Printer Friendly

Low Mooney viscosity HNBR polymers with high acrylonitrile content.

Therban hydrogenated nitrile butadiene rubber (HNBR) is made by the selective hydrogenation of the double bonds in nitrile rubber (ref. 1). It is a high-performance specialty elastomer having a combination of unique properties:

* High tensile strength and very good mechanical properties even at elevated temperatures;

* excellent abrasion resistance;

* low compression set;

* excellent heat resistance with a service temperature from -40[degrees]C to 165[degrees]C with short term exposure up to 190[degrees]C, dependent on grade;

* very good resistance to ozone, weathering and high energy radiation;

* low permeability to vapors and gases;

* very good resistance to oils, fluids, diesel, fuels and sour gasoline;

* very good resistance to lubricating oils with aggressive alkaline additives; and

* good resistance to crude oil even in the presence of hydrogen sulfide, amines and corrosion inhibitors.

Therban Advanced Technology (AT) products (ref. 2) are low Mooney viscosity HNBR polymers that have the properties of regular HNBR polymers, but in addition have all the benefits of improved processability in mixing, extrusion and injection molding. They also provide a variety of compounding options not possible with regular HNBR polymers. These include:

* Elimination or reduction of plasticizer, which provides improvements in physical properties, heat aging resistance, compression set, sealing force retention in sealing applications, better rubber-to-metal bonding and lower fluid extractables; and

* increased filler levels to formulate higher hardness compounds that have better processability and are more cost-effective. Higher filler levels also reduce swelling in fluids and improve permeation resistance.

This article will present two HNBR-AT low Mooney viscosity [ML(1+4) at 100[degrees]C = 39] polymers with 43% ACN (acrylonitrile)--a fully saturated polymer (0.9% max. residual double bond content), HNBR-AT A4304, and a partially saturated polymer, HNBR-AT C4364 (5.5% residual double bond content). Table 1 describes the raw polymers used in the studies. Both peroxide and sulfur cure recipes (see tables 2 and 3) will be used to investigate the effect of higher filler and plasticizer levels on performance, as well as compare them to a 49% ACN HNBR polymer.

Results and discussion

Fully saturated low Mooney viscosity HNBR with 43% ACN

Figures 1 and 2 show that HNBR-AT A4304, even when compounded with higher peroxide levels, still maintains better scorch safety and better processability (lower compound viscosity) when compared to regular HNBR polymers such as HNBR-A4307 and HNBR-49. Even at high filler loading (100 phr N-990 carbon black), HNBR-AT A4304 has a compound Mooney viscosity of 53 compared to 51 for a lightly loaded (50 phr) HNBR-49 compound (table 2). With the change to a mineral filler such as talc, an HNBR-AT compound also shows very good scorch safety and processability. These figures illustrate that such low Mooney viscosity HNBR polymers provide more options in formulating recipes for different hardness and mechanical properties, while still maintaining excellent processability. Such options are not possible with regular HNBR polymers.

A slightly higher peroxide level (10 phr vs. 8.5 phr) is used when compounding low Mooney viscosity HNBR polymers to make up for the higher number of dangling chain ends in AT grades, such as HNBR-AT A4304. This makes it possible to match the mechanical properties of HNBR-A4307 and even have a lower compression set. When compared to HNBR-49, HNBR-AT A4304 has faster cure, similar tensile, but higher elongation. Higher levels of N-990 carbon black and TOTM plasticizer, as well as using talc, lower the tensile values slightly, as expected, compared to HNBR-49, but the mechanical properties still remain very good (figure 3). Both HNBR-A4307 and HNBR-AT A4304 show similar compression set to HNBR-49 after 70 hours aging at 150[degrees]C, but they will have better long term compression set values (since they are fully saturated polymers), which is very critical for HNBR applications. Compounds containing higher plasticizer levels or talc filler exhibit increased compression set (table 2).

Both HNBR-A4307 and HNBR-AT A4304 show lower hardness change and better retention of elongation after aging in air for 504 hours at 150[degrees]C compared with HNBR-49. HNBR-49 shows higher hardness change than the HNBR-AT A4304 talc-filled compound. While HNBR-A4307 and HNBR-AT A4304 show similar or even slightly improved behavior in hot air aging (table 2), the volume swell in IRM 903 of the HNBR-AT A4304 is minimal (<5%), but slightly higher in comparison to HNBR-49, caused by the lower ACN content (figure 4). The positive effect is that HNBR-AT A4304 also shows a better retention of elongation and tensile.

