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Delrin® Solution Series
Low Wear, Low Friction
Want your products to be more reliable, produce less noise and have
a longer lifetime? Delrin® has inherent low friction and good wear
properties that can make it happen.
Delrin® Solution Series | Low Wear, Low Friction
What’s Inside
Introduction........................................ 3
Delrin® and tribology........................... 4
Talking tribology................................. 5
Friction............................................... 6
Noise.................................................. 6
Understanding Delrin performance
and the working environment.............. 7
Why partner with Delrin? .................... 9
Appendix: Delrin grade
selection chart................................. 10
Delrin® Solution Series | Low Wear, Low Friction
Introduction
All these advantages add up to new opportunities in design,
manufacturing and finished part costs.
Working with Delrin® can give your products that extra
competitive edge, offering key benefits such as:
• Lightweighting
• Integral color
• Resistance to corrosion
and abrasion
• Reduced finishing time
• Self-lubrication
• Greater customer
satisfaction
• Reduced molding costs
Our team of experts will provide an unrivaled experience to help
you optimize your design and select the best grade of Delrin to
meet your needs. Delrin specialists will partner with your team
from initial concept to full production, providing all the material
advice and support you need along the way.
• Easier assembly
Figure 1.
Delrin low-wear, lowfriction grades in conveyor
chains allow for longer
lifetime, smooth sliding of
the conveyed goods, silent
(squeak-free) motions
and lubrication-free
operations.
Our team of experts will provide an unrivaled
experience to help you optimize your design and
select the best grade of Delrin to meet your needs.
Delrin® Solution Series | Low Wear, Low Friction
Delrin® and tribology
Problems with wear, friction or noise? You’re not alone—whenever
two surfaces slide, roll or rub against each other, they can
generate problems including worn surfaces, high-friction forces,
heat buildup or squeak.
• Squeaking noise can be reduced below the audible limit.
By choosing a grade with a low COF, Delrin parts can slide
against each other without generating an audible squeak.
Choosing Delrin is a good starting point for applications in
which wear and friction are design challenges. Standard Delrin
inherently has one of the lowest COFs and one of the lowest wear
rates when compared with other polymer types. Friction-modified
grades of Delrin take the benefits even further. While a PTFEmodified grade is shown in Figure 2, it’s just one of many options
for low-friction grades.
Delrin offers a wide range of internally lubricated or
wear-resistant resins to help solve these problems.
Wear-resistant and/or lubricated grades of Delrin acetal resin
bring added value to applications:
• Parts have longer lifetimes due to reduced wear. Higher
wear-resistant materials allow an increase of time before
the need to change a critical part, reducing downtime and
maintenance costs.
Delrin also offers outstanding mechanical properties including a
unique balance of strength, stiffness and toughness not available
in either metals or other plastics.
• Moving systems have higher efficiency due to less energy
lost through friction. A low Coefficient of Friction (COF)
between two sliding surfaces reduces the amount of energy
transformed into heat or noise instead of motion. With Delrin,
the motion becomes smoother and more efficient.
Delrin inherently has one of the lowest COFs and
one of the lowest wear rates when compared
with other polymer types.
• By selecting the right material combinations, the load-bearing
capacity is higher, and the sliding speed can be increased,
making the system more reliable and powerful.
Figure 2.
Typical wear rate vs. dynamic COF
of polymer types against steel
Source: DuPont
Specific wear rate [10-6 mm3/Nm]
• System costs can be reduced by eliminating any external
lubricant. Internally lubricated, also known as friction modified,
Delrin grades can avoid the need for greases and lubricants,
while guaranteeing consistent friction performance over the
lifetime of the parts.
1,000
ABS
PPO
PA66
PBT
PA612
PA6
POM
POM + 20% PTFE
0.05
0.1
0.15
0.2
0.25
0.3
Dynamic coefficient of friction, μ
0.35
0.4
Delrin® Solution Series | Low Wear, Low Friction
Talking tribology
Figure 3. Different wear mechanisms
Tribology is the science of wear, friction and lubrication and
how interacting surfaces behave in relative motion. Delrin® can
help with each of these common issues.
Adhesive wear
Wear
Wear is the progressive loss of material due to interacting
surfaces in relative motion. It is quantitatively measured as
the specific wear rate Ws (defined as volume loss per sliding
distance and load [10–6 mm3/Nm]) of a material. Numerous
distinct and independent mechanisms are involved in the wear
of a polymer.
