Polycarbonate Multilayer Articles With Thermoformable Aliphatic TPU
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Solution Overview
Problem
Existing transparent films and sheets, particularly those used in glazing, automotive, electronics, and building applications, require surface treatments for scratch and abrasion resistance, but these treatments often make the materials brittle and limit thermoformability, especially for complex shapes, and existing methods are costly and time-consuming.
Innovation Solution
A thermoplastic multilayer article comprising a polycarbonate substrate with a laminated or coextruded aliphatic thermoplastic polyurethane layer, formed via a reaction of caprolactone and aliphatic isocyanate, and optionally a polyurethane UV stabilizer, providing improved scratch and abrasion resistance while maintaining flexibility and thermoformability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silicate or acrylic hardcoat is applied to polycarbonate films and sheets to improve scratch and abrasion resistance, then scratch and abrasion resistance is improved, but the coated material becomes brittle and cannot be vacuum formed or 3D shaped
Solution Approach 1:
The patent changes the chemical composition parameters of the coating by using a polyurethane system with specific hard segment content (20-80 wt%) and controlled molecular structure. This parameter change allows the coating to maintain flexibility and thermoformability while providing scratch and abrasion resistance, resolving the contradiction between hardness and formability.
Solution Approach 2:
The patent creates a composite multilayer structure combining polycarbonate substrate with polyurethane coating layers. The composite structure leverages the toughness of polycarbonate and the scratch resistance of polyurethane, while the controlled interface bonding maintains thermoformability. This composite approach resolves the contradiction by integrating materials with complementary properties.
2Strength
If UV curable hardcoat is applied and partially cured before thermoforming, then scratch and abrasion resistance is improved, but the process becomes costly and time consuming
Solution Approach 1:
The patent extracts the UV curing step from the manufacturing process, using a polyurethane coating that cures through moisture exposure rather than UV irradiation. This removal of the UV curing step eliminates the associated time delays and costs while maintaining the scratch and abrasion resistance benefits.
Solution Approach 2:
The patent employs a polyurethane coating system that uses inexpensive moisture as the curing agent rather than expensive UV curing equipment and processes. This substitution reduces manufacturing costs and cycle time while achieving the desired protective properties.
3Strength
If conventional coating methods are used to improve scratch resistance, then scratch resistance is improved, but the materials cannot be used to make articles having complex shapes
Solution Approach 1:
The patent changes the coating's physical parameters by controlling the polyurethane molecular weight, hard segment content, and crosslink density to achieve optimal flexibility and formability. These parameter adjustments enable the coating to conform to complex shapes during thermoforming while maintaining scratch resistance when fully cured.
Solution Approach 2:
The patent creates a dynamic coating system that transitions from a flexible, formable state during processing to a rigid, scratch-resistant state after curing. The polyurethane coating adapts its properties based on the processing stage, enabling both complex shape formation and scratch protection.
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 multilayer articles exhibit enhanced scratch and abrasion resistance, chemical resistance, weatherability, and optical properties, with minimal yellowing under UV exposure, and can be thermoformed without mechanical failure, offering improved performance over coated polycarbonate substrates.
Implementation Method 1
enhanced scratch and abrasion resistance
Implementation Method 2
polyurethane UV stabilizer... minimal yellowing under UV exposure
Implementation Method 3
formed via a reaction of caprolactone and an aliphatic isocyanate
Implementation Method 4
can be thermoformed without mechanical failure
Data Source
Figure 1~4
Figure 5~7
Figure 8
AI summary
A thermoplastic multilayer article comprises: a polycarbonate substrate comprising a polycarbonate composition comprising at least one of a polycarbonate homopolymer, a copolycarbonate, or a polycarbonate copolymer, the polycarbonate substrate having a first surface and an opposing second surface; and a first polyurethane layer laminated or coextruded on at least a portion of the first surface of the polycarbonate substrate, the first polyurethane layer comprising a first aliphatic thermoplastic polyurethane and a polyurethane UV stabilizer, wherien the first aliphatic thermoplastic polyurethane comprises first segments formed via a reaction of caprolactone and an aliphatic isocyanate, and second segments formed via a reaction of a chain extender and the aliphatic isocyanate.