E - Arkema Inc.

Thermoplastic Polymers for OFF-SHORE 

Flexible Pipes 

© ATOFINA Technical Polymers - document with controlled diffusion - ATO-API version 3.0 26/08/02 

1 

KYNAR ®

RILSAN ® , the unique polyamide from ATOFINA, today looks back at a service history of 30 

years in the petrol industry. After 14 years of research in a program launched in 1958 by the 

French Institut de Petrole, PA11 was chosen as the best material out of several hundred 

tested. The combined qualities of flexibility, excellent impact resistance even at low 

temperatures, high resistance to ageing and good compatibility to products common to the 

petrol industry environment have made RILSAN ® an unequaled standard. 

For even higher demands, especially when the temperature or combined high temperature 

and high water content requirements are too severe, ATOFINA proposes its unique KYNAR ® 

off-shore grade. KYNAR ® is a thermoplastic fluoropolymer resin initially developped by 

ATOFINA. Its outstanding thermomechanical properties combined with exceptional chemical 

and ageing resistance made it possible for KYNAR ® to meet the highest demands. 

This document is intended to provide detailed technical information on the properties of 

ATOFINAs thermoplastic polymers for flexible pipe use. The scope of the technical details is 

defined in the “ Specification for Unbonded Flexible Pipe ” - API Specification API 17J 

effective since March 1 st 1997. 

The diffusion of this document is controlled, that is, the document is available to costumers of 

ATOFINA, the flexible pipe manufacturers, and their costumers; the petrol industry. 

The data given in this document based on trials carried out in our Research Centres and data 

selected from litterature are given to the best of our knowledge and do not contribute or 

imply any warranty, undertaking, express or implied commitment from our part. Our formal 

specifications define the limit of our commitment. 

For specific questions on this document please contact : 

M. Michael Werth Tel +33 232466874 

M. Patrick Dang Tel +33 232466882 


2

Contents 

1. API 17J - Property Requirements for Extruded Polymer materials 

page 

4 

1.1 Mechanical/physical properties 4 

1.2 Thermal properties 4 

1.3 Permeation characteristics, compatibility and ageing 5 

1.4 Fluid permeability 5 

1.5 Blistering resistance 5 

1.6 Fluid compatibility 5 

1.7 Ageing tests 6 

BESNO P40 TLX and BESNO P40 TLXOS 7 

2. Mechanical/physical properties 8 

2.1 Density 8 

2.2 Hardness 8 

2.3 Compression strength 8 

2.4 Abrasion resistance 8 

2.5 Flexural test according to ISO 178-93 8 

2.6 Flexural test according to ASTM D790 8 

2.7 Impact test according to ISO 179 (type II) 8 

2.8 Impact test according to ISO 179-93 CA 8 

2.9 Tensile creep 9 

2.10 Stress relaxation 12 

2.11 Fatigue 13 

2.12 Tensile tests according to ISO 527-93 BA 14 

2.13 Tensile tests according to ASTM D638 type II 14 

2.14 Poisson ratio 14 

2.15 Compression test 17 

2.16 Creep in compression mode 18 

3. Thermal properties 20 

3.1 Thermal conductivity 20 

3.2 Thermal expansion 20 

3.3 Heat deflection temperature ASTM D648 20 

3.4 Softening point ASTM D1525 20 

3.5 Heat capacity 20 

3.6 Glass transition temperature 20 

3.7 Dynamic mechanical analysis 21 

3.8 Differential Scanning Calorimetry (DSC) 22 

4. Ageing behaviour, compatibility and permeation 23 

4.1 Lifetime models and end-of-life criteria based on polyamide hydrolysis 23 

4.2 Evolution of properties during ageing 25 

4.3 Compatibility with offshore fluids and gases 28 

4.4 Permeation characteristics 28 

4.5 Blistering resistance 30 

4.6 Weathering resistance 31 

4.7 Water absorption 32 

Annexes : Magnified plots 


3

1. API 17J - PROPERTY REQUIREMENTS FOR EXTRUDED POLYMER 

MATERIALS 

The API specification 17 J “ Specification for unbonded flexible pipe ” was edited in december 

1996 and is effective since 1st of march 1997. The intention of this specification is the 

harmonization of current practice in the off-shore industry with the particular aim of obtaining high 

safety standards and a common reference basis for all suppliers to the off-shore industry. 

The API specification 17 J contains a specific chapter 6.1.2 dealing with polymer materials. 

ATOFINA, a supplier of polymer materials to the off-shore industry, is adressing the specified 

properties in this given document. 

