HDPE Propylene Polymer Blend for Crack Resistance
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Solution Overview
Problem
Conventional high density polyethylene (HDPE) compositions lack sufficient environmental stress crack resistance and impact resistance, often requiring the addition of lower density ethylene copolymers which compromise stiffness.
Innovation Solution
A polymeric composition combining high density polyethylene with a polymer containing propylene-derived units, exhibiting controlled crystallinity, which is melt-blended and potentially crosslinked to enhance environmental stress crack resistance and impact resistance while maintaining or improving flexural modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lower density ethylene copolymers are added to improve environmental stress crack resistance, then environmental stress crack resistance is improved, but stiffness decreases
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating propylene-derived units with controlled crystallinity (1-15% as specified in claims) into the HDPE polymer structure. This parameter change allows achieving improved environmental stress crack resistance while maintaining the stiffness characteristic of HDPE, avoiding the trade-off present in conventional approaches.
Solution Approach 2:
The patent creates a composite polymeric material by combining HDPE with propylene-derived units having controlled crystallinity. This composite structure integrates the benefits of both components: the structural integrity and stiffness of HDPE with the enhanced environmental stress crack resistance provided by the propylene-derived units, resolving the contradiction between these two properties.
2Strength
If conventional HDPE compositions are used, then stiffness is maintained, but environmental stress crack resistance and impact resistance are insufficient
Solution Approach 1:
The patent modifies the molecular structure parameters of HDPE by incorporating propylene-derived units with specific crystallinity control (1-15% crystallinity as specified). This parameter modification enhances environmental stress crack resistance and impact resistance while preserving the stiffness property through controlled crystallinity levels.
Solution Approach 2:
The patent introduces local structural modifications by incorporating propylene-derived units at specific locations within the polymer matrix. These localized modifications provide enhanced environmental stress crack resistance and impact resistance in critical areas while maintaining the overall stiffness of the HDPE structure.
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 resulting composition demonstrates improved environmental stress crack resistance of up to 72 hours and enhanced impact resistance without a significant decrease in stiffness, making it suitable for various molded and extruded products.
Implementation Method 1
The at least one high density polyethylene polymer and the at least one polymer having propylene-derived units may be combined by any suitable methods including, melt-blending
Implementation Method 2
The at least one high density polyethylene polymer and the at least one polymer having propylene-derived units may also be crosslinked though a variety of processes known in the art such as dynamic vulcanization or static vulcanization of shaped articles
Data Source
AI summary
Polymeric compositions and methods of making and using such compositions are provided. The compositions incorporate a first polymeric component that is at least one high density polyethylene and a second polymeric component that is at least one polymer including propylene-derived units having a heat of fusion of less than 75 J/g wherein the propylene-derived units have an isotactic triad fraction of about 65% to about 99%. The polymeric compositions are found to have desirable environmental stress crack resistance properties and impact resistance properties. The polymeric compositions are useful in a variety of applications such as molded containers and extruded pipes.