.5
0.5
148.7
153.7
163.7
153.7
Total parts
7
Table 4: Results - SMA 3000 with Pre-catalyzed Polyester Hybrids
Gloss (60°)
Forward
Impact (in-lb)
Reverse
Impact (in-lb)
Crosshatch
Adhesion
MEK 50 Double
Rubs
H1 - 400/10
22.3
60
40
pass
sl. softening
H1 - 375/10
54.5
40
40
pass
softened
H2 - 400/10
11.0
20
< 20
pass
sl. softening
H2 - 350/10
58.2
20
20
pass
fail
H3 - 400/10
15.6
20
< 20
pass
sl. softening
H3 - 375/10
31.0
20
< 20
pass
softened
H4 - 400/10
48.3
20
< 20
pass
sl. softening
H4 - 350/10
81.0
< 20
< 20
pass
softened
Formulation - Cure
Temp(°F)/Time(min)
Inductively coupled plasma (ICP) analysis was used
to determine the type and amount of catalyst present
in some commercially-available polyester resins. Due
to the nature of the production of pre-catalyzed
polyesters, a high thermal stability catalyst is
required. All four polyester resins contained from
120 to 140 ppm tin. While tin compounds are
commonly used as an esterification catalyst between
alcohols and carboxylic acids, they are less effective
for acid-epoxy reactions. However, it was also found
that the active forms of the polyester resins contained
phosphorus (Crylcoat 7401 = 362 ppm P, Albester
2240 = 139 ppm P), while the uncatalyzed resins did
not (Crylcoat 7402 = 6 ppm P, Albester 2250 = 6
ppm P). Therefore, the effect of gloss reduction by
adding phosphorus catalysts to otherwise high gloss
formulations was investigated.
Table 5: Formulations - External Catalysts in SMA 3000 Hybrids
Material
H5
H6
H7
H8
H9
H10
H11
H12
H13
H14
Epon 2002
50
50
50
50
50
50
50
50
50
50
Albester 2250
50
50
50
50
50
50
50
50
50
50
Crylcoat 7402
SMA 3000P
10
Methyltriphenyl
phosphonium
bromide
Triphenylphosphine
Tetrabutyl
phosphonium
bromide
10
10
0.25
0.75
10
10
0.25
0.75
10
10
5
10
10
0.25
0.75
0.75
0.25
0.75
Carbon Black
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
Resiflow P-67
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
Barium sulfate
40
40
40
40
40
40
40
40
40
40
Benzoin
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
153.7
154.0
154.5
154.0
154.5
154.0
154.5
149.5
154.0
154.5
Total parts
8
SMA 3000 in Hybrids - Addition of External
Catalysts
In addition to using pre-catalyzed polyester resins, it
is possible to add catalyst independently. This should
give the formulator greater control over the properties
and cost of their coating, although a little more
development work is required to optimize the
formulation. Three different catalysts were tried at
different levels in hybrid formulations containing
Crylcoat 7402 and Albester 2250. Formulations
shown in Table 9 were prepared as described in
Section 2.
The results from formulations H5-H14 are summarized
in Table 10. The control experiment (H5) containing
no catalyst had a very high gloss with no solvent
resistance, indicating that no cure took place.
Formulations H6-H11 compare the effectiveness of
three different phosphorus-containing catalysts at low
and high levels in an Albester 2250 formulation. From
these results, it is apparent that tetrabutylphosphonium
bromide (TBPBr) is the best catalyst on an equivalent
weight basis giving a gloss as low as 18.5 when
incorporated at 0.75 phr.
Table 6: Results - Hybrids Containing Externally Added Catalysts
Formulation - Cure
Temp(°F)/Time(min)
Gloss (60°)
Forward
Impact (in-lb)
Reverse
Impact (in-lb)
Crosshatch
Adhesion
MEK 50
Double Rubs
H5 - 400/10
92.0
160
140
pass
removed
H5 - 350/10
88.3
20
< 20
pass
removed
H6 - 400/10
55.8
20
< 20
pass
sl. softening
H7 - 400/10
23.6
40
< 20
pass
sl. softening
H8 - 400/10
50.5
20
< 20
pass
sl. softening
H8 - 375/10
70.1
20
< 20
pass
softened
H9 - 400/10
23.7
40
20
pass
sl. softening
H9 - 375/10
48.2
40
< 20
pass
sl. softening
H10 - 400/10
44.3
20
< 20
pass
sl. softening
H10 - 375/10
48.7
20
< 20
pass
softened
H11 - 400/10
18.5
20
< 20
pass
sl. softening
H11 - 375/10
39.9
20
< 20
pass
softened
H12 - 400/10
33.3
40
20
pass
sl. softening
H12 - 375/10
57.9
20
< 20
pass
sl. softening
H13 - 400/10
17.1
60
40
pass
sl. softening
H13 - 375/10
47.9
20
< 20
pass
fail
H14 - 400/10
14.5
20
< 20
pass
sl. softening
H14 - 375/10
47.3
20
< 20
pass
fail
9
Effect of Phosphorus Content on SMA 3000Containing Hybrids Powder Coatings
A direct comparison of H11 with H14 indicates that
the most significant factor on gloss reduction is
actually the choice of polyester resin. In both these
externally catalyzed formulations and in the precatalyzed formulations (H1-H4), Crylcoat resins
outperform the Albester resins. Calculation of the
amount of phosphorus in all hybrid formulations
(H1-H14) allows us to examine the effect of
phosphorus content on the gloss (Figure 3). It is
apparent from Figure 3 that Albester formulations
are quite sensitive to the level of catalysis, while
Crylcoat formulations do not show much dependence
on catalyst levels. The reason for this difference is not
known, although the two polyesters do have different
viscosities.
