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Comparative study of chemical resistant Noxtite FKM and ACM for hose applications.

Unimatec's unique polymerization technology, in combination with high temperature acrylic materials, allowed for the development of a thermally stable and significantly improved media resistant polymer, while retaining resilient aging characteristics.

The aim in developing this material was to provide a solution for applications that required improved heat and fluid resistance, in particular for some hose and sealing applications such as positive crankcase ventilation hose or head cylinder cover gaskets, due to their uncontrolled contact with motor oils contaminated with fuels.

This article highlights Unimatec Noxtite HT-ACM grade developed for significantly improved fluid resistance in fuels and engine fluids highly contaminated with additives found in blow-by or EGR applications, in comparison with the peroxide curable Noxtite FKM grades, both copolymer (66% F-content) and terpolymer (68% F-content).

A comprehensive study including gasoline and diesel blow-by immersion data will also show the strength of Noxtite FKM grades in comparison to other competitive ACM grades.

Since the first introduction of Noxtite ACM back in 1964, Unimatec has developed varieties of products through unique synthetic technologies to meet customer needs. Noxtite ACMs are commonly used for oil seals, o-rings, gaskets, hoses and various other automotive and industrial applications where heat and oil resistance is a challenge.

The key for the dynamics and durability of Noxtite ACM or HT-ACM is in its ideal monomer compositions between ethylacrylate (EA), butylacrylate (BA), 2-methoxyethyl acrylate (MEA), as well as a suitable cure site monomer. The basic structural elements define the specific properties of Noxtite ACMs and HT-ACMs (figure 1).

Design of experiment: Formulations (table 1)

ACM

* PA-402B: Standard soap sulfur curable grade, mainly used in gaskets and extruded goods.

* PA-526: Diamine curable high temperature resistant HTACM grade, mainly used in air hose applications.

* AY-1215B: Biodiesel resistant, diamine curable HT-ACM grade.

* All ACM formulations are DOTG-free. FKM

* 66 weight-%: Peroxide curable FKM copolymer of VDFHFP-CSM construction.

* 68 weight-%: Peroxide curable FKM terpolymer of VDFHFP-TFE-CSM construction.

All measurements were performed on 2 mm test sheets (DIN 53504 S2 dumbbell) after ISO specified methods.

Cure conditions

* ACM: Press cure--180[degrees]C/10 minutes; post-cure--175[degrees]C/4 hours.

* FKM: Press cure--180[degrees]C/5 minutes; post-cure--230[degrees]C/22 hours.

Design of experiment: Fluids

Blow-by fluid A, representing gasoline engines, consists of:

* Acid solution: Hydrofluoric acid (0.1 M), nitric acid (0.5 M), sulfuric acid (0.25 M) and acetic acid (17.4 M) at a pH of 2.2 [+ or -] 0.2.

* Engine oil: Lubrizol OS 206304.

* FAM-B: FAM-A* (84.5 volume %) + methanol (15 volume %) + water (0.5 volume %).

*FAM-A: Toluene (50 volume %) + isooctane (30 volume %) + di-isobutylene (15 volume %) + ethanol (5 volume %). Blow-by fluid B, representing diesel engines, consists of:

* Acid solution: Same as fluid A

* Engine oil: Same as fluid A

* Diesel: Standard diesel fuel including 15 volume % each of RME/SME (30 volume % total of methyl ester).

Tests were done for a total of six cycles at 24 hours per cycle with specified temperature and specimens (DIN 53504 S2 dumbbells). The acid solution, FAM-B and the diesel/RME/ SME were changed to have fresh solutions at the beginning of each cycle. The engine oil remained unchanged throughout the six cycles. Figures 2 and 3 show the test procedures for tests with fluid A and fluid B, respectively.

Results and discussion

Fluid A: Gasoline engines (figures 4 and 5) Direct comparison between the two groups of materials is apparent, and we can see that peroxide curable FKM grades fare better than ACM grades in fluid A. The ACM grades show a significant loss in elongation at break, and relatively high weight/volume change as well.

On the other hand, both peroxide cured FKM grades (copolymer and terpolymer) show very low loss in elongation at break, as well as weight/volume change, indicating that the change is negligible for these peroxide cured Noxtite FKM grades.

Fluid B: Diesel engines (figures 6 and 7) Compared with fluid A test data, significant differences can be observed in the performance of AY-1215B in fluid B, as it shows minimal weight/volume and elongation change, in the same range as that of the peroxide cured Noxtite FKM grades. The other ACM grades also show resilience in elongation at break, while the FKM grades are at a notably higher level of physical properties and do not exhibit significant changes at all.

Conclusion

Based on the results we have obtained from blow-by fluid B aging, we can see that Noxtite ACM/HT-ACM grades show a strong physical property behavior, and thus can be recommended for diesel applications. As for gasoline applications, based on the blow-by fluid A aging data, we see the necessity to use peroxide cured Noxtite FKM grades. The FKM copolymer with 66% fluorine content exhibits more than sufficient aging performance in both fluids A and B, leading us to conclude that even though FKMs are necessary for the types of blow-by resistant application we are concerned with, there is not an absolute necessity to use a higher, 68% fluorine content Noxtite FKM terpolymer grade.

