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Delrin®
Acetal resins
Design with Delrin®
Start
with DuPont
Engineering Polymers
® D
uPon
t’s r
egis
tere
d tr
adem
ark
▲ ▲ ▲
Do You Speak Delrin®?▲▲
Introduction
Outstanding Attributes
List of Grades
Low Wear, Low Friction Series
Key Properties Table
Stiffness & Strength
Creep Resistance
Stress Relaxation
Fatigue Resistance
Impact Resistance
UV Resistance
Temperature
Chemical Resistance
Typical Applications
Radii
Uniform Wall Thickness
Ribs
Bosses
Threads
Snap Fits
Rapid Prototyping
Stockists/Machinists
Colours
Processing
Regrind & Recycling
Laser Marking
Medical Applications
Further Reading
Design Basics
Performance
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‘Design with Delrin®’Data at your fingertips
Delrin®
Acetal resins
Design
with
Delrin®
Start
with DuPont
Engineering Polymers
® D
uPon
t’s r
egis
tere
d tr
adem
ark
▲ ▲ ▲
Do You Speak Delrin®?
▲▲
Introduction
Outstanding Attributes
List of Grades
Low Wear, Low Friction Series
Key Properties TableStiffness & Strength
Creep Resistance
Stress Relaxation
Fatigue Resistance
Impact Resistance
UV Resistance
Temperature
Chemical Resistance
Typical ApplicationsRadii
Uniform Wall Thickness
Ribs
Bosses
Threads
Snap Fits
Rapid Prototyping
Stockists/Machinists
Colours
Processing
Regrind & Recycling
Laser Marking
Medical Applications
Further Reading
Samples
Design Basics
Performance
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& Strength
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This handbook makes basic information easily available todesigners and others and gives a quick reminder of theimpressive range of Delrin®
properties.
It is illustrated with a selectionof photographs showing someof the enormous variety ofapplications for which Delrin®
has already been successfullyused.
Use the colourcoded bars to helpyou ‘flick’ through tothe relevant sectionand data
‘Design with Delrin®’
Back to index
Delrin® versatility: snap fits to ski bindings, clips to conveyors,buckles to bicycle parts
Designers – use simple rules
to get the best from Delrin® in
“Design Basics”
View applications
throughout this binder
. . .Do you speak Delrin®? Are you as fluent as youwould like to be?
. . .Are you up to speed withall the new grades includingLow Wear, Low Friction, UVResistant and the ElevenSeries?
. . .Do you know whereDelrin® is used – and why?Have you heard of Delrin®
but don’t know what it feelslike?
. . .This Delrin® “phrase book”will help you brush up onyour acetal knowledge until itbecomes your first language.
Delrin® has a unique blend of
properties – understand them in
“Performance”
▲▲
Do You Speak Delrin®?▲
This publication is also available at http://www.dupont.com/enggpolymers/europe
127UV High viscosity, best UV527UV Medium viscosity, best UV927UV Low viscosity, best UV1727UV Very low viscosity, best UV107 High viscosity, UV507 Medium viscosity, UV
The natural lubricity of Delrin® means it may be found unlubricated in many gear and bearing applications
Choosing Delrin® is a good starting point for applications inwhich wear and friction are majorissues. Unmodified Delrin® haslow friction and wear against steelas can be seen from the chartbelow.
THE FACTORS AFFECTINGWEAR AND FRICTION ARE:* Pressure of contact* Relative velocity* Temperature* Geometry of motion* Frequency of motion* Nature and finish of surface
* Lubrication
For metal as acounter surface,
the harder the surface the better the wear and
friction behaviour of the system.
Aim for a hardness of greater than
50 HRc
1000
100
10
1
0.00 0.10 0.20 0.30 0.40
P R O T O T Y P E T E S T I N G I S I M P O R T A N T
Please refer to the grades list for details of Low Wear, Low Friction Resins
When two parts are in contact in a wearsituation it is normal to choosedissimilar materials (eg Delrin® acetaland Zytel® nylon). Factors such asdimensional stability may make such achoice impossible, in which case thenew Low Wear, Low Friction gradesof Delrin® may be suitable. The tablebelow shows the improvement inwear and friction compared tostandard grades.