Increasing the plasticizer level up to 20 phr leads to improved oil swell behavior, with compromises regarding higher hardening and loss in elongation. Aging in 5W30 engine oil results in plasticizer extraction, as indicated by the negative volume swell values, and both HNBR-A4307 and HNBR-AT A4304 show equivalent volume changes compared to HNBR-49.

All three polymers have similar swell in Fuel B; however, HNBR-AT A4304 compounds with higher filler and plasticizer loadings provide lower swell than HNBR-49. After immersion in the more aggressive Fuel C, HNBR-A4307 and HNBR-AT A4304 have a slightly higher swell compared with HNBR-49, but their swell values are improved by using higher filler levels. Higher filler levels also improve the retention of properties after aging in Fuels B and C. All polymers have very low swell and very good aging in Aral diesel (table 2).

This data shows that the low Mooney viscosity HNBR polymer HNBR-AT A4304 provides a variety of compounding options to match or even exceed the physical and aging properties of a higher acrylonitrile polymer, such as HNBR-49. In addition, HNBR-AT A4304 offers the benefits of improved scorch safety, improved processability and lower cost compounds (formulated with higher filler levels). HNBR-AT A4304 provides excellent mechanical properties, very good heat and oil resistance, and improved processability. These benefits are useful in a variety of demanding applications, including automotive, oil well, and industrial/heavy duty markets.

Partially saturated low Mooney viscosity HNBR with 43% ACN

HNBR-AT C4364 was compared to HNBR-49 in a basic sulfur recipe (table 3). Similar to the fully saturated low Mooney viscosity polymer HNBR-AT A4304, HNBR-AT C4364 shows improved processability as seen in its lower compound viscosity, 67, compared with 85 for the HNBR-49 compound (figure 5). HNBR-AT C4364 has a higher cure state, as evidenced by the rheometer torque, with a similar cure rate and mechanical properties to HNBR-49 (figure 6).

After aging in IRM903 and 5W30 engine oil (table 3), HNBR-AT C4364 has similar volume changes to HNBR-49, but shows less hardness change and better retention of tensile and elongation properties (figures 7 and 8).

Again, this illustrates that HNBR-AT C4364 can match the mechanical and aging properties of a higher ACN polymer (HNBR-49), while providing the benefits of improved flow and processability.

HNBR-AT C4364 can be either sulfur or peroxide cured. Sulfur cured formulations can be used in wide variety of automotive, industrial and oil well applications that require excellent mechanical and dynamic properties, as well as good fluid resistance. One such example is the use of HNBR-AT C4364 for stators (drilling motors and progressive cavity pumps) in the oil well industry. With its low polymer Mooney viscosity, HNBR-AT C4364 provides the advantages of:

* Improved flow is very critical in producing these stators.

* Using the unique AT (Advanced Technology) for manufacturing low Mooney viscosity HNBR-AT polymers provides the opportunity of using HNBR elastomers that can be processed as easily as regular nitrile polymers (NBR), while retaining the advantageous properties of HNBR. Utilizing these new HNBR-AT polymers offers unprecedented latitude of compounding, as well as novel ways of processing. One example is the formulation of recipes with reduced plasticizers and process aids, which improves rubber-to-metal adhesion.

* Improved performance compared to nitrile rubber is seen. The lifetime of parts can be extended, thereby reducing the maintenance frequency or extending the replacement cycle. This benefit can potentially translate into substantial operational cost savings without compromise to safety.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Conclusions

1. Fully saturated HNBR-AT A4304:

* Provides a variety of compounding routes to match or even exceed the physical and aging properties of a higher acrylonitrile polymer such as HNBR-49, but in addition has the added benefits of improved scorch safety, improved processability and lower cost compounds (formulated with higher filler levels);

* matches the mechanical properties of HNBR-A4307 and has a lower compression set; when compared with HNBR-49, HNBR-AT A4304 has faster cure, similar tensile, but higher elongation.