The DCS cure properties of formulations H1-H14
were measured as described in Section 4, and they
are summarized in Table 7. For these formulations
based on SMA 3000, fast cure kinetics, as measured
by either low onset temperatures or low curing
maxima, correlates with lower gloss properties.
This data highlights the differing cure behaviors of
formulations prepared from Crylcoat and Albester
resins (Figures 4 and 5). The gloss of Albester
formulations decreases with increasing reactivity
(lower To and Tmax), while the gloss of Crylcoat-based
formulations seems to be relatively independent.
Figure 3. Effect of phosphorus content on the gloss of Albester (•) and Crylcoat ( ) hybrid formulations.
Gloss of Hybrid Formulations
100
80
60° Gloss
Albester
Crylcoat
60
40
20
0
-0.005
0.005
0.015
0.025
0.035
Phosphorus (wt. %)
10
0.045
0.055
0.065
Table 7: DSC Analysis of Hybrid Formulations
Formulation
60° Gloss *
Cure Onset** (°C)
Cure Maxima** (°C)
H1
22.3
124.8
166.5, 176.8
H2
11.0
128.3
173.1
H4
48.3
134.8
176.5
H5
92.0
166.6
288.9
H6
55.8
132.6
194.7
H7
23.6
119.1
157.7
H8
50.5
134.7
168.8
H9
23.7
93.1
154.1, 169.6
H10
44.3
130.7
153.7, 195.9
H11
18.5
119.4
164.1
H12
33.3
116.3
165.7
H13
17.1
133.2
188.6
H14
14.5
112.7
161.6
*When cured at 400°F for 10min. ** Measured via DSC at 10°C/min.
Figure 4: Effect of powder coating reactivity, as shown by the temperature at the maximum in the curing
exotherm measured via DSC, on gloss reduction in both Albester (•) and Crylcoat ( ) formulations.
Effect of Reactivity on Gloss - Cure Maximum
100
60° Gloss
80
60
40
Albester
Crylcoat
20
0
140
160
180
200
220
240
Temp. at Cure Maximum (°C)
11
260
280
300
Figure 5: Effect of powder coating reactivity, as shown by the temperature at the onset of curing measured
via DSC, on gloss reduction in both Albester (•) and Crylcoat ( ) formulations.
Effect of Reactivity on Gloss - Cure Onset
100
60° Gloss
80
60
40
Albester
Crylcoat
20
0
80
100
120
140
160
180
Cure Onset (°C)
prepared. The same resins and catalysts were used
as in the SMA 3000 formulations, substituting SMA
10840 for 3000. These formulations are shown in
Table 8.
Hybrid Powder Coatings Formulations
WithAcid Functionalized SMA Resin (10840)
A number of formulations containing an acid
functionalized reactive additive, SMA 10840, were
Table 8. Formulations - SMA 10840 in Hybrid formulations
Material
I
II
III
IV
V
Epon 2002
50
50
50
50
50
Crylcoat 7401
50
50
50
50
Albester 2250
SMA 10840
50
5
10
12
20
Tetrabutyl phosphonium
bromide
5
0.75
Carbon Black
2.0
2.0
2.0
2.0
2.0
Resiflow P-67
1.2
1.2
1.2
1.2
1.2
Barium sulfate
40
40
40
40
40
Benzoin
0.5
0.5
0.5
0.5
0.5
148.7
153.7
155.7
163.7
149.5
Total parts
12
Table 9. Characterization of hybrid powder coatings containing SMA 10840.
