14 Rubber & News • March 9, 2020 www.rubbernews.com Technical Surface modi cation of ground rubber with trans-polyoctenamer By Alexander Paasche, Frank Lindner, Peter Hannen, Marco Gensheimer Executive summary Evonik Resource Efficiency GmbH Recycling rubber is gaining traction globally in efforts toward a circular economy. Beside sustainability, it also is recognized as a cost-efficient raw ma- and Ankur Kant terial in applications such as modified asphalt, virgin rubber blends and molded Evonik Corp. goods from ground rubber. Trans-polyoctenamer (TOR) was first However, its applicability is limited by performance gaps or processing chal- described by Natta et al. in the 1960’s,1 lenges whenever it is compared to virgin rubber products or polymer materials. but it took until the 1980’s to recognize The application of trans-polyoctenamer (TOR) has proved to be a valuable tool its value as a rubber material.2 Com- in overcoming these gaps. mercialized under the trade name We will review the literature and show the latest mechanistic insights on Paasche Vestenamer, trans-polyoctenamer was trans-polyoctenamer’s mode of action. The surface coating effect of TOR pro- first made available to the rubber indus- vides an effective method that turns recycling rubber into a valuable resource by improving performance and processing of rubberized asphalt, rubber blends The author TECHNICAL NOTEBOOK and molded goods. Alexander Paasche holds a doc- Edited by John Dick torate in chemistry as well as a trusion speeds. By looking at the molecular weight, degree in business administration. try by Huels A.G. of Germany, later part Some combinations of effects are coun- trans-polyoctenamer is in the range of His academic background has fo- of Degussa, and is today provided by the terintuitive and can exclusively be achieved 140.000 g/mol and can be understood as cused on physical and theoretical specialty chemical company Evonik. by TOR, like having a plasticizing effect a material between liquid rubbers and chemistry at the University of Wuer- TOR provides an unusual set of prop- and improving green strength at the same “real” rubbers (Fig. 1). In fact, TOR zburg, Germany. erties (Table I) like having partially time.12 This “magic behavior“ in rubber shares the best of two worlds by provid- Paasche’s industry career start- macrocyclic polymer structure,3 high applications also becomes visible by many ing processing benefits like liquid rub- ed in 2013 as a new business ana- crystallinity,4,5 a low melting point and formulation examples where TOR acts as a bers and giving performance like a spe- lyst at the strategic research unit glass transition temperature,6,7 and processing aid (lower Mooney viscosity, cialty rubber. Evonik Creavis GmbH. By heading high thermal stability,8 as well as the improved finish), without compromising The thermoplastic properties of TOR innovation project portfolios, he ability to be vulcanized like common and often improving mechanical and dy- provide additional advantages, like being gained experience in innovation rubber polymers. namical properties of the vulcanizate. an easy-to-dose pellet at room tempera- management and market assess- This unique combination of properties Some typical effects by TOR, when intro- ture or showing a fast recrystallization ment for a wide spectrum of indus- makes it a valuable tool in rubber prod- duced into formulations, are: that helps keep green compounds stable tries fields, like agricultural bio uct manufacturing. TOR typically is ap- • Hardness maintained in hard mix- in shape, reducing tack and improving chemicals, building and construc- plied as a component in rubber formula- tures; the storage stability of rubber blends. tion, industrial membrane separa- tions, and not as a base polymer, due to • Improved elasticity; This full package of properties is val- tion, and health care products. its very low Mooney viscosity. Typically, • Less heat build-up under dynamic ued today in almost all application fields Since 2017, he has been engaged 5-15phr of base polymer are replaced by stress; of rubber, such as , hoses, profiles, in global business development, TOR to achieve the desired effects. • Reduced abrasion; and belts, molded products, linings, calen- technical projects and market intel- Many benefits have been described in • No migration. dered articles, sporting goods, medical ligence for the trans-polyoctenamer processing:2,9-11 Due to its versatile nature in rubber products, foams and many others. The rubber additive Vestenamer at the • Plasticizing in mixing and processing; processing, it is difficult to categorize widespread use is underlined by the High Performance Polymer Division • Better dispersion; TOR in the sense of additive by function: growing number of scientific and patent of Evonik Resource Efficiency GmbH • Improved green strength and di- it shares features of a , green publications about trans-polyoctenamer in Marl, Germany. Today, his tech- mensional stability; strength enhancer, anti-tack agent, com- (Fig. 2), indicating that this material nical expertise focuses on applica- • Compatibility improvements in rub- patibilizer and others. Therefore, continuously undergoes a global applica- tion of Vestenamer in recycling rub- ber blends; and trans-polyoctenamers should be consid- tion innovation process—even beyond ber, tires and rubber goods. • Better surface finish and higher ex- ered as a class of their own. rubber applications. materials points clearly in the direction Table 1: Specification and properties of trans-polyoctenamer (Vestenamer 8012). Challenges in rubber recycling of material recovery (e.g. ground tire An appealing application on the rise is rubber) instead of energy recovery (e.g. the combination of TOR with recycling burning in cement kilns). In Europe, the rubber powders. Although first publica- material recovery has grown from a tion on this use was published by Died- one-digit minority share toward the rich and Burns some 20 years ago,13 the dominating valorization route over the meaning of recycling rubber has nowa- last 25 years.15 In 2016, the amount of days gained much more importance. end-of-life tires that undergoes material One reason is that end-of-life tires are recycling to ground tire rubber (GTR) more and more recognized as a serious has reached 1,424 metric tons, with global waste problem, but also as raw more than one third of the used tires material of ubiquitous availability. To- arising in the European Union.16 day the global amount of recovered tires Some typical applications of GTR and is estimated at 17.2 million metric tons.14 recycling rubber powders are rubber The trend of how to use tire-derived mats, molded goods, polymer component Fig. 2: Bibliometry of polyoctenamers in scientific and patent literature.

