Advanced Filler Systems for Rubber Reinforcement. André Wehmeier & Joachim Fröhlich

Transcription

1 Advanced Filler Systems for Rubber Reinforcement André Wehmeier & Joachim Fröhlich

2 Content filler morphology Payne effect in filled elastomers Payne effect of carbon blacks influenced by filler content specific surface area (CTAB) structure (DBP) surface activity model for the reinforcement mechanism application to silica silica / silane system influence of the temperature on the filler network conclusion Page 2

3 Filler Morphology µορφή, morphé = shape and λόγος, lógos = science primary particle size (and distribution thereof) aggregate size (and distribution thereof) aggregate shape (and distribution thereof) surface chemistry Page 3

4 Filler Morphology specific surface area and structure (basic understanding) same structure higher specific surface area aggregate (built up of 8 primary particles) same specific surface area higher structure Page 4

5 Payne Effect in Filled Elastomers??? shear modulus G*??? hydrodynamic effects polymer network shear amplitude Both strain dependent and strain independent contributions to G*. Both strain dependent and strain independent contributions to G*. Page 5

6 Rubber Process Analyzer upper die oscillating die rotor sample range of measurement: temperature range 40 C to 230 C frequency Hz strain (SSA) ± 0.28 % to ± 1250 % shear speed <= 30 s -1 theoretical: frequency / Hz max. SSA / % C: Page 6

7 Filler Content Payne Effect 0 phr 20 phr 35 phr 50 phr 65 phr 80 phr G* / MPa green compound SBR 1500 N 115 strain sweep: % 1.6 Hz, 60 C G* / MPa vulcanizate strain / % strain / % Shear modulus G* strongly depends on carbon black loading. Shear modulus G* strongly depends on carbon black loading. Page 7

8 Surface Area Payne Effect G* / MPa CTAB / (m 2 / g) COAN / (ml / 100 g) N N N SBR 1500 CB 60 phr vulcanizate strain sweep: % 1.6 Hz, 60 C tanδ 50 phr N phr N phr N strain / % strain / % Payne effect strongly increases with withincreasing CTAB surface area area (for (forsimilar structure). Page 8

9 Content and Surface Area of Filler 16 G* / MPa N 115 N 220 N 339 surface area CTAB / (m 2 / g) COAN / (ml / 100 g) N N N filler content / phr Payne effect depends on on filler loading and and CTAB surface area area (similar structure), which control the theaggregate distance [1]. [1]. [1] S. Wolff et al., Rubber Chem. Technol., 66, (1993) Page 9

10 Content and Surface Area of Filler For increasing path length the theprobability of of forming a filler network becomes higher. Page 10

11 TEM-pictures of SBR1500 vulcanizates, 40phr carbon black; sample preparation: Cryo-sectioning Surface Area Payne effect 400nm 400nm N 234 N 990 Fillernetworking: networking:visible visibleinfluence influenceof ofprimary primaryparticle particlesize. size. Filler Page 11

12 Proposed Model for Filler Networking filler-filler contacts Page 12

13 Payne effect filler-filler interaction shear modulus G*??? hydrodynamic effects polymer network shear amplitude Breakdown of the filler-filler network causes Payne effect. Breakdown of the filler-filler network causes Payne effect. Page 13

14 Structure Payne Effect CTAB / (m 2 / g) COAN / (ml / 100 g) N N N 326 N 330 G* / MPa strain sweep: CB 60 phr vulcanizate % 1.6 Hz, 60 C tan δ strain / % strain / % High-strain and and low-strain modulus strongly depend on on DBP resp. CDBP. Page 14

15 Surface Activity Payne Effect 6 5 N 347g N 347 N 347 graphitized N 347 ASTM 4 G* / MPa G* shear modulus structure +??? hydrodynamic effects strain / % polymer network shear amplitude Structure + filler-polymer interaction = in-rubber structure Structure + filler-polymer interaction = in-rubber structure Page 15

16 Proposed Model for Filler Networking and In-Rubber Structure in-rubber structure...given by structure of filler (in-rubber state) and filler-polymer interaction Page 16

17 In-Rubber Structure filler-filler interaction shear modulus G* in-rubber structure hydrodynamic effects polymer network shear amplitude Structure + filler-polymer interaction = in-rubber structure. Structure + filler-polymer interaction = in-rubber structure. Page 17

18 Visualization of Reinforcement 100 nm high stresses detachments Despite high stresses and and some polymer detachments in-rubber structure is isstable. Page 18