Abrasive wear
Primary mechanisms include:
• Adhesive wear—loss of polymer by transfer and adhesion to
the countersurface due to frictional heating.
• Abrasive wear—cutting caused by hard irregularities on the
countersurface.
As shown earlier in Figure 2, Delrin has a lower wear rate than
other polymer families and can be further improved with lowfriction additives or Delrin® 100KM with DuPont™ Kevlar® fibers.
Tribology is the science of wear, friction and
lubrication and how interacting surfaces behave
in relative motion.
Delrin® 100KM is a high-viscosity grade made with
DuPont™ Kevlar® aramid fibers that exhibits low wear
and friction loss. It does not create an aggressive wear
medium like glass-fiber-reinforced materials as wear
starts to occur.
Specific wear rate [10-6 mm3/Nm]
10,000
1,000
Delrin® 500P after wear test
(test specimen)
Delrin® 500AL after wear test
(test specimen)
Delrin® 500P
Delrin® 500AL
Under equivalent test conditions, Delrin® 500AL shows very
little wear, and consequently, no wear track can be seen.
Figure 4.
Specific wear rate and wear track of Delrin® 500P and
Delrin® 500AL after moving against itself
Source: DuPont
Delrin® Solution Series | Low Wear, Low Friction
Friction
and/or to deformation of the contact area. In almost all
cases, a lower COF will lead to a lower wear rate.
Friction is a measure of the resistance to motion (loss of
energy) of two interacting surfaces. The friction is quantitatively
described by the COF (µ) which can be dynamic or static.
There are a number of low-friction modified grades available
to mitigate these issues.
The COF between surfaces normally rises with increasing
temperature and decreasing load. The energy lost due to friction
can lead to an increase in temperature, to the emission of noise
Delrin® Portfolio Category
Product
Description
High-viscosity
Delrin 100AF
20% PTFE fibers
Delrin 100AL
Advanced lubrication
Delrin 100ALE
Advanced lubrication, low emissions
Delrin® 500AF
20% PTFE fibers
Delrin® 520MP
20% PTFE micropowder
Delrin® 500CL
Chemical lubricant
Delrin® 500AL
Advanced lubricant
Delrin® 500SC
Silicone lubricant concentrate
®
®
®
Medium-viscosity
Noise
Friction is a measure of
the resistance to motion
(loss of energy) of two
interacting surfaces.
Sound pressure level [dB(A)]
In many applications where a part is sliding, the noise emitted by
the system is undesired and has to be reduced. Noise is a difficult
concept to define and therefore it is important to distinguish the
two main types of noise which are encountered.
• Mechanical noise is in fact not related to friction but to the
impacts between moving parts. However, in the case of
high-frequency movements, this type of noise can sound like
squeaking. An improved design (e.g., of teeth in gears) can
often reduce noise intensity.
Another solution is to use a toughened material that has better
damping properties.
Delrin® 500P
• Squeaking is generated through friction and can therefore be
linked to the COF value. As a general rule, one can say that if
the dynamic COF is higher than the static one, the movement
between the two surfaces can get discontinuous (slip-stick
phenomenon). The noise is perceived as squeaking when this
slip and stick happens at an audible frequency. Selecting a
friction-modified Delrin allows you to run Delrin against itself
without creating an audible squeak.
Delrin® 500AL
Figure 5.
Squeaking noise is measured for Delrin® 500P
sliding against Delrin® 500P or Delrin® 500AL.
Sound pressure level is reduced from 83dB(A)
to 24dB(A), which is below the audible threshold.
Source: DuPont
Delrin® Solution Series | Low Wear, Low Friction
Understanding Delrin® performance
and the working environment
Selecting the best grade of Delrin
The intrinsically good wear resistance and frictional behavior
of Delrin often means that the standard grade can be used
without any internal or external lubrication. However, depending
on needs and technical requirements, some customers
may need to further improve on Delrin properties with other
technologies (PTFE, silicone, DuPont™ Kevlar® aramid resin,
chemical lubrication, etc.), to reduce wear or friction.
Working environment has perhaps the strongest influence on
friction, wear and noise.
The main factors to consider are:
• Contact pressure (p) and contact force (load) at the surfaces
• Relative velocity of the surfaces (v)
Choosing the perfect grade for your project may seem
intimidating, but classifying them according to wear rate (Ws)
and dynamic COF (µ) can help. It’s also important to carefully
control all other parameters like countersurface, sliding velocity,
contact pressure, test method and environmental conditions.