0.10 0.20 0.30 0.40
Spec
ific
wea
r ra
te(1
0-6 m
m3 /N
m)
New Grades
●900SP
StandardGrades
100P●
10000
100
1000
10
1
Countersurface
= Delrin®
Quieter too!Certain grades reduce noise(squeak) dramatically comparedwith standard grades
The exceptional elongation coupled with stiffness makes Delrin® suitable for snap fits
To judge the stiffness and springiness of Delrin® ask your nearest DuPont Engineering Polymers office for test bar samples.
The modulus of Delrin® isaffected by changes in thetemperature as shownbelow.
3
2
Temperature (°C)
Youn
g’s
mod
ulus
(G
Pa)
1
0 —20 0 20 40 60 80 100
The mechanical response to short term loads
is shown above
Strain (%)
Str
ess
(MPa
)
20
0 0 2 4 6 8 10
40
60
80
-20°C 23°C
90°C
Material chosen and whyDelrin® 100 was chosen for its unique balance of stiffness and strength
Description/ApplicationSnap fit buckle
18 19
P E R F O R M A N C E
Stiffness and Strength
Young’s modulus of Delrin®
as a function of temperature
Stress v Strain at –20°C,23°C and 90°C
Back to index
P E R F O R M A N C E
Upon removal of a 14 MPa deforming stress, Delrin® immediately recovers 40% of the imposed strain
Creep is defined as time dependentstrain, resulting from stress.
Str
ess
(M
Pa)
20
15
10
5
00 0,5 1,0 1,5 2,0 2,5
I s o c h r o n o u s s t r e s s / s t r a i nD e l r i n® 1 0 0 @ 2 3 ° C
1h10
h10
0 h
1000
h50
00 h
1000
0 h
Total strain (%)
Creep
Always try to design partsso that they arenot permanentlyloaded
The factors affecting creep are:*Stress level*Time*Temperature
Material chosen and whyDelrin® 100 was chosen for its good spring characteristics and superior creep
compared with polyamide, polypropylene and acetal copolymer
Description/ApplicationClothes peg
20 21
100
000
h
(proje
cted) Delrin® Acetal Resins
have extremely goodcreep resistance for anunreinforced polymer
Back to index
P E R F O R M A N C E
Stress free mouldings may be obtained by annealing Delrin®
at 160°C for 45 mins
Stress relaxation is defined asdecrease of the stress required to
maintain constant strain.
% o
f in
itia
l st
ress
100
80
40
20
10
0,01 0,1 1,0 10 100 1000 10000
Te n s i l e s t r e s s r e l a x a t i o n o fD e l r i n®1 0 0 a n d 5 0 0 @ 2 3 ° C
Hours
Stress relaxation
Strain 0,3%. 17 MPa0,9%. 34 MPa
5%. 66 MPa
12,5%.Yield point strain 69 MPa
Stress relaxation is particularlyimportant whenconsidering press-fit assembly
Material chosen and whyDelrin® 100P was chosen for its good friction properties and a balance of
impact and creep resistance with high dimensional stability
Description/ApplicationCar window guides
22 23
Back to index
P E R F O R M A N C E
Delrin® Acetal Resins have extremely high resistance to fatigue failure from –40°C to +80°C
Fatigue
When materials are stressed cyclically at high levels of stress in relation to their tensile strength,they tend to fail at levels of stressbelow their ultimate tensilestrength.
This phenomenon is termed “fatigue failure.”
Str
ess
(M
Pa)
50
40
30
20
10
0103 104 105 106 107
C y c l e s t o f a i l u r e
Fatigue failure stress of Delrin®compared withother plastics106 cycles, 23°CMaterial Stress
Material chosen and whyDelrin® 100 was chosen for the best balance of stiffness and strength coupledwith flex fatigue resistance needed for the spring fingers of the tool gripper
Description/ApplicationTool changer carousel
24 25
Back to index
P E R F O R M A N C E
Delrin® acetal maintains its high toughness down to very low temperatures
Impact resistance is definedas the ability to withstand asudden blow rather than aslowly applied load.
