Polyamide Resin Composition for Airtight Metal-Resin Joining
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Solution Overview
Problem
Conventional polyamide resin compositions fail to maintain high airtightness between resin and metal members, especially when subjected to cold-heat shocks, which is crucial for applications like in-vehicle accessories where oil leakage must be prevented.
Innovation Solution
A polyamide resin composition comprising specific polyamide resins, modified polyolefin resin, and a nucleating agent, with controlled melting points, heat of fusion, and glass transition temperatures, along with a surface roughening treatment of the metal member, to enhance joining strength and airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polyamide resin composition is joined to a metal member, then the joining process can be completed, but the airtightness at the initial stage of joining is not sufficiently high and the airtightness decreases when repeatedly subjected to cold-heat shocks
Solution Approach 1:
The patent applies parameter changes by carefully controlling the melting point (280°C or higher) and heat of fusion (5 J/g or lower) of the polyamide resin, as well as the glass transition temperature (70°C or lower) of at least part of the polyamide resin. These specific parameter ranges enable the resin to achieve high initial airtightness while maintaining stability under cold-heat shock conditions.
Solution Approach 2:
The patent uses composite materials by combining polyamide resin with specific additives including mold release agents, lubricants, and nucleating agents in controlled amounts. This composite formulation enhances both the initial airtightness and the stability of airtightness under repeated thermal cycling.
2Temperature
If the polyamide resin has high melting point for heat resistance, then the heat resistance is improved, but the moldability and joining fluidity may deteriorate
Solution Approach 1:
The patent resolves this contradiction by changing the resin composition parameters: using polyamide resin with melting point of 280°C or higher for heat resistance, while simultaneously controlling the glass transition temperature of at least part of the polyamide resin to be 70°C or lower. This dual parameter control ensures both heat resistance and adequate moldability.
Solution Approach 2:
The patent applies local quality by having different portions of the polyamide resin composition exhibit different thermal properties. Specifically, at least part of the polyamide resin has a glass transition temperature of 70°C or lower, which provides local flexibility and flow characteristics during molding, while the overall composition maintains high heat resistance through the high melting point polyamide resin.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves high initial airtightness and maintains it even under repeated cold-heat shocks, preventing oil leakage in applications such as bus bar units and drive units.
Implementation Method 1
a nucleating agent (C)
Implementation Method 2
a polyamide resin (A1) having a melting point (Tm) of 280°C or more as measured by differential scanning calorimetry (DSC), and a polyamide resin (A2) having a heat of fusion (ΔH) of 5 J/g or less as measured by the differential scanning calorimetry (DSC)
Data Source
Figure 1
Figure 2
AI summary
The present invention provides a polyamide resin composition that enables the fabrication of a metal/resin joined body that exhibits a high airtightness during the initial phase of joining and satisfactorily maintains airtightness when repeatedly subjected to thermal shock. This polyamide resin composition is intended for joining with a metal member and comprises a polyamide resin (A1) having a melting point (Tm) measured by differential scanning calorimetry (DSC) of at least 280°C, a polyamide resin (A2) having a heat of fusion (ΔH) measured by differential scanning calorimetry (DSC) of not more than 5 J/g, a modified polyolefin resin (B), and a nucleating agent (C). The content of the modified polyolefin resin (B) is 4.70 mass% to 20.00 mass% with reference to the total mass of the polyamide resin (A) and the modified polyolefin resin (B).