Bimodal Polyethylene Composition for Cable Jacket Crack Resistance

Solution Overview

Problem

Existing thermoplastic compositions for insulation and jacket layers in wires and cables face a trade-off between mechanical properties, processability, and environmental stress-cracking resistance, with high density polyethylene improving mechanical properties but reducing stress-cracking resistance, and lower density improving stress-cracking resistance but compromising mechanical properties and processability.

Innovation Solution

A bimodal polyethylene composition with a high molecular weight component and a low molecular weight component, characterized by specific density, melt index, melt flow ratio, molecular weight distribution, and shear thinning index, balances mechanical properties, processability, and environmental stress-cracking resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high density polyethylene is used to improve mechanical properties, then mechanical strength and abrasion resistance are improved, but environmental stress-cracking resistance deteriorates

Engineering Contradiction:

Improvemechanical propertiesVSAvoidenvironmental stress-cracking resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The polyethylene is segmented into two distinct molecular weight populations: a high molecular weight component (Mw ≥ 100,000 g/mol) that provides mechanical strength and abrasion resistance, and a low molecular weight component (Mw < 100,000 g/mol) that provides environmental stress-cracking resistance. This segmentation allows each component to fulfill its specific functional role without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite polyethylene system by combining two polyethylene fractions with different molecular weights in a controlled ratio (weight ratio of high Mw to low Mw component from 1:4 to 4:1). This composite structure enables the material to simultaneously exhibit the strength characteristics of high Mw polyethylene and the stress-cracking resistance of low Mw polyethylene.

Inventive Principle:

Principle #40Composite materials

2Reliability

If lower density polyethylene is used to improve environmental stress-cracking resistance, then stress-cracking resistance is improved, but mechanical properties and processability deteriorate

Engineering Contradiction:

Improveenvironmental stress-cracking resistanceVSAvoidmechanical properties

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The polyethylene is segmented into two distinct molecular weight populations: a high molecular weight component (Mw ≥ 100,000 g/mol) that provides mechanical strength and abrasion resistance, and a low molecular weight component (Mw < 100,000 g/mol) that provides environmental stress-cracking resistance. This segmentation allows each component to fulfill its specific functional role without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite polyethylene system by combining two polyethylene fractions with different molecular weights in a controlled ratio (weight ratio of high Mw to low Mw component from 1:4 to 4:1). This composite structure enables the material to simultaneously exhibit the strength characteristics of high Mw polyethylene and the stress-cracking resistance of low Mw polyethylene.

Inventive Principle:

Principle #40Composite materials

3Strength

If higher density polyethylene is used to improve mechanical properties, then processability deteriorates

Engineering Contradiction:

Improvemechanical propertiesVSAvoidprocessability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The polyethylene is segmented into two distinct molecular weight populations: a high molecular weight component (Mw ≥ 100,000 g/mol) that provides mechanical strength and abrasion resistance, and a low molecular weight component (Mw < 100,000 g/mol) that provides environmental stress-cracking resistance. This segmentation allows each component to fulfill its specific functional role without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the molecular weight distribution parameters of the polyethylene by controlling the weight average molecular weight (Mw) to be at least 100,000 g/mol and the melt flow ratio (MFR21) to be at least 80.0. These parameter changes enable the material to achieve both high mechanical properties and good processability, as the low Mw component facilitates flow and processing while the high Mw component maintains structural integrity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12565552B2Thermoplastic compositions comprising bimodal polyethylene and articles manufactured therefrom

Publication Date: 2026.03.03 DOW GLOBAL TECHNOLOGIES LLC

AI summary

In various embodiments, a bimodal polyethylene may include a high molecular weight component and a low molecular weight component. The bimodal polyethylene may have a density of from 0.933 grams per centimeter (g/cm3) to 0.960 g/cm3, a melt index (I2) of from 0.3 decigrams per minute (dg/min) to 1.2 dg/min, a melt flow ratio (MFR21) greater than 80.0, a molecular weight distribution (Mw/Mn) greater than 10, a reverse comonomer distribution, and a shear thinning index of from 5.0 to 20.0. Methods for producing the bimodal polyethylene, articles manufactured from the bimodal polyethylene are also provided.