UV-Cured Pipe Coating Adhesion and Thickness Control
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Solution Overview
Problem
Current methods for applying coatings to plastic piping, such as co-extrusion, face challenges including difficulty in achieving thin, consistent coating layers, limited flexibility in operating conditions, high energy requirements, costly start-up times, and quality control issues like inconsistent thickness and surface leveling.
Innovation Solution
A process involving a flexible tubular polymeric substrate with a UV radiation-cured crosslinked polymeric coating layer, applied using a pre-polymer formulation with a photoinitiator and monomer/oligomer, which is oxidized and then exposed to UV radiation to form a thin, crosslinked layer with excellent adhesion and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If co-extrusion is used to apply coating to plastic piping, then coating can be applied to the pipe surface, but it is difficult to achieve thin, consistent coating layers with uniform thickness
Solution Approach 1:
The patent replaces the mechanical co-extrusion system with a chemical/photopolymerization system. The coating is applied as a liquid pre-polymer formulation that is then cured in place using UV radiation or electron beam irradiation, eliminating the need for complex mechanical extrusion equipment and enabling much thinner, more consistent coating layers.
Solution Approach 2:
The patent changes the physical state of the coating material from a solid extruded polymer to a liquid pre-polymer formulation that can be applied at controlled thickness and then transformed into a solid crosslinked coating through photopolymerization. This parameter change enables precise control over coating thickness and uniformity.
2Productivity
If co-extrusion is used for coating application, then coating can be formed on the pipe, but energy requirements are high and start-up times are costly
Solution Approach 1:
The patent replaces the energy-intensive mechanical extrusion process with a photopolymerization process that uses UV radiation or electron beam irradiation. This substitution dramatically reduces energy consumption and eliminates the need for prolonged start-up times associated with heating and melting polymers in co-extrusion.
Solution Approach 2:
The patent uses rapid photopolymerization curing that occurs in seconds or minutes compared to the extended heating and extrusion times required by co-extrusion. This 'rushing through' of the coating process enables quick start-up and shutdown, improving productivity and reducing energy waste during transitions.
3Reliability
If traditional coating methods are used, then coating can be applied to the pipe surface, but quality control issues arise with inconsistent thickness and surface leveling
Solution Approach 1:
The patent replaces mechanical extrusion with liquid application followed by photopolymerization. The liquid pre-polymer formulation can be applied more uniformly and the in-place curing prevents the surface leveling issues that occur with mechanical extrusion, resulting in consistent thickness and finish quality.
Solution Approach 2:
The patent uses a composite formulation consisting of pre-polymer, photoinitiator, and crosslinking agents that work together to create a coating with superior consistency. The chemical composition is designed to ensure uniform curing and predictable final properties, improving reliability and quality control.
4Loss of substance
If co-extrusion is used to apply coating, then coating layer can be formed, but material consumption is high and thin layers cannot be achieved
Solution Approach 1:
The patent changes the coating from a thick extruded layer to a thin liquid film that is then crosslinked in place. The liquid pre-polymer formulation can be applied at much lower thicknesses because the photopolymerization process locks in the coating before it can drain or sag, enabling precise control of material consumption and achieving thin layers that are not possible with co-extrusion.
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
This method allows for precise control of coating thickness, improved adhesion to polyolefins, enhanced mechanical performance, and reduced material consumption, while providing UV resistance, oxygen barrier properties, and flexibility, overcoming the limitations of traditional co-extrusion processes.
Implementation Method 1
exposed to UV radiation to produce a first crosslinked coating layer
Implementation Method 2
oxidized outer surface of the flexible tubular substrate
Data Source
Figure 1~2
Figure 3
AI summary
Compositions and methods for producing multi-layered plastic pipes are described. Some embodiments of the compositions comprise a cross-linkable polymer system (for example, based on either acrylate or epoxy chemistry), a photoinitiator, and one or more additives such as a pigment, an antioxidant, a light stabilizer, or other additive. In an exemplary method of producing a multi-layered plastic pipe, a base pipe, for example comprising cross-linked polyethylene, is conveyed through an oxidizing step in which at least the outer surface of the base pipe is oxidized, through a coating step in which a pre-polymer system is applied to the outer surface of the base pipe and through a curing step in which the pre-polymer is cured to form a layer of the pipe.