Technical Report 7 Rhenogran P9 and Rhenogran AFP predispersed, polymer bound aramid short fiber pulp Harald Kleinknecht, Rubber Sales Western Europe, Rhein Chemie Rheinau GmbH, Mannheim [ Contact: harald.kleinknecht@rheinchemie.com] Key words: automotive, hoses, belts, profiles, seals, molded parts, EPDM, HNBR, Rhenogran AFP /EPDM, Rhenogran P9- /EPDM, fiber, fibre, reinforcement, pulp, aramid, Twaron Summary Rhenogran AFP-/EPDM (GE 99) and Rhenogran P9-/EPDM are two products from a series of predispersed, polymer-bound aramid short fiber pulp master batches. They are suitable for use in many high-quality technical rubber goods, usually on the basis of EPDM and HNBR. Rubber products made from such compounds are usually used in the automobile and mechanical engineering industries. Particularly where high standards have to be met in terms of quality, physical properties as well as the resistance of the parts to temperature and aggressive media, Rhenogran P9 and Rhenogran AFP are the materials of choice. Source: Gates
Technical report 7 Page 2 Rhenogran AFP-/EPDM and Rhenogran P9-/EPDM are used as highly reinforcing additives. Good mixing and dispersing properties, easy metering as well as integration and orientation of the fiber pulp in the rubber mixture are decisive for the end quality of the rubber products. EPDM and HNBR mixtures reinforced with aramid fiber pulp are used in many different applications, for example in belts, hoses, seals and molded parts. Good long-term temperature stability (>5 C), dynamic load capacity and good resistance to media, in particular to oil (HNBR products) are made possible. Rhenogran AFP is manufactured by a new process to achieve ultimate dispersability. Depending on the orientation of the fiber bundles, aramid fiber pulp in elastomer components produces an unusual high level of reinforcement, in particular at low elongation. The steel elasticity of aramid fibers leads to enormous modulus increase even when only few phr are used. While the reinforcement effect of filling materials is only felt at high elongation levels, and a higher degree of cross-linking only contributes towards a modulus increase at medium elongation levels, the use of aramid pulp in the field of low elongation creates a new field of application for designing materials with extremely high strength. The uniaxial orientation of the fibers and the associated strength anisotropy are ideal for the use of applications in which high loads occur with medium or low elongation in one direction. In particular, these are power transmission belts, pressure hoses or special tires (motor cycle, off-road vehicle). Source: Voith
Technical report 7 Page. Aramid fibers characterization The raw fiber material is polymerized from two components (P-phenylene diamine and terephthalyl dichlorine) and is then spun as an Fig. : Aramid fibers - chemical structure and manifestations endless fiber from a sulfuric acid solution. Fig. shows the composition and the various forms of aramid fibers. Chemical structure of aramid fibers: para-aramid (poly-p-phenylene terephthal amide) Microscopic structure of aramid fibers: Diameter approx. µm Length: endless filament From these high-quality endless fibers, the short fibers are obtained by cutting them to the required length (chopped or staple fibers). Aramid staple fibers Fiber pulp is then produced from these short fibers by means of special mechanical processing. Microscopic structure of aramid fiber pulp: Length approx. -2 mm Diameter: core/fibrils µm/µm Specific surface: approx. m 2 /g Visual appearance of fiber pulp: felted fluffs, yellowish mass Source: Teijin Aramid ()
Technical report 7 Page These fibers have outstanding technological properties: extremely high mechanical strength (approx. 8 MPa) low expansion very good resistance to chemicals very high resistance to high temperatures (approx. 5 C) no shrinking high dimensional stability no brittleness The processing of the smooth short fibers to form highly fibrillated pulp does not change the above-mentioned properties of the material. In fact, this fibrillation leads to outstanding mechanical anchoring of the pulp fibers in the polymer network and gives strength without the use of adhesion promoters. A precondition for this is, however, good dispersion of the pulp in the rubber compound. This is achieved by the use of specially processed Rhenogran AFP and Rhenogran P9 short fiber pulp master batches. 2. Range of Rhenogran aramid pulp products Tab. : An overview of the Rhenogran aramid short fiber pulp types Product Pulp % Binding system Appearance Rhenogran P9-/EPDM EPDM light yellow chips Rhenogran P9-/NR NR yellowish granules Rhenogran P9-/CR CR yellowish granules Rhenogran P9-/NBR NBR yellowish granules Development products Rhenogran AFP-/EPDM (GE 99) EPDM light yellow chips Rhenogran AFP-/NR (GE 9) NR light yellow granules Special types e.g. EVA, TPO, HNBR on request. Product examples: Rhenogran P9-/EPDM: light yellow chips, approx. xx5 mm Rhenogran AFP-/EPDM: light yellow chips, approx. 2-6 mm long To make use of the outstanding properties of the aramid short fibers, in particular the pulp fibers, for improvement of the technical efficiency of rubber compounds as well, it is necessary to process these highly fibrillated fibers by complete separation to distribute individual fibers in the compound. This is only possible when predispersing the fine bundles of fibers.
