Trade-off Between Filler Dispersion and Hysteresis

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1 Trade-off Between Filler Dispersion and Hysteresis Sadhan C. Jana Department of Polymer Engineering University of Akron Akron, OH Contributors: Akshata Kulkarni (University of Akron); Dr. Kushal Bahl (Teknor-Apex); Dr. Prasad Raut (Imerys); Hamad Albehaijan (University of Akron); Dr. Coleen Pugh (University of Akron)

2 Hysteresis Indicators DE ~ tan d/g =G /(G ) 2 Under constant-stress deformation process DE = energy loss during deformation P. Zhang, M. Morris, D. Doshi, Rubber Chem. Technol., 89, (2016) S. Futamura, Rubber Chem. Technol. 64, 57 (1991). Objectives: Reduce tan d Increase G 2

3 ENERGY DISSIPATION ON THE ROAD Needed for mechanical properties Mixed fillers Needed for wet track resistance Rolling resistance indicator: tan d at 60 C: get low values Wet track resistance indicator: tan d at 0 C: get high values 3

4 REINFORCEMENT POTENTIAL Already reinforcing Leblanc, J. L. Rubber-Filler Interactions and Rheological Properties in Filled Compounds. Prog. Polym. Sci. 2002, 27,

5 SEVERAL LENGTH SCALES Example: Precipitated silica This is what we get This is what we expect Schafer and Justice, Macromolecules, 40, (2007) 5

$bulk filler materials E agg = Young s modulus of the aggregate a = size of primary particles L = length of spanning path R = cluster size c = fractal dimension; c=1 means linear spanning path$

6 Modulus scales with cluster size N ~ R dm Witten-Rubinstein-Colby Analysis Journal de Physique II, 3, (1993) L a R a 3 c a Eagg Ef R c (for aggregated fillers) E f = Young s modulus of bulk filler materials E agg = Young s modulus of the aggregate a = size of primary particles L = length of spanning path R = cluster size c = fractal dimension; c=1 means linear spanning path 6

7 Contrasting scenarios Avoid aggregates to get modulus Keep aggregates to obtain toughness Avoid aggregates to reduce hysteresis Loading/breakup Hysteresis Unloading/reaggl. 7 Favors toughness (bound rubber) Favors modulus

8 REINFORCEMENT POTENTIAL Can we fix particle networks at this state? Starting material Out of reach in most cases during deformation networking 8

9 Approaches Synthesize polymers with reduced hysteresis Modification of polymer matrix to reduce hysteresis Surface modification of fillers Use of hybrid fillers subdue network breakdown Use of coupling agent improve dispersion 9

$size Non-fractal shape$ rubber Carbon black

10 Hybrid fillers As received lignin Large size Non-fractal shape Incompatible with rubber Carbon black Small particles Fractal aggregates Provides bound rubber Hollow spheres from acetone 10

11 Hybrid fillers Lignin p-p interactions Harder agglomerates Difficult to break 20 nm coating on CB 11

12 Lignin-CB N330 Lignin coated on CB particles abundantly Established by Raman spectra, zeta potential Bahl, K., Jana, S.C. J. Appl. Polym. Sci., 2014, 131 (7), 40123(1-9), Bahl, K., Miyoshi, T., Jana, S.C., Polymer, 2014,

13 lignosulphonate 21 ms 80 ms Heterogeneous length scale < 5 nm CB/lignosulphonate 13 C CPMAS NMR spectra T 1H relaxations 1:1 weight ratio Bahl, K., Miyoshi, T., Jana, S.C., Polymer, 2014,

14 Sample CB N330 in water -32 ± 1.4 Zeta potential (mv) CB N330 in solution of LS in water ± 2.4 Sr. no. Zeta Potential KL:CB wt. ratio in hybrid filler BET surface area (m 2 /g) 1 Carbon black N : : : Reduction, but not much Fractal aggregates Bahl, K., Miyoshi, T., Jana, S.C., Polymer, 2014,

15 Filler Flocculation Test Uncured rubber at 160 ºC Preparation: 25% strain, 5 min DG 30 phr CB 30 phr hybrid 30 phr CB DG 1% strain, 2 hours Strain sweep 15

