Engineering plastics – The Manual - F.wood-supply.dk

H
C O
H
POM-C
H
C O
H
H
C O
n
H
H H
C C O
l
m n
H H
POM-C Structural formula POM-C
l and m statistically distributed
POM-H Structural formula POM-H
H
C O
n
H
H H
C C O
l
m n
H H
• Stress [MPa]
100
80
60
40
PPSU
PPSU
20
H H
C C
0
n
0 H 10 20 30 40
50
• Strain [%]
TECAFORM AD
TECAFORM AH
H H TECAFORM AH
TECAFORM PS AD
C C
n
H
O
O
S
O
S
n
O
O
O
O
O
S
S
n
O
O
POM-H
PS
H H
TECAFORM
C
C
n
H CH 3
CH 3
O
C
O S
CH 3 O
O n
N
N
m
m
PP
POM H (DIN H designation)
C C
The different n designations polyacetal, polyoxymethylene or
H CH 3
polyformaldehyde (POM) are customary terms to describe
the same polymer in different languages. POM is a thermoplastic
produced by the polymerization of
PP
formaldehyde.
Two typical groups of polyacetals exist: homopolymers
CH 3
(POM-H / TECAFORM AD) and copolymers (POM-C /
O
n
TECAFORM AH). Both differ in terms of their manufac-
CH 3
turing process. Although their properties are very similar,
they do demonstrate a number of typical differences.
PPO > CH PPE? 3
O
Properties
n
CH
ˌˌHigh 3
crystallinity
ˌˌRelatively high density
PPO > PPE?
ˌˌGood degree of toughness, also in
the low temperature range
ˌˌHigh strength, hardness and spring stiffness
ˌˌVery good sliding friction properties,
S
n
abrasion-resistant, anti-adhesive
ˌˌHigh chemical resistance, especially
PPS
to alkalis, solvents and fuels
ˌˌGood thermal stability
S
n
ˌˌLow moisture absorption
ˌˌGood dimensional stability
PPS
ˌˌVery low dielectric constant
PSU
Values
CH 3
O
C
O TECAFORM S AD TECAFORM O AH
CH (POM-H)
n
(POM-C)
3 O
T g –60 °C –60 °C
Density PSU
1.43 g/cm 3 1.41 g/cm 3
Modulus of elasticity 3,600 MPa 2,800 MPa
Service temperature, long-term 110 °C 100 °C
F F
Service temperature, short-term 150 °C 140 °C
C C
n
Lower service temperature
F F
–50 °C –50 °C
PTFE
Identifying characteristics
F F
ˌˌColour white, C C slightly opaque,
n
slightly translucent F F at the edges
ˌˌHigh flammability
PTFE
ˌˌBurns with a feint blue flame with yellow tip,
produces droplets and continues to burn
ˌˌMinimal or no sooting
H F
ˌˌTypically Cgives C off pungent odour of
n
formaldehyde H F on thermal decomposition
ˌˌHigh density, sinks in water
PVDF
ˌˌSlightly waxy feel
H F
ˌˌQuickly destroyed C C in mineral acids
n
ˌˌMuffled sound H F on impact
PVDF
18