Two-Stage UV Adhesive Processing for Selective Cure Control
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Solution Overview
Problem
Existing adhesive systems are limited in flexibility and can only be used with specific polymeric systems having particular curing requirements, lacking the ability to be prepared, stored, and selectively applied or further processed.
Innovation Solution
A method involving a composition with at least one monomer and two actinic radiation initiators, where the second initiator is non-photoactive at the activation wavelength of the first, allowing for two-stage polymerization and crosslinking through different radiation wavelengths, forming a controlled architecture polymer adhesive with enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-stage curing method is used, then the process is simple and quick, but the adhesive lacks flexibility and cannot be selectively applied or stored
Solution Approach 1:
The curing process is divided into two distinct stages: first polymerization using a first photoinitiator, then crosslinking using a second photoinitiator. This segmentation allows the adhesive to be processed selectively - it can be partially cured for storage or fully cured for final application, providing flexibility while maintaining a relatively simple overall process
Solution Approach 2:
The adhesive undergoes preliminary polymerization in the first stage to form a stable pre-adhesive that can be stored and transported. This preliminary action enables selective application - the adhesive can be applied in its partially cured state and then fully crosslinked later when needed, rather than requiring complete curing before application
2Strength
If UV curing is used to toughen or harden the adhesive system, then adhesive strength is improved, but the system loses flexibility and cannot be selectively processed
Solution Approach 1:
The system transitions from a static fully-cured state to a dynamic multi-stage process. The adhesive can be cured to different degrees depending on requirements - partially cured for storage flexibility, fully cured for maximum strength. The two photoinitiators with different activation wavelengths provide dynamic control over the curing extent
Solution Approach 2:
The curing process uses parameter changes - specifically different wavelengths of UV radiation - to activate different photoinitiators. The first photoinitiator responds to one wavelength range for polymerization, while the second responds to another wavelength range for crosslinking. This allows selective activation and control over the strength-flexibility balance
3Adaptability or versatility
If conventional adhesive systems are used, then the formulation is simple, but the system is limited to specific polymeric systems with particular curing requirements
Solution Approach 1:
The dual photoinitiator system provides multi-functionality - it can work with various monomers and polymers that contain ethylenically unsaturated bonds. The first photoinitiator handles polymerization of diverse monomers, while the second handles crosslinking of different polymer systems. This universal approach replaces the need for specially formulated systems for each polymer type
Solution Approach 2:
The adhesive composition is a composite system containing multiple components: monomers with ethylenically unsaturated bonds, first photoinitiator, second photoinitiator, and optional solvents. This composite structure enables the system to accommodate different polymeric systems while maintaining a consistent formulation approach across applications
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 method produces adhesives with high peel strength and shear strength, enabling lower coatweights and viscosities, and allowing for better adhesive performance.
Implementation Method 1
at least partially polymerizing the pre-adhesive by exposing the pre-adhesive to actinic radiation
Implementation Method 2
at least partially crosslinking the pre-adhesive to thereby form the adhesive by exposing the pre-adhesive to actinic radiation
Data Source
AI summary
Methods for forming melt processable, actinic radiation polymerizable and crosslinkable adhesives are described. In certain versions, the adhesives or pre-adhesive compositions include two initiators and are polymerized and/or crosslinked by exposure to actinic radiation such as UV light or electron beam radiation. Also described are pre-adhesive compositions including polymerizable monomers, articles including the adhesives, and various methods and systems related to the adhesives and their application. In addition, various apparatuses are described for polymerizing or crosslinking the compositions.