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The principle and application of flatting agent
For more information : Matting extinction principle and its application related matting agent is sometimes necessary depending on the use of semi-gloss or matte powder coating . To reduce the gloss coating , matting agents are commonly used fine silica, talc , stearic acid , aluminum stearate, calcium stearate , low molecular weight thermoplastic resin. To get matting effect , the following methods can be used : a, the cured powder coating at different speeds , and mixed with a dry mixing method , the resulting coating film gloss decreased , play the role of extinction . Since high reactivity rapidly solidified powder coatings , the slower the continuous phase of the resin curing reaction hindered leveling , the final cured coating loses luster. Although this method is effective , but increased manufacturing processes and costs. b, add a thermoplastic resin. Adding the epoxy powder coating of cellulose acetate , polyester powder coating is added in finely powdered low molecular weight polyethylene , a polypropylene resin can be obtained extinction powder coatings. Gloss coating as manufacturing conditions. Because the thermoplastic resin is added , will affect the storage stability of the powder coating , so the added amount is limited to 2-3% of the amount of resin . c, with a special role of extinction curing agent. d, added with a filler extinction effect . Add ultrafine silica , talc and other fillers to make shiny decreased significantly. In particular filler particle size has a great influence on the film gloss . Larger the particle size , the lower gloss . It should be noted that increasing the amount of filler , causes the formation of a coating film and the mechanical strength. In epoxy powder coating , calcium carbonate particle size on the film gloss table . The acrylic , polyester powder coating superfine silica and kaolin coating can be obtained extinction . In addition , adding polyethylene wax , hydrogenated castor oil wax coating can be obtained extinction . Paint the light extinction principle and its application in recent years , China's paint industry in the ascendant , paint production has also leapt to the forefront of the world , forming a group of related industries , and actively promote the technological revolution in the field of traditional painting and development . In the light of this high-gloss paint during its bright color, bright and so loved by consumers , and for a long period of time dominate the paint market. However, with the continuous improvement of people's living standards , while consumers feel the light of the high-gloss reflective coating film after more serious , harmful to the human eye ; hand consumers increasingly prefer the aesthetic ideas of leisure, fashion and personalization. Coupled with China's automotive and appliance industries booming demand . These factors led to the appearance of the people to have a soft , low gloss coatings has increased dramatically. It also makes how to produce coatings having become Extinction Performance Coatings designers must consider. Sheen and gloss of a factor 1 Determination of luster and gloss to the surface of the object light projected light reflection occurs , the surface reflectance of light called sheen . Different surface gloss is not the same , to measure the surface reflectance of the light size , known gloss. Gloss, expressed as a percentage . The higher the surface gloss , the more its ability to reflect light intensity , the higher the brightness . The size of the glossiness was measured by optical gloss . According to the size of gloss , paint can be divided into light, matt , matt and so are several . Classification of gloss paint ( with a 60 ° specular glossiness ( i.e. the angle of incidence of 60 °) classified as an example ) : matt coating: gloss <10% ; matt coating: 15 to 60% gloss ; light coating: gloss> 60%. (2) the factors that affect the gloss ① the surface roughness of the coating film surface gloss and surface roughness are closely related. When the light strikes the surface , some will be absorbed by the object , reflection and scattering will occur part , there are some refraction occurs . The smaller the surface roughness , were more light reflected , the higher the gloss . Conversely , if the uneven surface , the scattered light increases, leading to reduced gloss . Human visual can feel the roughness of the surface luster (h), the use of micro surface theory , according to the formula : h = λ / cosα calculated , wherein the wavelength of incident light into the human ; α is the incident angle . Take for example 60 °, the angle of incidence can be calculated h = 1.1μm, when the surface roughness of h is larger than 1.1μm , it will show uneven , reduced gloss . ② paint brush coating film formation on the surface of the object , through solvent evaporation and curing film ( for the purposes of solvent-based paints ) . Paint film formation of the coating film surface roughness and gloss essential. In the wet film stage , the solvent by the solvent evaporation rate controlled by the diffusion of the coating film surface , the solvent evaporation rate of the components is not very different , it is possible to obtain a high gloss surface ; the contrary, when the solvent in the wet components film phase evaporation rate is not the same, it will tend to form polymer molecules curl , or precipitated particles or groups of different sizes into a bar, showing uneven coating surface . In the dry phase , the solvent is mainly affected by the