The influence of Anti-friction Treatment on Mechanical properties of NBR Compounds

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Antonia Garrett
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1 The influence of Anti-friction Treatment on Mechanical properties of NBR Compounds

How will anti-friction treatment affect a NBR compound? Will the service life of the anti-friction treated seal or custom molded rubber part last longer?

2 How will anti-friction treatment affect a NBR compound? Will the service life of the anti-friction treated seal or custom molded rubber part last longer? These questions and a few other variables will be covered in GBSA s Guide to Anti-friction Treatment The friction of elastomers sliding against a metallic surface is correlated with viscoelastic properties of rubber compounds and surface adhesion between sliding bodies. A very important reduction of the friction coefficient of NBR compounds can be obtained by a chemical treatment of the surface of the rubber body, performed by the immersion in a halogenated bath, followed by a neutralization bath for stopping the reaction. A-F Treatments can be applied to almost any rubber application The reduction of friction of treated V-Seals is over 50%, with a decrease of the same order of power applied to the lip, with the practical result of lower temperature and longer service life, without any loss of physio-mechanical properties of rubber compound. The variations of hardness and mechanical properties of the compound NBR , due to the immersion in the halogenated bath for very long periods, away from the industrial process, have been measured. The concentrations of halogenated and neutralization baths used were exactly the same as those adopted in the factory process. 125 Parker Court I Chardon, OH I P: I F: I Page Parker Court, Chardon, OH

-TABLE 1- NBR 60-100 (Hardness is expressed in IRHD) Hardness (IRHD) (IRHD) ( % ) Time of Treatment (min) Untreated Samples 1 2 5 10 20 64.0 63.7 63.7 64.0 64.3 64.6 0.32 0.60 1.12 0.32 0.30 0.73 0.

3 -TABLE 1- NBR (Hardness is expressed in IRHD) Hardness (IRHD) (IRHD) ( % ) Time of Treatment (min) Untreated Samples With a time of treatment of 20 min (over six times longer than the factory process) variation of hardness is not statistically significant. Influence on Hardness Samples of 2mm thickness of NBR were A-F Treated for increasing times; after a storage at standard laboratory temperatures for 72 h, protected from light, hardness was measured, following ISO , with a microhardness tester. On each test piece five measurements were performed and results averaged (Table 1) Parker Court Court, I Chardon, OH OH I P: I F: I Page 3

Test pieces used for detecting the influence of A-F treatment were micro-rings described in the following standards: ISO 37 UNI 6065 BS 903 Part AZ / 1985 Their dimensions are: External diameter : De

4 Test pieces used for detecting the influence of A-F treatment were micro-rings described in the following standards: ISO 37 UNI 6065 BS 903 Part AZ / 1985 Their dimensions are: External diameter : De = 10 mm Internal diameter : Di = 8 mm Thickness : h = 1 mm The reason for using such small test pieces is the connection between their surface to volume ratio, the highest among test pieces for measurements of dynamometric properties of rubber compounds and, as a consequence, the best suited for showing evidence of surface degradation. The value surface/volume for ring test pieces can be calculated with the expression: Surface = Volume h De Di = 4mm-1 almost twice the value of corresponding dumb-bells. -TABLE 2- NBR Time of treatment (min) Tensile strength (MPa) Ultimate elongation (%) 0 (reference) Percentage variations are plotted in fig. 1 as a function of logarithm of time of treatment. A progressive decrease of dynamometric properties has been clearly observed, but within the factory process (around 3 min) no sign of degradation has been detected Parker Court, I Chardon, OH I P: I F: I Page 4

The very important advantages in V-Seal s behavior of an A-F treatment are due to lower power dissipated in the lip zone with lower heat build-up, better aging conditions of compound and the service

The NBR compound has to be well protected against the action of the halogenated bath and the bath itself must be carefully controlled in order to obtain the reduction of friction coefficient without

5 The very important advantages in V-Seal s behavior of an A-F treatment are due to lower power dissipated in the lip zone with lower heat build-up, better aging conditions of compound and the service life of the seal almost doubled. The NBR compound has to be well protected against the action of the halogenated bath and the bath itself must be carefully controlled in order to obtain the reduction of friction coefficient without any detrimental effect on the physico-mechanical properties of the material. About the Author: GBSA, Inc. is a leading supplier of oil seals, v-seals, v-packing, u-cups, o-rings, molded rubber products, machined and stamped metal and plastics for the industrial and commercial markets. If you have a unique or even simple application, or would simply like to learn more about how our A-F Treatment can work for you, please contact us today: Cameron Orr - camerono@gbsa.com - Ph x204 Kristopher Hocevar - krish@gbsa.com - Ph x Parker Court, I Chardon, OH I P: I F: I Page 5

Specification

Specification 2015-05 CLASS: ELASTOMERS CLASS NO.: 26 NITRILE-BUTADIENE-RUBBER (NBR) JED 7080M PREVIOUS EDITION ABBREVIATED TITLE 2014-10 NBR, 70 IRHD, -40/-45 0 C 852 070 800 4 1 Scope The specification