PVDF Polymer Composition for Flexible Pipe Fatigue Resistance
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Solution Overview
Problem
Current polymeric compositions for flexible pipes used in oil and gas transportation, such as those based on PVDF, face limitations in mechanical and chemical properties, particularly in fatigue strength and stability over time, due to the extraction of plasticizers which affect the geometry and leaktightness of the pipes.
Innovation Solution
A thermoplastic polymeric composition comprising a PVDF homopolymer with chains of very high molar mass, an elastomeric VDF-based copolymer, and a VDF homopolymer of low viscosity, without plasticizers, which enhances mechanical and chemical properties and maintains stability over the life of the pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF homopolymer is used to ensure high operating temperature and chemical resistance, then thermal resistance and chemical resistance are improved, but stiffness increases excessively
Solution Approach 1:
The patent uses a composite material system consisting of PVDF homopolymer combined with VDF-based copolymer and plasticizer. This composite approach allows the mixture to achieve flexibility comparable to fluorinated elastomers while maintaining the high temperature and chemical resistance properties of PVDF, thereby resolving the contradiction between stiffness and operational performance.
2Strength
If fluorinated elastomer is used to reduce stiffness, then flexibility is improved, but extrudability deteriorates and thickness/diameter ratio cannot be achieved
Solution Approach 1:
The patent changes the compositional parameters by formulating a specific mixture of PVDF homopolymer, VDF-based copolymer, and plasticizer in controlled proportions. This parameter adjustment enables the composition to achieve both the desired flexibility and the required extrudability, allowing production of pipes with thickness/diameter ratio close to 1/10, which pure fluorinated elastomers cannot achieve.
3Strength
If plasticizer is added to reduce stiffness of PVDF, then flexibility is improved, but plasticizer extraction occurs over time affecting geometry and leaktightness
Solution Approach 1:
The patent extracts the harmful element (unstable plasticizer) from the system by replacing it with a more stable plasticizing agent that is specifically selected to resist extraction by chemical substances. This substitution maintains the flexibility benefits while eliminating the composition instability and geometry degradation issues associated with conventional plasticizers.
4Reliability
If high content of fluorinated elastomer is used to improve fatigue strength, then fatigue strength is improved, but the composition becomes too complex and difficult to process
Solution Approach 1:
The patent optimizes the compositional parameters by using a specific ratio of PVDF homopolymer to VDF-based copolymer to fluorinated elastomer. This parameter optimization achieves sufficient fatigue strength while keeping the composition manageable and processable, avoiding the complexity issues that would arise from using excessively high concentrations of fluorinated elastomer.
Data Source
AI summary
The present invention concerns a fluorinated polymer composition, methods for producing same, and products that can be produced from said composition. More particularly, the invention concerns a thermoplastic polymer composition comprising the following components A, B and C: A--a polyvinylidene fluoride (PVDF) homopolymer comprising a fraction of ultra high molecular weight chains (UHMCF); B--a vinylidene fluoride (VDF) elastomeric copolymer and at least one other fluorinated comonomer copolymerisable with VDF, and C--a VDF homopolymer having a lower viscosity than component A.