Measuring the Payne effect in filled rubber - VKRT

Measuring the Payne effect infilled rubberVKRT meeting, May 14, 2009ELASTOMER RESEARCH TESTING B.V.VKRT 1

ELASTOMER RESEARCH TESTING B.V.As is in the name: ERT B.V. provides research andtesting facilities in the rubber field for third parties.One of the properties of filled rubber we are workingon is the measurement of the Payne effect.The Payne effect is directly related to the dynamicproperties of the vulcanized rubber.ELASTOMER RESEARCH TESTING B.V.VKRT 2

The Payne effect in filled rubber is thephenomenon of a strain dependent dynamicmodulus.In carbon black or silica filled rubber we measure ahigh dynamic modulus at low strains (< 1%) whichdecreases at higher strains (> 10%).The reason for this phenomenon is the formation of anetwork formed by filler-filler interaction.For carbon black the interactions are Van der Waalsforces and for silica the much stronger hydrogenbondings.ELASTOMER RESEARCH TESTING B.V.VKRT 3

André Wehmeier, VKRT February 14, 2008.ELASTOMER RESEARCH TESTING B.V.VKRT 4

Possible mechanisms for the Payne effect.(i)(ii)(iii)(iv)the destruction-reformation of a filler networkadsorption-desorption of polymeric chains atthe filler interfacedisentanglement of bulk polymer from therubber bounded to the surfacestrain-softening of the glassy polymer shellsurrounding the particles surfacesIn real life this means an energy loss and the intentionis to minimize this effect in filled rubber (but with thereinforcement retained).ELASTOMER RESEARCH TESTING B.V.VKRT 5

How to measure this filler-filler interaction.The first remark about this phenomenon was in 1942by Gehman.The Dutch “Rubber Stichting” played a pronounced rollin the discovery of this phenomenon.In 1954 S. de Meij and G.J. van Amerongen presentedtheir results on the ‘DKG Tagung’ in Munich.Part of these results were published in 1956.ELASTOMER RESEARCH TESTING B.V.VKRT 6

Measuring device of Seel de Meij.ELASTOMER RESEARCH TESTING B.V.VKRT 7

KAUTSCHUK UND GUMMI, 9. Jahrgang, Nr. 3/1956ELASTOMER RESEARCH TESTING B.V.VKRT 8

L. Guy, IRC Lyon, 2006samples were tested in pure shear with a Metravib VA3000 analyzerELASTOMER RESEARCH TESTING B.V.VKRT 10

L. Guy, IRC Lyon, 2006ELASTOMER RESEARCH TESTING B.V.VKRT 11

Measuring the Payne effect.The Payne effect is difficult to measure in tension(single strain) and measuring in compression meansthat the test piece has to be glued as is done in theMetravib VA3000 analyzer.The other modes are shear and torsion; ERT hasthe option make use of an Eplexor and a RPA.ELASTOMER RESEARCH TESTING B.V.VKRT 12

Measurements in shear on the Eplexor.ELASTOMER RESEARCH TESTING B.V.VKRT 14

RPA Payne effect (G') of vulcanized samples2,01,5G' (MPa)1,0207-03207-040,50,00,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 15

Eplexor G' of vulcanized samples2,01,5G' (MPa)1,0207-03207-040,50,00,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 16

Comparison Payne effect (G') measurements2,0G' (MPa)1,51,00,5RPA-03RPA-04Eplexor-03Eplexor-040,00,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 17

RPA G" of vulcanized samples0,200,15G" (MPa)0,10207-03207-040,050,000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 18

Eplexor G" vulcanized samples0,100,08G" (MPa)0,060,04207-03207-040,020,000,1 1,0 10,0 100,0strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 19

Comparison of G" vs. strain0,20G" (MPa)0,150,100,05RPA-03RPA-04Eplexor-03Eplexor-040,000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 20

RPA tan δ of vulcanized samples0,300,25tan δ0,200,150,10207-03207-040,050,000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 21

Eplexor tan δ vulcanized samples0.3tan δ0.20.1207-03207-040.00.1 1.0 10.0 100.0strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 22

Comparison of tan δ vs. strain0,300,25tan δ0,200,150,10RPA-03RPA-04Eplexor-03Eplexor-040,050,000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 23

ResultsThe Payne effect as measured with the RPA oncured samples is higher than measured in shear onthe Eplexor∆(G’ 1,0 –G’ 20 ) = 0.548 vs. 0.432 MPa for 207-03 and∆(G’ 1,0 –G’ 20 ) = 0.307 vs. 0.234 MPa for 207-04.The storage modulus G’ is also much higher for theRPA measurements.Both the loss modulus and the tan δ show anunexpected increase at strains over 25%.(Most probably due to slip in the RPA die at higherstrains.)ELASTOMER RESEARCH TESTING B.V.VKRT 24

The Payne effect of unvulcanized compoundsThe Payne effect as measured with the RPA onunvulcanized compounds did not show this increasein loss modulus (G”) but the tan δ curve showedagain an increase.Note: the following curves G’ and G” for unvulcanizedcompounds are smoothened below 1% strain.ELASTOMER RESEARCH TESTING B.V.VKRT 25

RPA G' measured curves300250G' (kPa)200150100207-03207-045000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 26

Payne effect G', unvulcanized compound300250G' (kPa)200150100207-03207-045000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 27

G" vs. strain; unvulcanized compounds300250G' (kPa)200150100207-03207-045000,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 28

tan δ vs. strain; unvulcanized compounds1,41,21,0tan δ0,80,6207-03207-040,40,20,00,1 1 10 100strain (%)ELASTOMER RESEARCH TESTING B.V.VKRT 29

Conclusions:the Payne effect can not reliably be measured onvulcanized rubber with the RPA because ofunreliability below 1% strain and slip above (at least)25% strain.For unvulcanized compounds the RPA seems to bereliable between 1.0 and 25% strain.The Payne effect of vulcanized samples can reliablybe measured with the Eplexor in shear between 0.1and 40% strain.ELASTOMER RESEARCH TESTING B.V.VKRT 30

The Payne effect was defined by A.R. Payne as thedifference between G’ 0 and G’ ∞ but this is difficult todetermine.As a measure for the Payne effect in unvulcanizedcompounds, the differences between the G’ values at1% and 20% as determined with the RPA in torsionshear can be used in comparative studies.As a measure for the Payne effect in vulcanizedrubbers, the differences between the G’ values at 0.5%and 40% as determined with the Eplexor in puredynamic shear can be used in comparative studies.ELASTOMER RESEARCH TESTING B.V.VKRT 31