1.1 MECHANICAL/PHYSICAL PROPERTIES 

Internal pressure sheath : A, Intermediate sheath / Anti-Wear layer : B, 

Outer sheath : C 

A B C Test Procedure Comments 

Resistance to creep X X X ASTM D2990 due to temperature 

and pressure 

Yield strength/elongation X X X ASTM D638 

(ISO 527 93.1 BA) 

Ultimate strenth/elongation X X X ASTM D638 

Stress relaxation properties X ASTM E328 

Modulus of elsticity X X X ASTM D790 

(ISO 178 :39) 

Hardness X ASTM D2240 

(ISO 2039/2 et 868) 

Compression strenth X ASTM 695 

Impact strength X ASTM D25 

(ISO 179 type1 et 

ISO 179 :93CA6 

Abrasion resistance X ASTM D4060 

(ISO 9352 :1995F) 


4 

at design minimum 

temperatures 

or ASTM D1044 

Density X X X ASTM D792 ASTM D1505 

Fatigue X X X ASTM D671 dynamic applications 

only 

Notch sensitivity X ASTM D256 

1.2 THERMAL PROPERTIES 

Internal pressure sheath : A, Intermediate sheath / Anti-Wear layer : B, 

Outer sheath : C 


Coefficient of thermal conductivity X X X ASTM C177 

Coefficient of thermal expansion X X X ASTM E831 

Heat distortion temperatures X X X ASTM D648 

(ISO 75) 

Method A 

Softening point X X X ASTM D1525 

Heat capacity X X X ASTM E1269 

Brittleness 

temperature 

(or glass transition) X X ASTM D746 or ASTM E1356

1.3 PERMEATION CHARACTERISTICS, COMPATIBILITY AND AGING 


Fluid permeability X X X details in API 17J CH4, CO2, H2S and 

methanol 

Blistering resistance X details in API 17J at design conditions 

Fluid compatibility X X X details in API 17J 

Aging tests X X X details in API 17J 

Environmental stress cracking X X X ASTM D1693 

weathering resistance X Effectiveness of UV 

stabilizer 

Water absorption X X ASTM D570 Insulation material 

only 

For the characteristics listed in the last table API 17J recommends the following test requirements. 

1.4 FLUID PERMEABILITY 

a) The sample shall be taken from an extruded polymer sheath. 

b) The thickness is 1 mm as a minimum. 

c) The diameter is 70 mm as a minimum. 

d) Sufficient tests at different temperatures to allow for linear interpolation should be performed. 

e) Sufficient tests at different pressures to allow for linear interpolation should be performed. 

1.5 BLISTERING RESISTANCE 

a) Fluid mixtures - Use gas components of specified environment as documented in the test 

procedure.. 

b) Soak time - Use sufficient to ensure stauration. 

c) Test cycles - If available, use expected number of decompressions, or else use 20 cycles as a 

minimum. 

d) Decompression rate - If available, use expected decompression rate, or else use as a minimum 

70 bar per minute. 

e) Thickness - Internal pressure sheath wall thickness as a minimum. 

f) Temperature - Use the expected decompression temperature. 

g) Pressure - Use design pressure as a minimum. 

h) Procedure - After each depressurization the sample shall be examined at a magnification of × 

20 for signs of blistering, swelling and slitting. 

No blister formation or slitting shall be observed. 

1.6 FLUID COMPATIBILITY 

All components shall be evaluated in the environments to which the polymer is exposed. Tests shall 

be based on the design conditions of temperature, pressure and strain. As a minimum tensile 

strength, elongation at break, visual appearance and fluid absorption (weight gain) and desorption 

(weight loss) shall be measured and evaluated in the tests. 


5

1.7 AGEING TESTS 

Polymer aging models shall be based on testing and experience and shall predict the aging or 

deterioration of the polymer under the influence of environmental and load conditions that have 

benn identified to be relevant through testing. As a minimum, polymer aging models for PA-11 

shall consider temperature, water cut and pH. For PVDF materials the assessment of aging shall 

include the effect of temperature, chemicel environment and mechanical load. Special attention 

should be given to deplastification, fluid absorption and changes of dimensions. Creep, cyclic strain 

and relaxation shall be investigated on aged and unaged samples. The aging models may include 

accumulated damage concepts based on blocks of time or operational cycles of 

temperature/pressure under different exposure conditions. Aging may be determined by change in 

either specific mechanical properties or in specified physico-chemical characteristics which 

includes reduction in the plasticizer content of the material. 


6

BESNO P40 TLX 

BESNO P40 TLX OS 

DATA 

BESNO P40 TLX and BESNO P40 TLX OS are both plasticized PA11 grades 

destinated for off-shore flexible pipe use. Their respective compositions are strictly the 

same as well as their properties. Th difference between the two grades lies in different 

granules’ conditioning for shipment. 

In general and in case it is not specifically stated, experiments were conducted on 

extruded sheet material. Such extruded sheet gives similar experimental results as the 

extruded flexible pipe. 


7

2. MECHANICAL/PHYSICAL PROPERTIES 

2.1 DENSITY 

2.2 HARDNESS 

ASTM D792 1.05 

ISO 2039/2 (R SCALE) 75 

ISO 868 (D SCALE) 63 

2.3 COMPRESSION STRENGTH 

ASTM D695 (23°C) 50 MPa 

2.4 ABRASION RESISTANCE 

ISO 9352 : 1995(F) 

(loss in weight after 1000 rev under 500g 

load with H18 abrasive wheel) 22 mg 

2.5 FLEXURAL TESTS ACCORDING TO ISO 178 : 93 

Temperature °C -40 -20 23 80 

Flexural modulus 

(dry material) 

MPa 1950 1350 320 165 


(after conditionning 15 

days 23°C 50% R.H.) 

