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Material Selection Guide

Plastics are increasingly being used to replace other materials like bronze, stainless steel, aluminum and ceramics. The most popular reasons for switching to plastics include:

  • Longer part life
  • Elimination of lubrication
  • Reduced wear on mating parts
  • Faster operation of equipment/line speeds
  • Less power needed to run equipment
  • Corrosion resistance and inertness
  • Weight reduction

With the many plastic materials available today, selecting the best one can be an intimidating proposition. Here are guidelines to assist those less familiar with these plastics.

  • Step One
  • Step Two
  • Step Three
  • Step Four
  • Step Five
  • Step Six
  • Step Seven

Determine whether the component is a:

  • Bearing and Wear Application (i.e., frictional forces) OR
  • Structural (static or dynamic) Application

Determining the primary function of the finished component will direct you to a group of materials. For example, crystalline materials (i.e., Nylon, Acetal) outperform amorphous materials (i.e., Polysulfone, Duratron®  PEI or Polycarbonate) in bearing and wear applications. Within the material groups, you can further reduce your choices by knowing what additives are best suited to your application.

Wear properties are enhanced by MoS2, graphite, carbon fiber and polymeric lubricants (i.e., PTFE, waxes).

Structural properties are enhanced by reinforcement fibres like glass or carbon.

Once you have determined the nature of the application (B&W or Structural), you can further reduce your material choices by determining the application's mechanical property requirements. For bearing and wear applications, the first consideration is wear performance expressed in PV and"k" -factor. Calculate the PV (pressure (psi) x velocity (m/min) required. Using Figure 1, select materials whose limiting PV's are above the PV you have calculated for the application. Further selection can be made by noting the "k" wear factor of your material choices. In general the lower the "k" factor, the longer the wear life of the material.

Structural components are commonly designed for maximum continuous operating stresses equal to 25% of their ultimate strength at a specific temperature. This guideline is meant to compensate for the viscoelastic behavior of plastics that result in creep. Isometric stress-time curves are provided here to help you characterize a material's strength behavior as a function of time at both room temperature (Figure 2) and at 150 °C (300 °F) (Figure 3).

Additional Information on Material Performance

·Flammability Performance

Engineering Plastics are more or less flammable. Their flammability depends on the chemical structure, the fillers and additives, the environment - rich in oxygen or not, the ambient temperature, the part geometry, the presence or not of the ignition source, ect. Through the action of fire, certain polymers burn easily, others with difficulty or even not at all.

  • Classification* according to UL94 
  • Oxygen Index (ISO 4589)
    The Oxygen Index is certainly one of the most relevant tests, easy to reproduce. The test consists of measuring the critical oxygen concentration in a mixture O2 - N2, allowing inflammation under defined conditions. If the Oxygen index is lower than 21%, the material will burn easily in air after removing the ignition source. The higher the Oxygen index, the more difficult the material will ignite.

 

Classification*

according to UL94

Thickness

3.0 mm      6.0 mm

Oxygen index
ASTM D 2863
ISO 4589

Ertalon® 6 SA

HB

HB

25

Ertalon® 66 SA

HB

HB

26

Ertalon® 66 SA-C

HB

HB

24

Ertalon® 4.6

HB

HB

24

Ertalon® 66-GF30

HB

HB

-

Ertalon® 6 PLA

HB

HB

25

Ertalon® 6 XAU+

HB

HB

25

Ertalon® LFX

HB

HB

-

Nylatron® MC 901

HB

HB

25

Nylatron® GSM

HB

HB

25

Nylatron® NSM

HB

HB

-

Nylatron® GS

HB

HB

26

Ertacetal® C

HB

HB

15

Ertacetal® H

HB

HB

15

Ertacetal® H-TF

HB

HB

-

Ertalyte®

HB

HB

25

Ertalyte® TX

HB

HB

25

PC 1000

HB

HB

25

Duratron® PBI

V-0

V-0

58

Duratron® T4203 PAI

V-0

V-0

45

Duratron® T4301 PAI

V-0

V-0

44

Duratron® T5530 PAI

V-0

V-0

50

Ketron® PEEK-1000

V-0

V-0

35

Ketron® PEEK-HPV

V-0

V-0

43

Ketron® PEEK-GF30

V-0

V-0

40

Ketron® PEEK-CA30

V-0

V-0

40

Techtron® HPV PPS

V-0

V-0

47

Quadrant® PPSU

V-0

V-0

44

Duratron® U1000 PEI

V-0

V-0

47

Quadrant® PSU 1000

HB

HB

30

Symalit® PVDF 1000

V-0

V-0

44

Fluorosint® 500

V-0

V-0

-

Fluorosint® 207

V-0

V-0

-

Semitron® ESd 225

-

HB

< 20

Semitron® ESd 410C

V-0

V-0

47

Semitron® ESd 500HR

V-0

V-0

-

Semitron® ESd 520HR

V-0

V-0

48

Note: These mostly estimated ratings, derived from raw material supplier data, are not intended to reflect hazards presented by materials under actual fire conditions.

 

·Outgassing

In 1995, a number of Quadrant Engineering Plastic Products materials were tested according to the European Space Agency (ESA)-specification PSS-01-702 ("A thermal vacuum test for the screening of space materials"). Samples were heated to 125°C for 24 hours (Method "A"), collector plates kept at 25°C and the testing carried out in a vacuum of 10-3 P.

 

TML (%)

RML (%)

CVCM (%)

Ertalon® 66 SA

1.3

0.17

0.002

Ertalon® 6 PLA

1.5

0.06

0.005

Ertacetal® C

0.34

0.13

0.016

Ertacetal® H

0.47

0.24

0.005

Ertalyte®

0.33

0.2

0.005

Ertalyte® TX

0.25

0.03

0.003

Duratron® PBI

2.2

0.84

0.014

Symalit® PVDF 1000

0.05

0.02

0.006

Duratron® T4203 PAI

1.9

0.93

0.007

Duratron® T4301 PAI

1.4

0.42

0.018

Ketron® PEEK-1000

0.26

0.03

0.003

Ketron® PEEK-HPV

0.16

0.02

0.003

Techtron® HPV PPS

0.06

0.02

0.003

Duratron® U1000 PEI

0.82

0.32

0.002

Quadrant® PSU 1000

0.49

0.09

0.002


TML = Total Mass Loss
RML =  Recovered Mass Loss
CVCM = Collected Volatile Condensed Material

·Steam Sterilisation

Steam sterilization is commonly used in the medical industry for sterilizing all kinds of reusable equipment, devices, instruments, trays, ect. and is conducted in a pressurized vessel that allows the presence of superheated saturated steam. The main purpose of sterilization is to kill all viable micro-organisms on a certain part.     

Tests in which the effect of repeated steam sterilization on the charpy notched impact strength was measured according to ISO 179-1/1eA (measured on dry test specimens at 23°C) clearly show that :

  • Symalit® PVDF 1000, Duratron® U1000 PEI, Ketron® PEEK-1000 and Quadrant® PPSU are very suitable for repeated steam sterilization      
  • Quadrant® PSU 1000 and Techtron® HPV PPS also offer good steam sterilization, up to 500 cycles
  • Ertacetal® C and Ertalyte® can be used for parts which will only be steam sterilized a few times.