Fig. 1: Categorizing polyoctenamers by molecular weight (MW). www.rubbernews.com Rubber & Plastics News • March 9, 2020 15 Technical in virgin rubber compounds, infill for prove storage stability19 and reduce is inhibited by the TOR layer. This final- identified. The TOR coating layer thick- sports fields, rubber-modified asphalt, equilibrium swelling time even further.18 ly results in better dispersed blends and ness can be estimated around 3-5 µm. fillers for paints or coatings, and various When blending GTR into virgin rub- mechanical properties, even for practi- Whereas the outer boundary of the other applications. Because recycling ber compounds, smaller particles typi- cal immiscible combinations like EPDM/ surface layer is clearly visible, the inside rubber is offered at much lower prices cally result in better mechanical proper- NBR.21 of the particle shows a blurred transition compared to virgin polymer materials, it ties.17 Moreover, the different grinding The ability to compatibilitize rubbers from the TOR layer to the inside of the can significantly improve raw material methods such as ambient grinding, is a good pre-condition for application of GTR particle. This indicates a diffusion costs of manufactured products. cryogenic grinding, or water jetting in- TOR in recycling rubber powders. Mate- and interpenetration of TOR into the Nevertheless, there are some common fluence the particle morphology and re- rials like ground tire rubber typically surface of the GTR particle. This is in problems in the use of recycling rubber sult in different surface areas. comprise a wide spectrum of rubber line with expectations from the solubili- materials that limit its extended use in Finally, the surface modification of polymer types and compositions, de- ty point of view. TOR shares similar many cases. Recycling rubber is often ground tire rubber can improve process- pending on their source and sorting. For chemical characteristics like common difficult to process. Increased viscosity, ing and product performance to a large example, passenger car tires dominate rubber polymers, and hence shows good stickiness, and swelling by hydrocar- extent. It can help to reduce processing in polymer content, compatibility as expressed by their solu- bons are some examples. Moreover, a problems like stickiness, raised viscosi- whereas truck tire treads typically have bility parameters.20 Moreover, the con- serious loss of mechanical properties ty, or better compatibility and interfacial more content. cept of interpenetrating layers already limits the use of ground tire rubber as a bonding to matrix materials—whether Adding TOR to recycling rubber crumbs has been described by Wenig et al. for component in virgin rubber materials or it is about bitumen, virgin rubber or or powders results in a similar wetting blends of TOR with thermoplastics.23,24 thermoplastics. thermoplastic materials. effect like in virgin rubber compounds. The evidence for a good surface coating Ramarad et al. gives a comprehensive With regards to bonding, chemical The difference is the “domain” sizes that of GTR by TOR explains the well-de- overview about typical challenges in poly- crosslinking has been demonstrated to are limited by the sizes of the already scribed benefits in processing. TOR mer blends.17 In general, we can summa- improve mechanical properties.16 There vulcanized recycling rubber particles. At “masks” the GTR surface and thus pre- rize three major factors that determine are many ways to address the different temperatures above the melting point, vents difficulties like higher stickiness ease of processing and performance of challenges, e.g. using to im- TOR forms a surface layer on top of the and viscosity. It also can be assumed that ground tire rubber in applications: prove processing, or using chemical particles. Although the coating process the TOR layer influences diffusion kinet- • Source of GTR; treatments to improve compatibility. TOR has been described,13,22 little information ics, when it comes to migration processes • Particle size and morphology; and plays an outstanding role here, because on the surface coating itself is available. between GTR and the embedding matrix. • Surface treatment. it fulfills all aspects, namely being a To close this knowledge gap, we conduct- Reports about reduced emissions of GTR The source of GTR determines the processing aid, improving performance ed scanning electron microscopic (SEM) by TOR in asphalt applications25 give base polymer content of the recycling and being crosslinkable. and transmission electron microscopy some indications for that. material, such as whether it is from truck studies (TEM) to prove and investigate The performance improvements ob- tire tread (high natural rubber content), Mode of action the quality and morphology of the as- served also can be explained by the passenger car tires (higher synthetic In general, TOR forms dispersed sumed TOR coating layer. TOR-coating layer. Since TOR is unsatu- rubber content), or production scrap from phases in rubber polymers, as shown by Samples were prepared with an inter- rated and can be crosslinked like rubber, it EPDM products or other rubber types. DSC measurements and microscopic nal laboratory mixer by mixing cryogen- offers a reactive surface toward the outside For example, in rubber-modified asphalt, analysis.20 The fine-dispersed TOR phases ic milled GTR of 200µm size with 4.5 wt of the particle for compatibilization and/or the choice of rubber has influence on the provide a wetting effect, resulting in percent TOR for 7 minutes. Ten random- crosslinking and can further crosslink in- diffusion kinetics of bitumen—truck less shear forces, and hence easier mix- ly selected particles were taken from the side the GTR particle along the interpene- tires reach their swelling equilibrium ing and processing of the rubber com- prepared samples and analyzed by SEM, trating layer. FTIR studies on the surface state faster and can absorb more bitumen pound. In binary rubber blends, addition confirming successful coating for nine of of TOR-coated GTR in bitumen application than car tires do.18 This might be an ad- of TOR forms a third phase at the inter- the 10 samples. Fig. 3 shows an uncoat- have shown that TOR undergoes chemical vantage in application. phase. This intermediate layer compati- ed GTR particle with rough surface reaction at processing.26 The particle size also has significant bilitizes the rubber domains by reducing structure, compared to a TOR-coated Because all curing chemical additives influence on product performance. In the interfacial tension between the two particle covered by a smooth surface. and accelerators already are present in the above mentioned case of rubber-mod- rubber components. Furthermore, the This visually confirms the wetting effect the GTR particle (and furthermore under- ified asphalt, smaller particle sizes im- recombination of domains (coalescence) of TOR as well as the good compatibility go migration processes) this can be ex- and affinity to the recycling rubber pected. Improved performance by adding Fig. 3: SEM pictures of GTR particle (left) and coating layer of TOR. particle surface. additional sulfur has been reported.27,28 An even more detailed insight is re- From the gained insights by electron vealed by the transmission electron mi- microscopic analysis, as well as the lit- croscopy of samples that were prepared by erature review shown above, a mode of thin-film cuts. Fig. 4 shows the cross-sec- action for surface modification of GTR tion of a TOR-coated GTR particle, where by trans-polyoctenamer can be conclud- the different zones of the GTR particle, ed as depicted in Fig. 5. TOR layer, and sample matrix can be See TOR, page 17

