The factors affecting the spraying area of aluminum profiles with powder coating are discussed briefly

Abstract
By collecting a large amount of data in the actual spraying process of an aluminum profile factory, combined with the relevant experiments, the main factors affecting the spray area under the same spraying process are analyzed, and the control idea of improving the powder spraying area is put forward.
0 Introduction
With the aluminum profile enterprises energy conservation and emission reduction awareness and powder cost awareness, aluminum profile companies pay more and more attention to powder consumption, for different aluminum profiles to develop different methods of evaluation, some companies to each ton of profile needs to be sprayed powder weight to judge, and some companies are based on the average number of kg of powder spray squares to judge. This paper mainly discusses the main factors affecting the square size of each kg powder coating, and mainly refers to the total area of the sprayed aluminum profile per kg of powder (the total area refers to the decorative area of the profile and the sum of the non-decorative area)

. According to the actual production situation, the spraying process can be considered unchanged, from the powder electrostitectrecture spraying working principle and the actual spray data analysis of an aluminum profile factory to determine the impact of the total area per kg of powder spraying (the following referred to as spray area) size factors are mainly 4 aspects: First, the powder coating itself (formula, powder particle size distribution and mobility) factors;
1 The main factor affecting the total area of spraying is the powdering rate of powder
coatings in the same conditions as other external conditions (e.g. construction process, profile structure, etc.). According to the principle of powder electrostectrectrulation spray, the main adsorption force of electrostectrectrulation is the electric field force of powder particles. The powder rate on the powder depends mainly on how charged the powder particles are. According to Coulomb's law, in a certain period of time, the charge of powder coating particles has the following relationship:
type: Qs ε - powder particles with charge; d - particle size of powder particles; E- Plus electric field strength.
, to improve the charge capacity of powder particles, can improve the powder rate of powder coating, powder rate increased, the total area of spray will be increased under other conditions.
(1) can be known to affect the charge capacity of the powder ε dielem constant, d powder particle size, E electric field strength.
the most important influence on dielem constants in the composition of powder coatings is the base material in the formulation. For the powder coating substrate used in outdoor aluminum profiles are basically the choice of polyester resin, dielectic constant is basically close, so the powder coating dielectic constant has an impact on the main content of the substrate, the higher the general base content is more easily charged, then the higher the powder rate. Usually by testing the gray fraction of powder coating (refers to the powder coating in the Maffer furnace after 800 degrees C calcination residue content) to indicate the content of the substitin, the smaller the general gray, the less inorgeable material in the powder coating, that is, less fillers and inorgeable pigments, so gray fraction is basically pigments and fillers accounted for the powder coating quality percentage. Then the lower the proportion of pigments and fillers, the higher the content of the base material accordingly. The larger the dielecyte constant, the higher the powder rate of the powder, and the larger the relative spray area. Because each powder manufacturer to control the cost, in the powder coating added different content of fillers, so the gray content of different powder plants is a certain difference, the experiment selected 6 powder suppliers of products for ash testing, comparative analysis results see Table 1.
, the dielecyte constant is also related to the absorbent (water content) of the powder, and the slight moisture absorption reduces the charge of the powder belt and the powder rate decreases.
Further, the particle size distribution of the powder has a greater effect on the powder rate, and for ultra-fine powder (particle size<10 m of powder), it is also easy to be drawn away by the wind due to its small particle size, low charge or lack of power. And ultra-fine powder easy to absorb moisture, on the one hand, make the dielectural constant smaller, so that the overall charge of the powder is reduced, on the other hand, the powder is easy to cluster, so that Venturi tube blockage, spray gun blockage, serious can lead to unable to spray. For powders that are too coarse, due to gravity, it is not easy to absorb static electricity, which may easily land and cause spraying not to go up. Therefore, the powder particle size distribution has a greater impact on the powder rate, generally according to the coating film thickness requirements, powder particle size distribution control in a certain range of powder effect is good, in this range D50 smaller powder coating powder rate is better.
addition, the better the fluidity of the powder coating (related to the glass temperature of the resin, the particle size distribution of the powder, the composition of the formula), the better the atomization effect of the powder coating, which is beneficial to the powder. There are differences in particle size control and mobility between different powder manufacturers, the experiment tested various types of sample powders from 6 powder suppliers, and the particle size distribution range analysis results of each powder coating were found in Table 2. The results of the fluid analysis of powder coatings in each manufacturer are found in Table 3.
according to the above analysis, the factors that affect the spray area of powder coating itself can be compared and analyzed from three aspects, such as base content, particle size distribution range and mobility of powder coating formulation.
2 Effects of different appearance varieties of powder coatings
in normal spraying processes, if the coating film is thicker, it needs to consume more powder when spraying the same area. In a profile factory tracking site spraying found that the film thickness of the sand powder spray is about 50 to 70 m, flat flour spray film thickness is about 70 to 90 m, so the flat flour than the spraying area of the sand powder is less. Then according to the data provided by the company carried out statistical analysis, the manufacturers of sand powder and peace flour spraying the whole area gap comparison analysis results can be seen in Table 4.
from Table 4: The total square size of flat flour spray is smaller than the total area of sand powder spray, on average about 11% less than sand powder.
3 Impact of spray order size structure
Through a statistical analysis of a large number of spray data of an aluminum profile factory: excluding other factors, compare the impact of different powder manufacturers' products on the spray area.
Normal spraying, because of system waste, so in the spray process and spray work pieces are the same, when the spray order monochrome quality is smaller, the more times it will be sprayed color change, resulting in more system waste, then the final calculation of the total area of each kg of spray is smaller. A detailed data analysis of the schedule of all powder coatings for 3 months provided by an aluminum profile company shows table 5 for a comparative analysis of the total area difference between <300 Kg and >300 Kg per kilogram of spray.
From Table 5 can be known: small single than large single spraying of the total area square number than large single spraying of the total area square number is small, the average than large single about 40% smaller, indicating that the size of the order on the powder spraying of the entire area also has a great impact.
4 Impact of aluminum profile work parts structure
General aluminum profile plant statistics are per kg of powder spraying of the entire area, when in fact, the entire area of each profile is composed of decorative area (also known as production area) and non-decorative area. The film thickness of the decorative surface sprayed during the normal spraying process is obviously thicker than that of the non-decorative surface, then the same area of decorative surface than the non-decorative surface needs more powder coating, so the larger the decorative area of the profile accounted for the proportion of the total area, it will result in more powder consumption, that is, the total area per kg of powder spray is less. According to the detailed data analysis and demonstration of the powder spray schedule provided by a profile company for 3 months, the effect of different proportions of decorative area and non-decorative area on spray area can be found in Table 6.
from Table 6, the larger the proportion of the general decorative area to the total area, the lower the total area per kg of powder spray.
5 conclusion
through the detailed analysis of the above four factors, the factors affecting the total area of powder spraying are many. From the point of consideration of powder coating, the content of the base material, the distribution and fluidity of the powder particle size and the appearance of the coating film are important factors, and from the coating point of consideration, the size of the powder coating order, the structure of the aluminum profile work parts, etc. are important factors in determining the size of the spray area.
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