16 30 phr CB 30 phr CB/LS (90:10) 30 phr CB/LS (80:20) SBR Not acceptable 16

17 10% reduction 30 PHR CB At 60 C tan d= mm 1 mm 30 PHR CB/LS (90:10) tan d= mm 30 PHR CB/LS (80:20) Dropdown filler 17

Coupling between lignin and rubber Polybutadiene-g-polypentafluorostyrene (PB-g-PPFS) Collaborator: Coleen Pugh SBR and PB are compatible on one end Lignin and

18 Coupling between lignin and rubber Polybutadiene-g-polypentafluorostyrene (PB-g-PPFS) Collaborator: Coleen Pugh SBR and PB are compatible on one end Lignin and PPFS interact via areneperfluoroarene interactions Confirmed using UV-vis spectroscopy Bahl, K., Swanson, N., Pugh, C., Jana, S.C. Polymer, 2014, 55,

19 State of dispersion SBR- 30KLCB1090 Tensile strength = 11 Mpa Strain at break = 545% XLD = 0.08 kmol/m 3 SBR- 30KLCB1090 w/copolymer Tensile strength = 12 Mpa Strain at break = 556% XLD = 0.08 kmol/m 3 19

20 Coupling agent for CB π-π stacking Electron-deficient pentafluorostyrene (PFS) π-system Electron-rich carbon black π-system 20 nm Poly(butadiene-graft-pentafluorostyrene) CB- N234 Chains are interlocked with the filler particle networks. Polymer chain deformation and the associated energy dissipation are minimized. 20

Evidences of CB-CA interactions CA = Polybutadiene-graft-polypentafluorostyrene (PB-g-PPFS) Zeta potential: Sample Sample BET (m²/g) CB N234

14 BET surface area: Before Centrifuge After Centrifuge BET surface area measurements for neat CB N234, 1:1 CB:CA and 2:1 CB:CA (by weight)

21 Evidences of CB-CA interactions CA = Polybutadiene-graft-polypentafluorostyrene (PB-g-PPFS) Zeta potential: Sample Sample BET (m²/g) CB N CB:CA 1:1 70 CB:CA 2:1 74 Zeta Potential (mv) CB N234 in THF ± 2.46 CA Modified CB-N234 in THF -4.9 ± 2.14 BET surface area: Before Centrifuge After Centrifuge BET surface area measurements for neat CB N234, 1:1 CB:CA and 2:1 CB:CA (by weight) performed using Micromeritics Tristar-3020 Neat CB, 1:1 CB:CA and 2:1 CB:CA by weight dispersed in THF before and after sonication. CA stabilizes the dispersion of CB 21

22 Transmission Electron Microscopy (TEM) (a) (b) CA coating over CB 100nm 100nm TEM images of (a) carbon black N234, (b) 0.01% THF drop-cast solution of CB:PB-g-PPFS 1:1 w/w, respectively, at different magnifications. 22

23 Formulation & Compounding Scheme Material CB (phr) CB-CA (5.5k) (phr) CB-CA (8.5k) (phr) CB-CA (14.5k) (phr) SBR BR CB Coupling Agent Stearic Acid Zinc Oxide Process Oil (TDAE) Antioxidant TBBS Sulfur Mixing Stage 1: Fill factor = 0.7 for 85 cm 3 Brabender, 65 rpm, 80 C (1 min + 6 min) Mixing Stage 2: 2 roll mill at 50 C, 20 rpm 23

24 G' (kpa) Payne effect and filler flocculation Tests performed at curing temperature of the rubber compounds: 160 C and 0.1 Hz frequency Test sequence i. 25% strain for 5 min ii. 1% strain for 120 min iii. Strain sweep from 0.13 % to 70 % strain Storage modulus at 1 % strain DG' = 215 kpa CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) CB DG' = 93 kpa Time (min) 24

25 G' (kpa) Payne effect and filler flocculation 700 Strain sweep from 0.13 % to 70 % strain DG' = 130 kpa CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) DG' = 580 kpa 1) Use of CA1 shows lower flocculation tendency compared to carbon black. 2) The reduction of storage modulus values with strain is much less severe for the filler treated with CA1, indicating lower energy dissipation Strain (%) 25

26 (a) CB-N mm 10 mm 1 mm (b) CB:PB-g-PPFS Hybrid CA coating over CB 10 mm 10 mm 1 mm 26

