Curable Silsesquioxane Polymers for Scratch and UV Resistance
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Solution Overview
Problem
Epoxy- and acrylate-based hard coatings exhibit poor outdoor weatherability, necessitating the development of new polymers with improved durability and resistance to UV and moisture exposure.
Innovation Solution
Curable silsesquioxane polymers with a three-dimensional branched network structure, incorporating ethylenically unsaturated groups and hydroxyl (-OH) groups, are used to create a protective coating that includes a photoinitiator and optional nanoparticles, which can be UV-cured for enhanced durability and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy- or acrylate-based polymers are used to prepare hard coatings, then abrasion and scratch resistance are achieved, but outdoor weatherability deteriorates
Solution Approach 1:
The patent combines silsesquioxane polymer backbone with pendant epoxy or acrylate groups to create a composite polymer structure. The silsesquoxane core provides UV and moisture resistance, while the pendant groups contribute to crosslinking and mechanical properties, achieving both hardness and weatherability
Solution Approach 2:
The patent modifies the chemical structure by incorporating hydroxyl groups at specific concentrations (at least 15 wt-%) and controlling the silsesquoxane ring structure, thereby changing the polymer's resistance parameters to UV and moisture while maintaining crosslinking capability for hardness
2Strength
If silica nanoparticles are mixed with base polymer to create hard coats, then abrasion and scratch resistance are improved, but outdoor weatherability remains poor
Solution Approach 1:
The patent creates a composite where silsesquoxane polymer (which inherently resists UV and moisture) is combined with silica nanoparticles. The silsesquoxane structure protects the silica from UV-induced aggregation and moisture degradation, while the silica provides reinforcement for abrasion resistance
Solution Approach 2:
The silsesquoxane polymer acts as an intermediary matrix that protects silica nanoparticles from direct exposure to UV radiation and moisture. The polymer structure with hydroxyl groups forms a protective interface around the silica particles, preventing their degradation
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 resulting coatings demonstrate excellent outdoor weatherability, UV resistance, and moisture resistance, making them suitable for applications requiring anti-scratch and anti-abrasion properties, such as polycarbonate lenses and polyester films.
Implementation Method 1
UV curing the curable composition
Implementation Method 2
the —OH groups are present in an amount of at least 15 wt-% of the polymer
Data Source
AI summary
A curable silsesquioxane polymer, a composition including such polymer, an article having a layer disposed thereon that includes the curable polymer and/or the cured polymer, and a method of forming a cured coating, wherein the curable silsesquioxane polymer includes a three-dimensional branched network having the formula:wherein: the oxygen atom at the * is bonded to another Si atom within the three-dimensional branched network; R is an organic group comprising an ethylenically unsaturated group; n is an integer of greater than 3; and the —OH groups are present in an amount of at least 15 wt-% of the polymer.