Practical Guide to HNBR Chapter 2

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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.

2 Types of Hydrogenated Nitrile Rubber Polymers Available

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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 17 30 0.5

Zetpol 4300 Zeon 17 75 0.5

Zetpol 4310EP Zeon 17 30 5

Zetpol 4310 Zeon 17 62 5

Therban AT LT 2004 VP Lanxess 21 39 0.9

Therban LT 2007 Lanxess 21 74 0.9





Therban AP A 3404 Lanxess 34 39 0.9

Therban 3406 Lanxess 34 63 0.9


Therban AT C 3443 VP Lanxess 34 39 4

Therban 3446 Lanxess 34 61 4


Therban VP KA 8837 Lanxess 34 55 18

Zetpol 2000EP Zeon 36 30 0.5

Zetpol 2000L Zeon 36 65 0.5

Zetpol 2000 Zeon 36 85 0.5

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Types of Hydrogenated Nitrile Rubber Polymers Available


Therban 3627 Lanxess 36 87 2

Zetpol2010L Zeon 36 58 4


Zetpol 2010H Zeon 36 135 4

Therban AT A 3904 VP Lanxess 39 39 0.9


Therban AT 4304 VP Lanxess 43 39 0.9






Zetpol 1000L Zeon 44 65 2




Zetpol 1020L Zeon 44 57 9



Therban 5008 VP Lanxess 49 80 0.9

Therban AT 5065 VP Lanxess 49 55 6



Therban® is a registered trademark of Lanxess Zetpol® is a registered trademark of Zeon Chemicals

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In addition to these grades, speciality polymers are available for specific applications and end-products. These are summarised in Table 2.2.

Table 2.2 HNBR speciality grades available

Grade Manufacturer Mole% ACN

(nominal)

Mooney viscosity ML(1+4) at 100 °C (nominal)

Residual % unsaturation

(approximate)

Modification

Zeoforte ZSC 2295CX

Zeon 36 95 9 Zinc methacrylate

Zeoforte ZSC 2295L


Zeoforte ZSC 2385


Therban XT VP KA 8889

Lanxess 33 77 3.5 Carboxylated (XHNBR)

Therban VP KA 8796

Lanxess 34 22 5.5 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.

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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

0

50

100

150

200

250

300

050100150200

% Swell in ASTM IRM–903 Oil

Tem

per

atur

e re

sist

ance

(ºC

)

NRCR

AEM

VMQ FVMQ

FKM

NBR

ACM

Class by Oil Swell

EPDMHNBR

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

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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.

–60–50–40–30–20–10

010203040

35% ACN HNBR

25% ACN HNBR

ACM AEM

% E

lon

gati

on

Lo

ss

Material

Comparison of Oil-ResistantElastomers, 10W30SG engine oil at 150 °C

% Elongation Loss, 504 h


Figure 2.2 Comparison of engine oil resistance of HNBR, ACM and AEM elastomers

–30–25–20–15–10

–505

10152025

35% ACN HNBR

25% ACN HNBR

ACM AEM

% E

lon

gati

on

Lo

ss

Material

Comparison of Oil-resistant

Elastomers, Dexron III ATF at 150 °C



Figure 2.3 Comparison of resistance to automatic transmission fluid (ATF) of HNBR, ACM and AEM elastomers

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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

0

50

100

150

200

45% ACNHNBR

NBR ECO FKM ACM

Material

Rel

ativ

e re

sist

ance

to

ab

rasi

on

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.

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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 $1.22 100

ACM 1.32 $2.30 $3.04 150

AEM 1.32 $2.40 $3.17 150

HNBR 1.22 $10.40 $12.69 150

FVMQ 1.53 $23.00 $35.19 200

FKM 1.86 $16.00 $29.76 250

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, D2000-06.

2. A Comparison of Oil Resistant Elastomers in Engine Oil and ATF, Z7.3.16, Zeon Chemicals LP, Louisville, KY, USA, 1999, p.1.

3. Zetpol Product Guide, Zeon Chemicals LP, Louisville, KY, USA, 1999.

Documents

Practical Guide to HNBR Chapter 2