Polymer Surface Conductivity via Oxidation and Polyamine Treatment
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Solution Overview
Problem
Polymeric materials, especially non-polar polyolefins, are insulators and lack conductivity, making them unsuitable for electrostatic powder coating, which requires a conductive substrate, and they suffer from thermal distortion at high baking temperatures, limiting the application of powder coating technologies.
Innovation Solution
Oxidizing the polymer surface followed by treating it with a polyamine compound and an electroconductivity modifying agent, such as mono-carboxylic acids, to increase surface conductivity, allowing for electrostatic powder coating and improving adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If powder coating is applied to non-polar polyolefin surfaces, then coating efficiency is improved, but the surface lacks conductivity required for electrostatic deposition
Solution Approach 1:
The patent applies preliminary surface treatment steps before powder coating: (1) corona discharge treatment to generate conductive sites, (2) plasma treatment to enhance surface conductivity, (3) flame treatment to oxidize the surface. These preliminary actions create a conductive surface layer that enables subsequent electrostatic powder coating, resolving the contradiction between coating efficiency and surface conductivity.
Solution Approach 2:
The patent introduces intermediary substances and treatments between the non-conductive polyolefin surface and the electrostatic coating process. These intermediaries include plasma, corona discharge, flame treatment, and conductive primers that bridge the gap between the insulating substrate and the conductive coating requirement, enabling successful powder coating application.
2Reliability
If high baking temperature is used for powder coating, then coating cure is improved, but thermal distortion occurs in polyolefin substrates
Solution Approach 1:
The patent changes the curing temperature parameter from conventional high temperatures (150-200°C) to lower temperatures (80-120°C) suitable for polyolefin thermal stability. This parameter change enables coating cure without causing thermal distortion, while alternative curing methods (UV, electron beam) provide additional curing pathways at even lower temperatures.
Solution Approach 2:
The patent replaces thermal curing with alternative curing mechanisms: UV irradiation, electron beam irradiation, or combination of corona discharge and moderate heat. This substitution allows the coating to cure without subjecting the polyolefin substrate to high temperatures that would cause thermal distortion, resolving the contradiction between effective curing and thermal stability.
3Strength
If electrostatic coating is applied to insulating polymer surfaces, then coating adhesion is improved, but the substrate lacks the necessary electrical conductivity
Solution Approach 1:
The patent performs preliminary surface modification treatments before electrostatic coating: corona discharge to create conductive sites, plasma treatment to enhance conductivity, and flame treatment to oxidize the surface. These preliminary actions create a conductive surface layer that enables electrostatic coating adhesion, resolving the contradiction between coating adhesion and substrate conductivity.
Solution Approach 2:
The patent introduces intermediary surface treatment layers and treatments between the insulating polymer and the electrostatic coating. These intermediaries include plasma-generated conductive sites, corona discharge-induced surface modification, and conductive primers that provide the necessary electrical conductivity and adhesion for electrostatic coating on otherwise insulating surfaces.
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
Enhances the surface conductivity of polymeric materials, enabling successful electrostatic powder coating and improving the adhesion of coatings, even at lower curing temperatures, thus overcoming the thermal stability issues and conductivity limitations.
Implementation Method 1
oxidising at least part of the polymer surface
Implementation Method 2
treating the oxidised polymer surface with (a) a polyamine compound and (b) an electroconductivity modifying agent reactive with the polyamine
Implementation Method 3
electrostatically applying a coating, preferably a powder coating, to the treated polymer surface to bind the coating composition thereto
Data Source
AI summary
A method of electrostatic spraying of a polymer surface involves oxidation and treating the oxidized surface with a polyamine and an electroconductivity modifying agent which contains a mono-carboxylic acid of from one to 12 carbon atoms.