Polyolefin Composition Stiffness Impact Balance
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Solution Overview
Problem
Heterophasic polypropylene compositions face challenges in achieving a balance of high stiffness, high toughness, and high stress whitening resistance, as adding polyethylene improves impact strength and stress whitening resistance but reduces stiffness.
Innovation Solution
A polyolefin composition comprising a heterophasic polypropylene composition blended with 5.0 to 30.0 wt % of a high molecular weight high density ethylene homo- or copolymer, characterized by specific weight percentages of crystalline and soluble fractions, and an ethylene content, which enhances stiffness and impact strength while maintaining stress whitening resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene is added to heterophasic polypropylene composition, then impact strength and stress whitening resistance are improved, but stiffness is reduced
Solution Approach 1:
The patent applies parameter changes by carefully controlling the amount of polyethylene added (5.0 to 30.0 wt %) and specifying the molecular weight (≥200,000 g/mol) and density (≥0.941 g/cm³) parameters of the polyethylene. This optimization of physical parameters allows achieving improved impact strength and stress whitening resistance while minimizing the reduction in stiffness
Solution Approach 2:
The patent creates a composite material system by blending heterophasic polypropylene composition with high molecular weight polyethylene. The composite structure combines the crystalline matrix of polypropylene (providing stiffness) with the elastomeric phase and polyethylene additive (providing impact strength and stress whitening resistance), achieving a balanced property profile
2Reliability
If polyethylene is added to heterophasic polypropylene composition, then stress whitening resistance is improved, but stiffness is reduced
Solution Approach 1:
The patent optimizes the concentration parameter of polyethylene (5.0 to 30.0 wt %) and its molecular weight parameter (≥200,000 g/mol) to achieve the desired balance. This parameter optimization ensures sufficient stress whitening resistance while limiting the negative impact on stiffness
Solution Approach 2:
The patent uses high molecular weight polyethylene (≥200,000 g/mol) which has similar crystalline structure and properties to the polypropylene matrix. This similarity in material characteristics allows the polyethylene to integrate better with the matrix, providing stress whitening resistance with minimal disruption to the overall stiffness of the composition
Data Source
AI summary
The present invention is directed to a polyolefin composition comprising a blend of a heterophasic polypropylene composition and 5.0 to 30.0 wt % of an ethylene homo- or copolymer, the ethylene homo- or copolymer having a density of at least 941 kg/m3 and a melt flow rate MFR21 of 1 to 10 g/10 min. The heterophasic polypropylene composition comprises a propylene homopolymer or a propylene ethylene random copolymer and an elastomeric ethylene propylene rubber, and is characterized by 75.0 to 95.0 wt % of a crystalline fraction having an ethylene content of up to 4.0 wt % and an MFR2 of 0.1 to 100 g/10 min, and 5.0 to 25.0 wt % of a soluble fraction having an ethylene content of 10.0 to 70.0 wt % and an intrinsic viscosity of 1.0 to 4.0 dl/kg, wherein the crystalline fraction and the soluble fraction are determined in 1,2,4-trichlorobenzene at 40° C.