solvent evaporation rate was controlled by the diffusion coating the whole , but also on the coating film surface roughness impact. Furthermore , during the formation of the coating , with the solvent evaporation , the film becomes thinner and contraction , some of the coating weight of the suspended particles will rearrange the paint surface , resulting in uneven coating surface . ③ pigment fine particle size and distribution of coating material in the color ( fill ) material particle size and size distribution are important factors that affect the gloss of the coating . People in the study found that when the pigment particles have a diameter less than 0.3μm only when you can get a high gloss coating . Because: the coating of the pigment dispersion particles in the coating film made of a certain thickness , and dried, only the top part of the pigment particles of the ground projection , a pigment particle diameter of less than 0.3μm ionic surface roughness of the coating film caused by no more than 0.1μm. When the pigment has an average particle diameter of between 3 ~ 5μm , matting effect can be obtained a good coating film. In addition to these three factors can affect the coating film surface gloss , the pigment volume concentration (PVC), the pigment dispersion and the coating film surface reflection properties of the surface structure and other factors can also affect the coating surface gloss . Wherein , with the increase of the pigment PVC coating film surface gloss , first lower limit of the pigment volume concentration (CPVC) occurs at the minimum value and then increases along with the PVC , the gloss is increased. When the determined type and amount of the pigment dispersion as possible , the higher the gloss of the coating surface . Two coatings Extinction Extinction problem is the use of a certain way so that the coating surface gloss down. 1 the surface of the light extinction principle gloss coating produced with the mechanism and factors affect the gloss , it is believed that various means extinction , the smoothness of the coating damage , microscopic roughness of the coating film increases , reducing the surface coating of the light reflections. Chemistry can be divided into physical extinction and extinction in two ways. Physical extinction principle: adding matting agent , the coating film formation process , the surface uneven , increasing light scattering and minimize reflections. Eliminating chemical coatings alone against graft material such as polypropylene introduce some kind of structure can absorb light or a group to get the low gloss . 2 Extinction Methods ① matting agent in today's coatings industry , it is generally used is added matting agent approach. Are the following categories : ( 1 ) a metallic soap is a metal soap early often used as a matting agent , it is mainly a metallic stearates, such as aluminum stearate , zinc stearate , calcium stearate , hard magnesium stearate , etc. Applications where aluminum stearate up . Extinction of the metallic soap and coatings based on its principle of incompatibility of components , it is in very fine particles suspended in the coating , when the distribution of the coating film surface , the coating surface micro-roughness , reduces coating film surface reflection of light to achieve the purpose of matting . ( 2 ) Wax Wax is applied more widely used earlier as a matting agent , it belongs to the organic suspended matting agent . After the coating application , with the solvent evaporation , precipitation of the wax coating to fine crystals suspended in the coating surface , forming a rough surface of the light scattering and play the role of extinction . Wax as a matting agent is characterized by ease of use , and can impart a good feel and water film , heat resistance , anti- stain resistance . But the wax layer formed on the surface after the coating will prevent solvent evaporation and oxygen penetrate and affect the coating drying and overcoating . Future development trend is synthetic polymer wax and silica and used to get the best matting effect . ( 3 ) functional fines extender pigments , such as diatomaceous earth , kaolin, fumed silica , etc. are used exclusively for matting features fine material , it belongs to the inorganic filler matting agent . Drying the coating , the fine particles are formed on the surface micro- roughness of the coating film , and reduce the light reflection obtained extinction appearance. Such matting matting effect subject to many factors . Silica , for example, it is used as a matting agent, the pore volume of the particles , the average particle size and size distribution , dry film thickness and particle surface is treated and other factors will affect its extinction effect . Experiments show that a large pore volume , particle size and particle size distribution and the dry film thickness of the silica to match their performance is more excellent matting . In addition to these three types of matting agent used , some drying , such as: tung oil coating can also be used as a matting agent . It is the use of the conjugated double bond tung high reactivity , the coating of the bottom cross-linking of different speeds so that the coating surface irregularities to achieve the matting effect . In order to obtain low-gloss paint , matting agents played an irreplaceable role . But it is in use, there are still many defects wait improvements, such as matting agent selection and more demanding conditions of use ; the Company pursuant to the requirements of customers of different matting agent .
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