MPa 2050 1150 280 160 

2.6 FLEXURAL TESTS ACCORDING TO ASTM D790 

Temperature °C 23 80 


(dry material) 

MPa 330 170 

2.7 IMPACT TESTS ACCORDING TO ISO 179 (type 1) 

Temperature °C -40 23 

Unnotched KJ.m -2 N.B. N.B. 

Notched KJ.m -2 8 N.B. 

2.8 IMPACT TESTS ACCORDING TO ISO 179 :93 CA 

Temperature °C -40 -20 0 23 

Notched KJ.m -2 6.8 9.9 52.9 N.B. 


8

2.9 TENSILE CREEP - TRACTION MODE 

Tensile creep tests according to ASTM D2990 were performed under 2 MPa at different temperatures 

rangeing from 23°C to 80°C. Tensile specimens were of ISO R 527 injected type and a MTS 810 

servohydraulic machine is used. From the different curves a creep master curve was constructed by applying 

the time temperature superposition principle. The creep modulus can then be modeled by a linear function on 

a log-log scale. 

Creep curves at 2 MPa for different temperatures - strain data 

STRAIN (mm/mm) 

0.016 

0.014 

0.012 

0.01 

0.008 

0.006 

0.004 

0.002 

0 

1 10 100 1000 10000 100000 


9 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C 

Master plot at 2 MPa obtained using the time - temperature shifting principle scaled to 23°C 

STRAIN(mm/mm) 

0.016 

0.014 

0.012 

0.01 

0.008 

0.006 

0.004 

0.002 

0 

1 100 10000 1000000 1E+08 1E+10 1E+12 1E+14 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C modele

Plot of the shifting factor αΤ used to obtain the maste plot 

log(aT) 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

0 

0.0025 0.0027 0.0029 0.0031 0.0033 0.0035 


10 

1/T K-1 

Creep curves at 2 MPa for different temperatures - stress data 

MODULUS(MPa) 

1000 

100 

1 10 100 1000 10000 100000 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C

Tensile creep master curve constructed for 23°C 

MODULUS(MPa) 

1000 

100 

1 100 10000 1000000 1E+08 1E+10 1E+12 1E+14 


11 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C 

All these creep studies have been done on ISO R 527 injection molded samples for purpose 

of simplicity but we have checked that there is merely no difference in the creep behaviour 

between injection molded or extruded samples. 

Tensile creep curves under 5 Mpa at 23°C, 50°C and 80°C for both injection molded and 

extruded specimen

2.10 STRESS RELAXATION 

Stress relaxation measurements were performed according to ASTM standard E 328.86, but 

using ISO R 527 tensile specimens. The imposed strain was 1%. A stress relaxation master 

curve was built using time - temperature superposition principle. 

The stress relaxation modulus is seen to decrease linearly in time in a log - log plot. 

Stress relaxation curves for different temperatures at 1% strain 

MODULUS(MPa) 

1000 

100 

1 10 100 1000 10000 100000 

23°C 

Time(sec) 

30°C 40°C 

50°C 60°C Puissance (23°C) 

Puissance (30°C) 

Puissance (60°C) 

Puissance (40°C) Puissance (50°C) 

Master plot : Evolution of E Modulus during stress relaxation under 1% strain at 23°C 

MODULUS(MPa) 

1000 

100 

1 100 10000 1000000 1E+08 1E+10 1E+12 

Temps(sec) 

23°C 30°C 40°C 60°C 80°C 50°C 


12

Comparison between the creep master plot and the stress relaxation master plot at 23°C 

MODULUS(MPa) 

1000 

100 

2.11 FATIGUE 

STRESS RELAXATION 

1 100 10000 1000000 1E+08 1E+10 1E+12 1E+14 


13 

TIME (s) 

CREEP 

Measured according to NF T51-120 in replacement to the norm ASTM D671. We chose this 

standard which measures fatigue at constant deformation in contrast to the ASTM standard 

which measures at constant stress. To our knowledge the constant amplitude mode is more 

representative to the actual situation in a flexible riser. Furthermore, the constant stress 

mode would result in a considerable increase of deformation during the fatigue experiment 

due to stress relaxation of the material. 

