Grafted Heterophasic Polypropylene for Low-Temperature Impact
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Solution Overview
Problem
Current soft heterophasic propylene copolymers lack improved low temperature impact, high tensile modulus, and low gel content, with existing modification methods like blending with external rubbers or grafting being limited by compatibility issues and sensitivity to degradation.
Innovation Solution
A grafted heterophasic propylene copolymer composition comprising 30.0 to 95.0 wt% of a heterophasic polypropylene copolymer and 5.0 to 70.0 wt% of a styrene-based elastomer, where the styrene-based elastomer is grafted onto the polypropylene copolymer, achieving enhanced impact strength and low gel content through a reactive melt modification process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If soft heterophasic propylene copolymers are used to achieve softness and flexibility, then the material becomes soft and flexible, but the low temperature impact is poor
Solution Approach 1:
The patent creates a composite material system consisting of a propylene matrix phase and an elastomeric copolymer dispersed phase. The matrix provides structural integrity and temperature resistance, while the dispersed elastomeric phase provides softness and flexibility. This multiphase composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent applies local quality by creating distinct phases with different properties within the material. The matrix regions provide hardness and temperature stability, while the dispersed elastomeric inclusions provide local softness and flexibility. This spatial differentiation of properties allows the material to exhibit both softness and improved low-temperature impact resistance.
2Strength
If external rubber materials are blended to improve low temperature impact, then impact resistance improves, but compatibility issues cannot be resolved easily
Solution Approach 1:
The patent achieves homogeneity by using an elastomeric copolymer that is chemically compatible with the propylene matrix. The copolymer contains propylene units that are structurally similar to the matrix, ensuring good interfacial adhesion and homogeneous dispersion. This chemical compatibility resolves the compatibility issues that arise when blending incompatible external rubber materials.
3Adaptability or versatility
If grafting is used to modify soft heterophasic propylene copolymers, then properties can be tuned, but heterophasic propylene copolymers are particularly sensitive to degradation in combination with peroxides
Solution Approach 1:
The patent uses parameter changes by controlling the composition and molecular structure of the elastomeric copolymer phase. By adjusting the copolymer composition, molecular weight, and phase morphology, the material properties can be tuned to achieve desired softness, flexibility, and low-temperature impact resistance without requiring grafting reactions that would expose the material to peroxide degradation.
4Reliability
If gel content is reduced to improve material properties, then material quality improves, but achieving low gel content while maintaining softness and impact resistance is difficult
Solution Approach 1:
The patent applies segmentation by creating a multiphase structure where the elastomeric copolymer is dispersed as separate inclusions within the propylene matrix. This segmentation allows the material to achieve low overall gel content while the dispersed elastomeric phase provides the necessary softness and impact resistance. Each phase maintains its own properties without requiring high crosslinking density.
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 grafted composition exhibits superior mechanical properties, including high impact strength at low temperatures and low tensile modulus, with a significant reduction in gel content, making it suitable for applications such as medical tubes and pouches.
Implementation Method 1
wherein the styrene-based elastomer (B) is grafted onto the heterophasic polypropylene copolymer (A)
Implementation Method 2
mixing component (A), the heterophasic polypropylene copolymer, with component (B), the styrene-based elastomer and a thermally decomposing free radical-forming compound (C)
Data Source
AI summary
Polypropylene composition with improved low temperature impact, low tensile modulus and low gel content as well as to its manufacture and use and to articles made out of the new composition.