Ethylene/Alpha-Olefin Interpolymer for Flexible Heating Pipes
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Solution Overview
Problem
Polyethylene pipes used for under-floor heating require improved flexibility to facilitate expeditious installations while maintaining acceptable hoop stress resistance and slow crack growth resistance.
Innovation Solution
An ethylene/alpha-olefin interpolymer composition with specific properties, including greater than 80% ethylene units, 20% or less alpha-olefin co-monomers, and tailored physical properties such as density, melt index, and flexural modulus, is developed via solution polymerization for enhanced pipe performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional polyethylene compositions are used to meet hoop stress resistance and slow crack growth resistance requirements, then structural integrity is maintained, but pipe flexibility is insufficient
Solution Approach 1:
The patent employs a composite material system consisting of two distinct polyethylene resins: a first resin (HDPE or MDPE) providing structural integrity with high hoop stress resistance and slow crack growth resistance, and a second resin (LDPE or LLDPE) providing flexibility. These resins are combined in specific weight ratios (first resin 30-70 wt%, second resin 70-30 wt%) to create a composite composition that simultaneously achieves both flexibility and strength requirements for underfloor heating pipes.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the density range of the composite composition (0.920-0.940 g/cm³) and adjusting the molecular weight characteristics (melt flow rates) of each resin component. By modifying these physical parameters and their distributions, the composition achieves optimal balance between flexibility for easy installation and mechanical strength for safe operation under pressure and temperature conditions.
2Ease of operation
If pipe flexibility is improved to facilitate expeditious installations, then ease of installation increases, but hoop stress resistance and slow crack growth resistance may be compromised
Solution Approach 1:
The patent employs a composite material system consisting of two distinct polyethylene resins: a first resin (HDPE or MDPE) providing structural integrity with high hoop stress resistance and slow crack growth resistance, and a second resin (LDPE or LLDPE) providing flexibility. These resins are combined in specific weight ratios (first resin 30-70 wt%, second resin 70-30 wt%) to create a composite composition that simultaneously achieves both flexibility and strength requirements for underfloor heating pipes.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the density range of the composite composition (0.920-0.940 g/cm³) and adjusting the molecular weight characteristics (melt flow rates) of each resin component. By modifying these physical parameters and their distributions, the composition achieves optimal balance between flexibility for easy installation and mechanical strength for safe operation under pressure and temperature conditions.
Data Source
Figure 1
AI summary
An ethylene/alpha-olefin interpolymer composition suitable for pipe applications prepared via solution polymerization process, and pipes made therefrom. The ethylene/alpha-olefin interpolymer composition suitable for pipe applications according to the present invention comprises greater than 80 percent by weight of units derived from ethylene and 20 percent or less by weight of units derived from one or more alpha olefin co-monomers, wherein said ethylene/alpha-olefin interpolymer has a density in the range of from 0.925 to 0.935 g/cm3, a melt index I2 in the range of from 0.3 to 1.0 g/10 minutes, a melt flow ratio I10/I2 in the range of from 7.9 to 11, a melt strength in the range of from 3 to 10 cN, a DSC heat curve having a melting peak temperature in the range of from 120 to 130°C, a crystallinity in the range of from 50 to 70 percent, a 1% flexural modulus in the range from 350 to 600 MPa, and a zero shear viscosity ratio (ZSVR) in the range of from 2 to 10.