INITIAL STRESS (MPa) 

10.00 

9.00 

8.00 

7.00 

6.00 

5.00 

4.00 

3.00 

2.00 

1.00 

FATIGUE TEST OF BESNOP40TLX WITH AN END OF LIFE 

CRITERIA OF 20% REDUCTION OF THE INITIAL STRESS 

0.00 

1000 10000 100000 1000000 10000000 

N cycles

2.12 TENSILE TESTS ISO 527 93.1BA 

Samples injection moulded 

TEMPERATURE Yield strength Elongation at Ultimate strength Elongation at 

yield 

break 

MPa % MPa % 

-60°C 93.4 10 65.5 75 

-40°C 77.3 11 60.8 90 

-20°C 49.1 21 59.2 202 

0°C 36.4 33.2 56.8 231 

23°C - - 48.8 263 

40°C - - 43.8 260 

60°C - - 37.3 260 

80°C - - 34 262 

100°C - - 31.9 282 

120°C - - 32.7 323 

2.13 TENSILE TESTS ASTM D638 type II 

Samples cut from extruded sheaths 

TEMPERATURE Yield strength Elongation at Ultimate strength Elongation at 

yield 

break 

MPa % MPa % 

-40°C 64 16 33 128 

-20°C 46 30 > 39 > 230 

0°C 36 40 > 39 > 230 

20°C 26 44 > 27 > 230 

40°C 20 46 > 26 > 230 

60°C 20 46 > 26 > 230 

80°C 13 44 > 17 > 230 

100°C 11 42 > 15 > 230 

120°C 9 38 > 13 > 230 

Apparatus limited in size to reach maximum elongation 

2.14 POISSON RATIO 

Temperature (°C) -40 23 100 

Poisson ratio 0,385 0,47 0,45 

The poisson ratio at 100°C is decreasing contrary to theoretical prediction. This is due to 

loss of plasticizer which exerts a slight influence on dimensional change. 


14

Tensile test according ISO R 527-93 1BA 

120 

100 

80 

60 

40 

20 

0 

-60°C 

-40°C 

0 50 100 150 200 250 300 350 

Strain(%) 


15 

-20°C 

0°C 

20°C 

60°C 80°C 

note : Curve fluctuations at lower temperatures are a consequence of temperature fluctuations. 

40°C 

120°C

Tensile tests according ASTMD 638 type II 

Stress (MPa) 

70 

60 

50 

40 

30 

20 

10 

0 

0 50 100 150 200 250 300 

Strain (%) 


16 

-40°C 

-20°C 

0°C 

20°C 

40°C 

60°C 

80°C 

100°C 

120°C

2.15 COMPRESSION TESTS 

Compression tests were done on 10*10*5 mm specimen machined in an extruded pipe. The 

compression is applied along the thickness on an MTS 810 servohydraulic machine. 

The compression speed is 1mm/min. 

Compression tests on BESNO P40 TLX at 1 mm/min 

Stress (MPa) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

0 10 20 30 40 50 60 70 80 

Strain(%) 

23°c 40°c 60°c 80°c 100°c 


17

2.16 CREEP IN COMPRESSION MODE 

Creep tests in compression were done on 10*10*5 mm specimen machined in an extruded 

pipe. The compression is applied along the thickness on an MTS 810 servohydraulic 

machine. 

Creep in compression mode of BESNO P40 TLX under 10 MPa 

Strain(%) 

12 

10 

8 

6 

4 

2 

0 

1 10 100 1000 10000 100000 

Time(s) 

20°C 30°C 40°C 60°C 80°C 


18

Creep in compression mode of BESNO P40 TLX under 15 MPa 

Strain(%) 

25 

20 

15 

10 

5 

0 

1 10 100 1000 10000 100000 

Time(s) 

23°c 30°c 40°c 60°c 80°c 100°c 


19

3 THERMAL PROPERTIES 

3.1 THERMAL CONDUCTIVITY 

Temperature (°C) 39 61 82 102 122 142 163 182 202 223 

K (W/m°K) 0.21 0.21 0.24 0.24 0.24 0.24 0.25 0.25 0.25 0.25 

3.2 THERMAL EXPANSION 

ASTM E 821 

from -30°C to +50°C 11x10-5 °K-1 

from +50°C to +120°C 23x10-5 °K-1 

3.3 HEAT DISTORSION TEMPERATURE 

ASTM D648 

ISO 75 (0.46 Mpa) 130 °C 

ISO 75 (1.85 Mpa) 45 °C 

3.4 SOFTENING POINT 

ASTM D1525 

under 1daN 170 °C 

under 5 daN 140 °C 

3.5 HEAT CAPACITY 

Measured by D.S.C. 

Temperature (°C) 20 50 80 120 160 200 230 260 

cal/g.°C 0.40 0.50 0.56 0.6 0.63 0.66 0.66 0.67 

3.6 GLASS TRANSITION TEMPERATURE 

D.M.A. 0-10 °C 


20

3.7 DYNAMIC MECHANICAL ANALYSIS (full curve) 

Measurement in a 3-point bending flexural mode at 10 rad/s 

STORAGE MODULUS E' (Pa) , LOSS 

MODULUS E''(Pa) 

1.00E+10 

1.00E+09 

1.00E+08 

1.00E+07 

-140 

-120 

-100 

-80 

-60 

-40 

-20 

0 

20 

40 


21 

60 

Temperature(°C) 

The DMA curve obtained is characteristic for semicristalline polymers. Essentially four 

different relaxational transitions can be detected. 

