of Hydrogenated Nitrile Rubber Polymers Available

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1 2 Types of Hydrogenated Nitrile Rubber Polymers Available 2.1 Introduction This chapter provides an overview of the types and grades of HNBR polymers commercially available and their performance characteristics in the context of other oil-resistant polymers. 2.2 Summary of Grades Available Table 2.1 summarises the grades of HNBR polymers available from two manufacturers, Zeon Chemicals and Lanxess. The primary sort was made by mole% ACN, a secondary sort by approximate residual unsaturation and a tertiary sort by nominal Mooney viscosity. It is seen that HNBR polymers are available with mole% ACN within the range 17 to 50%, at a variety of residual unsaturation levels and bulk viscosities. For a given mole% ACN content, a higher residual unsaturation figure is useful for providing more rapid sulfur vulcanisation or when greater crosslink density is required in the finished product. A lower bulk Mooney viscosity results in improved high-shear flow in transfer or injection moulding. 13

2 Practical Guide to Hydrogenated Nitrile Butadiene Rubber Technology Table 2.1 HNBR grades commercially available, December 2010 Grade Manufacturer Mole% ACN (nominal) Mooney viscosity ML(1+4) at 100 C (nominal) Residual % unsaturation (approximate) Zetpol 4300EP Zeon Zetpol 4300 Zeon Zetpol 4310EP Zeon Zetpol 4310 Zeon Therban AT LT 2004 VP Lanxess Therban LT 2007 Lanxess Therban LT 2057 Lanxess Therban LT 2157 Lanxess Zetpol 3310EP Zeon Zetpol 3310 Zeon Therban AP A 3404 Lanxess Therban 3406 Lanxess Therban 3407 Lanxess Therban AT C 3443 VP Lanxess Therban 3446 Lanxess Therban 3467 Lanxess Therban VP KA 8837 Lanxess Zetpol 2000EP Zeon Zetpol 2000L Zeon Zetpol 2000 Zeon

3 Types of Hydrogenated Nitrile Rubber Polymers Available Therban 3607 Lanxess Therban 3627 Lanxess Zetpol2010L Zeon Zetpol 2010 Zeon Zetpol 2010H Zeon Therban AT A 3904 VP Lanxess Therban 3907 Lanxess Therban AT 4304 VP Lanxess Therban 4307 Lanxess Therban 4309 Lanxess Therban AT 4364 VP Lanxess Therban 4367 Lanxess Therban 4369 Lanxess Zetpol 1000L Zeon Zetpol 1010EP Zeon Zetpol 1010 Zeon Zetpol 1020EP Zeon Zetpol 1020L Zeon Zetpol 1020 Zeon Therban AT 5005 VP Lanxess Therban 5008 VP Lanxess Therban AT 5065 VP Lanxess Zetpol 0020EP Zeon Zetpol 0020 Zeon Therban is a registered trademark of Lanxess Zetpol is a registered trademark of Zeon Chemicals 15

4 Practical Guide to Hydrogenated Nitrile Butadiene Rubber Technology In addition to these grades, speciality polymers are available for specific applications and end-products. These are summarised in Table 2.2. Grade Manufacturer Mole% ACN (nominal) Zeoforte ZSC 2295CX Zeoforte ZSC 2295L Zeoforte ZSC 2385 Therban XT VP KA 8889 Therban VP KA 8796 Table 2.2 HNBR speciality grades available Mooney viscosity ML(1+4) at 100 C (nominal) Residual % unsaturation (approximate) Modification Zeon Zinc methacrylate Zeon Zinc methacrylate Zeon Zinc methacrylate Lanxess Carboxylated (XHNBR) Lanxess Acrylate Therban is a registered trademark of Lanxess Zetpol and Zeoforte are registered trademarks of Zeon Chemicals Modification with acrylates such as zinc methacrylate gives tough and mechanically durable materials for use in power transmission belts and conveyor belts, and in similar products requiring a high level of resistance to abrasion, cutting and wear. 16

5 Types of Hydrogenated Nitrile Rubber Polymers Available 2.3 HNBR Grades and Technology One way to illustrate the position of HNBR within the elastomer market is to employ the ASTM D2000 classification system [1]. This is illustrated in Figure 2.1, along with a selection of other elastomers for comparison. Not only does the HNBR family fill a gap in the properties identified, HNBR also offer tear resistance, abrasion resistance and overall toughness that polymers such as acrylic elastomers (ACM) and ethylene acrylic copolymer elastomers (AEM) cannot match. ASTM D2000 Classification % Swell in ASTM IRM 903 Oil 300 EPDM NR CR VMQ AEM FKM FVMQ ACM HNBR NBR Temperature resistance (ºC) Class by Oil Swell Figure 2.1 Graphical illustration of speciality elastomers, showing the position of HNBR within the ASTM D2000 system NBR are among the oldest and most widely used oil-resistant polymers and provide an excellent combination of properties and durability, but due to their high level of unsaturation they are prone to oxidation and to attack by sulfur. HNBR materials are much more resistant to oxidation and sulfur attack and combine the compounding flexibility and toughness of NBR with improved temperature and chemical resistance. This is illustrated in Figures 2.2 and 2.3 in the case of resistance to engine oil and automatic transmission fluids, respectively. The loss of elongation after 1008 hours at 150 ºC is shown for HNBR, NBR, ACM and AEM materials [2]. An estimate of the life of an elastomer is the time required to reduce the elongation to 50% of its original value. Figures 2.2 and 2.3 show that HNBR materials still retain some useful life after long-term ageing, whereas NBR and CSM materials had reached the 17

