Biaxially Oriented Polypropylene Pipe Composition for Hydrostatic Strength
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Solution Overview
Problem
Existing biaxially oriented polypropylene pipes do not consistently maintain improved properties in both axial and hoop directions, particularly in terms of long-term hydrostatic pressure resistance.
Innovation Solution
A biaxially oriented polypropylene pipe is developed using a propylene-based polymer composition with a random copolymer of propylene and ethylene or α-olefins, which is stretched in both the axial and peripheral directions to enhance mechanical properties, specifically incorporating a comonomer content of 0.1 to 3.8 wt% to achieve improved hydrostatic pressure performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biaxial orientation is applied to improve properties in both axial and hoop directions, then long-term hydrostatic pressure performance and low temperature impact are improved, but crack propagation resistance may worsen
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content within 0.1 to 3.8 wt% and the molecular weight distribution (Mw/Mn ratio between 2.0 to 10.0). These parameter optimizations enable the polymer to achieve both improved hydrostatic pressure performance through biaxial orientation and enhanced crack propagation resistance, resolving the technical contradiction between reliability and harmful factors.
Solution Approach 2:
The patent uses a composite polymer composition consisting of propylene homopolymer and propylene copolymer in specific proportions (80:20 to 20:80 weight ratio). This composite structure combines the rigidity and orientation response of homopolymer with the flexibility and crack resistance of copolymer, achieving both improved hydrostatic pressure performance and reduced crack propagation while maintaining reliability.
2Strength
If biaxial orientation is applied to improve mechanical properties, then strength and durability are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the polymer composition (comonomer content, molecular weight distribution, and polymer blend ratio) before the biaxial orientation process. This preliminary preparation ensures that the material responds predictably to orientation, achieving enhanced mechanical properties while simplifying the manufacturing process control and reducing complexity.
Solution Approach 2:
The patent optimizes specific parameters including comonomer content (0.1-3.8 wt%), molecular weight ratio (Mw/Mn: 2.0-10.0), and polymer composition ratio (homopolymer:copolymer: 80:20 to 20:80). These parameter changes enable the material to achieve desired mechanical properties through standard biaxial orientation processes, avoiding the need for complex specialized equipment or multi-step procedures.
3Object-affected harmful factors
If comonomer content is increased to improve crack propagation resistance, then durability is enhanced, but hydrostatic pressure performance may worsen
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content within the optimal range of 0.1 to 3.8 wt%. This precise parameter control ensures that sufficient comonomer is present to provide crack propagation resistance while maintaining enough crystallinity and structural integrity to achieve excellent hydrostatic pressure performance, thereby resolving the contradiction between durability and reliability.
Solution Approach 2:
The patent applies local quality by distributing the comonomer units throughout the polymer chains in a controlled manner, creating local regions with enhanced flexibility and crack resistance while maintaining overall structural integrity. This localized modification through controlled comonomer incorporation allows the material to resist crack propagation without sacrificing the hydrostatic pressure performance required for reliability.
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 biaxially oriented pipe exhibits excellent long-term hydrostatic pressure performance, with a time to failure of at least 100 hours under 20 MPa stress at 20°C, demonstrating enhanced resistance to crack propagation and durability.
Implementation Method 1
The biaxial orientation means that the polymer material is oriented in two directions, perpendicular to one another. A pipe can be oriented in the axial direction and peripheral direction (hoop direction)
Implementation Method 2
A biaxially oriented pipe made from a propylene-based polymer composition... stretching the tube... to obtain the biaxially oriented pipe
Data Source
AI summary
The invention relates to a biaxially oriented pipe made of a polymer composition comprising a propylene- based polymer, wherein the propylene- based polymer comprises a random copolymer of propylene and a comonomer which is ethylene and/or an a-olefin having 4 to 10 carbon atoms, wherein the propylene-based polymer has a comonomer content of 0.5 to 3.8 wt% based on the propylene-based polymer.