The γ transition at the lowest temperature (-130°C) is commonly attributed to localized 

motion of methylene segments. The intermittent low temperature relaxation, denominated 

β- relaxation, is attributed to localized motion of H-bonded groups like the amide functions 

and its amplitude varies depending on water content. 

The α-relaxation around -10°C is also called the glass transition. It implies large segmental 

motion of the polymer chains enabling diffusion processes to take place . 

Finally the last transition with an onset at 140°C is linked to the melting of the cristalline 

phase. 

For a textbook on the comprehensive analysis of DMA data refer to “ Anelastic and 

dielectric effects in polymer solids ” by N.G. McCrum, B.E. Read, G. Williams Dover 

Publication New York 1991. 

80 

100 

120 

140 

E' 

E'' 

160 

180

3.8 DSC CURVE OF BESNO P40 TLX 

The DSC curve is obtained on a PERKIN ELMER DSC 7 calorimeter at a heating rate of 

20°C/min. On the thermogram, one can easily observe the melting zone and the melting 

peak that gives the melting temperature. 

Heat Flow (mW) 

50 

45 

40 

35 

30 

25 

-80 -40 0 40 80 120 160 200 240 



22 

Heating rate : 20°C/min

4. AGEING BEHAVIOUR, COMPATIBILITY AND PERMEATION 

4.1 LIFETIME MODELS AND FAILURE CRITERIA BASED ON 

POLYAMIDE HYDROLYSIS 

From a point of view of material evolution due to ageing the following effects have been 

demonstrated in plasticized PA11 : 

- molecular weight loss due to a hydrolysis reaction in the presence of water 

- plasticizer loss 

- absorption of oil components, gases and moisture 

- annealing which leads to a higher crystalline content. 

Hydrolysis has been reckognized as the most important ageing phenomenon in PA11. The 

process is well understood due to intense recent research. The kinetics of molecular weight 

loss are known in detail and can rather well be correlated with material performance [1 2 3 

4]. 

The importance and the complexity of the PA11 ageing behaviour have resulted in a 

combined industry effort. The main result of the industry working group is a document 

which states specifically the end-of-life criteria and typical lifetime curves for environments 

of different acidity. The reference of this document is 

API Technical Bulletin 17 RUG. 

The reference ageing criterion defined is based on average molecular weight as expressed in 

Corrected Inherent Viscosity (CIV). Guidelines how to measure CIV are given in detail in 

API TB 17 RUG and refer to standards ASTM D2857-95 and ISO 307:1994. However, 

special procedures not outlined in the ASTM or ISO standards apply. 

The failure criterion for PA11 in flexible pipes has been determined as CIV = 1,05 dl/g. The 

initial acceptance criterion has been defined as 1,20 dl/g which includes a safety factor. 

For further information, in particular lifetime estimations and Arrhenius curves based on 

above acceptance and failure criteria, the reader should refer to API TB 17 RUG. 

Special attention is drawn to the necessity of appropriate procedures for ageing 

experiments. The oxygen content in long term ageing experiments must be tightly 

controlled and kept below a minimum to avoid a significant increase in ageing severity. 

Also the preparation of test samples and factors such as the weigth ratio testing medium / 

samples are important parameters. For detailed information please refer to API TB 17 RUG. 

1. “Lifetime prediction of PA11 and PVDF thermoplastics in oilfield service– a synthetic 

approach” Patrick Dang, Yves Germain, Bernard Jacques, James Mason, Michael R.G. 

Werth, American Chemical Society Rubber Division meeting in Dallas, 3/04/2000 

2. "Durability of polyamide 11 for offshore flexible pipe applications", J. Jarrin, A. 

Driancourt, R.Brunet, B. Pierre, Communication at MERL Oilfield engineering with 

polymers, London, October 1998. 

3. "Ageing of polyamide 11 in acid solutions", G. Serpe, N. Chaupart, J. Verdu, Polymer, 

Vol 38 n°8, 1911-1917, 1997 


23

4. "Molecular weight distribution and mass changes during polyamide hydrolysis", G. 

Serpe, N. Chaupart, J. Verdu, Polymer, Vol 39 n°6-7, 1375-1380, 1998 

5. “Recommended practice for flexible pipe” API 17B, 2 nd edition 1998 

6. “Specification for unbonded flexible pipe” API Specification 17J, revised edition 1997 

7. “Progress towards a better understanding of the performances of Polyaminde 11 in 

flexible pipe applications” S. Groves Proceedings of OMAE’01, n° 3570 

8. "Improved thermoplastic materials for offshore flexible pipes", F. Dawans, J. Jarrin, T. 

Lefevre, M. Pelisson, Communication OTC 5231, 1986. 

9. “Lifetime prediction of PA11 and PVDF thermoplastics in oilfield service– a synthetic 

approach” Patrick Dang, Yves Germain, Bernard Jacques, James Mason, Michael R.G. 

