Delivered as part of the RAPRA automotive engineering session at the Advanced Engineering UK 2015 Show

2 Novel Tyre Recycling M. Bennett & Dr C. Norris ARTIS

Contents 3 o Reclaimed Carbon Black (rCB) Global Benchmarking Programme. o Colloidal Properties o Composition o In-rubber Performance o rCB Process o Current European Passenger Tyre Compositions. o Novel Pyrolysis Outcomes (PO). o Preliminary Trials o Reclaimed Silica Composition o Tyre Tread Applications Study o Conclusions

ARTIS – Independent Materials Consultancy 4 o ARTIS has been involved in the development and analysis of pyrolysis carbon since being established in The services that ARTIS offer to this sector include… o Process optimisations – reactor. o Process optimisations – post-reactor. o Feedstock and product characterisations. o Carbon and oil quality assessment. o Quality assurance testing. o Applications data generation. o Customer facing/ support in the use of pyrolysis carbon. o Surface treatments to modify performance. o ARTIS assets include… o Fully equipped chemical analysis facility. o Rubber processing capabilities. o Rubber applications laboratory, rheometry, physical, dynamic, ageing... o Experienced scientists and engineers, including carbon black experts. o Extensive contact with potential users of pyrolysis carbon black. o Facilities to assess the capacity of activated carbons.

rCB Colloidal Map 5 o Characterisation of rCB produced from differing processes and feedstock. Batch, continuous, microwave, European, NA… Carcass Tread o Majority of the rCB samples fall in the colloidal space between N500→N300 series carbon blacks (carcass and tread grades). o Unsurprising: whole tyre feedstock will contain a blend of carcass and tread grades. o Is this a good indicator of in- rubber performance of rCB?

rCB Composition 6 o Determined via TGA and energy dispersive X-ray analysis. rCB o rCB known to contain: o Originally compounded carbon black. o Carbonaceous residues formed during pyrolysis. o Inorganic materials. o Large variance in ash content, 14 to 38wt% (function of feedstock).

rCB In-Rubber Performance 7 Generic SBR Formulation Ingredientphr SBR Carbon Black60 TDAE Oil10 Zinc Oxide5 Stearic Acid2 6PPD1.5 TBBS1.5 Sulphur1.5 o Performance: majority of rCB materials fall in the region of N600→N700 series carbon blacks for rheometry, physical and dynamic properties. o Contrary to colloidal properties which suggest N300→N500 series.

rCB In-Rubber Performance – Dispersion 8 EXP1 N330 N115 pCB_A pCB_D Refined rCB N772 Un-refined rCB o Not all rCB the same. o A number of post-reactor refining steps required to produce the final beaded product. o Often overlooked. o Refined material approaching the dispersion level of conventional carbon black.

rCB Strain Dependency 9 o Dynamic mechanical analysis (DMA); strain sweeps. o Networking efficiency = ∆E’ = E’ 0 – E’ ∞ o rCB networking efficiency potentially dictated by: o Surface area, composition, surface activity and dispersion. pCB_A pCB_D pCB_E * ∆E’

rCB Filler-Filler Interactions 10 o Networking efficiency of carbon black increases with surface area. o ∆E’ values of rCB well below that predicted from STSA. o Partially due to reduced surface activity (carbonaceous residue coating the graphitic crystallite ends of the virgin carbon black). o Also indicates that STSA is overestimating the surface area available to the polymer matrix. o Ash content (14 to 38wt%) has little influence.

rCB Process 11 o Carbonaceous residue dictating: Surface Activity. Dispersibility. o Both reduce reinforcing potential. Disparity between performance predicted from colloidal properties and in-rubber performance. Representation of the spatial arrangement of aggregates within the rubber feedstock. Representation of the formation of carbonaceous residues formed during pyrolysis Representation of aggregate size distribution in final rCB

Current rCB Summary 12 o Performance: Classified as a semi-reinforcing filler in the region of N600-N700 series carbon blacks. Using colloidal properties alone is a poor indicator of performance. o The result of modified surface chemistry. o Classification: (ASTM or other) urgently required to define rCB. This will allow: o Differentiation between refined and poor quality recyclate. o Potential customers to make informed choices. o Applications: Potential 100% replacement for N700→N600 series for some applications such as inner-liner. Part-replacement also possible. Applications data essential given the disparity between colloidal properties and in-rubber properties.