Fig. 4: TEM pictures of thin-film cuts of TOR-coated GTR particle. R ANKINGS & LISTS

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finic oil. Rubber process oils like TDAE needed for TOR compared to PU, it also and hence must withstand an acid envi- work as well. Different solubilities of can compete economically by taking the ronment. Therefore, TOR improves the TOR TOR have been observed by us in vari- total costs of formulation and processing price performance ratio of such products ous oil types (Table 2). into account. The effective amount of TOR by enhancing their lifetime. Continued from page 15 A further option is extruding equip- needed is three parts per 100 parts of Recyclability becomes more and more TOR coating process ment used for continuous mixing of GTR GTR. A standard formulation for GTR important in the long-term transforma- For a proper function of the “TOR ef- with TOR. If curing chemicals are add- compound with TOR binder, and the tion of our society that pushes toward a fects,” a good coating of the rubber parti- ed, recycling rubber compounds can be range of the respective physical properties circular economy. In this respect, we see cles is an important prerequisite. From produced that are ready for the press, or for 20-40 mesh size GTRs of various some further general advantage of using our experience, there are different ways injection-molding process. This has sources is shown in Table 3. TOR compared to other binder systems. on how to achieve this, depending on the proven to be an efficient process for It also can be assumed that the chem- Because TOR is a rubber material itself, available mixing equipment. large-scale production of rubber mats ical resistance of TOR-bound GTR arti- “rubber stays rubber” and does not be- If an internal mixer is available, like from recycling rubber powders. cles is superior in many points compared come a composite product like PU/GTR. in rubber compounding facilities, TOR to PU because it shares characteristics This could simplify a further recycling simply can be added together with GTR TOR as binder system for molded of polyolefinic materials and has a non- step of GTR products and might help to to get the desired result.13 In laboratory products from GTR branched chemical structure. This is give tires not only a second life, but even procedures, a pre-heating of TOR can The dominating binder system for desirable for products that undergo a third life—in rubber products or improve results and lower the mixing molded products from GTR is polyure- chemical stress, like animal bedding up-cycling to other applications such as time. The samples shown in Figs. 4 and thane), which is easy to process and mats that are exposed to excrements, See TOR, page 18 5 were prepared with a mixing time of needs no elevated tem- seven minutes, without addition of oil. peratures for production of molded Fig. 6 - Influence of TOR-coating on Mooney viscosity (left) and tensile strength. If an internal mixer is not available, goods. TOR is an alternative binder op- powder blenders also can be used. This tion to make new molded products from states a less capital-intensive mixing GTR, but needs vulcanization tempera- option. Because this option provides less tures in press-curing comparable to intensive mixing compared to internal, production of virgin rubber products. or Banbury-type mixers, the coating Although the energy consumption process of the particles can be facilitated might be higher than in PU processing, by employing an oil solution of TOR. A TOR can be an attractive option due to the common formulation is 20 wt percent of good mechanical properties of the vulca- TOR dissolved at elevated temperatures nizates and their superior weathering re- (100-120°C) in a suitable oil, like paraf- sistance.29 Considering the lower dosage

Table 2: Solubility of TOR in different oils at 100°C.

Fig. 7: Influence of TOR-coating on compression set.

Table 3: Standard recipe for GTR products with TOR (left) and properties of the vulcanizate.

Figure 8: Compaction resistance reduction of rubber-modified asphalt by TOR.

Table 4: Test formulations of SBR and NR.

Fig. 9: Rutting depth results by Hamburg-tests of rubber-modified asphalt by GTR and GTR/TOR. 18 Rubber & Plastics News • March 9, 2020 www.rubbernews.com Technical