27 CB a b b-i CB-CA c d d-i 27

28 Time (min) Cure and Scorch Time 20 cure Cure Time (min) Scorch Time (min) scorch 0 CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) 28

29 tan d Storage Modulus (MPa) Loss Tangent and Storage Modulus tan d Storage modulus 0 C 0 C 60 C C 0 C 60 C C C CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) 0 CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) 29

30 Tensile strength (MPa) Strain at break (%) Tensile Strength and Strain at Break Tensile Strength 500 Strain at break CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) 0 CB CB-CA (5.5 kda) CB-CA (8.5 kda) CB-CA (14.5 kda) 30

31 Coupling agent for silica and carbon black dispersion Polybutadiene-graft-poly(pentafluorostyene-co-trialkoxy(4-vinylphenethyl)silane) [PB-g-P(PFS-co-StSi(OR) 3 ] RO: ethoxy, propoxy Silica T g ~100 C Granular solid CB SI 69: liquid 31

32 PHYSICAL STATE OF THE COUPLING AGENT PPFS CB PBD Silica Credit: Hamad Albehaijan, University of Akron 32

33 Storage Modulus (KPa) Storage Modulus (kpa) Overview of Major Results Filler Flocculation and Payne effect - using APA-2000 Alpha technologies Tests performed at 160 o C and 0.1 Hz frequency Neat SI69 Et1 Pr Time (min) Test Sequence i. 25% strain for 5 min ii. 1% strain for 120 min iii. Strain sweep from 0.13% to 70% strain Storage Modulus at 1% strain/120 min Strain Sweep 0.1% - 100% Neat SI69 Et1 Pr Strain (%)

34 Tan δ G' (Mpa) Overview of Major Results Dynamic Mechanical Analysis Using TA Q800 Sample Preparation: Compression molding of a 1.5 mm tensile slab at 160 ⁰C for 20 min DMA (Temperature sweep at 0.1% strain, 1 Hz frequency) Tan δ at 0 ⁰C Tan δ at 60 ⁰C G' at 0 ⁰C G' at 60 ⁰C Neat SI69 Et1 Pr1 0 Neat SI69 Et1 Pr1 60 C: Rolling resistance indicator 0 C: Wet traction indicator 34

35 DO WE HAVE TO LIVE WITH A CURING TEMPERATURE OF C? Opportunity: Low Temperature Curatives Reduction of Curing Times 35

36 Coupling Agent With Curing Function van der Waals p-p curing 10/3/

37 Curing by Diels-Alder Cycloadditions and Oligomerization Crosslinking by Diels-Alder Reaction (crosslinking by oligomerization not shown) 10/3/2018

38 Material Performance Lower the curing time due to the thermally activated BCB ring-opening isomerization Improve aging properties due to the replacement of C-S with C-C covalent crosslinks Improve the hysteresis loss Improve permanent set properties Potential unique properties: increased crack-growth resistance, ability to self-heal, increased fatigue-to-failure, increased abrasion resistance Crosslinking by Diels-Alder Reaction (crosslinking by oligomerization not shown) 10/3/

39 Curatives XA2 (PPFS substituted w multiple BCBs) XA4 (BCB-PB-BCB) XA5 (BCB-EO-EO-BCB) 39

40 Cure characteristics using PPFS BCB n at 180 Formulations PPFS-BCB n : white powder Control (phr) XA2 (phr) SBR Curing Agent 0 3 Stearic Acid 2 2 Zinc Oxide Sulfur TBBS 3 3 Mixing Procedure Stage 1 (80 C, 60 rpm) Step Time (min) Rubber 0 St. Acid + ZnO 1 Sweep 3 Discharge 5 Stage 2 (50 C, 40 rpm) Step Time (min) Masterbatch 0 Sulfur + TBBS + PPFS- BCB n 1 Sweep 2 Discharge 3 40

41 Torque (dnm) Torque (dnm) Cure characteristics using PPFS BCB n at 180 Control XA2(10%) ML(dNm) MH (dnm) MH-ML (dnm) 10% BCB substitution 20% BCB substitution ts1 (min) ts2(min) t10 (min) t90(min) S95(dNm) t95(min) Cure Characteristics Control XA2(10%) Time (min) Control XA2 (20%) ML(dNm) MH (dnm) MH-ML (dnm) ts1 (min) ts2(min) t10 (min) t90(min) S95(dNm) t95(min) Cure Characteristics Control XA2(20%) Time (min) 10/3/

Selection of Accelerator system Torque (dnm) Cure Characteristics with two different accelerator systems Ingredient TBBS TMTD+MBT SBR 100 100 Curing Agent 0 0 Stearic Acid 2 2 ZnO 2.5 2.5 Sulfur 1.