Werth, American Chemical Society Rubber Division meeting in Dallas, 3/04/2000 

10. "Durability of polyamide 11 for offshore flexible pipe applications", J. Jarrin, A. 

Driancourt, R.Brunet, B. Pierre, Communication at MERL Oilfield engineering with 

polymers, London, October 1998. 

11. "Ageing of polyamide 11 in acid solutions", G. Serpe, N. Chaupart, J. Verdu, Polymer, 

Vol 38 n°8, 1911-1917, 1997 

12. "Molecular weight distribution and mass changes during polyamide hydrolysis", G. 

Serpe, N. Chaupart, J. Verdu, Polymer, Vol 39 n°6-7, 1375-1380, 1998 

13. “Accelerated ageing of polyamide 11 : evidence of physical ageing playing a role in the 

end-of-life criteria” H.J. Fell, M.H. Ottoy, Proceedings of Oilffield Engineering with 

polymers 2001, MERL Conference 28-29/11/2002-03-18 

14. “The Rilsan User Group and APUI TR 17RUG” S. Groves, K. Caveny, R. Thompson, 

M. Ottoy, J. Rigaud, E. Oeren, J. Belcher, S. Buchner, B. Jacques, M. Werth, D. 

Kranbuehl, J. Chang, OTC 14062 6 – 9 may 2002 

15. “Polyamide 11 – a high tenacity thermoplastic, its material properties and the influence 

of ageing in offshore conditions” M? Werth, G. Hochstetter, P. Dang, N. Chedozeau, 

OMAE ’02 –28570 , June 23 – 28 2002 Oslo 

16. API TB 17 RUG 


24

4.2 EVOLUTION OF PROPERTIES DURING AGEING 

Tensile properties 

For demonstration purposes the evolution of tensile properties in an accelerated ageing 

experiment at 120°C in diluted sulfuric acid (pH = 4) are given. 

ISO R527 samples with 3 mm thickness are machined out of extruded sheath and tesile tests 

performed at 23°C and 50 mm/min traction speed. 

The data presented shows a limited performance reduction for samples aged for “ and 10 

days. However, after 19 days a considerable reduction in elongation is observed. The 

material can be considered brittle and not fit for purpose. 

Such rather steep transitions between slightly affected aged material and a strong drop in 

tensile properties is characteristic of polyamide 11 behaviour upon ageing. 

Moreover, the ageing performance and CIV are well correlated ; after 19 days the CIV = 

0,97 dl/g. 

Contrainte (MPa) 

40 

35 

30 

25 

20 

15 

10 

5 

BESNO P 40TL Influence du vieillissement H2SO4/120°C Traction 50mm/min 23°C 

Haltère ISO R257 épaisseur 3mm usinée dans tube Coflexip 

0 

0 20 40 60 80 100 120 140 160 180 200 

Allongement rupture (%) 

Fracture toughness 


25 

non vieilli 

3 jours 

10 jours 

19 jours 

29 jours 

40 jours 

Ecart-type en pointillés 

A pertinent property for the flexible application is fracture toughness, in particular at lower 

temperatures. This method is very sensitive for material changes due to ageing effects. 

Following the protocols developed by the J.G. Williams research team, notched Compact 

test (CT) specimen with a thickness of 8 mm were tractioned at 5°C and a high speed of 85 

mm/s. 

Ageing conditions and durations were similar to the tensile tests. The K1c values thus 

obtained are well correlated with the CIV values. This type of test reveals a more gradual 

properties’ transition upon ageing than the tensile test.

Allongement rupture (%) 

K1c (MPa.√m) 

200 

180 

160 

140 

120 

100 

80 

60 

40 

20 

5 

4.5 

4 

3.5 

3 

2.5 

2 

1.5 

1 

Comparison of K1c values obatined on compact test specimen and 

charpy bars aged in H2SO4 pH 4 at 120°C and water at 140°C 

0.5 

0 

bars charpy water/140°C 

0 0.5 1 1.5 2 2.5 

CIV (dl/g) 

BESNO P40TL Traction 23°C et 50mm/min 

H2SO4/120°C pH=4 Haltères ISO R527 épaisseur 3mm 

Eau/140°C Haltères 53448A Visco cœur 

Eau/140°C Haltères DIN53448A Visco peau 

0 

0.0 0.5 1.0 1.5 2.0 2.5 

Viscosité corrigée ISO (dl/g) 


26 

CT tensile H2SO4/120°C 

CT tensile water/140°C

Fatigue experiments 

Fatigue experiments have been performed on strips cut from aged pressure sheath in the 

extrusion direction and thus including the interior extrusion band on the specimen and also 

on strips cut from smooth bore pipes. The specimens are aged to different levels, some cut 

from retrived pipes presenting a viscosity gradient. The imposed starting strain is 4 % 

corresponding to 12.5 MPa. The fatigue cycles are stress controlled and oscillate at 1 Hz 

(maximum frequency without self heating) between 10 and 100 % of imposed maximum 

stress. 