* even at a high filler loading of 100 phr N-990, HNBR-AT A4304 has excellent processability (compound viscosity of 53) compared to a lightly loaded (50 phr) HNBR-49 compound (Mooney viscosity of 51);

* both HNBR-A4307 and HNBR-AT A4304 show less hardness change and better retention of elongation after aging in air for 504 hours/150[degrees]C compared with HNBR-49, which shows even more hardening than HNBR-AT A4304 compounds containing high filler and plasticizer levels;

* has better retention of elongation and tensile in IRM903 compared to HNBR-49; and

* higher filler levels improve the retention of properties after aging in Fuels B and C.

2. Partially saturated HNBR-AT C4364 has improved processability, similar cure rate, higher state of cure and similar mechanical properties to HNBR-49. It shows better aging in IRM903 and 5W30 engine oil.

3. These high acrylonitrile, low Mooney viscosity HNBR-AT polymers can be formulated to match the performance of regular HNBRs, but provide the added benefits of excellent scorch safety and processability, while at the same time extending the window of opportunities to formulate compounds to specific industry needs.

4. Currently, developments are underway to make new and novel fully and partially saturated low Mooney viscosity HNBR-AT polymers with acrylonitrile contents higher than 43%. Such polymers will be useful where the highest possible fluid resistance of HNBR elastomers is needed, such as in automotive, oil well, industrial, heavy duty and potentially flex-fuel applications.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

This article is based on a paper presented at a meeting of the Rubber Division, ACS (www.rubber.org).
Appendix 1--compounding ingredients

ZMMBI (Vulkanox ZMB 2/C5) Zinc-4-and
 5-methyl-2-mercaptobenzimidazole
 from Lanxess

CDPA (Luvomaxx CDPA) p-dicumyl diphenylamine from
 Lehmann & Voss

MgO Maglite D magnesium oxide from
 HallStar

ZnO Kadox 920 zinc oxide from Horsehead

Stearic acid Edenor C, 18 98-100 from Cognis

Carbon black N 990 Carbon black from Cabot

Carbon black N 660 Carbon black from Cabot

Plasthall TOTM Trioctyl trimellitate available
 from HallStar

Polyether ester type plasticizer ADK CIZER RS735 from Adeka
 Palmorale

Mistron Vapor talc Magnesium silicate (talc) from
 Luzenac America

Vinyl silane vinyl tris (methoxyethoxy) silane
 from Witco

TAIC DIAK #7 triallylisocyanurate from
 R.T. Vanderbilt

Perkadox 14-40 peroxide 40% active
 di(tertbuiylperoxyisopropyl)
 benzene from Akzo

Vulkacit CZ/EGC Benzothiazi-2-cyclohexyl
 sulfonamide, oil coated from
 Lanxess

TMTD Vulkacit thiuram/C from Lanxess

Spider sulfur Sulfur from Taber

Appendix 2--test procedures

Air aging DIN 53508
Compression set DIN ISO 815
Fluid resistance DIN 53521
Hardness DIN 53505
Mooney scorch DIN 53523
Mooney viscosity ASTM D1646
Moving die rheometer (MDR) ASTM D5289
Stress strain DIN 53504


References

(1.) H. Bender, et al, "Manual for the rubber industry," Bayer AG Rubber Business Group, Leverkusen, 1993, p. 119.

(2.) V. Nasreddine, R.J. Pazur and W. von Hellens, Rubber Division, ACS, Paper No. 52, Cincinnati, OH, October 10-12, 2006.

by Victor Nasreddine, John Dato, Martin Mezger, Dirk Schaefer and Juergen Wassen, Lanxess
Table 1--raw polymers

 Residual ML (1+4)
 ACN double at 100
HNBR type Tradename (wt. %) bond (%) [degrees]C Supplier

HNBR-A Therban 43 <0.9 63 Lanxess
4307 A4307

HNBR-AT Therban AT 43 <0.9 39 Lanxess
A4304 A4304

HNBR-AT Therban AT 43 5.5 39 Lanxess
C4364 C4364

HNBR-49 Zetpol 0020 49.2 9 65 Nippon Zeon

Table 2--peroxide recipes

 HNBR-A4307 HNBR-AT
 /50 CB A4304150 CB
 /10 P /10 P

CB: carbon black;
P: plasticizer
Formulations (see appendix)
HNBR-A4307 100
HNBR-AT A4304 100
HNBR-49
ZMMBI 0.4 0.4
CDPA 1.1 1.1
MgO 5 5
ZnO 3 3
N 990 carbon black 50 50
Vinyl silane
Mistron vapor talc
TOTM plasticizer 10 10
TAIC 1.5 1.5
Perkadox 14-40 peroxide 8.5 10

