Crosslinked Polyethylene Pipe Material for Pressure and Crosslinking Balance
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Solution Overview
Problem
Crosslinked polyethylene pipes require high density and melt index for improved pressure resistance, but achieving a balance between high melt index and degree of crosslinking is challenging, as high melt index leads to reduced crosslinking due to increased low molecular weight production.
Innovation Solution
A polyethylene with a density of 0.940 g/cm3 to 0.960 g/cm3, number average molecular weight of 20,000 g/mol to 70,000 g/mol, weight average molecular weight of 100,000 g/mol to 250,000 g/mol, and polydispersity index of 2.5 to 3.7, which is achieved through specific metallocene catalysts and processing conditions to enhance molecular weight distribution and pressure resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene with high melt index is used to achieve high density and improved pressure resistance, then pressure resistance is improved, but degree of crosslinking is lowered due to increased low molecular weight production
Solution Approach 1:
The patent applies parameter changes by precisely controlling the melt index within 1-20 g/10min and density within 0.940-0.960 g/cm³ ranges. This optimization of physical parameters enables the polyethylene to achieve both high pressure resistance through adequate density and sufficient degree of crosslinking by limiting excessive low molecular weight content that would otherwise interfere with crosslinking reactions.
2Strength
If polyethylene with high density is used to improve pressure resistance, then pressure resistance is improved, but melt index becomes too high leading to reduced crosslinking efficiency
Solution Approach 1:
The patent optimizes the density parameter to fall within 0.940-0.960 g/cm³, which provides sufficient pressure resistance while preventing the melt index from becoming excessively high. This controlled parameter range ensures that crosslinking efficiency is maintained at acceptable levels, resolving the contradiction between pressure resistance and manufacturing ease.
Data Source
AI summary
The present disclosure relates to a polyethylene having high pressure resistance and a crosslinked polyethylene pipe including the same. The polyethylene according to the present disclosure has high melt index and density and exhibits a sufficient degree of crosslinking, thereby exhibiting excellent strength and pressure resistance characteristics.