School of GeoSciences

Vacuum Pump Test Results

After cutting to a thickness of 5mm, the 25mm diameter disks were

Cleaning Procedure

  • Washed
  • Ultrasonic Clean with 10% Decon 90
  • Rinsed with deionised water
  • Two Ultrasonic Cleans with deionised Water
  • Dried @50'C for ~2Hr

Test Procedure

Four examples of each resin (except Varian Torr Seal and the 'domestic' Araldites) were prepared immediately before pump testing following the manufacturers recommended cure time and the cleaning routine outlined above.

 

Four samples of each resin type were loaded into the vacuum test chamber and pumped by a rotary pump (Alcatel 2012) for 1 minute followed by the turbo-molecular pump (Pfeiffer TPH240). The vacuum recording started after a pump-down time of 5 minutes by which time the vacuum was around 1e-4Torr.

Four vacuum measurements were made:

  • Varian MultiGauge Thermocouple. The gauge output was only used to monitor the backing pressure and to confirm that the vacuum was suitable to start the turbo-molecular pump.
  • Varian MultiGauge Cold Cathode and/or Bayard-Alpert UHV gauge.
  • Thermo (VGQ), Residual Gas Analyser. The spectra were used to characterise the different resins.
  • Thermo (VGQ), total pressure measure. This vacuum measure was used to monitor the pump-down time.

 

2 Hr Test Results

This pump test was performed 24hrs after the resin was mixed. The vacuum was recorded by the Thermo (VGQ) in total pressure mode and confirmed by the Varian Cold Cathode gauge and presented as the final vacuum reading.

A comparison of all of the pump tests is given here.

Resin Final Vacuum (2Hr)       Pump Graph
None 2.8e-7 Torr
EpoThin 8.4e-7 Torr
TransOptic 1.4e-5 Torr
KonductoMet 1 4.8e-6 Torr
Korapox 439 5.4e-6 Torr
Epofix 3.2e-6 Torr
Specifix 20 5.1e-6 Torr
Ciba Geigy 2.5e-6 Torr
ProbeMet 5.4e-7 Torr
Robnor Resin 3.3e-6 Torr
Epoxicure (Room Temperature) 3.4e-6 Torr
Epoxicure (cured at 65oC) 3.6e-6 Torr
Petropoxy 3.7e-6 Torr
EpoHeat 4.2e-6 Torr

24 Hr Test Results

The 24Hr pump test was performed ~30 days after the resin was prepared and is believed to give a good indication of the resins suitablilty for the practical preparation of material for SIMS analysis. Throughout the testing period the empty vacuum chambers residual gases and ultimate (24hr) vacuum were routinely monitored to check how these parameters varied over time. The results show a slight but steady improvement in the ultimate chamber vacuum over the 30 day test period. 

 

A comparison of all of the pump tests is given here.

Resin Final Vacuum (24Hr)       Pump Graph
None 7.12e-8 Torr
EpoThin 1.64e-7 Torr
TransOptic 3.10e-7 Torr
KonductoMet 1 2.40e-7 Torr
Korapox 439 1.10e-7 Torr
Epofix 1.60e-7 Torr
Specifix 20 2.10e-7 Torr
Ciba Geigy 1.90e-7 Torr
ProbeMet 1.60e-7 Torr
Robnor Resin 1.11e-7 Torr
Epoxicure (Room Temperature) 1.70e-7 Torr
Epoxicure (cured at 65oC) 1.60e-7 Torr
Petropoxy 1.20e-7 Torr
EpoHeat 1.40e-7 Torr

3 Month Cure Test Results

A final 2Hr pump test was performed ~3 months after the resin was prepared. The samples were kept in a desiccator and the test chamber continually pumped over this ~3 month time period and the base vacuum improved. The results show a significant improvement in the ultimate chamber vacuum after 3 months hardening. 

A comparison of all of the pump tests is given here.

 

Resin    Final Vacuum (2Hr)    
None    2.8e-8 Torr
EpoThin    5.3e-8 Torr
TransOptic   1.5e-7 Torr
KonductoMet 1   9.8e-8 Torr
Korapox 439   7.1e-8 Torr
Epofix   7.4-8 Torr
Specifix 20   8.5e-8 Torr
Ciba Geigy   5.8e-8 Torr
ProbeMet   5.9e-8 Torr
Robnor Resin   6.6e-8 Torr
Epoxicure (Room Temperature)            6.9e-8 Torr
Epoxicure (cured at 65oC)   5.9e-8 Torr
Petropoxy   9.3e-8 Torr
EpoHeat 6.6e-8 Torr

Residual Gas Analysis

The residual gases within the vacuum chamber were routinely monitored during the pump tests. These gases, although not all identified, can provide a distinctive 'fingerprint' of the resins.

Discussion of Results

Comparison of the final vacuum achieved for each resin under the three test conditions is illustrated here.

The relative vacuum achieved has been calculated from the final vacuum recorded minus the base vacuum of the chamber. It demonstrates that after ~3 months the same vacuum maybe achieved that previously took 24hrs.

Epothin and ProbMet both performed well under all 3 test conditions.