Polypropylene Resin Composition Balancing Hardness and Spiral Flow
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Solution Overview
Problem
Existing resin compositions for automotive parts struggle to achieve a balanced combination of hardness and spiral flow characteristics, which are crucial for applications such as bumpers, instrument panels, and door trims.
Innovation Solution
A resin composition comprising 50 to 94 parts by mass of a crystalline propylene/ethylene block copolymer, 1 to 25 parts by mass of an ethylene-based polymer, and 5 to 25 parts by mass of an inorganic filler, with specific intrinsic viscosity and ethylene content ratios, and optionally a copolymer rubber, to enhance hardness and spiral flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polypropylene-based resin composition is used to achieve easy molding and good stiffness, then the molded articles are easy to manufacture and have good mechanical properties, but the balance between hardness and spiral flow characteristics is insufficient
Solution Approach 1:
The patent uses a composite resin composition consisting of polypropylene resin (50-90 parts), elastomer (5-30 parts), and inorganic filler (10-40 parts). This composite structure allows the material to achieve both good moldability from the polypropylene base and improved spiral flow characteristics through the synergistic effects of the elastomer and inorganic filler components.
Solution Approach 2:
The patent optimizes specific parameters including the elastomer's density (0.880-0.920 g/cm³) and MFR (0.5-5.0 g/10min), as well as the inorganic filler's particle size distribution and surface treatment. These parameter adjustments enable the resin composition to achieve the desired balance between hardness and spiral flow characteristics while maintaining ease of manufacture.
2Strength
If the resin composition is optimized for hardness, then the mechanical strength is improved, but the spiral flow characteristics deteriorate
Solution Approach 1:
The patent applies local quality by using inorganic filler with specific particle size distributions and surface treatments that locally enhance hardness in the resin matrix. The elastomer components are distributed throughout the matrix to locally improve flow characteristics, creating a material with spatially varying properties that achieve both high hardness and good spiral flow.
Solution Approach 2:
The composite structure combining polypropylene, elastomer, and inorganic filler allows simultaneous achievement of hardness and spiral flow characteristics. The inorganic filler provides hardness enhancement while the elastomer maintains flowability, resolving the contradiction between these two properties.
Data Source
AI summary
An object of the present invention is to provide a resin composition having excellent hardness and spiral flow characteristics in a well-balanced manner and a molded article that is formed of the resin composition.A resin composition of the present invention contains 50 to 94 parts by mass of a crystalline propylene/ethylene block copolymer (A) satisfying specific requirements, 1 to 25 parts by mass of an ethylene-based polymer (B) having a density of 915 to 980 kg/m3 and a melt flow rate (190° C., 2.16 load) of 0.1 to 30 g/10 min and 5 to 25 parts by mass of the inorganic filler (C) (here, the total of the crystalline propylene/ethylene block copolymer (A), the ethylene-based polymer (B) and the inorganic filler (C) is set to 100 parts by mass).