Number of cycles to rupture 

450000 

400000 

350000 

300000 

250000 

200000 

150000 

100000 

50000 

pipe 864N 

sheath 864N 

no break 

Tensile fatigue : samples cut from pipe and sheath 

aged in benzoic acid at 120°C 

0 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 

CIV (dl/g) 

The bars indicate viscosity gradients over the sheath thickness. 

The fatigue experiments demonstrate good performance for sheath material above CIV = 

1,0 dl/g. 

Literature on fracture mechanics with references on methodology : 

- ISO task group working on the compact test K1C method : ISO/TC61/SC2 n° 572, ISO/DIS 

13586-2,1998 : Determination of Fracture Toughness (Gc and Kc) Linear Fracture Mechanics (LEFM) Approach 

- J.G. Williams testing Protocol, march 1990, Mech. Eng. Dept. Imperial College, London 

- ASTM E 399-81 Standatd test method for plane strain Fracture Toughness of metallic 

materials 

- J.G. Williams, M.J. Cawood, Polym. Testing, 9, 15 (1990) 

- J.G. Williams “Fracture Mechanics of Polymers” Ellis Horwood Ltd. Chichester (1984) 

- ISO/TC61 N5015 : Plastics, Test method for Tension-Tension Fatigue Crack Propagation 


27

4.3 COMPATIBILITY 

The compatibility of RILSAN® offshore grades BESNO P40 TLX, BESNO P40 TLO, 

BESNO P40 TL is specified in detail in a separate document : 

RILSAN® Polyamide 11 in Oil & Gas 

OFF-SHORE Applications Reference © 2001/11/08. 

This document gives comprehensive information on ageing of polyamide 11 in all offshore 

environments. Furthermore, information is given relative to diverse injection fluids used in 

combination with thermoplastic umbilicals. 

Reference 

“A more realistic method for predicting the compatibility of thermoplastic hoses when used 

in subsea umbilical systems” J.D. Stables, I.R. Dodge, D. MacRaild OTC 7272 1993 

4.4 PERMEATION CHARACTERISTICS 

Permeability of gases 

Gas permeabilities were measured at the Institut de Pétrole (IFP) France following the 

“time-lag” method. 

Circular samples were cut from extruded sheath. The dimensions were 2 mm thickness and 

70 mm diameter. 

Details are described in the confidential report n° 52 735, octobre 1999 issued by IFP. 

Fluid 

CH4 

Conditions 

40°C, 100 bars 

60°C, 100 bars 

80°C, 100 bars 

Permeation value / 

10-8 cm3.cm/cm2.s.bar 

0,4. 

0,8 

2 

100°C, 100 bars 

4 

CO2 40°C, 100 bars 

1,5 

60°C, 100 bars 

4,5 

80°C, 100 bars 

10 

H2O 70°C 

50 to 100 bars 

200 - 700 

H2S 80°C, 40 bars 51 

The data correlates well with data published elsewhere. 


28

Permeability of PA11 to methanol 

Temperature in °C 4 23 40 50 

PA11 unplastizised 6 18 

PA11 plastizised 13.5 40 115 190 

units : g mm/m2 day atm 

The activation energies for the unplasticized and plasticized grades are respectively 39.4 kJ 

mol-1 and 43.1 kJ mol-1. 

Permeability (g mm/m2 day atm) 

1000 

100 

10 

1 

50°C 

40°C 

30°C 

1/Temperature 


29 

BESNO TL 

BESNO P40 TL 

20°C 

10°C 

Litterature 

17. “Permeability of methane, carbin dioxide and water in PA11 and PVDF for flexible 

pipes” T.R. Andersen, J.I. Skar, C. Hansteen, Eurocorr Congress 99, n°410 

18. “High pressure permeation of gases in semicrystalline polymers : measurement method 

and experimental data” B. Flaconneche, M.H. Klopffer, C. Taravel-Condat, Proceedings 

of Oilffield Engineering with polymers 2001, MERL Conference 28-29/11/2002-03-18 

19. "Improved thermoplastic materials for offshore flexible pipes", F. Dawans, J. Jarrin, T. 

Lefevre, M. Pelisson, Communication OTC 5231, 1986. 

0°C

4.5 BLISTERING RESISTANCE 

A blistering resistance study was performed at Institut Français du Pétrole (Solaize France). 

Material tested : BESNOP40TLX, samples taken from extruded pipe (8 mm thickness) 

Conditions : 

Sample size 35× 45 × 8 mm 

Test medium 85 % CH4 + 15 % CO2 

Test temperature 90°C 

Test pressure 1000 bar 

Soak time > 30 h 

Decompression rate explosive , > 70 bars/min 

Conclusion : 

No blister and no slitting have been observed after 20 cycles of compression – 

decompression, the RILSAN® BESNOP40TLX saturated by Diesel type II is qualified at 

90°C / 1000 bar toward blistering according to the IFP’s test procedure issued from the API 

17 J specification. 


30

4.6 WEATHERING RESISTANCE 

The UV resistance is measured under accelerated conditions on a standardized machine 

XENOTEST 1200 according to the RENAULT standard n° 1380. 

