Continued from page 20
This lack of uniformity was the starting point for developing a standardised test procedure. The approach was via the ISO 1817 Rubber, vulcanised or thermoplastic — Determination of the effect of liquids. The ISO 1817 describes methods of evaluating the resistance of vulcanised and thermoplastic rubbers to the action of liquids by measurement of properties of the rubbers before and after immersion in test liquids. This would allow the selection of suitable compatible materials for the design and construction of tool machines and avoidance of unexpected problems during filling and commissioning of tool machines. Auxiliary equipment such as cables and hoses can also be included.
The ISO test description is a more general method with details about test equipment and test conditions contained in the annexes. In order to determine a new test method we set drafted a proposal for a new annex that details the test equipment, elastomers and liquid description. After a number of preliminary tests, a closed vessel containing shouldered test bar S2 was selected as the optimal test condition (Figure 2). Optimal storage time turned out to be 1000h at 60°C.
Figure 3: Results obtained during the laboratory test phase: Volume Change with various materials in VSI 031B, a conventional mineral oil based MWF.
It is up to the testing laboratory to select the elastomers and MWF for testing, since each pair of MWF and elastomer could give different results.
For reference and test method verification, tests could be performed by using reference fluids and standard elastomers. For reference, some MWF fluid formulations have been selected. The MWF concentrates are close to formulations available on the market and represent typical formulation technologies made available by VSI member companies. A description of the formulation will also be a part of the ISO annex.
Three different formulation types were selected for the ISO 1817 annex: “VSI 14”: a boron free high pH polyalkylene glycol-based formulation, “VSI 22”, a boron free ester-based formulation and “VSI 34”, a boron-free high pH mineral oil-based formulation. VSI 031B was also tested, but represented a conventional boron containing formulation and will not be included in the ISO test description.
Figure 2: Test equipment with test bars in a non-water miscible cutting fluid. The detailed test equipment description can be found in the ISO, when approved.
After the time has elapsed, the following test results were documented: • volume change • shore A hardness change • tensile strength change • elongation (change).
The MWF was tested for a change of pH and change of conductivity to assess the influence of sealing materials on MWFs.
22 LUBE MAGAZINE NO.170 AUGUST 2022
As can be seen from Figure 3, a high volume change was observed for Elastomers M-P, while the other materials show only a limited interaction with VSI 031B and have been found in the same magnitude by various labs. The combination of results obtained for tensile strength and volume change would allow the MWF supplier as well as the OEM to select the optimum MWF / Elastomer combinations and identify problematic combinations of certain formulation technologies and elastomer compositions,
The Annex to the ISO 1817 was submitted and waits now for approval and publication.
LINKS
www.vsi-schmierstoffe.de
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
