Propylene 1-hexene copolymer beta nucleation
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Solution Overview
Problem
Polypropylene pipes face challenges in achieving a balance between high resistance to slow crack propagation, thermal resistance, rigidity, and impact strength, with existing copolymers often compromising one property for another, and risking material washout by pressurized fluids.
Innovation Solution
A β-nucleated propylene 1-hexene copolymer with a comonomer content of 1.0 to 3.0 wt.%, a xylene soluble fraction below 2.5 wt.%, and a polydispersity index of 4.0 Pa−1 or less, partially crystallized in the β-modification, incorporating a β-nucleating agent to enhance stiffness and impact resistance while minimizing material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If propylene copolymers are used to improve resistance to slow crack growth, then slow crack propagation resistance is improved, but thermal resistance and rigidity deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content (1.0-3.0 wt.%) and utilizing β-nucleation to achieve a specific crystalline structure. This transforms the polymer's physical parameters to simultaneously improve slow crack resistance while maintaining thermal resistance and rigidity, resolving the contradiction through quantitative optimization of composition and structure.
Solution Approach 2:
The invention creates a composite-like structure within the copolymer by incorporating β-nucleating agents that induce a specific β-crystalline modification. This internal structural composition allows the material to exhibit both the ductility needed for slow crack resistance and the crystalline order required for thermal resistance and rigidity, effectively combining beneficial properties.
2Reliability
If comonomer content is increased to improve slow crack growth properties, then slow crack propagation resistance is improved, but the risk of material washout increases
Solution Approach 1:
The patent resolves this contradiction by changing the physical state and crystalline structure parameters through β-nucleation. By inducing the β-modification, the material achieves optimal balance between ductility (for crack resistance) and structural integrity (to prevent washout), allowing higher comonomer content without increasing washout risk.
3Strength
If propylene homopolymer is used to achieve high thermal resistance and rigidity, then thermal resistance and rigidity are improved, but resistance to slow crack growth deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the comonomer content at low levels (1.0-3.0 wt.%) and utilizing β-nucleation to achieve a specific crystalline structure. This transforms the polymer's physical parameters to simultaneously improve slow crack resistance while maintaining thermal resistance and rigidity, resolving the contradiction through quantitative optimization of composition and structure.
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 propylene copolymer exhibits superior slow crack propagation performance, excellent stiffness, and high Izod impact resistance, maintaining thermal resistance and reducing the risk of material washout, as demonstrated by improved flexural modulus and Charpy impact strength.
Implementation Method 1
incorporating a β-nucleating agent to enhance stiffness and impact resistance
Implementation Method 2
partially crystallized in the β-modification
Data Source
AI summary
Propylene copolymer a. comprising at least 1-hexene as a comonomer, b. having a comonomer content in the range of 1.0 to 3.0 wt.-%, c. having a xylene soluble fraction equal or below 2.5 wt.-%, d. having a polydispersity index (PI) of equal or below 4.0 Pa−1, and e. being partially crystallized in the β-modification.