This article is based on a paper presented at the 190th Technical Meeting of the Rubber Division, ACS, October 2016.

by Konstantin Zoumis and David Bernardi, Unimatec Chemicals America

Caption: Figure 1--structure of Noxtite ACM

Caption: Figure 2-24 hour cycle test with fluid A

Caption: Figure 3-24 hour cycle test with fluid B
Table 1 - Noxtite ACM, HT-ACM and FKM formulations

                      Noxtite PA-402B   Noxtite PA-526

                        Standard ACM           HT-ACM
                             ACM-206          ACM-207

Noxtite PA-402B               100.00
Noxtite PA-526                    --           100.00
Noxtite AY-1215B                  --               --
Noxtite RE635                     --               --
Noxtite RE461                     --               --
Stearic acid                    1.50             1.50
Carbon black N550              60.00            60.00
Carbon black N990                 --
Plasticizer                     5.00             5.00
Antioxidants                    2.00             2.00
Processing aid                  0.70             0.70
Sulfur                          0.30               --
Sodium stearate                 3.00               --
Potassium stearate              0.25               --
Stearylamine                    0.30             0.30
HDC                               --             0.70
Accelerator                       --             2.00
TAIC-70%                          --               --
DBPH-45%                          --               --

                         Noxtite AY-1215B     Noxtite RE635

                      Biodiesel resistant
                                   HT-ACM    Peroxide cured
                                  ACM-208     66% F-content

Noxtite PA-402B                       --               --
Noxtite PA-526                        --               --
Noxtite AY-1215B                  100.00               --
Noxtite RE635                         --           100.00
Noxtite RE461                         --               --
Stearic acid                        1.50               --
Carbon black N550                  60.00               --
Carbon black N990                                   12.00
Plasticizer                         5.00               --
Antioxidants                        2.00               --
Processing aid                      0.70               --
Sulfur                                --               --
Sodium stearate                       --               --
Potassium stearate                    --               --
Stearylamine                        0.30             0.30
HDC                                 0.70               --
Accelerator                         2.00               --
TAIC-70%                              --             4.00
DBPH-45%                              --             3.00

                      Noxtite RE461

                      Peroxide cured
                       68% F-conten

Noxtite PA-402B                  --
Noxtite PA-526                   --
Noxtite AY-1215B                 --
Noxtite RE635                    --
Noxtite RE461                100.00
Stearic acid                     --
Carbon black N550                --
Carbon black N990             12.00
Plasticizer                      --
Antioxidants                     --
Processing aid                   --
Sulfur                           --
Sodium stearate                  --
Potassium stearate
Stearylamine                   0.30
HDC                              --
Accelerator                      --
TAIC-70%                       4.00
DBPH-45%                       3.00

Noxtite and Cheminox are registered trademarks
of Unimatec Co. Ltd., Japan

Figure 4--elongation change after aging in
fluid A for six cycles (%)/DIN 53504

                    Original   After six cycles   Change (%)
                                of exposure to
                                    fluid A

Standard Noxtite      226             131           -42.0
ACM 206

Noxtite HT-ACM        236             116           -50.80
207

Noxtite HT-ACM        150              79            -47.3
208

Noxtite FKM           459             376            -20.0
Peroxide
Copolymer
66% F-content

Noxtite FKM            400            342            -14.5
Perioxide
Terpolymer
68% F-content

Note: Table made from bar graph.

Figure 5--weight/volume change after
aging in fluid A for six cycles (weight
% and volume %)/DIN ISO 1817

                  Weight change         Volume change
                     after six            after six
                  cycles exposure      cycles exposure
                    to fluid A            to fluid A

Standard              28.2                  46.2
Noxtite
ACM 206

Noxtite               31.4                  50.9
HT-ACM 207

Noxtite               26.0                   43.0
HT-ACM 208

Noxtite FKM           5.7                    12.9
Peroxide
Copolymer
66% F-content

Noxtite FKM           3.6                     8.3
Perioxide
terpolymer
68% F-content

Note: Table made from bar graph.

Figure 6--elongation change after aging in
fluid B for six cycles (%)/DIN 53504

                    Original    After six cycles   Change (%)
                                 of exposure to
                                fluid B (diesel
                                  + 30% RME)

Standard Noxtite      226             219           -3.1
ACM 206

Noxtite HT-ACM        236             187           -20.8
207

Noxtite HT-ACM        150             149            -0.7
208

Noxtite FKM           459             428            -6.8
Peroxide
copolymer
66% F-content

Noxtite FKM            400            386            -3.5
Perioxide
terpolymer
68% F-content

Note: Table made from bar graph.

Figure 7--weight/volume change after
aging in fluid B for six cycles (%)/DIN
ISO 1817

                  Weight change         Volume change
                     after six            after six
                  cycles exposure      cycles exposure
                    to fluid B            to fluid A
                  (diesel + 30%       (diesel + 30% RME)
                        RME)

Standard              13.5                  20.4
Noxtite
ACM 206

Noxtite               11.4                  17.1
HT-ACM 207

Noxtite               2.0                   3.4
HT-ACM 208

Noxtite FKM           0.9                   1.9
Peroxide
copolymer
66% F-content

Noxtite FKM           1.0                   2.1
Perioxide
terpolymer
68% F-content

Note: Table made from bar graph.
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Author:Zoumis, Konstantin; Bernardi, David
Publication:Rubber World
Date:Apr 1, 2017
Words:1418
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