The influence factors and improvement methods of powder coating mobility energy

China Coatings Online News Information1, powder coating fluidity and its detection
powder mobility refers to the degree to which powder coating is airflowed in fluidized beds, which is an important basis for evaluating the performance of powder coating construction. The fluidity of powder coatings is usually measured by resting angles or flow coefficients. The resting angle is a direct detection method of powder fluidity, the smaller the resting angle, the better the fluidity. At present, there are two commonly used detection methods for fluidity:
1.1 standard funnel method
(Hall flow meter)
GB/T1482-2010
This method is mainly used to detect the flow of metal powder, measuring the time required for 50g metal powder to flow through standard size funnel holes, unit s/50g, the longer the time, the worse the liquidity, the better the liquidity.
1.2 Natural stacking angle
(resting angle, pile powder angle)
allows powder to flow naturally through a set of screens and accumulate on a flat round plate with a diameter of 1 inch, and when the powder is stacked with round plates, the bottom corner of the powder cone is called the resting angle or the powder angle. The larger the powder angle, the worse the fluidity of the powder, and the better the fluidity.
2, the effect of fluidity
powder fluidity is the basic characteristics of powder, refers to the degree of difficulty of powder flow. Powder fluidity can be related to many factors, such as powder particle size, shape, roughness, dry humidity, etc. Generally speaking, increasing the coefficient of friction between particles can make powder flow difficult. Usually the powder flow of spherical particles is the best, while the particle shape is irregular, small size, rough surface of the powder, its mobility is poor.
In addition, powder fluidity is affected by the adhesion between particles, particle surface if adsorption of moisture, gas or added forming agent will reduce the flow of powder, powder flow directly affects the mixing uniformity, mobility is too poor, easy to adhere to in the mixing, clumps can not mix it evenly.
temperature of the powder coating resin determines the fluidity and storage stability of the powder coating. The glass temperature of T high-polymer is improved, the stability of powder is improved, the lumpness is reduced, and the fluidity of powder coating is improved. The glass temperature increases with the increase of molecular weight, and the glass temperature of the polymer does not change significantly when the molecular weight increases to a certain degree. The glass temperature is too high, the average molecular weight of the resin is large, the melt viscosity is large, the flow is poor, and the mechanical performance of the powder coating film is decreased. In the production of the general selection of resin molecular weight in 2000 to 5000, glass temperature control in the range of 50 to 65 degrees C is more appropriate.
3, the effect of fluidity on powder coating
3.1 on the effect of coating construction
in the process of static spraying of powder coating, the liquid powder, like boiling water, appears very fluffy, flowing effect, from powder barrel to spray gun, powder transmission light, powder from the nozzle atomized well, overcome powder coating grouping and cause spray blocking gun or "spitting powder" and other production anomalies. Poorly liquid powders are reversed in powder drums, resulting in inefficient coating.
3.2 on the production storage process
the fluidity of powder coatings directly affects the storage stability of the product, in the production and packaging process, the powder began to group. As time longer and as the storage process squeezes, the powder begins to harden. Textured powders lose texture effect after spraying, and flat-light powders also experienced steroids.
4, powder coating mobility energy improvement
powder coating mobility and storage stability are closely related, powder storage stability is mainly determined by the glass temperature of resins and curing agents, they occupy a large proportion in the formulation design, so play a more important role. Although the amount of curing agent is small, it has obvious effect on the storage of powder coating. In order to ensure the appearance of the coating film, try to choose a high glass temperature resin and curing agent.
In powder coating formulation, pigment and filler quality score has a significant impact on mobility, powder paint pigment is mainly used to color and improve stiffness, pigment quality fraction is too high resin relatively less, powder coating mobility is worse. At the same time in the formulation design process, as little or no effect on the glass temperature and storage stability of additives, such as less leveling agents, wax-type anti-lighting agents and promoters
Group, after the addition of the adjustment of the powder coating between the film affinity and cohesion, can improve the powder coating anti-clump temperature, improve the storage stability of powder coating, improve the flow of dry powder energy, in addition, when electrostectantic powder spray, so that the powder coating is not easy to block the spray gun, to avoid clumping and sticky wall phenomenon. Hubei Rice Chemical New Materials Co., Ltd. dry powder flow agent 445 belongs to this type of additive.
plus the way to add larger than the surface area, strong moisture absorption capacity of gas phase white carbon black and alumina and other additives, so that powder coating particles form a compartment, reduce the opportunity for powder coating particle collision and condensation, reduce the mutual attraction and friction between powder coating particles, prevent particles from contacting each other, so that powder coating is not easy to group. Hubei Lis anti-blocking agent 466, is an inorganic mineral as the main body, auxiliary organic surfactant, using air flow crushing processing, anti-blocking agent particles and density and powder coating similar. The addition of 0.4%, can be directly added to the finished powder, can also be crushed with the sheet sieve.
5, conclusion,
of powder coatings is the result of a combination of factors. In addition to the main factors discussed above, but also related to other factors, such as commonly used pigments, filler properties and additions, spray operation process conditions, rest angle detection methods, etc. , need scientific and technical personnel in the production of continuous exploration. It is of great significance to discuss the flow of powder coating and improve the control parameters of powder coating formulation and spraying production process.
。