Plasma modification of polymeric single end cords as an alternative to RFL treatment

1. Plasma modification of polymeric single end cords as an alternative to RFL treatment A. Louis, J. Noordermeer, W. Dierkes*, A. Blume Department of Elastomer Technology and Engineering University of Twente Enschede, the Netherlands, Nicaragua

2. OUTLOOK Precursors INTRODUCTION conclusions Process steps Process conditions Acknowledgements

3. Introduction Incompatibility of cord and rubber http://5.imimg.com/data5/WC/WT/MY-3702991/heavy-duty-conveyor-belt-500x500.jpg Apollo Tyres Global R&D B.V., Enschede, The Netherlands, (2014). https://img4.fastenal.com/productimages/0453391_hr4c.jpg Cord high strength lowelongation polar lowreactivity Rubber high elongation lowstrength non-polar reactive compatibilityproblem chemically mechanically Bridging of these property differences in order to achieve the best overall performance

4. Introduction Current technology: RFL Disadvantages: • Elaborative process • High energy consumption • Health and environmental concerns regarding resorcinol • Toxicity of formaldehyde: reclassified by the European Committee of Risk Assessment (RAC) to be carcinogenic and mutagenic W. B. Wennekes, PhD thesis, University of Twente, Enschede, The Netherlands, (2008). K. Uihlein, Dipping of Tire Cord Fabrics, Tire Technology Expo (2015), Presentation, Cordenka GmbH & Co. KG, Obernburg, Germany.

5. Introduction Alternatives to RFL RF-free dip: only for nylon cord yet + RF resin is replaced by eg polyisocyanate-based resin (US 20170130396) or epoxide / higher amines (WO2005080481) + Aqueous dipping solution, similar processing + Dip pick-up is lower compared to RFL at a similar adhesion level Plasma treatment: physical surface modification + Commonly used for adhesion promotion of polymeric sheets + Replacement for preparative steps before adhesive application + Relativly compact and inexpensive system Plasmatreat GmbH, Steinhagen, Germany, 2015

6. Draft research program Introduction Plasma liquid gas plasma solid electron cation strong bonds weak bonds no bonds ionization J. Schombert, http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec05.html, Dept. of Physics, University of Orgon, USA (2012) • Fourth state of matter • Ionized gas due to extremely high energy state • Mixture of oppositely charged particles • Contains excited particles → radicals → chemically very active molecules

7. Draft research program Introduction Types of plasma reactors Electrode Dielectric Barrier Discharge (DBD) High voltage Quarz Electrode Sample Sample Journal.hep.com.cn HV electrode Tube electrode Nozzle Atmospheric Pressure Plasma Jet (APPJ) Gas inlet RF power supply Plasma jet http://iopscience.iop.org/article/10.1088/0963-0252/21/3/034005

8. Draft research program Introduction Requirements for alternative treatment systems • Good to excellent fiber-rubber adhesion • Hazard-free storage, mixing, dipping • Applicability to the majority of: • Established polymeric cords • Established rubber compounds • Crosslinking must be fast and reliable (ideally thermal) • Stable at ambient temperatures (several days) • Aqueous solutions / suspensions preferred • Tunable penetration depth into the fiber • Intermediate modulus of adhesive layer (mechanical compatible) • Adequate performance during the whole tire life at all conditions Cordenka GmbH & Co KG, paper presented at the Tire Technology Expo 2015, Cologne, Germany, (2015).

9. Experimentals Plasma reaction chamber Channel to avoid contamination with plasma gases 2 APPJs for cleaning 2 APPJs for chemical modification Standard conditions Rayon (S1)

10. Draft research program Process steps Cleaning  polymerization  rubberizing Rayon, 2-ply, 1840 dtex Thiophene Rubberized samples CU: cleaning unit PU: polymerization unit Rubberized CU & rub. PU & rub. CU & PU & rub. PU & rub. CU & PU & rub. RFL H-Pullout force [N] H-pullout test ASTM 4776 Un- treated With precursor RFL Decontamination (no precursor)

11. Draft research program Process steps SPAF test: Force-elongation diagram Rayon RFL Plasma polymerized Plasma cleaned Untreated Extra rubber layer SPAF Strap Peel Adhesion Force ASTM 4393 Rubber layer Cord Rubber layer Rubber layer Cord Rubber layer Extra rubber layer

12. Precursors S-, N-, double bond moieties Rayon No cleaning No rubberizing Dimethyl disulfide Diallyl disulfide Thiophene Pyrrole

13. Draft research program Precursors & process conditions S-, N-moieties & generator power Rayon Thiophene, S1 Thiophene, S2 Pyrrole, S2 Pyrrole, S1

14. Draft research program Precursors & process conditions S-moieties & generator power Rayon • Crucial structural elements • for the precursor: • a five membered ring-structure • two double bonds • one sulfur atom Untreated Thiophene, S1 Thiophene, S2

15. Draft research program Precursors & process conditions Double bonds & generator power Rayon

16. Draft research program Process conditions Precursor flow rate & generator power Rayon Thiophene

17. Draft research program Process conditions Process time effects Rayon Thiophene

18. Draft research program Force-elongation diagram of a plasma coated and an untreated cord Rayon

19. Draft research program Fibers in the matrix after H-pullout test Rayon Thiophene RFL Plasma polymerized

20. Draft research program Fibers in the matrix after H-pullout test Rayon Thiophene Plasma polymerized

21. Draft research program Conclusion Requirements for alternative treatment systems  Good to excellent fiber-rubber adhesion • Hazard-free storage, mixing, dipping ? Applicability to the majority of: Established polymeric cords: rayon • Established rubber compounds Crosslinking must be fast and reliable (ideally thermal) Stable at ambient temperatures (several days) if rubberized • Aqueous solutions / suspensions preferred ? Tunable penetration depth into the fiber ? Intermediate modulus of adhesive layer (mechanical compatible) Adequate performance during the whole tire life at all conditions Cordenka GmbH & Co KG, paper presented at the Tire Technology Expo 2015, Cologne, Germany, (2015).

22. Summary Atmospheric plasma treatment … • is a promising technology to create adhesion between cords and rubber • is a good alternative to RFL in terms of toxicity and process waste generation • requires a 2-step process (cleaning & polymerization) • uses precursor with by preference a S-moiety and double bonds (thiophene) • is very sensitive to plasma power • undergoes a loss in efficiency if plasma gases are present • has to be followed by immediate rubberizing • is sensitive to and has to be tailored for the type of fiber

23. Acknowledgements Thank you for your attention