Airbag Multilayer Composite Balancing Flexibility and Scrub Resistance
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Solution Overview
Problem
Existing airbag multilayer films face issues with insufficient adhesive strength, blocking during production, and poor scrub resistance and flexibility, leading to instability and functionality problems.
Innovation Solution
A multilayer composite for airbags with a specific ratio of interface deployment area ratios (Sdr1/Sdr2) between 0.986 and 1.1, featuring a multilayer film with an adhesive layer and outer layer, and an air gap of 6 μm or less, combined with a thermal lamination and subsequent heating process to enhance adhesion and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If copolyamide, polyamide elastomer, or polyester elastomer with glass transition temperature of -10°C or lower is used in the adhesive layer, then flexibility and adhesiveness are improved, but crystallinity is low and blocking occurs during production
Solution Approach 1:
The patent changes the glass transition temperature parameter of the adhesive layer resin from -10°C or lower to -50°C or lower. This parameter change resolves the contradiction by providing sufficient flexibility and adhesiveness while preventing blocking during production and storage, as demonstrated in Example 1 where copolyamide with Tg of -60°C showed no blocking issues
Solution Approach 2:
The patent uses a composite multilayer film structure with an adhesive layer and an outer layer made of different resins. The adhesive layer uses resin with Tg ≤ -50°C for flexibility, while the outer layer uses resin with higher melting point for blocking resistance, creating a composite material that achieves both flexibility and production stability
2Strength
If high pressure during lamination is applied to obtain sufficient adhesive strength, then adhesive strength is improved, but expensive equipment requirement and low productivity result
Solution Approach 1:
The patent changes the glass transition temperature parameter of the adhesive layer resin to -50°C or lower, which fundamentally alters the adhesion mechanism. This allows sufficient adhesive strength to be achieved at low pressure and high speed during lamination, eliminating the need for expensive high-pressure equipment and maintaining high productivity
Solution Approach 2:
The patent replaces the mechanical adhesion mechanism (relying on high pressure and heat) with a chemical adhesion mechanism based on molecular mobility at low glass transition temperature. This substitution allows adhesion to occur effectively under milder conditions, improving productivity and reducing equipment requirements
3Ease of manufacture
If modified polyolefin is used in the adhesive layer, then processing is simplified, but affinity with polyamide or polyester base fabric is poor and adhesive strength is insufficient
Solution Approach 1:
The patent changes the glass transition temperature parameter to -50°C or lower and selects specific resin types (copolyamide, polyamide elastomer, polyester elastomer) that have inherent chemical affinity with polyamide or polyester base fabrics. This combination maintains processing simplicity while dramatically improving adhesive strength through both chemical compatibility and enhanced molecular mobility
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 solution provides improved scrub resistance and flexibility, ensuring stable adhesion and functionality of the airbag, reducing the likelihood of peeling and blocking issues, while maintaining airtightness and durability.
Implementation Method 1
a layer that adheres to the base fabric is an adhesive layer, and a layer on a side opposite to the adhesive layer is an outer layer, each layer being formed using a resin that has a different melting point and glass transition temperature
Implementation Method 2
a thermal lamination and subsequent heating process to enhance adhesion and flexibility
Data Source
AI summary
To provide a multilayer composite for an airbag that has both scrub resistance and flexibility, the multilayer composite for an airbag includes a base fabric, and a multilayer film including an outer layer and an adhesive layer adhered to a surface of the base fabric in which a ratio Sdr1/Sdr2 is from 0.986 to 1.1, where Sdr1 is an interface deployment area ratio of a multilayer film side surface of the multilayer composite for an airbag and Sdr2 is an interface deployment area ratio of a base fabric side surface of the multilayer composite for an airbag.