Polypropylene Resin Composition Flow Mark Reduction
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Solution Overview
Problem
Polypropylene resin compositions and molded articles face challenges in achieving improved flow mark appearance, toughness, low temperature impact strength, and a balance between rigidity and surface hardness.
Innovation Solution
A polypropylene resin composition comprising 50-94% crystalline propylene-ethylene block copolymer, 1-25% ethylene-α-olefin copolymer rubber, and 5-25% inorganic filler, specifically tailored to optimize melt fluidity, isotactic pentad fraction, and ethylene content for enhanced mechanical properties and reduced flow marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polypropylene resin compositions are used, then manufacturing simplicity is maintained, but flow mark appearance and surface hardness are insufficient
Solution Approach 1:
The patent employs a composite resin system combining polypropylene homopolymer, polypropylene copolymer, and polyethylene-rubber-modified polypropylene copolymer in specific ratios (60-85%, 5-30%, 5-30% respectively). This multi-component composite approach enables simultaneous achievement of improved flow mark appearance, surface hardness, and mechanical properties that cannot be obtained with conventional single-component polypropylene compositions.
Solution Approach 2:
The patent systematically optimizes multiple parameters including the proportion of each polymer component, ethylene content (2-11 mol%), rubber content (3-20 parts by weight per 100 parts polypropylene), and molecular weight characteristics (intrinsic viscosity, melt flow rate). By precisely controlling these parameters within specified ranges, the invention achieves superior flow mark resistance and surface hardness while maintaining manufacturability.
2Strength
If rubber content is increased to improve toughness and impact strength, then mechanical properties are enhanced, but rigidity and surface hardness deteriorate
Solution Approach 1:
The patent introduces a tri-component system where each component serves a specific functional role: polypropylene homopolymer provides rigidity and surface hardness, polypropylene copolymer contributes to toughness, and polyethylene-rubber-modified polypropylene copolymer enhances impact strength while maintaining processability. This localized functional assignment within the composite enables simultaneous optimization of contradictory properties.
Solution Approach 2:
The invention uses a carefully balanced composite of three distinct polymer systems with specific composition ranges. The polyethylene-rubber-modified polypropylene copolymer acts as a bridge, providing both rubber-like toughness and polypropylene compatibility. This composite structure allows the material to exhibit both high impact strength and maintained rigidity, resolving the traditional trade-off between toughness and stiffness.
3Manufacturing precision
If ethylene content in copolymer is increased to improve flowability and reduce flow marks, then surface appearance is enhanced, but molecular weight and mechanical strength decrease
Solution Approach 1:
The patent optimizes ethylene content within a controlled range of 2-11 mol% in the polypropylene copolymer component. This precise parameter control ensures sufficient flowability and reduced flow marks while preventing excessive ethylene content that would compromise molecular weight and mechanical strength. The balanced composition achieves optimal flow mark resistance without sacrificing structural integrity.
Data Source
AI summary
The polypropylene resin composition is disclosed which includes 50-94% by weight of a polypropylene resin having a specific structure, 1-25% by weight of an ethylene-α-olefin copolymer rubber composed of an ethylene-α-olefin (C4-20) copolymer rubber having a density of 0.85-0.91 g/cm3 and an MFR of 0.9-20 g/10 min and/or an ethylene-α-olefin (C5-20) copolymer rubber having a density of 0.85-0.91 g/cm3 and MFR of not less than 0.01 but less than 0.9 g/10 min, and 5-25% by weight of an inorganic filler.