Mooney scorch at 135[degrees]C
Ts 5 (min.) 18 19
Mooney visc., ML 1+4 100[degrees]C 55.0 38.1

MDR at 180[degrees]C
S' min. [dNm] 0.64 0.33
S' max. [dNm] 17.2 17.1
t 95 [s] 394 393

Unaged stress-strain
Hardness, durometer A 57.5 56
Ultimate tensile, MPa 20 20
Elongation at break, % 383 389
Stress at 100%, MPa 2 2

Compression set, %
70 hrs./150[degrees]C, 25% deflection 31 29

Air aging, 504 hrs. at 150[degrees]C
Chg. in hardness, points +13 +14
Chg. in tensile, % -6% -11%
Chg. in EB, % -15% -16%

IRM903 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points -2.5 -2
Chg. in tensile, % -4 -3
Chg. in EB, % -5 -6
Volume change, % +2.8 +2.4

5W30 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points +4 +5
Chg. in tensile, % -4 -9
Chg. in EB, % -20 -23
Volume change, % -5 -5

Fuel B, 70 hrs. at 40[degrees]C
Chg. in hardness, points -11 -11
Chg. in tensile, % -48 -50
Chg. in EB, % -34 -38
Volume change, % +22 +22

Fuel C, 70 hrs. at 40[degrees]C
Chg. in hardness, points -14 -13
Chg. in tensile, % -72 -63
Chg. in EB, % -55 -49
Volume change, % +37 +35

Aral diesel, 70 hrs. at 40[degrees]C
Chg. in hardness, points -4 -3
Chg. in tensile, % +5 0
Chg. in EB, % +4 -1
Volume change, % +2 +2

 AT A4304 AT A4304
 /100 CB /100 CB
 /10 P /120 P

CB: carbon black;
P: plasticizer
Formulations (see appendix)
HNBR-A4307
HNBR-AT A4304 100 100
HNBR-49
ZMMBI 0.4 0.4
CDPA 1.1 1.1
MgO 5 5
ZnO 3 3
N 990 carbon black 100 100
Vinyl silane
Mistron vapor talc
TOTM plasticizer 10 20
TAIC 1.5 1.5
Perkadox 14-40 peroxide 10 10

Mooney scorch at 135[degrees]C
Ts 5 (min.) 13 16
Mooney visc., ML 1+4 100[degrees]C 53.0 30.4

MDR at 180[degrees]C
S' min. [dNm] 0.53 0.39
S' max. [dNm] 23.8 16.1
t 95 [s] 396 396

Unaged stress-strain
Hardness, durometer A 68 61
Ultimate tensile, MPa 17 15
Elongation at break, % 273 351
Stress at 100%, MPa 5 3

Compression set, %
70 hrs./150[degrees]C, 25% deflection 30 37

Air aging, 504 hrs. at 150[degrees]C
Chg. in hardness, points +14 +15
Chg. in tensile, % -8% -6%
Chg. in EB, % -26% -33%

IRM903 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points -1 +3
Chg. in tensile, % +2 +6
Chg. in EB, % -5 -13
Volume change, % +1.9 -0.3

5W30 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points +7 +12
Chg. in tensile, % -2 +6
Chg. in EB, % -23 -25
Volume change, % -5 -7

Fuel B, 70 hrs. at 40[degrees]C
Chg. in hardness, points -13 -12
Chg. in tensile, % -23 -25
Chg. in EB, % -19 -21
Volume change, % +19 +18

Fuel C, 70 hrs. at 40[degrees]C
Chg. in hardness, points -15 -16
Chg. in tensile, % -34 -33
Chg. in EB, % -32 -30
Volume change, % +29 +29

Aral diesel, 70 hrs. at 40[degrees]C
Chg. in hardness, points -1 -1
Chg. in tensile, % +2 -1
Chg. in EB, % +2 -7
Volume change, % +1 +1