42 Selection of Accelerator system Torque (dnm) Cure Characteristics with two different accelerator systems Ingredient TBBS TMTD+MBT SBR Curing Agent 0 0 Stearic Acid 2 2 ZnO Sulfur TBBS 3 0 MBT TMTD Temp ( ) MBT+ MBT+ Accelerator TBBS TBBS TMTD TMTD ML(dNm) MH(dNm) MH-ML (dnm) ts1(min) ts2(min) t10(min) t90(min) S95(dNm) t95(min) Cure Characteristics at TBBS TBBS TMTD 2 MBT+TMTD MBT Time (min) 42

43 Torque (dnm) Cure characteristics using PPFS BCB n at 160 To study curing at 160, the accelerator system was changed. The compounds were cured at 160 at their respective t 95 using a compression molding press. Ingredient Control XA2 (20%) SBR Curing Agent 0 3 St. ACID 2 2 ZnO Sulfur MBT TMTD Cure Characteristics at 160 Control XA2(20%) ML(dNm) MH (dnm) MH-ML (dnm) ts1 (min) ts2(min) t10 (min) t90 (min) S95(dNm) t95(min) XA2 PPFS-BCB n Control XA2 TMTD MBT Time (min) 43

44 Compounding with PPFS-BCB n 20% [XA2] curing agent Formulations PPFS-BCB n : white powder Control (phr) XA2 (phr) SBR Curing Agent 0 3 Stearic Acid 2 2 Zinc Oxide Sulfur TBBS 3 3 Mixing Procedure Stage 1 (80 C, 60 rpm) Step Time (min) Rubber 0 St. Acid + ZnO 1 Sweep 3 Discharge 5 Stage 2 (50 C, 40 rpm) Step Time (min) Masterbatch 0 Sulfur + TBBS + PPFS- BCB 1 Sweep 2 Discharge 3 44

45 Compounding with PPFS-BCB n (20%) + CB filler Formulation Ingredient Control XA2 (PPFS-BCB n ) SBR Curing Agent 0 3 Carbon black TDAE Stearic Acid 2 2 ZnO Sulfur TBBS 3 3 Mixing Procedure Stage 1 Brabender mixer (80 C, 72 rpm) Step Time (min) Rubber 0 ½ Carbon black 1 ½ carbon black + TDAE 3 ZnO + stearic acid 5 Discharge 7 Stage 2 Brabender mixer (80 C, 72 rpm) Step Time (min) Mastication 4 Stage 3 Two roll mill (50 C, 40 passes) Step Passes Curatives+Accelerator 5 passes XA2 (PPFS-BCB n ) 45 45

Torque (dnm) Effect of carbon black on compounding with PPFS-BCB n at 160 Without CBlack With CBlack 9 8 7 6 5 4 3 2 1 0 Cure Characteristics at 160 5% decrease Control XA2 0 10 20 30 40 50 60 Time

47 Torque (dnm) Effect of carbon black on compounding with PPFS-BCB n at 160 Without CBlack With CBlack Cure Characteristics at 160 5% decrease Control XA Time (min) Control XA2(20%) ML(dNm) MH (dnm) MH-ML (dnm) ts1 (min) ts2(min) t10 (min) t90 (min) S95(dNm) t95(min) Control XA2 (20%) ML(dNm) MH (dnm) MH-ML (dnm) ts1 (min) ts2(min) t10 (min) t90(min) S95(dNm) t95(min)

48 Some concluding remarks The data suggest a trade-off between G and tan d values. The coupling agent concept is very useful for achieving fine scale dispersion of CB and silica, but it needs more work. A coupling agent with BCB moieties are useful in reducing curing times. 48

49 Acknowledgment NSF Tire Center (CenTiRE) for partial funding Industrial Advisory Board Members and Project Mentors of CenTiRE 49