Polypropylene Composition Low-Temperature Impact Resistance
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Solution Overview
Problem
Isotactic polypropylene exhibits insufficient impact resistance at low temperatures, limiting its applications despite its exceptional properties.
Innovation Solution
A polymer composition comprising 30-90% propylene polymer and 10-70% multimodal ethylene copolymer, produced using specific catalyst systems, which enhances impact resistance and processability without compromising other polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If isotactic polypropylene is used, then excellent mechanical properties are achieved, but impact resistance at low temperatures is insufficient
Solution Approach 1:
The patent uses a composite material system consisting of isotactic polypropylene as the matrix and ethylene-alpha olefin copolymer as the dispersed rubber phase. This composite structure combines the excellent mechanical properties of polypropylene with the low-temperature impact resistance of the copolymer rubber, resolving the contradiction between strength and low-temperature reliability
Solution Approach 2:
The patent introduces a copolymer rubber phase with specific local properties (higher elasticity and low-temperature flexibility) into the polypropylene matrix. This local quality modification occurs at the microstructural level through controlled phase separation, where the copolymer domains provide localized impact resistance without compromising the overall mechanical properties of the polypropylene matrix
2Strength
If rubbers and polyethylene are added to polypropylene, then impact resistance is improved, but other polymer properties are affected
Solution Approach 1:
The patent precisely controls critical parameters including the copolymer content (5-30% by weight), comonomer content (5-30 mol%), and molecular weight distribution (Mw/Mn ratio). By optimizing these parameters, the patent achieves high impact resistance while maintaining property consistency across different batches and applications
Solution Approach 2:
The patent creates a controlled microstructure with distinct phases: an isotactic polypropylene matrix and dispersed copolymer rubber domains. This local quality differentiation allows the copolymer to provide impact resistance specifically where needed, while the polypropylene matrix maintains its mechanical properties, thus improving impact resistance without adversely affecting other polymer properties
3Strength
If ethylene-propylene copolymer rubber is used, then impact strength is improved, but whitening resistance deteriorates
Solution Approach 1:
The patent extracts the harmful aspect (whitening tendency) by replacing ethylene-propylene copolymer rubber with ethylene-alpha olefin copolymer rubber that has superior whitening resistance. The essential beneficial function (impact strength) is retained through the copolymer rubber phase, while the detrimental effect (whitening) is eliminated by choosing a different copolymer system
Solution Approach 2:
The patent uses ethylene-alpha olefin copolymer rubber as a dispersible phase that can be easily incorporated and processed. This copolymer provides the necessary impact modification without the long-term whitening issues associated with other rubber types, effectively serving as a temporary impact modifier that does not compromise aesthetic properties
Data Source
AI summary
A polypropylene composition comprising:A) from 30% to 90% by weight of a propylene polymer composition comprising:a1) from 20% to 90% of a propylene homopolymer, or a copolymer of propylene containing 3% or less of derived units of ethylene or C4-C10 α-olefin(s) or of combinations thereof, said homopolymer or copolymer having a content of isotactic pentads (mmmm), measured by 13C NMR on the fraction insoluble in xylene at 25° C., higher than 96;a2) from 10% to 80%, of a copolymer of ethylene containing from 40% to 70% of derived units of propylene or C4-C10 α-olefin(s) or of combinations thereof;B) from 10% to 70% by weight of a multimodal ethylene copolymer wherein the comonomer is selected from the derived units of alpha olefins of formula CH2═CHT wherein T is a C3-C10 alkyl group; having the following properties:i) density (with ISO 1183) comprised in the range from 0.850 to 0.935 g/cm3;ii) total comonomer content ranging from 6% to 30% by weight;iii) content of 1-butene derived units ranging from 0 to 2% by weight;iv) Mw/Mn comprised from 4 to 20;v) intrinsic viscosity (decalin at 135° C. as determined according to EN IS0 1628-312003) comprised between 1.0 and 4.0 dL/g, andC) from 0 to 50% by weight; preferably from 0 to 20% of a filler.