Flameless Thermal Spray System for Polymer Coatings
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Solution Overview
Problem
Conventional thermal spray processes using flames or plasmas degrade polymers due to high temperatures and oxidative environments, leading to reduced mechanical properties and accelerated degradation of polymer coatings.
Innovation Solution
A flameless thermal spray system that heats a stream of air within a defined combustion zone, allowing for the introduction of secondary gas flows to cool the carrier gas temperature, preventing polymer degradation, and using a thermal spray gun design that contains the flame, preventing it from contacting the substrate or polymer particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a flame or plasma is used to heat polymer particles for thermal spray coating, then the polymer particles can be melted and deposited onto substrates, but the high temperature and oxidative environment causes polymer degradation including chain scission, crosslinking, and formation of unstable carbonyl groups
Solution Approach 1:
The heating process is segmented into distinct zones: a combustion zone for heat generation, a transition zone with decreasing temperature, and a deposition zone with controlled temperature. This spatial segmentation allows the polymer particles to be heated without prolonged exposure to extreme temperatures that cause degradation.
Solution Approach 2:
The flame is ignited and stabilized in the combustion zone before polymer particles are introduced. This preliminary action ensures that the thermal field is established and controlled, allowing subsequent polymer heating to occur in a predictable temperature gradient rather than direct flame contact.
2Power
If a flame is used for thermal spray processing, then sufficient heat is provided for melting polymers, but the flame impinging on the target surface degrades the substrate and causes defects such as burned particles, carbon inclusions, yellowing and discoloration
Solution Approach 1:
The harmful visible flame and reactive radicals are extracted from the deposition zone through controlled combustion in a separate combustion zone. The flame is confined to the combustion zone where it performs its heating function, while the polymer particles traverse through a cooler transition zone to the deposition zone, avoiding direct flame contact and associated defects.
3Productivity
If high temperature flame is used to melt polymer particles quickly, then deposition efficiency is improved, but the exposure time to harsh oxidative environments increases causing accelerated polymer degradation
Solution Approach 1:
The system creates a dynamic thermal environment where temperature varies spatially along the particle trajectory. Polymer particles experience rapid heating in the transition zone followed by controlled cooling in the deposition zone, optimizing both melting speed and minimizing degradation exposure time through controlled residence times in different temperature zones.
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 approach minimizes polymer degradation, maintains mechanical properties, and allows for the efficient deposition of fusible polymer coatings while being portable and easy to use, achieving the necessary heat for melting and fusing without exposing materials to harsh oxidative environments.
Implementation Method 1
a flame or plasma is projected from a tube and a stream of the polymer (or other fusible powder) is introduced into the projected flame or plasma. In the flame or plasma, the polymer particles are heated and melted
Implementation Method 2
the fusible polymer particles or other materials are introduced into the heated carrier gas stream that melts the particles while propelling them toward the target surface
Implementation Method 3
when they impinge on the surface, they 'splat' (flatten) and fuse together to form a more or less continuous coating
Data Source
AI summary
An apparatus and method for forming a fusible coating or structure comprising a combustor that is operative to combust a fuel and contain the resulting flame to produce combustion products; means for cooling the combustion products to produce a hot carrier gas stream; and means for introducing fusible material into the hot carrier gas stream.