6 Practical Guide to Hydrogenated Nitrile Butadiene Rubber Technology end of their useful life before the end of the ageing test. The ACM material showed excellent long-term ageing performance in these fluids, but did not have the tear and abrasion resistance of HNBR materials. Comparison of Oil-Resistant Elastomers, 10W30SG engine oil at 150 C % Elongation Loss % ACN 25% ACN HNBR HNBR ACM AEM % Elongation Loss, 504 h % Elongation Loss, 1008 h Material Figure 2.2 Comparison of engine oil resistance of HNBR, ACM and AEM elastomers Comparison of Oil-resistant Elastomers, Dexron III ATF at 150 C % Elongation Loss % ACN 25% ACN HNBR HNBR Material ACM AEM % Elongation Loss, 504 h % Elongation Loss, 1008 h Figure 2.3 Comparison of resistance to automatic transmission fluid (ATF) of HNBR, ACM and AEM elastomers 18

7 Types of Hydrogenated Nitrile Rubber Polymers Available The relative abrasion resistance of HNBR materials compared to other oil-resistant elastomers, such as NBR, epichlorohydrin ethylene oxide copolymers (ECO), fluorocarbons (FKM) and ACM, is shown in Figure 2.4 [3]. Traditional NBR materials are given a relative rating of 100. Akron-type abrasion resistance rating Relative resistance to abrasion % ACN HNBR NBR ECO FKM ACM Material Figure 2.4 Comparison of the abrasion resistance of various elastomers The effects of abrasion, wear and friction are not well understood, but this type of testing is valuable in providing a relative rating for a range of materials. The combination of increased high temperature performance and improved wear resistance emphasises the niche occupied by HNBR among the available oil-resistant elastomers. In the remainder of this chapter the effect of HNBR and compounding ingredients on the final properties of the compound are discussed. This is not intended to be an exhaustive account of every compounding possibility, but the use of statistical experimental design will be emphasised and illustrated as a cost-effective way of studying the compounding variables. Finally, it is important to compare the relative cost of the various oil-resistant elastomers. The pound volume cost is used, which is simply the cost of the compound multiplied by its specific gravity. This gives the relative cost of the compound required to fill a given volume such as a mould cavity. This has been shown earlier in Table 2.2, along with the upper temperature limits of the various materials. While acrylic elastomers such as ACM and AEM are cost-effective up to 150 ºC, HNBR are much tougher and more abrasion-resistant. FKM and fluorosilicones (FVMQ) have excellent upper temperature limits, but their pound volume cost is heavily influenced by their relatively high specific gravity. 19

8 Practical Guide to Hydrogenated Nitrile Butadiene Rubber Technology Table 2.3 gives a cost comparison of oil-resistant elastomers, and a combination of Table 2.3 and Figures 2.2 to 2.4 puts the niche filled by HNBR materials in perspective. HNBR combine toughness, abrasion resistance, fluid resistance and good cost effectiveness at temperatures up to 150 ºC. Table 2.3 Commercial comparison of oil-resistant elastomers Polymer SG Cost of compound ($) lb vol cost ($) Operating temperature, upper limit (ºC) NBR 1.22 $1.00 $ ACM 1.32 $2.30 $ AEM 1.32 $2.40 $ HNBR 1.22 $10.40 $ FVMQ 1.53 $23.00 $ FKM 1.86 $16.00 $ Note: 75 Shore A, assumes carbon black filler, except for FVMQ 2.4 Summary This chapter has given a brief overview of the polymers currently available and how these fit into the overall range of oil-resistant elastomers. Formulation guidelines and examples of formulations for specific applications will be given in detail later. References 1. Rubber, American Society of Testing and Materials, Washington, DC, USA, 2006, 9, 2, D A Comparison of Oil Resistant Elastomers in Engine Oil and ATF, Z7.3.16, Zeon Chemicals LP, Louisville, KY, USA, 1999, p Zetpol Product Guide, Zeon Chemicals LP, Louisville, KY, USA,

TRP Leading supplier of specialty elastomers for automotive applications

TRP Leading supplier of specialty elastomers for automotive applications Sebastiaan van Gemert Director Sales Africa, Middle East, Eastern Europe and Central America LANXESS Business Unit Technical Rubber