Propylene Copolymer Pipes Impact Stiffness Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polypropylene-based pipe materials face challenges in achieving a balance between high impact resistance and flexural modulus, especially at low temperatures, which is crucial for small diameter pipes to prevent brittleness and ensure rigidity.
Innovation Solution
A polyolefin composition comprising 90.0-99.0 wt % of a propylene homopolymer with specific properties and 1.0-10.0 wt % of a propylene/ethylene copolymer composition, optimized to achieve a balance between impact resistance and stiffness without compromising flexural modulus, is used for pipe production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wall thickness of small diameter pipes is reduced to improve material efficiency and internal diameter, then the pipe becomes more prone to brittleness and lower impact resistance, especially at low temperatures
Solution Approach 1:
The patent uses a composite polyolefin composition combining propylene homopolymer (90-99 wt%) with specific heterophasic copolymer (1-10 wt%) to achieve both thin-wall capability and high impact resistance. The heterophasic copolymer contains two distinct phases: a crystalline propylene phase providing stiffness and an elastomeric propylene-ethylene phase providing impact resistance, creating a synergistic composite material that resolves the contradiction between wall thickness reduction and impact strength maintenance.
2Strength
If impact resistance is improved by adding elastomeric modifiers to polypropylene, then the flexural modulus decreases, resulting in lower pipe rigidity
Solution Approach 1:
The heterophasic copolymer creates local quality differentiation within the material structure. The crystalline propylene domains provide local stiffness and rigidity, while the elastomeric propylene-ethylene domains provide local impact absorption. This spatial differentiation of properties within the composite allows simultaneous achievement of high flexural modulus and high impact resistance, resolving the trade-off between these two properties.
Solution Approach 2:
The patent employs a composite heterophasic copolymer system where two distinct polymer phases are combined: a rigid crystalline propylene phase maintaining flexural modulus and a flexible elastomeric propylene-ethylene phase enhancing impact resistance. This composite structure enables the material to exhibit both high rigidity and high impact strength, overcoming the conventional trade-off.
Data Source
AI summary
The present disclosure relates to a polyolefin composition comprising, in some embodiments:A) 90.0-99.0 wt % of a propylene homopolymer;B) f1.0-10.0 wt % of a propylene/ethylene copolymer composition comprising:b1) 14-52 wt % of a propylene homopolymer or a propylene/ethylene copolymer;b2) 48-86 wt % of a propylene ethylene copolymer comprising an ethylene derived units content of 20.0-55.0 wt %;wherein the resulting polyolefin composition has a melt flow rate (MFR; ISO 1133, 230° C., 5 kg) of 0.2-4.0 g/10 min; the sum of A+B equals 100% by weight and the sum of b1+b2 equals 100% by weight.