Formulation - Cure
Temp(°F)/Time(min)
Gloss (60°)
Forward
Impact (in-lb)
Reverse
Impact (in-lb)
Crosshatch
Adhesion
MEK 50
Double Rubs
I - 400/10
81.2
20
< 20
pass
sl. Softening
I - 375/10
89.8
20
< 20
pass
sl. Softening
II - 400/10
83.5
80
40
pass
sl. Softening
II - 300/20
95.1
20
< 20
pass
sl. Softening
III - 400/10
80.1
40
40
pass
sl. Softening
III - 375/10
88.6
20
< 20
pass
sl. Softening
IV - 400/10
85.4
40
40
pass
sl. Softening
IV - 375/10
88.6
20
< 20
pass
sl. Softening
V - 400/10
83.5
40
40
pass
sl. Softening
V - 375/10
86.0
20
< 20
pass
sl. Softening
Conclusions
SMA Resins work as reactive gloss reducing agents
in epoxy/polyester hybrid powder coatings through
formation of a two-phase micro-texture
morphology. Models studies indicated that catalysis
of the SMA resin anhydride – epoxy resin alcohol
reaction is necessary to develop the proper
morphology during curing to give a low gloss
surface. The catalyst can be present is a component
of the polyester resin, or can be added separately
to the powder paint formulation. Phosphonium salts
were found to highly effective in giving low gloss
powder coatings, and tetrabutylphosphonium
bromide is particularly recommended as a catalyst
for use at 0.25-1 phr in these types of formulations.
Characterization of formulations I-V is summarized
in Table 9. Surprisingly, all powder coatings
prepared with SMA 10840 exhibited high gloss.
However, the coatings exhibited good solvent
resistance indicating that the coatings were fully
cured. From the DSC studies in Section 4, it is clear
that SMA 10840 reacts more readily with EPON
2002 than does SMA 3000. This is probably due to
there being two reactive pathways available for the
10840 resin: reaction of the 10840 carboxylic acid
groups with the EPON epoxy groups, and reaction
of the 10840 anhydride groups with the EPON
alcohol groups. Therefore, the overall reactivity of
10840 with EPON is similar to that of the polyester
resin with EPON. This could explain the difference
in matting behavior exhibited by SMA 3000 and
10840, since it is believed that different cure rates
are needed to set up the two-network morphology
needed for a low gloss finish. As such, SMA 3000
and EPON cure at a different rate than the polyester
and EPON, giving a low gloss finish, while 10840
and the polyester cure at similar rates with EPON,
giving a uniform, single phase high gloss surface to
those powder coatings.
Acknowledgments
Thanks to Doug Richart of D. S. Richart Associates
for preparing and coating the formulations outlined
in this report, and thanks also for many helpful
suggestions and discussions. The assistance of Reta
Tanjala, Jeanine Willcox and Wes Robinson of the
ATOFINA Chemicals, Inc. King of Prussia
Analytical Department are much appreciated.
13
5. May, C. A. “Epoxy Resins, Chemistry and
Technology”, 2nd Ed., Marcel Dekker, New
York, 1988, p. 501.
References
1. Richart, D. S. “The surface topography of
powder coatings and its relation to gloss,”
Powder Coating 1999, 2, 25-35.
6. a) Pielichowski, K.; Czub, P.; Pielichowski, J.
“Characterization of the cure of some epoxides
and their sulphur-containing analogs with
hexahydrophthalic anhydride by DSC and TGA,”
J. Appl. Poly. Sci. 1998, 69, 451-460.
2. Salitros, J. J.; Patarcity, R. “Gloss modification
of thermoset powder coatings with styrene,
maleic anhydride copolymers,” Proceedings of
the Int. Waterborne, High-Solids and Powder
Coatings Symp. 1992.
b) Vora, R. A.; Trivedi, H. C.; Patel, C. P.;
Kazlauciunas, A.; Guthrie, J. T.; Trivedi, M. C.
“Cure kinetics of epoxy resin with styrene maleic
anhydride copolymer by DSC technique,”
Polymers & Polymer Composites 1995, 4(1), 6167.
3. Lee, S. S.; Han, H. Z. Y.; Hilborn, J. G.; Månson,
J.-A. E. “Surface structure build-up in thermosetting powder coatings during curing,” Prog.
Org. Coat. 1999, 36, 79-88.
4. Panandiker, K. P.; Wiedow, T. “Low Temperature
Cure Carboxyl Terminated Polyesters” US
Patent 5,637,654, 1997.
The information in this bulletin is believed to be accurate, but all recommendations are made without warranty since the conditions of use are beyond Cray Valley Company's
control. The listed properties are illustrative only, and not product specifications. Cray Valley Company disclaims any liability in connection with the use of the information,
and does not warrant against infringement by reason of the use of its products in combination with other material or in any process.
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