Polysiloxane Primer with Side-Chain UV Absorbers
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Solution Overview
Problem
Polycarbonate resin molded articles face challenges with inferior surface properties such as scratch resistance and weatherability compared to glass, leading to issues like cracks, peeling, and yellowing due to the limitations of existing UV absorbent incorporation methods in primer layers.
Innovation Solution
A primer composition containing a vinyl polymer with hydrolyzable silyl groups and organic UV absorbing groups bonded to its side chain, combined with fine silica particles in an organic solvent, forming a compact crosslink network that reduces the coefficient of linear expansion and secures UV absorbers within the coating, enhancing adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of UV absorbent is incorporated in the primer layer, then weatherability is improved, but adhesion with the underlying substrate and overlying protective coating deteriorates
Solution Approach 1:
The patent changes the chemical structure of the UV absorbent by introducing a silane group that can undergo hydrolysis and condensation reactions. This transforms the UV absorbent from a simple organic compound into a crosslinking agent that forms a three-dimensional network structure, thereby maintaining adhesion while providing UV protection.
Solution Approach 2:
The patent creates a composite system by combining the UV absorbent containing silane groups with a polysiloxane protective coating. The silane groups in the primer layer react with the polysiloxane to form a crosslinked interface, creating a composite structure that enhances both adhesion and weatherability.
2Reliability
If a large amount of UV absorbent is incorporated in the primer layer, then weatherability is improved, but the UV absorbent is removed by volatilization during curing at elevated temperature
Solution Approach 1:
The patent changes the physical and chemical state of the UV absorbent by incorporating silane groups that form crosslinked bonds during curing. This prevents the UV absorbent from volatilizing by creating a stable three-dimensional network structure that anchors the UV absorbent molecules in place.
3Reliability
If a large amount of UV absorbent is incorporated in the primer layer, then weatherability is improved, but cracks and whitening or yellowing are generated by the bleeding out of the UV absorbent in the long term outdoor use
Solution Approach 1:
The patent changes the mobility and distribution of the UV absorbent by incorporating silane groups that form a crosslinked network. This prevents the UV absorbent from migrating or bleeding out over time, thereby maintaining coating stability and preventing whitening or yellowing.
Solution Approach 2:
The patent creates a composite structure where the UV absorbent is integrated into a crosslinked network formed by silane groups and polysiloxane. This composite structure prevents the UV absorbent from separating or migrating, thereby maintaining long-term stability and preventing defects like cracks and discoloration.
4Strength
If the coefficient of linear expansion of the primer layer is reduced, then adhesion with the substrate and overlying coating is improved, but the complexity of the primer composition increases
Solution Approach 1:
The patent changes the thermal expansion properties of the primer layer by incorporating silane groups that form crosslinked networks with low thermal expansion coefficients. This reduces the coefficient of linear expansion to improve adhesion, while the crosslinking mechanism provides a straightforward way to achieve this without excessive complexity.
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 solution provides a primer layer with improved weatherability, scratch resistance, and heat resistance, preventing cracks and peeling, and maintaining UV absorption over time, making polycarbonate resin articles suitable for outdoor use.
Implementation Method 1
a vinyl polymer having a hydrolyzable silyl group and/or SiOH group
Implementation Method 2
forming a compact crosslink network that reduces the coefficient of linear expansion
Implementation Method 3
an organic UV absorbing group bonded to its side chain
Implementation Method 4
fine silica particles dispersed in an organic solvent
Implementation Method 5
a primer layer formed by coating and curing the primer composition has a coefficient of linear expansion of up to 150×10−6/° C.
Data Source
AI summary
A primer composition for a polysiloxane hard coating is provided. This primer composition comprises (A) a vinyl polymer having a hydrolyzable silyl group and/or SiOH group and an organic UV absorbing group bonded to its side chain, and (B) fine silica particles dispersed in an organic solvent, and the primer layer formed after coating and curing has a coefficient of linear expansion of up to 150×10−6/° C.