Technical report 7 Page 5. Typical applications The products from the Rhenogran AFP and the Rhenogran P9 series are suitable for use in mixtures of the common polymer types such as for example NR, IR, BR, SBR, EPDM, CR, NBR, HNBR. Rubber mixtures can be optimized for specific applications by adding Rhenogran AFP or Rhenogran P9. Similar improvements can be found in all types of rubber mixtures. An important factor here is the anisotropic orientation of the fibers, that is, orientation in the direction of flow. In the direction of flow, the improvement in the properties is normally significantly more pronounced than at right angles to the direction of flow. For individual properties such as wear behavior, it may make sense to align the fibers perpendicular to the stress level. Tab. 2: Applications and improvements in properties Component V-belts, toothed belts, power transmission belts, conveyor belts hoses seals, bushings membranes cables profiles rubber padding for tracked vehicles, dock fenders, bearings shoe soles tires rollers, roller coverings Significant property improvement service life wear, reduced running noise increased load, breaking strength properties under high thermal load, rigidity, dimensional stability, pressure stability properties under high thermal load, creep, shrinking, replacement for fabric reinforcement puncture strength, stiffness modulus, cut resistance, dimensional stability green strength, dimensional stability cut resistance, wear resistance wear resistance green strength, wear resistance, cut resistance, chip and chunk resistance, tire stability (emergency running properties), cross-dimensional stability, apex and beadfiller reinforcement stability under load, apex resilience, cut resistance, modulus increase
Technical report 7 Page 6. Example recipes with test results In the test compounds, and 2 phr Rhenogran AFP-/EPDM and Rhenogran P9-/EPDM respectively were used. In the compounds with Rhenogran, the content of carbon black was reduced by phr and 2 phr respectively compared with control with 5 phr carbon black N 55, in order to achieve an approximately comparable hardness level. Tab. : EPDM mixture approx. 7 Sh A with phr and 2 phr Rhenogran AFP aramid fiber batches Control 2 Control 2 P9, AFP, P9, 2 2 AFP, 2 Buna TM EP G 85 EPDM CB N-55 carbon black 5 Paraffinic oil plasticizer 7 7 7 7 7 7 Rhenofit TAC/S activator Aflux 2 dispersing aid TMQ antioxidant Rhenogran ZMMBI-5 antioxidant Poly-Dispersion VC-6P peroxide 5 5 5 5 6 6 Rhenogran P9-/EPDM aramid pulp 2 Rhenogran AFP-/EPDM aramid pulp 2 In the control compounds and 2, the additional polymer content of the mixtures with added Rhenogran AFP-/EPDM was not compensated. In the compounds with 2 phr Rhenogran, the peroxide Poly-Dispersion VC-6P was increased from 5 phr to 6 phr in order to compensate for the higher content of polymer binder.. Mooney, scorch and rheometer measurements Fig. 2: Viscosity, Mooney ML +/ C ME 2 8 6 Control Control 2 P9-/EPDM, phr AFP-/EPDM, phr P9-/EPDM, 2 phr AFP-/EPDM, 2 phr 2 2 5 6 min. With higher carbon black content, the mixtures show correspondingly higher viscosity levels. A higher fiber content, by contrast, does not lead to an increase in viscosity.
