The principle of polymer’s flame spray application (FSA) was originally borrowed from metal flame spraying technology. Coating touches more decorative properties and has restrictions on type of used polymers. Spraying is more generic definition which emphasizes the functionality of the coating.
Each of these methods has its own advantages and disadvantages that determine its effective scope. It is based on the geometric parameters of coated parts and products, their design, technological features and future operating environment. The only factor that brings together all of this ways is heat treatment, which is necessary to form a stable adhesive bond between primer and polymer. The first two methods involve a complex of operations and presence of special booths, bathtubs and ovens. Therefore, the first and the main limitation of their use concern fixed and large-sized products. In this case, the only cost-effective and simple are methods of thermal jet spray, allowing forming a polymer coating in a single operation.
At present, many important questions about FSA are not yet fully clear. Difficulties in its studying are created because of complexity of combustion and heat transfer processes, parameters dependence on a variety of factors.
Before we come closer to development of equipment for the thermal jet powder coating, we conducted a systematic analysis of the issue. We have studied in detail the structure and experience of both modern facilities and first created in the USSR in late 80-ies. The first gas-oxygen thermal sprayings were very good at powder spraying of polyvinyl butyral, polyamide powders, and a select group of foreign powders. In recent years a greater interest have gas thermal spraying, which provides powder coating by polymers with melting points from 365 K to 670 K.
We have conducted technical consultations with Paton Electric Welding Institute, with well-known manufacturer of flame spraying equipment Xiom Corporation (USA). We have analyzed applications, modern and advanced level of industrial implementation of this technology in developed countries (USA, Britain, Italy). By the way, the US has implemented more than 400 installations.
We establish a sufficiently cooperation with the largest producer of thermoplastic powder coatings — Pulron (Pulver -Turkey). The goal is to achieve technical advice on development of technological processes and creation of new compositions of thermoplastic powder coatings for special purposes. Currently, we offer Plascoat Systems Limited products in Ukraine, and consider it the main material in industrial application of flame spraying method.
Undoubtedly, the quality of formed coating largely depends on the chemical nature of polymeric material, its size and shape of dispersed particles, their density, moisture, thermal and electrical properties. Moreover, maintaining of strict technological rules of surface preparation is very important from the point of view of adhesive contact formation. However, as the theory and practice show, the main reason lies in the initial heat treatment cycle. Its task is to give an adequate supply of heat and kinetic energy to powder particles.
Based on our analysis of literature data and results of mathematical modeling of complex engineering calculations, industrial device MFSS (p) -1-50 was designed and built. It is used for manual application of powder polymeric coatings on surfaces prepared by flame spraying.
General view of installation is shown in the photo
MSPU (p) -1-50 is currently in an active stage of industrial testing.
Consider the points.
Activation of coated surface is achieved by exposing. It means temperature rise, creation of stress and increase of surface roughness.
It is much harder to control spraying regimes. This problem is more related to the technical implementation of the equipment.
Effective modifiers may be dispersed metals and their oxides.
The validity of these findings and conclusions is confirmed by necessary volume and repeatability of experimental data.