Current European Passenger Tyre Compositions 13 o Increasing utilisation of silica filler. o Current, leading, passenger tyre treads contain very little CB. Same trend emerging for Truck and some other components/ applications. o Not a good feedstock for rCB production!

Novel Pyrolysis Outcomes 14 o Given the current trends in formulation changes, ARTIS have developed a process for recovering silica filler (rSilica). o Patent application filed April o Uses a conventional approach (initially) to reclaim gas and oil from polymer volatilisation. o Important that process conditions are optimised to minimise carbonaceous residue formation. o Possibility to significantly reduce run times.

Preliminary Trials 15 o Control compounds produced at ARTIS containing Ultrasil VN2, VN3 and 7000GR grades of silica. o Silica reclaimed using ARTIS process and re-compounded into the same formulation. 100% replacement (~5wt% ZnO not accounted for). o Virgin and rSilica performance compared… VN2 Filler VN3 Filler 7000GR Filler

Tyre Tread Applications Study – I 16 o Current leading European tyre treads analysed to yield the representative formulation. o Tread and sub-tread feedstock recycled to produced the recovered silica (rSilica). o Tread performance of rSilica compared to Ultrasil 7000GR highly dispersible silica. 50:50 blend also included within the study. Ingredientphr Solution SBR (oil extended) N375 carbon black10 Silica (7000GR or rSilica)70 Zinc Oxide1.3 Wax1.5 6PPD1.5 TMQ1 PEG40002 Stearic Acid1 Silane coupling agent6 CBS-80%1.5 Sulphur1.5

Tyre Tread Applications Study – II 17 ElementWt% Si45.3 O50.2 Zn3.0 Al1.0 S0.5 o rSilica yields >30% achieved with careful selection of the feedstock. o No post-reactor processing. o Typically >95wt% silica. o ~3-4wt% zinc oxide (active, so should be beneficial). o <2wt% trace elements. o The non-silica components were not accounted for in this study.

Tyre Tread Applications Study – III 18 o Slight reduction in dispersion compared to virgin highly dispersible Ultrasil 7000GR. o Note: No post reactor treatment of rSilica. o Best ‘refined’ rCB from crosscheck programme achieved Ra = 0.78µm. o Note that Ra values for the tyre treads = 0.40 to 1.28µm. 7000GR50:50rSilica Ra = 0.55µmRa = 0.65µmRa = 0.71µm

Tyre Tread Applications Study – IV 19 o Impressive performance compared to Ultrasil 7000GR control. o Note that rSilica is ~95wt% silica, therefore ~5wt% non-reinforcing.

Tyre Tread Applications Study – V GR 50:50 rSilica o Akron abrasion resistance, normalised volume loss data (note: lower = better performance)… 7000GR = :50 = 83 rSilica = 114 o No significant change in performance.

Tyre Tread Applications Study – VI 21 o Greater level of filler-filler interactions with the 7000GR. ΔE’ = E’ 0 -E’ ∞ 7000GR ΔE’ = :50 ΔE’ = 5.98 rSilica ΔE’ = 6.09 o Reduced energy losses with rSilica. o ~5wt% non-reinforcing content of rSilica a significant contributor.

Tyre Tread Applications Study – VII 22 o Slight reduction in stiffness, as noted previously. o No statistically significant impact on T g. Wet grip performance, therefore, expected to be similar.

rSilica Further Summary 23 o Encouraging performance of recycled silica in comparison to one of the market leading highly dispersible grades. o Minor reductions in reinforcing properties noted. o Further Work: Some process optimisation work to improve dispersion Scale up

Conclusions 24 o rCB and rSilica can offer green alternatives to conventional fillers. Recycling route dependent on feedstock composition. o Predicted future growth of tyre production will demand raw ingredients from alternative sources. o Potential for part or 100% replacement (formulation dependant). o ARTIS currently pursuing ‘up-scaling’ and optimisation of the rSilica process.

25 Thank you