Technical report No. 7 Page 7 Fig. : Scorch behavior (2 C) ME 2 8 6 Control Control 2 P9-/EPDM, phr AFP-/EPDM, phr P9-/EPDM, 2 phr AFP-/EPDM, 2 phr 2 5 5 2 25 5 5 min. No systems show any scorching at 2 C curing temperature. Fig. : Rheometer test Nm,6,,2,8,6,,2 Control Control 2 P9-/EPDM, phr AFP-/EPDM, phr P9-/EPDM, 2 phr AFP-/EPDM, 2 phr 2 6 8 2 6 8 min. The rheometer curves are similar in terms of cross-linking speed as well as in terms of torque maximum. With an increased carbon black content as well as a higher content of Rhenogran AFP-, however, the torque maximum achieves a higher level than control compound 2 ( phr carbon black).
Technical report 7 Page 8.2 Physical properties Hardness An increase of carbon black content of phr (control 2 versus control ) results in an increase in hardness of ShA units. The addition of and 2 phr Rhenogran AFP-/EPDM and Rhenogran P9-/EPDM respectively leads to an increase in hardness of approximately 7 to 9 ShA units, independent from fiber load. Basically the same picture arises after aging ( days/25 C). Aramid short fiber pulp thus has a considerable reinforcing effect even at rather low dosage. Fig. 5: Hardness ShA, vulcanization ( min, 8 C) ShA 76 7 72 7 68 66 6 62 6 2 P9, AFP, P9, 2 AFP, 2 Fig. 6: Hardness ShA, after aging ( d/25 C) ShA 96 9 92 9 88 86 8 82 8 2 P9, AFP, P9, 2 AFP, 2
Technical report 7 Page 9 Modulus Carbon black leads to a slight modulus increase. Compared with carbon black, short fiber pulp leads to a significant modulus increase in the direction of the fiber orientation, and depending on the amounts added (2 phr Rhenogran AFP-/EPDM) can cause the modulus to increase fourfold (2% elongation) (Fig. 7). In cross direction (at right angles to fiber orientation) the level of modulus remains widely unchanged (Fig. 8). This is of major significance for components with an uniaxial direction of stress (e.g. power transmission belts). Ideal fiber orientation is achieved by calendering or extruding the compounds. Laboratory mixes are prepared on an open mill. Fig. 7: Modulus at low elongation levels, longitudinal MPa 5.5.5 2.5 2.5.5 Modulus 2% Modulus 5% Modulus % 2 P9, AFP, P9, 2 AFP, 2 Fig. 8: Modulus at low elongation levels, transverse MPa 2.5 Modulus 2% 2 Modulus 5%.5 Modulus %.5 2 P9, AFP, P9, 2 AFP, 2
Technical report 7 Page Tear strength Tear strength increases when Rhenogran aramid short fiber pulp types are used. N/mm 5 5 5 This effect becomes particularly clear after aging. Fig. 9: Tear resistance after vulcanization and after hot air aging vulc. 9 min/8 C longitudinal vulc. 9 min/8 C transversal 25 2 5 5 aging d/25 C longitudinal aging d/25 C transversal 2 P9, AFP, P9, 2 AFP, 2 Dynamic performance and flex crack stability The dynamic lifetime of fiber reinforced elastomers is highly dependent on fiber dispersion. While evenly dispersed fibers exhibit equivalent lifetime of comparable carbon black filled compounds. When rating Rhenogran AFP in comparison to Rhenogran P9 elastomers containing AFP-dispersion showed the best flex crack stability as a result of further dispersion improvement. Visual characterization of the fiber dispersion The dispersion of the fibers plays a significant role in the property profile of the material, in particular with respect to uniaxial reinforcement, as well as in the dynamic service life of the component. As can be seen from Fig., when pure aramid pulp is mixed into EPDM mixtures, large, undispersed agglomerates of pulp remain, and these can reach a length of several millimeters in diameter.
