Wood-like Coating Method for Aromatic Polyurethane Substrates
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Solution Overview
Problem
Aromatic polyurethane substrates used in exterior applications degrade and discolor due to exposure to ultra-violet light, limiting their use in exterior conditions.
Innovation Solution
A multi-step coating process involving mechanical sanding to create porosity, pressure embossing for a wood grain appearance, application of an under-indexed contrasting agent, and a final over-indexed clear coating to enhance adhesion and provide abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If aromatic polyurethane is used for exterior applications, then it provides versatile material properties, but it degrades and discolors due to UV exposure
Solution Approach 1:
A clear coat layer is applied as an intermediary between the UV environment and the aromatic polyurethane substrate. This clear coat acts as a mediator that blocks UV radiation from reaching the substrate, preventing degradation and discoloration while allowing the substrate to maintain its versatile material properties
Solution Approach 2:
A thin film clear coat is applied over the aromatic polyurethane substrate to provide UV protection. This thin film layer is flexible enough to conform to the substrate while providing a barrier against harmful UV radiation, thereby protecting the substrate for exterior applications
2Reliability
If a clear coating is applied to protect the substrate, then UV protection is achieved, but adhesion to the smooth substrate surface is poor
Solution Approach 1:
The substrate surface is mechanically sanded before applying the clear coat to create a porous surface structure. This preliminary action of surface preparation increases the surface area and creates mechanical interlocking features that enhance adhesion of the subsequent clear coat layer
Solution Approach 2:
The substrate surface is mechanically sanded to create a porous structure. This porous surface increases the surface area and provides mechanical interlocking features that significantly improve the adhesion of the clear coat, allowing the protective coating to bond strongly to the substrate
3Strength
If mechanical sanding is performed to enhance adhesion, then coating adhesion is improved, but the wood-like appearance is compromised
Solution Approach 1:
The coating process is segmented into distinct steps: mechanical sanding to create porosity for adhesion, followed by embossing to create the wood grain pattern, and finally clear coating for UV protection. This segmentation allows each function to be optimized independently without compromising the others
Solution Approach 2:
Mechanical sanding is performed as a preliminary action before embossing to ensure proper adhesion. The sanding creates the necessary porous surface structure, and subsequent embossing restores the wood-like appearance by creating the grain pattern on top of the sanded surface
4Shape
If embossing is used to create wood grain appearance, then aesthetic quality is improved, but the surface becomes less uniform for coating
Solution Approach 1:
The manufacturing process is segmented so that embossing is performed after the base coat is applied but before the clear coat. This segmentation allows the embossed pattern to be created on a uniform coated surface, and the clear coat is then applied to provide a uniform protective layer over the textured surface
Solution Approach 2:
A thin film clear coat is applied over the embossed surface. This thin film is flexible enough to conform to the embossed wood grain pattern while providing a uniform protective layer that maintains UV protection and abrasion resistance without requiring perfect surface uniformity
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 process protects the substrate from UV degradation, creates a wood-like appearance, and offers high abrasion resistance for durability in exterior applications.
Implementation Method 1
The substrate is then coated with a plural-component coating via air assisted airless spray. The substrate can be embossed prior to or after this coating process to create the wood grain appearance.
Implementation Method 2
The embossed pattern is then filled with a contrasting agent that is under-indexed to prevent adhesion to all surfaces of the substrate.
Implementation Method 3
The excess contrasting agent is then removed using a reverse roll-coater, which is self-cleaning and provides for the reuse of the excess contrasting agent.
Implementation Method 4
This final coat adds sheen to the substrate as well as abrasion resistance to allow for high traffic on the substrate with minimal wear and tear.
Data Source
AI summary
A protective coating method of a material such as aromatic polyurethane substrates is effected through a process that promotes coating adhesion to the substrate while providing a wood-like aesthetic. Closed cells on the surface of the aromatic polyurethane are opened via sanding techniques to promote adhesion. Once a sufficient surface is achieved, the substrate is coated using spray techniques to protect the aromatic polyurethane from ultra-violet light exposure. The wood-like appearance is achieved through embossing a wood-grain on the deformable surface and subsequently filling the grain with a contrasting agent to highlight its appearance through a reverse-roll-coating technique. Abrasion properties are achieved through a final clear top coat that allows both the contrast agent and the top coat to fully cure.