Impact Resistance
60
Charpy Impact Strength (23°C)
Impa
ct s
tren
gth,
kJ/m
2
500 500T 100 100T 100ST
50
40
30
20
10
0
20
15
10
Temperature, °C
Impa
ct s
tren
gth,
kJ/m
2
5
0
R
-40 -20 0 20 40 60
Izod Impact v Temp Delrin 100
See also Effect of Radii in‘Design Basics’
▲
Description/ApplicationRollerblade brake
Material chosen and whyDelrin® 100ST was chosen for the best combination of stiffness and
impact resistance at low temperature, combined with good mouldability
2726
Back to index
P E R F O R M A N C E
The Delrin® UV family of resins are well suited for sporting goods and otheritems which are used outdoors but stored indoors
Acetal resins, like mostpolymers, are affected bylight, particularly sunlightwhich includes ultra-violetradiation of wavelength290-400 nm.
UV Resistance
R
Exposure, kJ/m2
Rel
ativ
eG
loss
0
1,0
0,5
500 1000
x27UV BK
x07 BKx00 BK
Exposure, kJ/m2
Rel
ativ
eTe
nsile
Stre
ngth
0
0,5
500 1000
UV Stabilised
Standard
1,0
Accelarated Interior Weatheringaccording to SAE J-1885
Coloured Delrin® resinsoffer some UVprotection. High levelsof carbon black act asan effective UV screenfor non-critical outdoorapplications
Typical values for Delrin® grade 527UV compared with other grades.
Material chosen and whyDelrin® 127UV was chosen for its excellent balance of mechanical
properties combined with good UV resistance
Description/ApplicationMoped brake lever
29
Colours
▲
28
Back to index
P E R F O R M A N C E
The thermal stability ofDelrin® means it finds use in applications from –50°C to +90°C
The highly crystallinenature of Delrin® means it is suitable for short-termexposure to temperaturesclose to the melting pointof 177°C.
Delrin® like many plastics, is notch-sensitive but unlike other resinsit has high impact strength at low temperatures
Str
ess
Fac
tor
R/T
Radii use of radii has three main functions* Reduces notch effect * Helps material flow* Eases ejection frommould
see also
ImpactPerformace
▲
Always use radii
at rib junctions
and stressed areas
but also consider
thread terminations,
knurled inserts and
surface textures
Material chosen/Design commentDelrin® 111P was chosen for this application. Radii lowers stress
concentration when parts are put under load
Description/ApplicationSpring clips
38 39
0 0,2 0,4 0,6 0,8 1,0 1,2 1,41,0
1,5
2,0
2,0
Usual
P = Applied LoadR = Fillet RadiusT = Thickness
P
T
R3,0
Back to index
Even wall section will greatly benefit highly crystallinepolymers such as Delrin®
Even wall thickness
gives:
* Even shrinkage
– less distortion
* Even set-up
– quickest moulding
cycle
* Less material
– low cost
Choosing the correct wallthickness for a moulded partis a function of end useconstraints (what does thepart have to do?), moulding factors, (what is the thinnestsection that can be moulded?)and overall cost.
The exact thickness may beestimated by the use of FiniteElement Analysis (FEA) usedin both part design and flowanalysis, but where possibleshould be relatively constant throughout.
D E S I G N B A S I C S
Uniform Wall Thicknesses
Description/ApplicationRatchet mechanism
Material chosen/Design commentDelrin® 500P. Low distortion and cost efective part ensured
by use of even wall thickness
40 41
Back to index
If ribbing is unacceptable, Delrin® 510GR and 525GRoffer significant increase in stiffness
Ribs are an effective way
to improve the rigidity of
moulded parts.
For Delrin®, ribs should be
1/2 to 2 /3 the general wall
thickness, with 1/4° to
1/2°draft angle per side.
Sink marks caused byribs may be hidden
by use of textured surface orsuitable interruption in thearea of the sink.
D E S I G N B A S I C S
Ribs
Proper use of ribs will:
* Save material and weight
* Shorten moulding cycle
* Eliminate voids in thicksections
Description/ApplicationCross beam
Material chosen/Design commentDelrin® 100P enables increased stiffness to be achieved by
use of ribs without compromising surface finish
42 43
Back to index
Weld lines should be avoided in bosses. Delrin® being generallyunreinforced, has excellent weld line strength
D E S I G N B A S I C S
Bosses are used for
mounting purposes or for
reinforcement around holes.
