Case Study
Bakelite® Engineering Thermosets
Take the Heat in Water Pump Housing Applications
New fuel economy and
emission regulations are
prompting automakers to
redesign almost every aspect
of new vehicles to reduce
weight and increase engine
efficiency. Wherever aluminum
has been used as a lightweight
alternative to steel, engineers
are seeking even greater
weight or cost savings from
glass and carbon reinforced
composite materials. While
thermoplastics work in many
instances, under-the-hood
parts exposed to corrosive
chemicals, high heat or heavy
structural loads may be
best made from engineering
thermosets.
One such application is the water pump.
Water pumps circulate coolant to
protect internal combustion engines
from overheating. Under-the-hood
temperatures greater than 200 °C can
quickly destroy engine parts designed
with inappropriate materials. Water
pumps must not only hold critical
dimensions and maintain their
mechanical properties at these high
temperatures, but also must withstand
the chemical impact of newer “long
life” coolants.
With this in mind, one automotive
customer was seeking alternative
materials for a water pump design that
would uphold performance, yet reduce
weight and cost. The incumbent material
was die cast aluminum. The following
data regarding the behavior of various
possible water pump housing materials
under circumstances similar to this
customer’s final application served as the
basis for the next generation production
design and material selection.
In Figure 1, flexural moduli were
measured for Bakelite® engineering
thermoset PF 6510 and Bakelite®
engineering thermoset PF 1110
reinforced with 30% glass fiber, as a
function of temperature. Comparisons
were made against values for a 50%
glass fiber reinforced polyphthalamide
(PPA) material and 40% and 60% glass
fiber reinforced polyphenylene sulfide
(PPS) materials.1 The results indicated
that the engineering thermosets resisted
high temperatures better than the other
material candidates.
Figure 1.
Flexural Modulus according to ISO:178 of Bakelite® PF 1110,
PF 6510 vs. Candidate Engineering Thermoplastic Materials at
Elevated Temperatures.
High Temperature Resistance
Under normal operating conditions,
typical engine oil and coolant
temperatures reach 120 °C. Surface
and ambient temperatures near the
engine can easily reach 200 °C for
extended periods of time, requiring
engineers to design with materials that
maintain their physical properties at
these higher temperatures.
Bakelite ® PF 1110
Bakelite ® PF 6510
Engineering PPA 30% GF
Engineering PPS 65% GF
Engineering PPS 40% GF
In addition to chemical resistance,
dimensional stability as a function
of time and temperature is critical to
water pump operation. Most pumps
rely on accurate movement and
precise clearances in order to function.
Materials with high thermal expansion
coefficients can exhibit interference and
premature wear.
Figure 2 demonstrates the dimensional
stability of Bakelite® engineering
thermoset PF 6510 after 3000 hours of
exposure to a coolant mixture at 120 °C.
Width and thickness remained nearly
constant for the engineering thermoset,
while total mass absorption was less
than 2.5%.
Figure 2.
Dimensional Stability (%) of Bakelite® PF 6510 in Long Life
Coolant at 120 °C, over 3000 h.
Relative dimensions [ % ]
105%
100%
Water pump components subject to
sustained loads are more likely to fail if
the creep strain exceeds design limits.
Internal component gears can slip as a
result of dimensional changes. Housings
and attachment locations can distort,
causing leaks, alignment issues, or
noise and vibration (NVH) problems.
Figure 3 shows the long-term creep
behavior of Bakelite® engineering
thermoset PF 6510, PPA, PPS and
AZ91 magnesium. Even at higher stress
loading, results indicate a superior,
low creep strain for the engineering
thermoset versus PPA and PPS. In fact,
the measured creep of the engineering
thermoset was low enough to make
threaded inserts in the water pump
housing unnecessary. Assembly screws
could be directly fastened into threaded
holes, reducing the part complexity and
the number of required assembly steps.
These results indicate that, compared
with alternative materials, the Bakelite®
engineering thermosets are more
resistant to the temperatures found
under the hood with today’s compactly
designed components; are more
resistant to long life coolant, even
without additional corrosion protection;
maintain their dimensions remarkably
well, making even parts with very low
tolerances feasible; and exhibit superior
creep strain properties. These findings,
Figure 3.
Creep Strain (%) according to ISO:899 of Bakelite® PF 6510
(72 MPa) vs. PPA (60 MPa) and PPS (30 MPa) at 120 °C,
over 1000 h.
1.4
1.2
[%]
Over time, long life coolants become
acidic and can deteriorate water pump
materials.1 Standard die cast aluminum
components must be protected by
post-treatment. Such post-treatment
is undesirable, though, as it may
contribute to cost, complexity and
environmental concerns.
Long-Term Creep Behavior
1.0
Creep Strain
Water Pump Material
Dimensional Stability in the
Face of Coolant and High
Temperature
0.8
0.6
0.4
0.2
0.0
0.1
1
10
100
log10 time t [ hours ]
1000
Bakelite® PF 6510 (72 MPa)
Engineering PPA 50% GF (60 MPa)
Engineering PPS 65% GF (30 MPa)
Magnesium AZ91 (50 MPa) estimate
summarized in Table 1, when combined
with cost and weight-savings data,
make Bakelite® engineering thermosets
an obvious choice for improved water
pump housings.
References
1
Messer, Curtis, Messer Moteren Werke,
Cooling Systems,
http://www.messermotorenwerke.com/
mechanicalPOP.htm, 2012
95%
90%
85%
80%
Width
Thickness
Mass
0[h]
1500 [ h ]
3000 [ h ]
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