Bonded Magnet Composition Fluidity and Thermal Shock Durability
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Solution Overview
Problem
Existing compositions for bonded magnets face challenges with fluidity during molding, durability in thermal shock tests, and bonding strength when combined with metal components via adhesives, due to high magnetic powder ratios affecting processing and adhesion.
Innovation Solution
A composition comprising 88-91% samarium-iron-nitrogen magnet powder, 0.5-2.5% polyamide elastomer, 0.5-2.0% carbon fibers, and 0.3-1.0% carboxylic acid ester, with polyamide 12 resin as the binder, enhancing fluidity, thermal shock resistance, and bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blending ratio of magnet powder is increased to improve magnetic properties, then magnetic properties are improved, but fluidity of the composition deteriorates making injection molding difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the binder resin by specifying a polyamide resin with a particular imide group content (3-15 mol%) and using a polyamide elastomer with specific molecular weight and composition. These parameter changes optimize the balance between fluidity and strength, enabling high magnet powder content (80-95 mass%) while maintaining processability and preventing cracking during thermal shock tests.
Solution Approach 2:
The patent creates a composite binder system combining polyamide resin with imide groups and polyamide elastomer in specific ratios. This composite material approach provides both the fluidity needed for injection molding with high magnet powder content and the strength required to prevent cracking during thermal shock testing, resolving the contradiction between magnetic properties and manufacturability.
2Ease of manufacture
If fluidity is improved by adding lubricant, then fluidity is improved, but bonding strength between bonded magnet and metal component deteriorates
Solution Approach 1:
Instead of adding lubricants, the patent changes the chemical structure of the binder resin by incorporating polyamide resin with imide groups and polyamide elastomer. This parameter change provides inherent fluidity improvement through the elastomer's low viscosity and molecular weight characteristics, while simultaneously maintaining or enhancing bonding strength through the polyamide's adhesive properties and strong interfacial bonding with metal components.
Solution Approach 2:
The polyamide resin with imide groups acts as an intermediary between the magnet powder and metal component. The imide groups provide chemical functionality that enhances adhesion to both the magnetic particles and the metal surface, creating a strong bonding interface without requiring additional lubricants that would compromise bonding strength.
Data Source
AI summary
Provided is a composition for bonded magnets, which exhibits good fluidity during molding and enables the production of a bonded magnet having durability in terms of thermal shock test. This composition for bonded magnets is capable of providing a bonded magnet obtained therefrom with excellent bonding strength in cases where the bonded magnet is bonded with a metal component via an adhesive. A composition for bonded magnets according to the present invention contains from 88% by mass to 91% by mass (inclusive) of a samarium-iron-nitrogen magnet powder having an average particle diameter of from 1.8 µm to 2.8 µm (inclusive), from 0.5% by mass to 2.5% by mass (inclusive) of a polyamide elastomer having a tensile elongation at break of 400% or more and a bending modulus of elasticity of 100 MPa or more, from 0.5% by mass to 2.0% by mass (inclusive) of carbon fibers having fiber diameters of from 10 µm to 12 µm (inclusive) and from 0.3% by mass to 1.0% by mass (inclusive) of a carboxylic acid ester, with the balance made up of a polyamide resin which is composed of a polyamide 12 having a weight average molecular weight (Mw) of from 4,500 to 7,500 (inclusive) as determined by molecular weight distribution measurement.