As a rule the outside
diameter of a boss should be
2 to 3 times the hole
diameter.
Heavy sections may be
avoided by stepping the boss
off the adjoining wall.
Use radii at all junctions.
Always use screws designed forplastics when consideringassembly. These may be singleor twin-start threaded ortrilobular screws. Repeatedassembly and disassembly ispossible with Delrin®.
Bosses
Boss Design
***
Hole dia = 0,75 x nominaldia of screw
Boss dia : 2 to 3 times hole dia
Hole depth 2 x nominalscrew dia minimum
Description/ApplicationFuel flange
Material chosen/Design commentDelrin® 511P. Boss and linking rib design
provides accurate hole centres
4544
Back to index
D E S I G N B A S I C S
When required, threads maybe automatically mouldedinto the part, eliminating theneed for mechanical thread-forming operations.For external threads, it maybe possible to locate theparting line on the centre ofthe thread.For internal threads, anautomatic unscrewing deviceis used in the tool.
To avoid ‘squeak’ on heavilyloaded threads, consider theLow Wear, Low Friction gradesof Delrin®
Use of a buttress
type thread will
avoid unnecessary
radial forces on
the mating part
Correct termination of threads
▲
The dimensional stability ofDelrin® makes it very suitable for the moulding of accurate thread forms
Threads
Description/ApplicationIndustrial valve
Material chosen/Design commentDelrin® 500P. Moulded thread form avoids machining
4746
1mm
Round threads
Back to index
The combination of stiffness and elongation makesDelrin® very suitable for snap fits
L
R
D E S I G N B A S I C S
Snap Fits are a cost effectiveway of assembling partstogether without the use ofspecial tools.
Usually the parts are at restbefore and after assemblyand pass through a stressedcondition as the snap fit ismade to work.
With Delrin®, a single use snapfit may be stressed up to 8%strain (Delrin® 100). For afrequently used one refer tothe fatigue stress graph
Snap Fits
Delrin® is also excellent forcircular and spherical snapfit designs
Cantilever Snap Fits
***
Make ‘L’ as long
as possible
Taper snap fit lug
Use radii at root
▲
Description/ApplicationCable guide
Material chosen/Design commentSnap fit in Delrin® 500 gives strong, rattle-free connection
48 49
Back to index
Prototyping tipsKeep heat generatedduring machining to aminimum
Support thin wallsand long partsBe aware of the notcheffect of machiningparts
R A P I D P R O T O T Y P I N G
Delrin® has excellent machining characteristics using conventional tools
In order to test parts in the actualmaterial it is normally necessaryto mould them. Due to the easeof machining of Delrin®, it maybe possible to prototype partsby NC machining, utilising theCAD data which describesthe part geometry.
ModifyGeometry
Mould Parts
7
5a
*
*
*
Delrin®
stockists/machinists
▲Shoehorn prototype
CNC machining of simple shapes possible in Delrin®
50 51
CAD Data
1
Test Parts
5
NC MachineMould Tool
6
Hand Finish
4
Create Tool
Paths
Machine Stock Shapes(Block, Rod)
32
Back to index
S T O C K I S T S / M A C H I N I S T S
Details of companies experienced in machining Delrin® acetal resinsare also available from your DuPont representative
Contact your DuPont representative for detailedinformation on your local Delrin® stockist
Rod stock, slab
Always ask for Delrin® by name
52 53
Back to index
C O L O U R S
No heavy metals are used in Delrin® Colours
Typical referencecodes for
Delrin® colours
I d e a l l y a n y m a s t e r b a t c h s h o u l d b e a c e t a l b a s e d
NC = Natural
BK = Black
WT = White
GY = Grey
GN = Green
BL = Blue
YL = Yellow
RD = Red
Pigmentsmay affectshrinkage –test first!
Custom colours areavailable as fully
compounded productfrom DuPont or bymasterbatch from pigment suppliers
S h r i n k a g e v. C o l o u r
NC
WT
YL
BK
BL
GY
RD
GNCOLOUR
SHR
INK
AG
E(%
)
2,1
2,0
1,9
1,8
Delrin® The heart of a good product
54 55
1,7
Back to index
For specific processing information ask for the free booklet‘Delrin® Moulding Manual’
The most important variablesin producing good parts by
injection moulding are:
Above all, a good qualityhomogeneous melt is required.
