EoW March 2010

technical article

Hardness and moduli values are higher when compared to compound 1. If a comparison is made between 2 and 3 an increased crosslinking density (higher hardness) and higher moduli (M50 and M100) can be observed on compound 3, which was prepared with Silquest RC-1. Compounds 4 and 5 are difficult to com- pare since filler and plasticiser content are not the same. Initially a compound with the same amount of filler and plasticiser as the other formulations showed very poor stress-strain properties (6.4 MPa and 290% EB) as well as low hardness and tear strength. For this reason an optimisation via increase of filler and reduction of plasticiser (30 parts per hundred of rubber (phr) more ATH and 5 phr less DOS) was conducted. Fischer et al [8] found a correlation between the VA content and the crosslinking density for Levapren® compounds prepared under the same conditions (constant peroxide and other additives content). This could explain the poor stress-strain properties found in the initial compound 5.

Properties

Units [MPa]

Requirements

Tensile strength

11±2

Elongation at break

[%]

200±15

Hardness

Shore A [N/mm]

75±5

Tear strength

4-6

Cold bending test

[ºC] [%] [%]

@-40ºC No Cracks

Limiting oxygen index (LOI)

32

Hot air ageing Immersion in

TS/EB ±30

[MPa]/[%] [MPa]/[%] [MPa]/[%] [MPa]/[%]

TS/EB ±40 V: 15 TS/EB ±30 W/V: 30 TS/EB ±25 W/V: 20/15 TS/EB ±25 W/V: 20/15

Immersion in oil based mud Immersion in water based mud Immersion in Ester based mud

Mooney

ML

40=60 20cm

Vertical flame test

[cm]

Table 1 ▲ ▲ : Main properties described in standards for offshore cable compounds

content which covers a range between approximately 20% and 50%. In an homo- logous series of HNBR polymers there is no strict linear correlation between the glass transition temperature (Tg) and the ACN content, mainly because the glass process is also influenced by the crystallisation of ethylene sequences of more than 8-12 CH 2 groups. Copolymers with less than 37% acrylo- nitrile content are partly crystalline at low temperatures [7] . 2 Experimentation 2.1 Cable compounds for offshore platforms in Arctic regions Table 2 shows the formulations of compounds preparedwith HNBR grade (ACN = 21 %, RDB= 0,9 %; ML1+4/100°C = 72±4 MU); EVM grades (VA content = 50±5 % and 70±5 %; ML1+4100°C= 27±4 and 27±4 MU).

Compounds 2 and 3, based on blends of polymers, show similar TS values but EB values up to 100% lower than HNBR-based compounds.

Table 2 ▼ ▼ : Formulations based on EVM and HNBR special elastomers

Composition

1

2

3

4

5

THERBAN® LT 2007 (HNBR (ACN= 21%) LEVAPREN® 500 HV (EVM (VA=50%) LEVAPREN® 700 HV (EVM (VA=70%) APYRAL® 120 E (ATH BET= 12 m 2 /g) APYRAL® SM 200 (ATH BET= 22 m 2 /g)

100

50 50

50 50

100

80 60 10

80 60 10

80 60 10

80 60 10

100

70 10

ZINC BORATE

SILQUEST® RC-1 SILANE

2

GENIOSIL® XL 33

2

2

2

2

EDENOL® 888 (DOS)

10 10 1,4

10 10 1,4

10 10 1,4

10 10 1,4

10

DIPLAST® TM 8-10/ST (TOTM)

5

RHENOFIT DDA-70

1,4

STABAXOL® P-Powder (PCD)

1 3 1 1 5 2

1 3 1 1 5 2

1 3 1 1 5 2

1 3 1 1 5 2

1 3 1 1 5 2

MAGLITE® DE (MgO)

ZINC STEARATE

CALCIUM STEARATE

1,5

1,5

1,5

1,5

1,5

3 Results and discussion 3.1 Mechanical properties

EDENOR® C 18 98-100

CORAX® N 550/30 (Carbon Black)

RHENOFIT® TRIM/S

PERKADOX® 14-40 B-PD

6,5

6,5

6,5

6,5

6,5

The main properties were measured accor- ding to the standards described in NEK 606 specification. Compound 5, prepared with EVM 70% VA, shows the lowest tensile strength value of all compounds. This is borderline and not desirable since some margin for the variation of properties after ageing and immersion is required. TS values of the other four compounds are comparable and in the same range (11 MPa). Compound 1 shows robust stress-strain properties with a high elongation at break and the lowest hardness, shore A, of the whole study ( Table 3 ).

Total

294,4 1,453

294,4 294,40 294,40 319,40

Density

1,468

1,560

1,484

1,609

Table 3 ▼ ▼ : Mechanical properties for developed compounds

Mechanical properties Tensile Strength (MPa) Elongation at Break (%)

1

2

3

4

5

11,1 384

11,0 270

11,7 236

11,5 251

8,5

265

M 50 (MPa) M 100 (MPa)

1,8 4,0 65 6,4

2,5 5,9 69 3,2

3,1 7,3 76 3,2

2,8 6,4 73 4,1

3,0 6,2 76 3,9

Hardness Shore A at 23˚ Tear Strength ASTM D-470

177

EuroWire – March 2010