Flexibilizing Capped Prepolymers for Structural Adhesives
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Solution Overview
Problem
Traditional epoxy-based structural adhesives have low impact peel strength, particularly at low temperatures, which can lead to reduced flexibility and increased brittleness, making them inadequate for withstanding high dynamic loads and temperature variations.
Innovation Solution
The development of flexibilizing capped prepolymers, formed by reacting polyisocyanates with isocyanate-reactive components such as polyols and branching agents, and subsequently capping with specific agents to enhance the structural adhesive's low-temperature high impact peel strength and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional epoxy-based structural adhesives are used, then structural integrity and strength are achieved, but impact peel strength and flexibility are reduced
Solution Approach 1:
The patent combines epoxy resin with flexibilizing capped prepolymers to create a composite adhesive system. The epoxy provides structural strength while the capped prepolymer component provides flexibility and impact resistance, resolving the contradiction between strength and brittleness through material composition
2Adaptability or versatility
If flexibilizing capped prepolymers are added to improve impact peel strength, then flexibility and low-temperature performance are enhanced, but adhesive composition complexity increases
Solution Approach 1:
The flexibilizing capped prepolymers are prepared in advance through a controlled reaction between polyisocyanate and isocyanate-reactive components, then capped with specific agents. This preliminary preparation allows the complex flexibilizing functionality to be incorporated as a pre-formed component, simplifying the final adhesive formulation process
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 use of flexibilizing capped prepolymers significantly improves the low-temperature high impact peel strength and flexibility of structural adhesives, reducing brittleness and enhancing their performance in automotive and other applications by adjusting the glass transition and crystallization temperatures.
Implementation Method 1
The flexibilizing capped prepolymer can be a reaction product of a reaction mixture including a polyisocyanate and an isocyanate-reactive component
Implementation Method 2
The NCO-functional prepolymer can be combined with a capping agent to terminate the NCO-functional prepolymer and form the flexibilizing capped prepolymer
Implementation Method 3
A structural adhesive is an adhesive that is intended to cure to hold two or more substrates together for the lifetime of the product
Data Source
AI summary
A flexibilizing capped prepolymer can include a reaction product of reaction mixture including a polyisocyanate and an isocyanate-reactive component at an equivalent ratio of polyisocyanate equivalents to isocyanate-reactive component equivalents of from 1.4:1 to 2.1:1. The isocyanate-reactive component can include a polyol component and a branching agent component. The branching agent component can include a monoglyceride, a diglyceride, a triglyceride, or a combination thereof having a number average functionality of from 3 to 6 NCO-reactive functional groups. The reaction product is terminated with a capping agent to form the flexibilizing capped prepolymer.