Polypropylene Pipe Composition for Creep and Impact Resistance
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Solution Overview
Problem
Existing polypropylene compositions for pipes lack sufficient creep resistance and Charpy impact strength, particularly for pressure pipes that require high durability and resistance to varying temperatures and hydraulic pressures.
Innovation Solution
A polypropylene composition comprising 88.0 wt.% to 98.0 wt.% of a propylene copolymer with 0.8 wt.% to 4.8 wt.% 1-hexene derived units and 2.0 wt.% to 12.0 wt.% of a propylene ethylene 1-hexene terpolymer, with specific Melt Flow Rate and ethylene content, enhancing tensile modulus and Charpy impact strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If polypropylene composition is used for pressure pipes, then hydraulic pressure resistance is improved, but creep resistance and Charpy impact strength are insufficient
Solution Approach 1:
The patent employs a composite polypropylene composition consisting of two distinct components: Component A (propylene copolymer with 0.1-4.0 wt% 1-hexene derived units and MFR 0.5-4.4 g/10min) and Component B (propylene-ethylene copolymer with 35-60 wt% ethylene units). This composite structure combines the hydraulic pressure resistance of Component A with the creep and impact resistance of Component B, achieving balanced mechanical properties suitable for pressure pipes.
2Strength
If high ethylene content copolymer is used, then Charpy impact strength is improved, but creep resistance deteriorates
Solution Approach 1:
The patent applies local quality by assigning different functional roles to each component: Component A (with lower ethylene content and specific MFR) provides creep resistance and structural stability, while Component B (with high ethylene content of 35-60 wt%) provides Charpy impact strength. The synergistic combination allows each component to excel at its specific function without compromising the other.
3Strength
If 1-hexene content is increased, then tensile modulus is improved, but processability and Melt Flow Rate are affected
Solution Approach 1:
The patent optimizes the 1-hexene content parameter within a specific range (0.1-4.0 wt% in Component A and 1.0-6.0 wt% in Component B) to achieve the desired balance between tensile modulus and processability. Additionally, the MFR of Component A is controlled within 0.5-4.4 g/10min, allowing adjustment of flow characteristics while maintaining mechanical strength requirements.
Data Source
AI summary
A polypropylene composition comprising: A) from 88.0 wt. % to 98.0 wt. %, of a copolymer of propylene containing from 0.8 wt. % to 4.8 wt. % of 1-hexene derived units; said random copolymers of propylene having: - a Melt Flow Rate: measured according to ISO 1133 (230 °C, 5 Kg) ranging from 0.5 to 4.4 g/10 min; B) from 2.0 wt. % to 12.0 wt. % of a terpolymer of propylene ethylene and 1-hexene having a content of ethylene derived units ranging from 35 wt. % to 60 wt. %; and a content of 1-hexene derived units ranging from 1 wt. % to 6 wt. %; wherein the polypropylene composition is endowed with a Melt Flow Rate: measured according to ISO 1133 (230 °C, 5 Kg) ranging from 0.5 to 5.0 g/10 min.