Urethane-Urea-Acrylic Cast Sheet Impact Resistance
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Solution Overview
Problem
Current materials for impact-resistant clear plastic sheets, such as acrylic and polyurethane, face challenges in achieving both excellent impact resistance and desirable hardness while maintaining low haze, with existing solutions either being costly, difficult to produce, or compromising on optical properties.
Innovation Solution
The development of urethane-urea-acrylic cast sheet materials formed by reacting a curative with at least two amine functional groups, a polyisocyanate compound or pre-reacted urethane prepolymer, an acrylic monomer, and a multifunctional monomer, which results in a reaction product that combines excellent impact properties, hardness, and low haze.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cast acrylic sheet is used to maintain optical properties and ease of manufacture, then haze is low and casting is easy, but impact resistance is insufficient and sheets must be very thick or laminated
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a hybrid polymer system containing polyurethane segments (for toughness), acrylic segments (for optical clarity), and epoxide crosslinking agents (for enhanced strength). This compositional parameter change enables achieving high impact resistance in thinner sheets while maintaining optical properties.
Solution Approach 2:
The invention creates a composite polymer material that combines multiple polymer systems (polyurethane-acrylic hybrid) with epoxide crosslinking. This composite structure integrates the advantages of different materials: the toughness of polyurethane, the optical clarity of acrylic, and the strength from epoxide crosslinks, resolving the contradiction between impact resistance and thickness.
2Reliability
If cast polyurethane sheet is used to improve impact resistance, then impact properties are superior, but raw materials are more expensive and production is difficult due to high viscosity and hazardous chemicals
Solution Approach 1:
The patent modifies the manufacturing parameters by using a prepolymer formulation approach where polyisocyanate and polyol are reacted to form urethane prepolymer with controlled molecular weight and functionality. This parameter change reduces the viscosity of the casting mixture compared to conventional polyurethane, making it easier to pour and process while maintaining impact resistance through subsequent crosslinking.
Solution Approach 2:
The invention introduces an intermediary step of forming urethane prepolymer before casting. This intermediary formulation acts as a mediator between the high-performance requirements of polyurethane and the ease of processing needed for casting. The prepolymer has lower viscosity and can be combined with acrylic monomers and epoxide crosslinkers to create a processable mixture that cures to high-performance material.
3Reliability
If urethane vinyl copolymers are used to obtain improved impact resistance, then impact properties are enhanced, but hardness decreases which is unacceptable for many applications
Solution Approach 1:
The patent changes the crosslinking parameters by incorporating epoxide functional groups that react with hydroxyl groups in the polymer chains to form dense crosslinked networks. This crosslinking parameter change simultaneously enhances both impact resistance (toughness) and hardness, eliminating the trade-off present in uncrosslinked or lightly crosslinked urethane vinyl copolymers.
Solution Approach 2:
The invention creates a composite polymer system that combines urethane vinyl copolymer base material with epoxide crosslinking agents. This composite approach allows the urethane vinyl segments to provide impact resistance while the epoxide crosslinks provide hardness and structural rigidity, achieving both properties simultaneously rather than requiring a trade-off.
4Reliability
If acrylic sheet is laminated with polycarbonate or polyurethane to provide impact resistance, then impact resistance is sufficient, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple polymer systems (polyurethane and acrylic) into a single homogeneous casting mixture that cures as one integrated material. This merging eliminates the need for separate lamination of acrylic and polyurethane sheets, simplifying the manufacturing process from multi-step lamination to single-step casting while maintaining the combined benefits of both polymer systems for impact resistance and optical properties.
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 urethane-urea-acrylic cast sheet materials exhibit Rockwell hardness of at least 35, haze of less than 5%, and impact resistance exceeding 11.3 Nm, with a V50 critical velocity ballistic rating significantly higher than conventional poly(methyl methacrylate) sheets, making them suitable for security and protection applications.
Implementation Method 1
a reaction product, which is formed by adding curative having at least two amine functional groups to polyisocyanate compound and polyol (or pre-reacted urethane prepolymer having at least two isocyanate functionalities)
Implementation Method 2
acrylic monomer, and multifunctional monomer, which results in a reaction product
Data Source
AI summary
Urethane-urea-acrylic cast sheet materials are made from a reaction product of components including polyisocyanate compound having at least two isocyanate functional groups and optional polyol (or pre-reacted urethane prepolymer having at least two isocyanate functional groups), curative having at least two amine functional groups, acrylic monomer, and optional multifunctional monomer having a first functional group having an active hydrogen and a second functional group having at least one double bond. The urethane-urea-acrylic cast sheet materials exhibit excellent impact properties and desirable hardness while also maintaining optical properties such as low haze that can be comparable to that of conventional cast acrylic sheet.