 AT A4304 HNBR-49
 /70 CB, 30 /50 CB,
 talc/l0 P /10 P

CB: carbon black;
P: plasticizer
Formulations (see appendix)
HNBR-A4307
HNBR-AT A4304 100
HNBR-49 100
ZMMBI 0.4 0.4
CDPA 1.1 1.1
MgO 5 5
ZnO 3 3
N 990 carbon black 70 50
Vinyl silane 1.7
Mistron vapor talc 30
TOTM plasticizer 10 10
TAIC 1.5 1.5
Perkadox 14-40 peroxide 10 8.5

Mooney scorch at 135[degrees]C
Ts 5 (min.) 14 14
Mooney visc., ML 1+4 100[degrees]C 44.6 50.5

MDR at 180[degrees]C
S' min. [dNm] 0.46 0.55
S' max. [dNm] 22.7 21.1
t 95 [s] 431 424

Unaged stress-strain
Hardness, durometer A 74.50 60
Ultimate tensile, MPa 16 19
Elongation at break, % 238 314
Stress at 100%, MPa 9 3

Compression set, %
70 hrs./150[degrees]C, 25% deflection 38 29

Air aging, 504 hrs. at 150[degrees]C
Chg. in hardness, points +11 +16
Chg. in tensile, % +9% +10%
Chg. in EB, % -29% -32%

IRM903 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points +2 0
Chg. in tensile, % +9 -9
Chg. in EB, % -4 -16
Volume change, % +1.2 +0.2

5W30 oil, 168 hrs. at 150[degrees]C
Chg. in hardness, points +8 +6
Chg. in tensile, % +18 -8
Chg. in EB, % -17 -22
Volume change, % -5 -5

Fuel B, 70 hrs. at 40[degrees]C
Chg. in hardness, points -10 -10
Chg. in tensile, % -26 -52
Chg. in EB, % -23 -35
Volume change, % +19 +20

Fuel C, 70 hrs. at 40[degrees]C
Chg. in hardness, points -13 -12
Chg. in tensile, % -30 -66
Chg. in EB, % -26 -48
Volume change, % +31 +31

Aral diesel, 70 hrs. at 40[degrees]C
Chg. in hardness, points 0 -2
Chg. in tensile, % +4 +4
Chg. in EB, % +11 +6
Volume change, % +1 +1

Table 3--sulfur recipes

 HNBR-ATT
 C4364 HNBR-49

Sulfur formulations
(see appendix)
HNBR-AT C4364 100
HNBR-49 100
N 660 carbon black 50 50
ZMMBI 1.5 1.5
CDPA 1.5 1.5
Polyether ester type plasticizer 5 5
ZnO 3 3
Stearic acid 0.5 0.5
Vulkacit CZ/EGC 0.5 0.5
TMTD 2 2
Spider sulfur 0.5 0.5
Mooney viscosity, ML 1+4 100[degrees]C 67 85
MDR
S' min. [dNm] 0.82 1.07
S' max. [dNm] 18.4 12.2
t 95 [s] 279 272
Unaged stress-strain properties
Hardness, durometer A 67 67
Ultimate tensile, MPa 25 26
Elongation at break, % 487 592
Stress at 100%, MPa 3.2 3.1
IRM903 oil, 168 hrs. at 135[degrees]C
Chg. in hardness, points -1 +4
Chg. in tensile, % 0 -10
Chg. in EB, % +10 -29
Volume change, % +3 0
5W30 oil, 168 hrs. at 135[degrees]C
Chg. in hardness, points +7 +10
Chg. in tensile, % +7 -1
Chg. in EB, % -31 -46
Volume change, % -4 -5
COPYRIGHT 2008 Lippincott & Peto, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2008, Gale Group. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Nasreddine, Victor; Dato, John; Mezger, Martin; Schaefer, Dirk; Wassen, Juergen
Publication:Rubber World
Date:Feb 1, 2008
Words:3062
Previous Article:Stabilization of millable polyurethane rubber.
Next Article:Technical seminars scheduled.
Topics:


Related Articles
Processability by Mooney relaxation for isobutylene elastomers.
New developments in curing halogen-containing polymers.
Excel Polymers.
Enhancing compound properties and aging resistance by using low viscosity HNBR.
HNBR for use in oilfield applications.
Polymer composites comprising low molecular weight nitrile rubber.
HNBR polymers.
Advances in CM technology for thermoset applications.
Techniques for improving elastomer processing and crosslinking performance.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters