Propylene Random Copolymer Composition for Uniform Pipe Shrinkage
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Solution Overview
Problem
Existing polypropylene random copolymers for pipe applications face a trade-off between impact and stiffness properties, and variations in nucleating agents used for coloration can lead to dimensional issues due to different shrinkage effects, while current solutions are not optimally suited for pressure pipe applications with high mechanical and processing requirements.
Innovation Solution
A multimodal propylene random copolymer composition with a nucleating agent, specifically designed to have a Charpy Notched Impact Strength of at least 30 kJ/m² and featuring a broadened molecular weight distribution, combining high flexural modulus, impact resistance, creep resistance, and improved processing behavior for uniform shrinkage and surface quality in pressure pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different pigments are used for coloration, then various colors are achieved, but dimensional variations occur due to different nucleation effects and shrinkage
Solution Approach 1:
The patent introduces a specific nucleating agent as an intermediary substance that mediates between the pigment additives and the polymer matrix. This nucleating agent controls the crystallization process and shrinkage behavior, ensuring dimensional consistency regardless of which color pigment is used.
Solution Approach 2:
The patent changes the crystallization parameters by selecting specific nucleating agents that provide consistent nucleation effects across different pigment systems. This allows the polymer to maintain uniform shrinkage behavior and dimensional properties while being available in various colors.
2Strength
If high impact strength is achieved, then good mechanical properties are obtained, but processing properties and extrusion output rate deteriorate
Solution Approach 1:
The patent segments the molecular weight distribution into distinct low and high molecular weight fractions. The low molecular weight fraction improves processability and extrusion output rate, while the high molecular weight fraction provides impact strength. This segmentation allows both requirements to be met simultaneously.
Solution Approach 2:
The patent changes the molecular weight distribution parameters by creating a bimodal or multimodal distribution with specific weight ratios between fractions. This parameter optimization allows the material to exhibit both good impact strength and acceptable processing properties.
3Strength
If heterophasic copolymers with high flexural modulus are used, then stiffness is improved, but the material becomes too stiff for general pressure pipe applications
Solution Approach 1:
The patent changes the stiffness parameter by controlling the flexural modulus to be in the range of 700-1400 MPa, which is lower than heterophasic copolymers (1500-1600 MPa) but provides better overall suitability for pressure pipe applications. This parameter optimization balances stiffness with other required properties like impact strength and processability.
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 composition achieves a balanced set of mechanical and processing properties, including enhanced impact strength, creep resistance, and processing efficiency, suitable for pressure pipes with uniform shrinkage and improved surface quality, addressing the limitations of previous solutions.
Implementation Method 1
nucleated propylene random copolymer compositions
Data Source
AI summary
The present invention relates to a polypropylene composition comprisinga multimodal propylene random copolymer (A) with at least one comonomer selected from alpha-olefins with 2 or 4 to 8 carbon atoms anda nucleating agent (B),wherein the polypropylene composition has a Charpy Notched Impact Strength at 23° C. of at least 30 kJ/m2, determined according to ISO 179/1eA:2000 using notched injection moulded specimens, a process for producing said polypropylene composition, an article comprising said polypropylene composition and the use of said polypropylene composition for the production of an article.