Conditions : 

Xenon lamps with filters eliminating radiation with wave lengths inferior to 300 nm. 

Intermittent exposure -è equal periods of light and darkness. 

During a 20 minute cycle the specimens are exposed to 3 minutes of distillated water spray 

and 17 minutes of exposure without spraying. The relative humidity of the cabinet during 

period without spray is approximately 65%. 

Black panel temperature in the measurement cabinet : 

65°C ± 2°C before spraying 

45°C ± 2°C after spraying. 

The specimens are dumbells according to ISO/NFT 51034 cut from a film of 1 mm 

thickness. Tensile tests are carried out at 50 mm/minute. 

time (h) 0 500 1000 1400 2000 

EB (%) 380 330 275 85 33 

EB / EB0 1 0.87 0.72 0.22 0.09 

MB (MPa) 72 61 47 34 25 

YI 6 14 16 13 13 

EB (%) 

400 

350 

300 

250 

200 

150 

100 

50 

0 

UV ageing : loss of elongation at break 

0 500 1000 1500 2000 2500 

time (h) 


31

4.7 WATER ABSORPTION 

ASTM D570 0.8% (23°C 50%R.H.) 

1.6% (23°C saturation) 

Water Absorption of BESNO P40 TLX at different temperatures - cinetics 

Abs (%) 

3 

2.5 

2 

1.5 

1 

0.5 

0 

0 200 400 600 800 1000 1200 1400 1600 1800 2000 

rac t / L (min^0.5/cm) 


32 

23°C 

80°C 

60°C 

100°C

STRAIN (mm/mm) 

0,018 

0,016 

0,014 

0,012 

0,01 

0,008 

0,006 

0,004 

0,002 

0 

TENSILE CREEP OF RILSAN BESNOP40TLX UNDER 2 MPa 

1 10 100 1000 10000 100000 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C 

© ATOFINA Technical Polymers division - document with controlled diffusion - ATO-API version version 3.0 26/08/02 33

0,018 

0,016 

0,014 

0,012 

0,01 

0,008 

0,006 

0,004 

0,002 

0 

CREEP MASTER CURVE OF BESNOP40TLX UNDER 2 MPa 

1 100 10000 1000000 100000000 1E+10 1E+12 1E+14 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C modele 


1000 

100 

TENSILE CREEP OF RILSAN BESNO P40 TLX UNDER 2 MPa 

1 10 100 1000 10000 100000 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C 


MODULUS(MPa) 

1000 

100 

TENSILE CREEP MASTER CURVE OF RILSAN BESNOP40TLX 

UNDER 2 MPa 

1 100 10000 1000000 100000000 1E+10 1E+12 1E+14 

TIME (s) 

23°C 30°C 40°C 50°C 60°C 80°C 100°C 


12 

10 

8 

6 

4 

2 

0 

SHIFT FACTOR FOR THE CREEP MASTER CURVE 

OF BESNO P40 TLX 

0,0025 0,0026 0,0027 0,0028 0,0029 0,003 0,0031 0,0032 0,0033 0,0034 0,0035 

1/T K-1 


12 

10 

8 

6 

4 

2 

0 

BESNO P40 TLX - COMPRESSION CREEP UNDER 10 MPa 

1 10 100 1000 10000 100000 

Time(s) 

23°c - 10 MPa 40°c -10 MPa 60°c- 10 MPa 80°c -10 MPa 30°c-10 MPa 23°c - 10 MPa 


Strain(%) 

12 

10 

8 

6 

4 

2 

CREEP COMPRESSION OF BESNO P40 TLX UNDER 10 MPa 

0 

1 10 100 1000 

Time(s) 

10000 100000 1000000 

23°C 30°C 40°C 60°C 80°C 


25 

20 

15 

10 

5 

0 

BESNO P40 TLX - CREEP IN COMPRESSION UNDER 15 MPa 

1 10 100 1000 10000 100000 

Time(s) 

23°c 30°c 40°c 60°c 80°c 100°c 


Strain(%) 

25 

20 

15 

10 

5 

COMPRESSION CREEP OF BESNOP40TLX UNDER 15MPa 

0 

1 10 100 1000 

Time(s) 

10000 100000 1000000 

23°C 30°C 40°C 60°C 80°C 100°C 


STORAGE MODULUS E' (Pa) , LOSS MODULUS 

E''(Pa) 

1.00E+10 

1.00E+09 

1.00E+08 

DYNAMIC MECHANICAL ANALYSIS OF BESNOP40TLX 

(3 POINT BENDING FLEXURAL MODE AT 10rad/s) 

1.00E+07 

-140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 


© ATOFINA Technical Polymers division - document with controlled diffusion - ATO-API version version 3.0 26/08/02 42 

E' 

E''

Heat Flow (mW) 

50 

45 

40 

35 

30 

25 

DSC curve of BESNO P40 TLX 

-80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 220 240 


Heating rate : 20°C/min

E - Arkema Inc.

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