Laminated Foldable Duct Foil for Fire Resistance and Flexibility
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Solution Overview
Problem
Existing foils used for laminating ducts, typically made of metal and polymer layers, exhibit low mechanical properties and are prone to rupture under bending, stretching, and pressure, which is a concern for their use in ventilation systems and fire protection applications.
Innovation Solution
A foil structure comprising an outer aluminium layer, an intermediate thermoplastic polymer layer with a melting point below polyethylene, and an inner polyethylene terephthalate (PET) layer, which provides flexibility and mechanical strength, along with an optional glass fibre layer for enhanced properties, ensuring the foil can withstand repeated folding and pressure without breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a foil is made with metal and polymer layers for duct lamination, then fire protection and basic structural integrity are achieved, but the foil breaks easily when bent, stretched, or exposed to concentrated pressures
Solution Approach 1:
The patent applies composite materials by combining multiple layers with different properties: an outer aluminium layer for fire protection and structural integrity, an intermediate PET layer for flexibility and mechanical strength, and an inner PE layer for adhesion and sealing. This multi-layer composite structure resolves the contradiction by integrating the strengths of different materials to achieve both fire resistance and mechanical durability without rupture under stress.
Solution Approach 2:
The patent changes the physical and chemical parameters of the foil structure by selecting specific materials with defined melting points (PET with melting point below polyethylene), specific layer thicknesses, and specific weight ratios (inner PE layer 20-30 g/m2, intermediate PET layer 10-20 g/m2). These parameter optimizations enable the foil to withstand mechanical forces while maintaining fire protection properties.
2Reliability
If a foil is made rigid for fire protection, then fire resistance and air tightness are improved, but the foil cannot withstand repeated folding and stretching
Solution Approach 1:
The patent uses composite materials to reconcile fire protection rigidity with folding flexibility. The outer aluminium layer provides fire resistance and structural stability, while the intermediate PET layer contributes flexibility and elongation capacity. This composite approach allows the foil to maintain its fire protective function while being foldable and unfoldable repeatedly without breaking.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers: the outer aluminium layer is optimized for fire protection and rigidity, the intermediate PET layer for flexibility and mechanical strength, and the inner PE layer for adhesion. Each layer performs its specific function locally, allowing the overall structure to be both rigid enough for fire protection and flexible enough for repeated folding.
3Strength
If additional layers are added to improve mechanical properties, then flexibility and strength are enhanced, but the foil structure becomes more complex
Solution Approach 1:
The patent employs a three-layer composite structure (outer aluminium, intermediate PET, inner PE) that balances mechanical property enhancement with structural simplicity. Each layer serves a specific function, and the total structure remains manageable with a thickness of 40-60 μm and weight of 75-105 g/m2. The complexity is minimized by selecting materials that can be laminated together using standard processes.
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 proposed foil structure offers improved mechanical properties, fire resistance, and air-tightness, meeting specific fire protection classifications like A2s1d0, with enhanced durability and flexibility, ensuring the foil remains intact during repeated folding and exposure to mechanical forces.
Implementation Method 1
The adhesion arises when the polymer is melted. Thus the intermediate layer of a thermoplastic polymer having a melting point below PET functions as an adhesive.
Implementation Method 2
The adhesion arises when the polymer is melted.
Implementation Method 3
This layer of polyethylene such as PET brings a flexibility to the foil at the same time as it does not break easily when it is exposed to mechanical forces, such as bending, stretching and pressure.
Data Source
AI summary
The present invention concerns a foldable duct (4) made of glass or stone fibers and binder agent having a foil (1) laminated thereon, on the inside and outside of the duct, wherein the foil (1) at least comprises:an outer layer of aluminum (5),an intermediate layer of a thermoplastic polymer (6) having a lower melt point than polyethylene, positioned closest to the outer layer of aluminum (5),an intermediate layer of polyethylene (7), positioned between the intermediate layer of thermoplastic polymer (6), andan inner layer of a thermoplastic polymer (8) having a lower melt point than polyethylene.