Flexible pipe body and method of producing same

1. A method of producing a flexible pipe body for transporting production fluids from a sub-sea location, comprising:

providing a tubular layer; and

directing a chemical reagent towards a surface portion of the tubular layer,

wherein the tubular layer comprises an extruded polymer comprising a fluoropolymer, a polyamide, polyphenylene sulphide (PPS), PP, PFA, HDPE, PEEK, PEX, or a combination thereof, and wherein the chemical reagent has the effect of softening the polymer without dissolving the polymer and is suitable for changing one or more physical or mechanical property of a proportion of the extruded tubular layer thickness to thereby reduce, inhibit or prevent microcrazing.

2. A method as claimed in claim 1 wherein the tubular layer is a second tubular layer applied by extrusion over a first tubular layer, and the directing step of claim 1 is applied to the first tubular layer prior to the extrusion of the second tubular layer.

3. A method as claimed in claim 1 wherein the tubular layer is a second tubular layer applied by extrusion over a first tubular layer, and the directing step of claim 1 is applied to the second tubular layer after the extrusion of the second tubular layer.

4. A method as claimed in claim 1 wherein the tubular layer is a second tubular layer applied by extrusion over a first tubular layer, and wherein the first tubular layer comprises a polymer doped with the chemical reagent, and wherein the directing step comprises releasing the chemical reagent from the first tubular layer.

5. A method as claimed in claim 1 wherein the polymer comprises PVDF, PA-11, PA-12or a mixture thereof.

6. A method as claimed in claim 1 , wherein the chemical reagent comprises acetone, toluene, dibutyl sebacate, methyl ethyl ketone, ethyl acetate, dimethyl sulfoxide, xylene, monoethylene glycol, silicon oil having a kinematic viscosity of about 50 cSt (50 mm 2 ·s −1 ) or less, or a combination thereof, or a dilution in water or otherwise benign fluid of such chemical agent.

7. A method as claimed in claim 1 , further comprising changing a physical property of part of the tubular layer, temporarily or permanently, with the chemical reagent.

8. A method as claimed in claim 7 wherein the physical property includes shape, modulus of elasticity, yield strength, stress-strain relationship, threshold strain for crazing, surface hardness, surface tension, friction for movement of polymer fibre chains, microstructure of polymer chain distribution, and density.

9. A method as claimed in claim 1 further comprising providing an armour layer and an outer sheath over the tubular layer.