19 Visualization of Reinforcement N 234, stretched N 234 graph, stretched in-rubber structure polymer detachment Page 19

20 Reinforcement by the Silica-Silane System Name BET surface CTAB surface primary particle DBP-number moisture brand name area / (m²/g) area / (m²/g) size / nm ml / 100g % silica A Ultrasil 360 silica B Ultrasil VN 2 GR silica C Ultrasil VN 3 GR silica D Ultrasil 7000 GR N <1 N <1 N <1 N <1 primary particle size silica A silica B silica C N 774 N 550 N 220 N 115 Page 20

21 Filler Content Payne Effect storage modulus G' / MPa phr 60 phr 40 phr silica C: CTAB = 165 m²/g strain / % (1 st sweep) Loss modulus G'' / MPa phr 60 phr 40 phr RPA: vulcanizate, 60 C, 1.6 Hz maximum : 3-4 % strain 0, strain / % (1 st sweep) Shear modulus G* strongly depends on silica loading. Shear modulus G* strongly depends on silica loading. Page 21

22 Surface Area Payne Effect phr silica 175 m²/g RPA: vulcanizate 60 C, 1.0 Hz 1.0 storage modulus G' / MPa m²/g loss modulus G'' / MPa m²/g 175 m²/g 2 50 m²/g m²/g strain / % (1 st sweep) strain / % (1 st sweep) Payne effect strongly increases with withincreasing CTAB surface area. Page 22

23 Content and Surface Area of Filler Payne effect: G* surface area filler content Filler network increases with filler loading and surface area. Filler network increases with filler loading and surface area. Page 23

24 Structure Payne Effect m²/g RPA: vulcanizate 60 C, 1.0 Hz storage modulus G' / MPa m²/g CTAB / (m 2 / g) DBP / (ml / 100 g) silica A silica B silica D m²/g strain / % (1 st sweep) DBP number of silicas has no influence on in-rubber structure. DBP number of silicas has no influence on in-rubber structure. Page 24

25 Decrease of the Silica-Silica Network by Hydrophobation O Si O Si O Si O shielding of the polar silica surface O H EtO Mooney viscosity S-SBR / BR with 80 phr silica Si O Si O EtO C 8 amount of OTES / phr Page 25

26 Decrease of the Silica-Silica Network by Hydrophobation 2.0 equimolar silica without silane 2.0 equal per weight silica without silane shear modulus G* / MPa VP Si phr VP Si phr VP Si phr Shear modulus G* / MPa VP Si phr VP Si phr VP Si phr strain / % Si 203: Propyltriethoxysilane Si 208: Oktyltriethoxysilane Si 216: Hexadecyltriethoxysilane green compound strain / % Page 26

27 Principle of the Silica-Silane-Rubber Coupling silica surface OH OH OH RO RO RO silica coupling Si triethoxysilylgroup propyl spacer rubber coupling S X sulfur-functional group rubber coupling during mixing coupling during vulcanization Page 27

28 Silanization of Different Silicas with TESPT and HDTES TESPT RPA: vulcanizate, 60 C, 1.0 Hz modulus G* / MPa HDTES Kaoline in-rubber structure coupling strain / % (3 rd sweep), silica B, silica C, silica D Page 28

29 Visualization of Reinforcement Ultrasil 7000 GR + Si 69 Ultrasil 7000 GR 150nm polymer detachment almost no polymer detachment S-SBR//BR BRvulcanizates vulcanizatesunder underdeformation deformation S-SBR Page 29

30 Payne Effect in Filled Elastomers filler-filler Interaction shear Modulus G* in-rubber structure hydrodynamic effects polymer network shear Amplitude Model for carbon black, silica and silica / silane. Model for carbon black, silica and silica / silane. Page 30

31 Proposed Model for Filler Networking filler-polymer-filler interaction...controlled by filler-filler interaction filler-polymer interaction polymer chain mobility filler-filler distance occluded rubber Page 31

32 Proposed Model for Filler Networking immobilized polymer shell ( glassy state ) polymer shell with certain mobility temperature (1) high mobile polymer shell reduction of the mobility of the polymer shell between the particles reduction of the distance between the filler particles higher filler networking temperature (2) low E*(1) < E*(2) Page 32

33 Proposed Model for Filler Networking high temp. temperature (1) high only mobile polymer chains are stretched low temp. also some polymer chains near / in the glassy state take place on the deformation temperature (2) low Page 33

34 Conclusion modulus at small amplitudes filler networking modulus at large amplitudes in-rubber structure increasing filler-polymer interaction reduced filler networking higher in-rubber structure reinforcement model is applicable both to carbon black and to silica and the silica / silane system respectively filler networking: polymer plays a significant role Page 34