Formation of shrinkage cavity problems in waterborne coatings The surface defects of the coating film are mainly depressions, pinholes, and the edges or thick edges of the corners. There are two kinds of cases on the surface of the coating film, one is a circular depression, and a hexagonal polygonal depression. The depression on the surface of the coating film is caused by the surface tension gradient. The surface tension is uneven due to the change of the composition of the coating and the temperature change. The fluid flows from the low surface tension to the high surface tension, and as a result, a depression is formed on the surface of the fluid, which is also called The Maragoni effect eventually leads to edge bulges, shrinkage cavities that are centered in a circle, or Benaldo vortices with edge ridges and central depressions into hexagonal grooves. The material with low surface tension in the center of the shrinkage cavity exists, and the surface tension of the surrounding paint is poor. This difference is the power of the shrinkage hole formation, which causes the surrounding liquid fluid to flow away from it (the shrinkage source) and flow away. And flow into a depression - shrinkage cavity. The coating forms shrinkage holes during the construction drying process, which has problems with the coating itself and the problem of cleaning the substrate. The surface tension is caused by the presence of low surface tension droplets in the coating itself or due to contamination of the coated surface due to contamination. Uneven, the coating flows from a low surface tension to a high surface tension under the effect of surface tension, resulting in a centrally depressed hole-shrinkage. We classify the unevenness of surface tension as the internal cause of shrinkage formation. In fact, some properties of the coating itself, such as paint viscosity, thixotropy, paint drying speed and film thickness, can aggravate or reduce the flow ability of the coating fluid, which will aggravate or weaken the degree of shrinkage. We classify these factors as shrinking. The external cause of the hole. The internal cause is an inevitable condition for shrinkage, and the external cause can appropriately control or aggravate the degree of shrinkage. After coating application, during the dry film forming process, the surface solvent volatilizes, the concentration of the surface polymer increases, and the viscosity of the coating increases, which causes the surface tension and surface density to exceed the bulk and form a depression. In general, thicker coatings (> 4 mm) of liquid coatings, mainly density gradients drive the flow, and thinner liquid coatings are surface tension gradients that control the flow to form individual shrinkage cavities. Sinograce Chemical produces water based coating,Water-based glue, polyurethane coating,Acrylic solution. visit us sinograce chemical: https://www.sinogracechem.com Get a Quote Now :sales@sinogracechem...

Wood closed primer formula solves the outstanding problem of wood grain Wood bulges and deforms or wood grain protuberant,It is a common problem in wood painting. We discussed the causes and solutions of this problem in this year's topic.In the article on wood grain protrusions - water-based paints, we recommend three technical solutions: 1. Use a saturated coating of 3-4% binder solids. 2. Use a quick-drying coating such as sinograce's SPECIAL RESIN POLYMER PF-136 waterborne acrylic primer primer transparent primer formulation 3. Use a hybrid system, water-based coating and solvent-based coating. After the article was published, some readers wanted to know the formulation of solvent-based coatings for water-based paints. Special offers are as follows: materials weight notes 1. YP3170D alkyd resin 43.00 2. Xylene mixture of isomer 42.00 3. n-butyl acetate 0.10 4. PMA 0.05 total protein 100.00 Solvent - based closed primer formula for wood Formula manufacturing method 1. Curing agent: 40% TDI 2. Paint: curing agent: 5:1 product performance technical indicator Technical index Fineness/cleanliness ≤15 microns Density (kg/l) 1.00±0.001 colour transparent Solid content (W/W) 30.0±1% Viscosity (25 ℃) 13±1s application property good adhesive force 0-1 class transparency Transparent film without blue light The construction scale direct use Sinograce Chemical produces water based coating,Water-based glue, polyurethane coating,Acrylic solution . visit us sinograce chemical: https://www.sinogracechem.com Get a Quote Now :sales@sinogracechem.com Telephone               :+86 0551 63459511

The relationship between film formation and MFFT of waterborne coatings This week, Mr. Li asked us three questions through our questioning water-based paint expert column. This is the second problem: Problem: Film formation above MFFT, no film formation below MFFT, what happens during above or below the MFFT, resulting in film formation? Above MFFT, the emulsion particles are soft and hard below. This phenomenon is associated with glass transition.

Waterborne two-component paint seeds and loss of light - ask water-based paint experts Question: Hello! I have two problems with the double-surface water-based topcoat. One is that when the film is thick, it is easy to produce rash [related to defoaming agent or related to water and curing agent to produce CO2?]. One is a double component. After mixing for 2 hours, it will lose light. What is the reason? Is there a solution? Thank you. Answer: Our team of experts has had a heated discussion about your issue. Because we don't know your specific formula, we only guess based on the phenomenon you describe. Our experts have different opinions about your issue. We will now hand over the views of all the parties we have collected, and we hope to have a multi-faceted reference value for you. View 1: The seedsphenomenon that occurs when you encounter a thick film in a two-component water-based topcoat is due to the "Bernard vortex" phenomenon. Specifically, the solvent in the aqueous resin or the aqueous formulation system is not coordinated during the volatilization process. When the gas is generated, the surface of the paint film is dried and the gas is not discharged, so that dark bubbles or scorpions are formed below the paint film. To solve this problem, you need to adjust the recipe structure, especially to adjust the drying process of the recipe: 1. Pay attention to the drying speed of the resin itself 2. Pay attention to the coordination of additives 3. Pay attention to the choice of surface desiccant As for your second question, this is due to the mismatch between the crosslinker and the resin and other additives in the formulation, and the cross-linking reaction is not normal. It is recommended to adjust the formulation structure and pay attention to the type and amount of additives. View 2: Question 1, if this phenomenon occurs only in thick film, it is likely that it is not caused by the problem of surface tension, that is, it is not necessarily the problem of defoaming. You can use a coating that avoids bubbles, such as scraping, to confirm. Question 2, the two-component system has a certain period of use. After mixing the two components, the reaction starts in the prevention process, the molecular weight increases, and even cross-linking occurs. Intermolecular infiltration is affected during film formation, and it is impossible to form a microscopically flat film, which is macroscopically loss of light. The first and second questions add up to look like you should use better quality resins and crosslinkers. Sinograce Chemical produces water based coating,Water-based glue, polyurethane coating,Acrylic solution. visit us sinograce chemical: https://www.sinogracechem.com Get a Quote Now :sales@sinogracechem.com Telephone               :+86 0551 63459511