Corrosion-Resistant
Polyester Resins
Based on Eastman TMPD Glycol
eastman
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Resin Preparation, Physical Properties, and Cure . . . . . . . . . . . . . 2
Resin Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Notes on Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Field Testing Pipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Testing Castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Introduction
In the corrosion-resistant equipment industry,
products are engineered to withstand the attack of
extremely harsh environmental products such as
sulfuric acid, hydrochloric acid, and hypochlorite
solutions. Unsaturated polyester resins have become
widely accepted in this industry because of their
ability to prevail in such conditions without the
degradation usually evident in products manufactured
from metals, such as steel and aluminum.The
resulting composite materials can be found in
storage tanks, process tanks, pipes, etc.
The branched, asymmetrical structure of TMPD
glycol permits the preparation of noncrystalline
polyesters. A sterically hindered secondary hydroxyl
group and the hydrophobic nature of this glycol
combine to contribute outstanding performance
and resistance to acids, alkali, and other corrosive
environments.
The bulky molecular structure prevents the close
packing of resin molecules, imparting lower density
to unsaturated polyester resins in comparison
with PG-based formulations. This provides the
advantage of allowing a higher number of parts to
be produced per unit weight of resin.
The highly hindered secondary hydroxyl group of
TMPD glycol does react more slowly during resin
synthesis than do primary or less hindered
secondary hydroxyl groups. As a result, special
synthetic considerations are required to produce
resins that provide the stated performance levels.
Eastman recommends the use of a synthesis catalyst
and a cook stabilizer to facilitate the synthesis of
TMPD glycol-based resins.
This market consists of both relatively low-cost,
general-purpose corrosion resistant resins produced
from propylene glycol (PG), isophthalic acid
(PIA), and maleic anhydride (MA); and premiumquality resins based primarily on either bisphenol
A (BIS A), vinyl ester (VE), or halogenated (HAL)
unsaturated polyester (NPG glycol/chlorendic
anhydride/MA) formulations.
Unsaturated polyester resins based on TMPD
glycol provide superior corrosion resistance in
comparison to general-purpose resins and have
other performance advantages that are useful in the
fabrication of corrosion-resistant products. In
addition, TMPD glycol-based polyesters are more
economical than premium-quality formulations
while providing comparable performance.
Laboratory evaluations have demonstrated many
advantages of TMPD glycol in corrosion-resistant
applications. However, for improved processability
and cure characteristics, resin formulations should
consist of a blend of TMPD glycol and PG with
PIA/MA rather than using TMPD glycol as the sole
glycol component.
HO
OH
OH
OH
TMPD Glycol
Propylene Glycol
1
Resin Preparation,
Physical Properties, and Cure
Table 1
Composition and Physical Properties of LaboratoryPrepared Unsaturated Polyesters
TMPD Glycol/
Physical Properties
Glycol weight ratio
Glycol excess, mole %
Acid molar ratio, sat:unsat acidsc
Maleic content, wt %c
Acid number
Molecular weight, Mn
Viscosity, Gardner
Viscosity in 42% styrene, cP
Color, Gardner
Density in 40% styrene, kg/L (lb/gal)
Typical reaction time, h
Catalyst, butylstannoic acid, wt %
PG/PIAa//MAb
PG/PIA//MA
75/25
10
1:2
29
25–30
2,300–2,600
U–V
500
2–3
1.05 (8.73)
15
0.1
—
10
1:1
26
25–30
2,400–2,600
V
600
1–2
1.09 (9.11)
22
—
aManufactured
by Eastman Chemical Company.
slash indicates first stage reactants and second stage reactants.
c To maintain comparable maleic content in each of the resin formulations, it is necessary to adjust the
acid molar ratios due to the higher molecular weight of TMPD glycol compared with PG (146.22 vs.
76.10, respectively).
bDouble
Resin Synthesis
1. Purge with nitrogen and charge first stage
reactants1 to a reactor equipped with a heating
mantle, agitator, partial condenser, temperature
probe, water trap, and total condenser. Refer to
Eastman publication N-345.
2. Slowly melt contents and increase temperature
to 200°C.
3. Process at 200°C until an acid number of 15
is reached.
4. Cool to 180°C and add maleic anhydride.
5. Reheat to 200°C and process to an acid
number of 25.
6. Cool to 140°C and rapidly add styrene monomer
inhibited with 100–150 ppm hydroquinone.
1For
the TMPD glycol-based formulation, a catalyst (0.1% butylstannoic
acid) was also added.
2
Notes on Curing
A copromoter should always be used for roomtemperature curing of resins based on TMPD
glycol. DMA (N,N-dimethylaniline) and DMAA
(N,N-dimethylacetoacetamide) have been found to
be effective copromoters when used with cobalt
promoters (refer to Eastman publications GN-396,
N-315, and N-317). It is important to note that the
cure window for maximizing the physical properties
of fabricated equipment is more narrow for TMPD
glycol-based resins than for resins based on PG.
The additional time required to optimize the cure
for these resins will pay significant dividends in
terms of performance of the equipment produced.
Some cure systems for TMPD glycol-based resins
are shown in Table 2.
