Bonded Magnet Composition for High-Flow Thermal Shock Durability
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Solution Overview
Problem
Existing bonded magnet compositions face limitations in fluidity while maintaining durability against thermal shock and adhesiveness, particularly when filled into narrow cavities.
Innovation Solution
A composition for a bonded magnet comprising specific ratios of samarium-iron-nitrogen-based magnet powder, polyamide elastomer, carbon fiber, carboxylic acid ester, and polyamide resin, optimized for enhanced fluidity and durability, with a fluidity of 1.5 cm³/sec or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide elastomer or carbon fiber is added to improve durability against thermal shock, then durability is improved, but fluidity during molding deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters by introducing a carboxylic acid ester plasticizer in specific amounts (0.3-1.0% by mass) to modify the rheological properties of the polyamide resin system. This parameter change enables the composition to achieve both high fluidity (1.5 cm³/10min or more) and durability against thermal shock, resolving the contradiction between manufacturability and reliability
Solution Approach 2:
The invention creates a composite material system combining polyamide resin, polyamide elastomer, carbon fiber, and carboxylic acid ester plasticizer in specific proportions. This composite approach allows the material to exhibit both excellent fluidity for easy molding and high durability against thermal shock, simultaneously satisfying both requirements that were previously contradictory
2Ease of manufacture
If fluidity is increased by modifying composition, then moldability is improved, but durability against thermal shock may deteriorate
Solution Approach 1:
The carboxylic acid ester plasticizer acts as an intermediary substance that mediates between the conflicting requirements of fluidity and durability. It modifies the polymer matrix properties to enable high fluidity while the carbon fiber reinforcement and polyamide elastomer maintain the structural integrity and thermal shock resistance, allowing both properties to coexist
Data Source
AI summary
Provided is a composition for a bonded magnet, the composition having higher flowability than conventional ones while enabling the bonded magnet to retain durability and adhesion in a thermal impact test. Also provided are: a bonded magnet which is a molded object of such composition for a bonded magnet; and an integrally molded component including the bonded magnet. This composition for a bonded magnet comprises 88.0-91.0 mass% samarium-iron-nitrogen magnet powder having an average particle diameter of 1.7-2.8 um, 3.0-7.0 mass% polyamide elastomer having a tensile elongation at rupture of 400% or greater and a flexural modulus of 70 MPa or greater, 0.5-2.0 mass% carbon fibers having a fiber diameter of 5-12 µm, 0.3-1.0 mass% carboxylic acid ester, and 1.0-8.0 mass% polyamide 12 resin having, in a molecular-weight distribution examination, a weight-average molecular weight Mw of 4,500-7,500. This composition for a bonded magnet has a flowability of 1.5 cm3/sec or greater when examined using a flow tester under the conditions of a capillary temperature of 250°C, a load of 588 N, an orifice diameter 1 mm, an orifice length of 1 mm, and a preheating time of 300 seconds.