Polyolefin Composition Balancing Stiffness and Impact Resistance
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Solution Overview
Problem
Existing polyolefin compositions struggle to achieve a balance of high flexural modulus, impact resistance, elongation at break, and low thermal shrinkage, which are critical for applications like automotive components, where dimensional stability and mechanical properties are essential.
Innovation Solution
A thermoplastic polyolefin composition comprising 50-70% crystalline propylene homopolymer or copolymer and 30-50% ethylene/α-olefin copolymers, with specific melt flow rates and intrinsic viscosity values, optionally combined with elastomeric polymers and mineral fillers, to achieve high flexural modulus and low thermal shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high flexural modulus is achieved through propylene polymer content, then stiffness is improved, but impact resistance deteriorates
Solution Approach 1:
The patent employs a composite material system combining propylene homopolymer/copolymer (A1) with ethylene/α-olefin copolymer (A2) in specific proportions (50-70% and 30-50% respectively). This composite structure allows the crystalline propylene component to provide high flexural modulus while the ethylene/α-olefin copolymer component contributes impact resistance, resolving the contradiction between stiffness and impact resistance through material composition design.
2Stability of the object's composition
If thermal shrinkage is reduced through polymer selection, then dimensional stability is improved, but processing complexity increases
Solution Approach 1:
The patent achieves low thermal shrinkage and high dimensional stability by carefully controlling specific parameters of the polymer components: MFR of propylene polymer (50-200 g/10 min), xylene solubility (7% or less), and copolymer composition (15-35% α-olefin content). These parameter specifications enable predictable processing behavior and reduced thermal shrinkage while maintaining manufacturability through clear processing windows.
3Reliability
If impact resistance is enhanced through elastomer addition, then toughness is improved, but flexural modulus deteriorates
Solution Approach 1:
The patent applies local quality by selecting specific types and proportions of elastomeric polymers (B component with Shore A hardness ≤90) to be added in controlled amounts (1-15%). This localized addition of elastomeric properties to specific regions of the polymer blend allows impact resistance enhancement while maintaining overall flexural modulus through the dominant propylene polymer matrix.
Data Source
AI summary
Polymer composition showing an improved balance of flexural modulus, IZOD impact strength and elongation at break comprising (percent by weight): A) a polymer blend comprising: A1) 50-70% of a crystalline propylene homopolymer or copolymer; and A2) 30-50% of one or more copolymer(s) of ethylene with one or more C4-C10 α-olefin(s) containing from 15 to 35% of said C4-C10 α-olefin(s); said polymer blend (A) having values of MFR equal to or higher than 10 g/10 min., a total content C4-C10 α-olefin(s) equal to or higher than 8% and an intrinsic viscosity value of the fraction soluble in xylene at room temperature of from 1.3 to 2 dl/g, the amounts of (A1) and (A2) being referred to the total weight of the polymer blend; and optionally B) 1-15% of an elastomeric polymer different from A2), having a hardness (Shore A, ASTM D-2240) value equal to or lower than 90 points; and/or C) 0.5-20% of a mineral filler; the amounts of optional components (B) and (C) being referred to the total weight of the composition.