• The countersurface
Additional considerations include:
• Temperature of the surfaces
• Geometry of motion (sliding, fretting, rolling)
Low-wear/low-friction grades of Delrin are classified in the graph
below according to their specific wear rate and COF measured
against either a steel countersurface or against a countersurface
made in the same grade of Delrin (i.e., against itself).
• Nature of the motion (continuous, intermittent,
reciprocating, etc.)
• Lubrication (initial, continuous, dry-running, moisture)
Selecting a Delrin grade for an application requires a detailed
understanding of the tribological system. Standardized tests
can give indications of the relative wear rates of polymers,
but prototype testing is an essential stage in application
development.
Figure 6. Wear rate vs. dynamic COF
Blue: Delrin against
itselfViscosity Grades
Medium
Orange: Delrin against steel
High Viscosity Grades
Source: Delrin
10,000
Specific wear rate [10-6 mm 3/Nm]
Specific wear rate [10-6 mm 3/Nm]
Choosing the perfect grade for your project
may seem intimidating, but classifying them
according to wear rate (Ws) and dynamic
COF (µ) can help.
1,000
100TL
100 + 5% 500SC
100KM
100AF
100AL
100 + 5% 500SC
100AL
100AF
0.1
0.15
0.2
100KM
0.25
0.3
0.35
10,000
500P
500CL
1,000
500TL
500 + 5% 500SC
500AF
500AL
0.15
0.2
0.1
0.4
Dynamic coefficient of friction μ
520MP
500 + 5% 500SC
500TL
520MP
500CL
500AF
0.25
0.3
500P
0.35
Dynamic coefficient of friction μ
High-viscosity grades
Medium-viscosity grades
Specific wear rate and COF against steel and against
itself for Delrin acetal high-viscosity grades
Specific wear rate and COF against steel and against
itself for Delrin acetal medium-viscosity grades
0.4
Influence of pressure (p) and sliding velocity (v)
Figure 6 not only shows the effect of the different technologies
on wear rate and COF but also the effect of the countersurface.
Pressure (p) and sliding velocity (v) have a strong influence on the
wear rate of a material. An increase in pressure generally leads to
an increase in the wear rate and a decrease in friction, whereas
an increase in sliding speed results in an increase in both wear
and friction. Pv is often used to describe the severity of a wear
situation since, at a given temperature, it is roughly proportional
to the wear rate.
The nature and finish of the countersurface strongly affect wear
and friction. Two parameters that define the finish of a surface and
which can easily be controlled are its roughness and its hardness.
• Generally, the harder the metal surface, the better the wear and
friction behavior of the system
• The rougher the metal countersurface, the higher the wear
The very strong influence of pressure and speed on wear, as
well as the improvements which can be achieved in this respect,
are shown in Figures 7 and 8. The specific wear rate has been
measured against steel at different combinations of speed and
pressure. The graphs clearly demonstrate that the wear rate not
only depends on the pv, but also if this pv is composed by high
pressure/low speed or low pressure/high speed.
Against steel, the wear rate, as well as the COF of unmodified
Delrin®, is much lower compared to the values measured
against itself.
The use of different ingredients, however, makes it possible to
close the performance gap and therefore open the possibility of
using Delrin against other Delrin surfaces.
Figures 7 and 8 have the same axis for wear rate so that the
advantage of a low-friction grade can be easily quantified.
Figure 8.
Specific wear rate of
Delrin® 520MP against
steel at different
pv (method thrust
washer)
Source: DuPont
0.32
0.1
0.107
0.035
Specific wear rate [10-6 mm3/Nm]
Fig. 8
0.32
0.1
0.172
0.104
0.107
0.035
Specific wear rate [10-6 mm3/Nm]
Source: DuPont
0.4
Pv [MPa x m/s]
Lorem ipsum
0.32
0.1
0.435
0.276
0.172
0.104
Pv [MPa x m/s]
v [MPa x m/s]
Lorem ipsum
0.07
0.035
Velocity [m/s]
Figure 7.
Specific wear rate of
Delrin® 500 against
steel at different pv
(method thrust washer)
Fig. 8
Velocity [m/s]
Specific wear rate [10-6 mm3/Nm]
The graphs clearly demonstrate that the wear
rate not only depends on the pv, but also if this
pv is composed by high pressure/low speed or
Fig. 7
low pressure/high speed.
Velocity [m/s]
Delrin® Solution Series | Low Wear, Low Friction
Delrin® Solution Series | Low Wear, Low Friction
Why partner with Delrin®?
There are many factors to consider when designing products
that have running surfaces.