Co-continuous PVDF Copolymers for High Melting Point and Flexibility
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Solution Overview
Problem
Polyvinylidene fluoride (PVDF) copolymers face challenges in achieving a balance between high melting points, flexibility, and low-temperature impact resistance, with existing methods either compromising on melting temperature or rigidity, and there is a need for an alternative to costly fluoropolymers that offer better processing and performance.
Innovation Solution
A heterogeneous copolymer composition of vinylidene fluoride and hexafluoropropylene or perfluoro vinyl ether is formed by introducing the co-monomer between 25 to 50 weight percent of the VDF monomer addition, creating a co-continuous morphological structure that maintains high melting points while enhancing flexibility and low-temperature impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If co-monomers are introduced to improve low-temperature impact resistance and flexibility, then low-temperature properties are improved, but melting temperature decreases significantly
Solution Approach 1:
The copolymer is segmented into distinct phases: a PVDF homopolymer phase (90-100 wt% VDF) and a copolymer phase (65-95 wt% VDF with co-monomer). This phase separation allows the high-melting PVDF phase to maintain structural integrity while the copolymer phase provides low-temperature flexibility and impact resistance.
Solution Approach 2:
Different regions of the copolymer have different compositions and properties. The PVDF homopolymer phase provides high melting point and rigidity, while the copolymer phase with elastomeric properties provides flexibility and low-temperature impact resistance. Each phase is optimized for its specific function.
2Reliability
If heterogeneous copolymer is formed by adding co-monomer late in polymerization, then phase separation occurs improving low-temperature properties, but co-monomer incorporation level is limited
Solution Approach 1:
The PVDF homopolymer phase is formed first by polymerizing VDF alone or with minimal co-monomer before the majority of VDF is added. This preliminary phase formation enables subsequent incorporation of higher levels of co-monomer in the copolymer phase without compromising the overall melting point, as the homopolymer phase acts as a high-melting matrix.
3Shape
If discrete rubber phase domains are formed in PVDF continuous phase, then heterogeneous structure is achieved, but co-continuous morphology and improved rheological properties are not obtained
Solution Approach 1:
The phase morphology transitions from static discrete domains to a dynamic co-continuous structure where both phases are interconnected. This co-continuous morphology, achieved by controlling phase separation during polymerization, provides superior rheological properties and melt processability compared to discrete domain structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The co-continuous copolymer achieves a unique balance of high and low-temperature properties, offering improved rheological characteristics and melt processability, making it suitable for applications like wire and cable markets and oil and gas industries without significant decreases in melting point.
Implementation Method 1
adding one or more co-monomers before half of the original monomer stream has been added, to create a second-phase at an effective level to cause phase separation within the copolymer
Data Source
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AI summary
The invention relates to a heterogeneous, co-continuous copolymer composition of vinylidene fluoride and at least one other comonomer. Preferred comonomers are hexafluoropropylene and perfluoroalkylvinyl ether. The co-continuous morphology is provide by first forming a first phase polymer, then adding one or more comonomers before half of the original monomer stream has been added, and at an effective level to cause phase separation of the copolymer. The co-continuous morphology provides a means for incorporating a high level of comonomer into the copolymer with little or no adverse effect on the melting temperature. The morphology also provides the copolymer composition with a unique combination of properties, including a high melting point, good flexibility and good low temperature impact resistance. The unique properties of the polymer make it useful in end-use application where those properties provide performance advantages, such as in the wire and cable market, and in oil and gas applications.