* Melt temperature
* Injection speed
* Hold pressure
* Screw forward time
* Mould temperature
Always dry toughened gradesfor 4 hours at 80°C
P R O C E S S I N G
Melt Temp(°C)
215 90 100 8 30 1,9 - 2,2
MouldTemp(°C)
HoldPressure
(MPa)Hold PressureTime (s/mm)
Max Hold Up Time
(min)Shrinkage
(%)
Typical set-up conditions forDelrin® 100 are shown below.
Material chosen and whyDelrin® 927UV was chosen for its excellent mouldability and impact resistance.
Its resistance to UV and easy colourability are additional assets
Description/ApplicationVenting system grille
5756
Grades based on the ‘P’ stabilisation system are suitablefor hot runner tools,these include
It is important to use analytical techniques in part design to reduce the impact of recyclate on the environment
RECYCLING
The combination of
stiffness and elongation
that makes Delrin® so
effective in snap fits also
means that parts may be
disassembled prior
to recycling.
The long term stability
of Delrin® means that
parts may be reground
and remoulded with
little effect on
properties.
Incineration is an energy
efficient alternative
>POM<
Description/ApplicationGolf tee
Material chosen and whyDelrin®100 regrind was chosen for the shank. Capable ofwithstanding high impact, it provides the correct rigidity
5958
REGRIND
Up to 25% of properlyground sprues and runners may be mixedwith virgin resin with little or no effect onmechanical properties.Toughened grades willneed to be dried priorto moulding.For glass reinforcedgrades, use a slow speedon the grinder rotor.
Back to index
L A S E R M A R K I N G
See also Delrin® colours
Laser marking is particularly suitable when
the batch sizes are small and marking variability is required
(e.g. serial numbers or different languages).
. . .BK-L01 Black
. . .BL-L01 Blue
. . .BN-L01 Brown
. . .GN-L01 Green
. . .GY-L01 Grey
. . .RD-L01 Red
. . .WT-L01 White
Advantages* High rate contactlessprocess
* Flexibility, easy changeof layout and charactertype
* No surface pre-treatment,no solvent, no ink* High durability of themarking
A range of colours specially optimised for laser marking is available in Delrin®.Tested with severalNd:YAG lasersystems, thesecolours provide highcontrast markingswith almost noengraving
LASER = Light Amplification by
Stimulated Emission of Radiation
Colours for laser marking 500LM ...
▲Material chosen and whyDelrin® 500LM BK-L01 was chosen for its clarity of laser marking
plus its mechanical properties
Description/ApplicationSki adjuster
6160
Back to index
M E D I C A L A P P L I C AT I O N S
Delrin® acetal resin is notcertified for implants
Do not use DuPont materials in medicalapplications involving
permanent implantation in thehuman body or permanentcontact with internal body
fluids or tissue.
Do not use DuPont materials in medical
applications involving brief ortemporary implantation in thehuman body or contact withbody fluids or tissues unless
the material has been provideddirectly from DuPont under a
contract which expresslyacknowledges the
contemplated uses.
For food contact or pharmaceutical
applications, regulatorycompliance statements are
available, please contact your local DuPont
representative fordetails.
DuPont makes norepresentation, promise,express warranty or impliedwarranty concerning thesuitability of these materialsfor implantation in the humanbody or in contact withinternal body fluids or tissues.
✠CAUTION
✚
Description/ApplicationMedical tube clip
Material chosen and whyDelrin® 500P was chosen for its chemical resistance and springiness
6362
Back to index
F U R T H E R R E A D I N G
The general brochure covering all DuPont engineering polymersis called ‘From concept to commercialisation’
To access furtherinformation concerningany topic covered in this
binder, please contactyour local DuPont office
Access information onDelrin® at our internet
address:http://www.dupont.com/
enggpolymers/europe
Delrin® Product guide and properties
DesignInformation
MouldingManual
Main Literature for Delrin®
▲▲
▲
▲
DuPont has a wide
selection of literature
covering specific
application areas
such as Appliances,
Automotive, Electrical,
Furniture etc.,
together with a
General Design Principles
handbook which covers all
DuPont engineering resins
Technical Information
A wealth of experience available in various formats64 65