Fig. 10: Rubber-modified industrial area in Germany after 11 years of heavy load. production scrap or ground tire rubber materials are introduced into virgin TOR rubber compounds. The reason for this is due to migration processes between Continued from page 17 GTR and rubber matrix, as well as in- rubber-modified bitumen and asphalt. sufficient incorporation and bonding of Nevertheless, studies are needed to the embedded GTR particles. show the practical feasibility of such a The problems typically scale with the third life concept. percentage of recycling rubber com- pounded into the virgin formulations.17 TOR-coated GTR in virgin rubber Hence, its applicability is limited The cost of GTR can go down to one strongly, especially in safety-critical ap- order of magnitude lower than virgin plications like tires. rubber materials, depending on grind- Technologies that enable the use of ing method and size. This makes it an production scrap or ground tire rubber attractive raw material from an ecologi- materials are key to extend the use of cal and economic point of view. these recycling materials. TOR can On the other side, serious processing narrow, or even close, many technical and performance problems arise when gaps that are often prohibitive factors for using GTR in virgin rubber com- pounds. This has been demonstrated by trials with some test SBR and NR com- pounds that were filled by 20 and 40 phr GTR. The reviewed formulations29 are summarized in Table 4. A typical challenge is the viscosity in- crease of the green compound that arises when GTR is added in larger amounts. The use of TOR-coated GTR shows im- provements over untreated GTR as summarized in Fig. 6. This is a result of the TOR/oil solution coating that reduc- es Mooney viscosity very close to the level of the reference compound. Further data reveals improved tensile strength where TOR improves by around 1 Mpa. The test data on compression set shows an impressive effect that illustrates the SEPTEMBER 15-17, 2020 | AKRON, OH crosslinking function of TOR between GTR and virgin polymer matrix quite well. As visible from the data in Fig. 7, THE LARGEST TIRE MANUFACTURING SHOW IN NORTH AMERICA the loss in compression set by GTR incor- poration can be completely prevented by applying the TOR coating. This can be of great advantage for applications in seals, gaskets or dampers, where compression BOOTHS AVAILABLE FOR 2020 SHOW set is an important property. Rubber modification of bitumen and asphalt Trans-polyoctenamer has a track re- Network with the Generate Leads Raise your cord of more than 25 years as a process- ing additive in the bitumen and asphalt Best in the Industry and New Business Company Pro le industry. Recycling rubber acts as a polymer modifier that improves binder properties of bitumen, and hence of the modified asphalt.30 The environmental benefits of using recycling rubber is an additional argument from the perspec- tive of sustainability and circular econo- my discussions.31–33 Although the benefits of rubber in road construction have been known for a long time, rubber in road construction is faced with practical problems in pro- cessing like stickiness, storage problems or emission. Moreover, lack of knowledge about best practices in working with rubber has been a hurdle that inhibited wider adoption of rubber modification in asphalt in the past. For example, swell- ing times18 and working tempera- tures34,35 are critical issues to take care of in rubber modification. The situation has changed today as rubber modification moves toward more Interested in Exhibiting? acceptance and has even found entry into national strategies.36 TOR is part of this process, as it helps to overcome the Looking to Register? critical challenges in the practical appli- cation of rubber in road construction. The benefits of reduced stickiness, im- Have a Paper to Present? proved rutting resistance and reduced cracks have been confirmed by many researchers all over the world.26,27,37-47 Moreover, TOR helps to improve stor- NOW ACCEPTING HERZLICH age stability and pumpability of rubber- ized asphalt,26,48 which is a key challenge AWARD SUBMISSIONS in wet process. Positive effects on ther- mal stability also have been reported recently. 