Technical report 7 Page Fig. : Dispersion of the fibers in the compound AFP-/EPDM (2 phr) in EPDM compound (magnification: -fold) Rhenogran AFP-/EPDM, homogeneously distributed and fully dispersed (line of cut parallel to fiber orientation) AFP-/EPDM (2 phr) in EPDM mixture (magnification: -fold) Rhenogran AFP-/EPDM, homogeneously distributed and fully dispersed (line of cut perpendicular to fiber orientation) Pure short fiber pulp, (8 phr) in EPDM mixture (magnification: -fold) undispersed fiber pulp (line of cut parallel to fiber orientation) Undistributed pulp leads to imperfections, which in general can lower the level of physical properties and can lead to premature failure of the component. From the photos in Fig. it can clearly be seen that correct dispersing is achieved with conventional mixing methods when using predispersed aramid short fiber pulp, parallel as well as perpendicular to the direction of fiber orientation. Pure pulp fiber result in large undispersed structures that resist prolonged mixing even at high shear.
Technical report 7 Page 2 5. Summary Aramid short fiber pulp is characterized by unusually high strength, under static and dynamic load. In particular at low elongation, extremely high moduli can be achieved in the direction of fiber orientation. Aramid short fibre pulp is extremely resistant to thermal load and chemical influences. Aramid short fiber pulp only achieves practical dispersibility when predispersed qualities are used, such as for example Rhenogran AFP-/EPDM or Rhenogran P9-/EPDM. In terms of the level of strength, dynamic resistance and the morphological evaluation of the quality of distribution, Rhenogran AFP-/EPDM proves to be the best dispersing product quality. For this reason, the types from the Rhenogran AFP and Rhenogran P9 series are used for modern high-performance materials for belts, pressurized hoses, special tires and molded goods for heavy duty applications.
Our technical advice - whether verbal, in writing or by way of trials - is given in good faith but without warranty, and this also applies where proprietary rights of third parties are involved. It does not release you from the obligation to test the products supplied by us as to their suitability for the intended processes and uses. The application, use and processing of the products are beyond our control and, therefore, entirely your own responsibility. Should, in spite of this, liability be established for any damage, it will be limited to the value of the goods delivered by us and used by you. We will, of course, provide products of consistent quality within the scope of our General Conditions of Sale and Delivery. Aflux, Rhenofit and Rhenogran are registered trademarks of Rhein Chemie Rheinau GmbH, Germany. Buna TM is a registered trademark of Lanxess Deutschland AG, Germany. Poly-Dispersion is a registered trademark of Rhein Chemie Corporation, USA. Twaron is a registered trademark of Teijin Aramid BV, Netherlands. Images by courtesy of Gates Power Transmission Europe BVBA, Belgium, Teijin Aramid BV, The Netherlands and Voith Paper Holding GmbH & Co. KG, Germany. Rhein Chemie Rheinau GmbH Duesseldorfer Strasse 2-27 6829 Mannheim, Germany Phone: +9 ()62-897- Fax: +9 ()62-897-269 rubber.rcr@rheinchemie.com Rhein Chemie Corporation 5 Parker Court Chardon, OH 2, USA Phone: +--285-57 Fax: +--285-26 rubber.rcc@rheinchemie.com Rhein Chemie Japan Ltd. Marunouchi Kitaguchi, Bldg. 2 F -6-5 Marunouchi, Chiyoda-ku Tokyo -5, Japan Phone: +8-529-8 Fax: +8-529-9779 Rubber.rcj@rheinchemie.com Rhein Chemie (Qingdao) Ltd. Siliubei Road Li Cang District Qingdao 266, PR China Phone: +86-52-882-67 Fax: +86-52-882-596 rc.asia@rheinchemie.com G29/pdf/KR/8 www.rheinchemie.com