Bimodal Ethylene/1-Hexene Copolymer for Pressure-Resistant Pipe Extrusion
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Solution Overview
Problem
Current polyolefin resins used for large-diameter high-pressure pipe tubes face challenges in achieving a balance between high pressure-resistance and processability, as high density leads to brittle fracture and poor processing characteristics, while narrow molecular weight distribution results in reduced extrusion productivity and non-uniform surfaces.
Innovation Solution
An ethylene/1-hexene copolymer with a bimodal molecular weight distribution and specific shear viscosity and melt flow rate ratio is developed using a hybrid supported metallocene catalyst, allowing for controlled ratios of high and low molecular weight regions to enhance both physical properties and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high density polyolefin resin is used to increase pressure-resistance, then strength increases, but resistance against brittle fracture deteriorates and long-term pressure-resistance characteristic deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution (Mw/Mn ratio of 15-30) and comonomer content (1-hexene at 3-15 wt%) of the polyolefin resin. This creates an optimized balance between crystallinity (for strength) and amorphous region content (for ductility and long-term stability), resolving the contradiction between high pressure-resistance and long-term reliability.
Solution Approach 2:
The patent creates a composite molecular structure within the polyolefin by incorporating 1-hexene comonomer units alongside ethylene units. This forms a heterogeneous polymer structure with both crystalline regions (from ethylene sequences providing strength) and amorphous regions (from 1-hexene sequences providing flexibility and fracture resistance), simultaneously achieving high strength and long-term reliability.
2Strength
If high molecular weight polyolefin is used to prevent sagging, then mechanical properties improve, but extrusion load increases and processability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution to achieve Mw/Mn ratio of 15-30, with specific control of weight average molecular weight (Mw) and number average molecular weight (Mn). This broad distribution ensures sufficient high molecular weight components for mechanical strength while maintaining low molecular weight components for processability, resolving the contradiction between mechanical properties and ease of manufacture.
3Device complexity
If narrow molecular weight distribution is used to simplify processing, then manufacturing complexity decreases, but extrusion productivity decreases and surface uniformity deteriorates
Solution Approach 1:
The patent applies parameter changes by deliberately creating a broad molecular weight distribution (Mw/Mn ratio of 15-30) through controlled polymerization conditions. This broad distribution provides different molecular weight fractions that respond differently to shear forces during extrusion, enabling high productivity and uniform surface quality while maintaining manageable processing complexity through standardized manufacturing procedures.
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 ethylene/1-hexene copolymer exhibits improved long-term physical properties and processability, suitable for high-pressure resistant heating pipes and large-diameter pipes, with enhanced sagging time and reduced processing load, leading to better mechanical properties and extrusion performance.
Implementation Method 1
An ethylene/1-hexene copolymer with a bimodal molecular weight distribution and specific shear viscosity and melt flow rate ratio is developed using a hybrid supported metallocene catalyst
Data Source
AI summary
Provided is an ethylene/1-hexene copolymer which has excellent long-term physical properties and processability, and thus may be usefully applied to manufacturing high-pressure resistant heating pipes, PE-RT pipes, large-diameter pipes, or the like.