25,44 See TOR, page 19 visit itec-tireshow.com www.rubbernews.com Rubber & Plastics News • March 9, 2020 19 Goodyear to supply new EV touring-car racing series By Bruce Davis into account that EVs are heavier and have more Tire Business torque. Tires developed for EVs have to cope with in- PARIS—Goodyear has landed the tire supply contract stant power delivery while also delivering high grip/ for a new touring-car-based electric-vehicle racing se- traction as well as low rolling resistance to increase ries that’s being organized by Eurosport Events, the range and efficiency. promoter of the FIA World Touring Car Cup and other Securing this contract—and becoming a founding motorsports series. partner of Pure ETCR—is a further step in the return The new series, dubbed Pure ETCR, will take flight of the Goodyear brand to the international motorsports in 2021 after four demonstration events in 2020. The scene, which began last summer. series will invite car makers to participate with race- The company now has secured tire supply deals with prepped small touring cars that initially will use a the FIA World Endurance Championship, European standard electric motor/battery combination—rated at LeMans Series, FIA World Touring Car Cup and Brit- 500 kW (670 hp)—connected to a rear-wheel-drive ish Touring Car Championship. chassis layout. The new EV series will feature bracket-style, short- Goodyear said it is developing a treaded race tire for sprint elimination racing that commits drivers to Pure ETCR that will incorporate technologies used in pushing their cars to their limits with no need for ener- the tire maker’s latest electric vehicle tires and its Ea- gy-saving tactics, the organizers said. It also will challenge Goodyear to design tires that gle F1 SuperSport ultra-high-performance range. François Ribeiro, head of Eurosport Events, the Pure ETCR have rapid warm-up times, so drivers can go flat out The definitive tire specification—using a “proven” promoter; and Mike Rytokoski, vice president and chief mar- from the very beginning of a race. motorsport construction with a treaded design—will be keting of cer, Goodyear Europe, pose for a photo at a recent The organizers envision having two entries from unveiled in spring 2021, ahead of the first Pure ETCR press conference to announce the launch of ETCR. event, Eurosport Events said. each manufacturer/vehicle brand. To date, only two car Having a treaded tire design means Pure ETCR drivers la car-based electric racing series that debuted in 2014. companies—Hyundai Motor Co. and Volkswagen A.G.’s can use the same tires in wet and dry conditions, reducing Mike Rytokoski, vice president and chief marketing SEAT brand/division—have committed to the series. the number of tires needed per event. This aligns with officer, Goodyear Europe, said this partnership with The trial race events in 2020 are set for courses in Goodyear’s and Pure ETCR’s mission of working together Pure ETCR is “much more than just supplying race Austria, Denmark, South Korea and China, according to find sustainable solutions for the future of mobility and tires. Together, we will use racing to develop technology to Eurosport Events. motorsport. to thrill the next generation of high-performance driver.” The organizer also is planning a demonstration event It also mirrors the philosophy and the FIA Rytokoski said Goodyear considers itself a leader in in January 2021 in Daytona, Fla., in conjunction with espouse for Formula-e, the single-seat, open-wheel formu- electric vehicle tire development, which has to take the 24 Hours of Daytona. Technical