Table 2
Room-Temperature Cure Systems for Unsaturated Polyester Resins
Based on TMPD Glycol/PG/PIA//MA
TMPD Glycol/PG/PIA//MA Cure Systems
1
2
3
Promoters, wt
Cobalt octoate (6% Co)
0.5
0.5
0.5
Copromoters, wt %
DMA
Eastman DMAA
0.3
—
—
0.3
0.3
—
Catalyst, wt %
MEKP
1.0
1.0
1.5
150
150
100
200
150
150
22
10
179 (355)
19
8
185 (365)
12
7
188 (370)
%a
Inhibitor, ppm
Eastman Hydroquinone (HQ)
Eastman Mono-t -butylhydroquinone
(MTBHQ)
Properties
Gel time, min
Time to peak exotherm, min
Peak exotherm, °C (°F )
aBased
on total resin weight.
3
Field Testing Pipes
Fiberglass reinforced pipe samples were prepared
by a fabricator of commercial equipment using the
experimental TMPD glycol/PG/PIA//MA resin, a
commercial PG/PIA//MA, and a commercial BIS A
resin. The pipe samples were installed in a feed line
from a chemical manufacturing process to a waste
treatment facility at Eastman.
The feed line provided an extremely severe
environment for testing. The line carried a strong
aqueous solution of sulfuric and hydrochloric acids
containing small amounts of low molecular weight
organic solvents, dissolved gases such as sulfur
dioxide, and acid salts at temperatures varying from
32° to 93°C (148° to 200°F). This environment
would be considered too corrosive for metal pipes.
Pipe Samples
(6 Months Exposure)
TMPD glycol/PG/PIA
After 6 months exposure, the pipe sections were
removed and examined. The results indicated the
formulation based on TMPD glycol provided
better performance than formulations based on
either the general-purpose or the premium-quality
corrosion-resistant resin.
These in-service test results agree with laboratory
data on unreinforced castings that unsaturated
polyester resins based on TMPD glycol/PG/PIA//MA
provide better performance than commonly used
corrosion-resistant resins.
PG/PIA
BIS A
4
Testing Castings
The corrosion resistance of unreinforced castings
was evaluated by determining the percentage of
original flexural strength retained after accelerated
aging in various chemical environments for
specified test intervals.
The castings were prepared in the laboratory to
1
⁄8-inch thickness and cured for 3 hours at 70°C
(158°F), 1 hour at 100°C (212°F), and 1 hour at
150°C (302°F) using 0.5% benzoyl peroxide as
a catalyst. Note: Elevated temperature cures
generally do not require the use of copromoters.
The overall corrosion resistance of the castings is
shown in Figure 1. The castings prepared with
resins based on TMPD glycol were found to have
excellent resistance to corrosive environments.
These samples provided better flexural strength
retention than samples prepared with the
PG/PIA//MA resin in most environments tested.
The TMPD glycol/PG/PIA//MA resin exhibited
favorable strength retention when compared with
the commercial formulations as well.
Figure 1
Flexural Strength Retention of Castings
(6 Months Exposure)
5.25 wt %
Sodium Hypochlorite
@ 52°C (125.6°F)
1
2
3
4
5
25 wt %
Sulfuric Acid
@ 99°C (210.2°F)
1
2
3
4
5
15 wt %
Hydrochloric Acid
@ 99°C (210.2°F)
1
2
3
4
5
5 wt %
Sodium Hydroxide
@ 66°C (150.8°F)
1
2
3
4
5
Distilled Water
@ 93°C (199.4°F)
1
2
3
4
5
0
1 Vinyl ester (VE)
2 Halogenated unsaturated
polyester (HAL)
3 Bisphenol A (BIS A)
4 Propylene glycol/
isophthalic acid (PG/PIA)
5 TMPD glycol/propylene
glycol/isophthalic acid
(TMPD/PG/PIA)
20
40
60
80
100
120
140
% Retention
Summary
Data from this study demonstrates that resins based
on TMPD glycol offer excellent corrosion resistance
properties that exceed the performance of both
low-cost, general-purpose corrosion-resistant resins
and of more expensive, premium-quality resins in
many chemical environments. High performance
and low cost makes TMPD glycol an attractive
choice for manufacturers and fabricators of
corrosion-resistant polyester-based composites.
5
EASTMAN
■
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Material Safety Data Sheets providing
safety precautions that should be observed
in handling and storing Eastman products
are available online or on request. You
should obtain and review the available
material safety information before handling
any of these products. If any materials
mentioned are not Eastman products,
appropriate industrial hygiene and other
safety precautions recommended by their
manufacturers should be observed.
Neither Eastman Chemical Company nor
its marketing affiliates shall be responsible
for the use of this information, or of any
product, method, or apparatus mentioned,
and you must make your own determination
of its suitability and completeness for
your own use, for the protection of the
environment, and for the health and safety
of your employees and purchasers of your
products. No warranty is made of the
merchantability or fitness of any product,
and nothing herein waives any of the
Seller’s conditions of sale.
Eastman and TMPD are trademarks of
Eastman Chemical Company.
© Eastman Chemical Company, 2003.
Publication N-349A
September 2003
Printed in U.S.A.