In asphalt application, the use of re- 14. Deloitte. Global ELT Management–A global (Copenhagen Resource Institute, 2009). claimed asphalt pavement (RAP) is fur- state of knowledge on collection rates, recovery 32. Wang, T. et al. Energy consumption and envi- routes and management methods. (World Business ronmental impact of rubberized asphalt pavement. TOR ther leverage toward more sustainability Council for Sustainable Development, 2018). J. Clean. Prod. 180, 139-158 (2018). in road construction. The use of rubber 15. Shulman, V.L. Introduction to Tyre Recy- 33. Feraldi, R., Cashman, S., Huff, M. & Raahauge, Continued from page 18 modification is a perfect fit to improve cling: 2018. (European Tyre Recycling Association L. Comparative LCA of treatment options for U.S. the aged binders in reclaimed asphalt. (ETRA), 2018). scrap tires: material recycling and tire-derived fuel From a road construction perspective, 16. ETRMA. Used Tyres/ELT Management in Eu- combustion. Int. J. Life Cycle Assess. 18, 613-625 rubber is a temperature-sensitive raw From our recent studies that will be rope—Volumes Situation 2016. (European Tire (2013). material, which means that working at published soon, we see that use of 50 & Rubber Manufacturers Association (ETRMA), 34. Fornai, D., Persici, V. & Lupi, C. Occupational lower temperature is favorable in terms percent RAP in top layer is possible with- 2018). health risk assessment for the workers exposed to out compromising standards and expec- 17. Ramarad, S., Khalid, M., Ratnam, C.T., Chuah, rubberized asphalt fumes. in 4-7 (2015). of emission. On the other side, low tem- A.L. & Rashmi, W. Waste tire rubber in polymer 35. Fornai, D.S., Mazzotta, C., Bermejo, F. & J.M., peratures lead to higher viscosities, tations of modern road construction. blends: A review on the evolution, properties and Saiz, L. A new era for rubber asphalt concretes for which can be a problem when bitumen is future. Prog. Mater. Sci. 72, 100–140 (2015). the green public procurement in road construction. processed at too-low temperatures. Summary 18. Artamendi, I. et al. Diffusion kinetics of bitu- Eur. Union Road Fed. (2016). In summary, TOR is a unique tool to men into waste tyre rubber. in Journal of the Asso- 36. Genever, M., O’Farrell, K., Randell, P. & Reb- During paving the TOR effect brings ciation of Asphalt Paving Technologists: From the bechi, J. National market development strategy for significant benefit, because it reduces overcome many challenges that arise in Proceedings of the Technical Sessions 75, (2006). used tyres 2017-2022. 180 (Tyre Stewardship Aus- the compaction resistance of rub- the use of GTR, hence pushing boundar- 19. Sienkiewicz, M., Borzedowska-Labuda, K., Wo- tralia, 2017). ber-modified asphalt. This opens a wider ies of what is possible with the cost-effi- jtkiewicz, A. & Janik, H. Development of methods 37. Diedrich, K. & Burns, B. Pavements from as- cient, sustainable and ubiquitous avail- improving storage stability of bitumen modified phalts modified with ground tire rubber (GTR). temperature window for processing and with ground tire rubber: A review. Fuel Process. Elastomery 4, 9-14 (2000). therefore gives more process safety. In- able raw material ground tire rubber. Technol. 159, 272–279 (2017). 38. Yadollahi, G. & Sabbagh Mollahosseini, H. fluence of TOR on lower compaction re- 20. Issel. Thermodynamische und rheologische Improving the performance of Crumb Rubber bitu- sistance is shown in Fig. 8. Steuerung der Materialeigenschaften von Elasto- men by means of Poly Phosphoric Acid (PPA) and References mersystemen durch trans-Poly(octenylen). (Univer- Vestenamer additives. Constr. Build. Mater. 25, 1. Natta Giulio, Dall’Asta Gino, Bassi Ivano Walter The effect also can be explained by the sitat Hannover, 1993). 3,108-3,116 (2011). & Carella Giovanna. 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