The complete selection logic of defoamers in the system
The selection of defoamers should not only focus on the defoaming effect, but also on the five dimensions of system type, foaming source, construction conditions, side effect risk, and compatibility with the system. Once compatibility fails, it will cause problems such as fish eyes, shrinkage, loss of gloss, decreased adhesion, and paint film defects, which are far more harmful than the bubbles themselves.
I、Firstly, clarify the four core basic prerequisites corresponding to the first step of selection
1. The root cause of the continuous generation of bubbles within the system is the core bubble formation
-Mechanical foaming is caused by the introduction of air during high-speed dispersion, stirring, pumping, immersion coating, and spraying processes, with foam suppression as the core direction while also considering the defoaming effect.
-The chemical reaction foaming is caused by the reaction releasing gas, lotion polymerization, and curing reaction gas production process. It is necessary to select special defoamers that are chemical resistant and reactive resistant.
-The bubbles in the raw materials are caused by the microbubbles brought into the system by lotion, color paste and powder. Defoamer products with targeted microbubble breaking ability are required.
2. Covering water-based, solvent based, solvent-free UV、 A full range of system media categories for five dispersion scenarios of powder slurry
The chemical structures of defoamers corresponding to different media cannot be mixed at all. For example, some grades of organic silicon defoamers are prone to shrinkage in solvent systems, and mineral oil defoamers cannot be used in high light system scenarios.
3. Various process condition parameters corresponding to the entire construction process
Covering temperature (room temperature/baking), shear strength, coating method (spray coating, dip coating, brush coating, inkjet), film thickness parameters, high-temperature baking system should use heat-resistant defoamers to avoid paint film defects caused by high-temperature decomposition.
4. Bottom line of core key indicators for finished product control
Control gloss requirements (high gloss/matte), adhesion, water and boiling resistance, transparency, and no shrinkage fish eye index. The use of mineral oil defoamers should be cautious in high gloss systems.
II、 The core performance characteristics of various types of defoamers and the selection reference content for corresponding adaptation application systems
1. Solvent based system specific defoamer
The defoamer product category mainly consists of acrylic ester, modified silicon, and polymer raw materials as the core components;
Mineral oil defoamers are generally not recommended for direct use in solvent based systems.
2. UV curing system defoamer
Special defoamers that are compatible with UV systems and do not contain interfering free radical polymerization components must be selected. Ordinary water-based defoamers should not be used, otherwise it may cause poor curing problems..
3. Mineral oil defoamer
-The advantages are long-lasting anti foaming effect, low procurement cost, and less likely to cause shrinkage defects in the paint film during application;
-The core weakness is that it will interfere with the high gloss and transparency performance of the system, and the water resistance is in the general level range;
- ✅ Suitable for downstream application scenarios of matte water-based coatings, architectural coatings, and ordinary industrial primers;
- ❌ Not suitable for high gloss paint, ink, UV system, transparent system, and topcoat applications with high water resistance requirements.
4. Compound defoamer (mineral oil silicon polyether compound)
The most widely circulated mainstream product model in the market can achieve an ideal balance between defoaming power and system compatibility;
5. The third generation mainstream organic silicone defoamer product category with polysiloxane as the core active component
Specifically divided into two subcategories: modified polysiloxane and polyether modified organosilicon
-The core advantages are outstanding defoaming efficiency, low addition amount, excellent temperature resistance, and strong ability to break microbubbles;
-The core weakness is the high risk of system compatibility, and excessive addition can easily cause shrinkage and fisheye paint film defects;
- ✅ Suitable for five downstream application scenarios: water-based industrial paint, water-based ink, solvent-free system, baking system, and powder slurry;
- ❌ Attention: The solvent system should use specialized modified silicone defoamers. Directly adding ordinary organosilicon to the solvent system is likely to cause shrinkage defects.
6. Non silicone polyether defoamer
-The core advantage is excellent system compatibility, which almost does not cause shrinkage problems and does not interfere with the original gloss and transparency performance of the system;
-The core weakness is that the defoaming effect is relatively weak, and the effectiveness will significantly decrease when used under high temperature conditions;
- ✅ Suitable for high gloss water-based topcoat, digital inkjet, transparent system, zero tolerance system for appearance defects, suitable for microbubble breaking scenarios, with certain limitations in the ability to eliminate large bubbles.
- ✅ Suitable for most downstream dispersed application scenarios of general water-based coatings and colorants;
- ❌ For special high-end systems such as inkjet and high transparency new material slurries, it is not recommended to directly use universal compound defoamer products.
III、 Quick selection comparison table based on the system
1. Two types of products: solvent based coatings, ink adapted polymer defoamers, and organic silicon defoamers modified with solvents;
2. Special solvent-free defoamers suitable for solvent-free epoxy and PU systems should pay special attention not to interfere with the curing reaction of the system;
3. Ordinary matte water-based industrial primer is compatible with mineral oil compound defoamers, and the selection focuses on the defoaming effect, with cost priority as the core principle;
4. Non silicone polyether or low silicon modified polyether defoamers are preferred for water-based high gloss topcoats and varnishes, with system compatibility as the top priority, sacrificing some defoaming power for a non shrinkage, high gloss paint film effect;
5. Water based ink and screen ink are compatible with modified polyether organosilicon defoamers, taking into account both microbubble breaking and printing leveling effects, and strictly controlling the addition range;
6. The immersion coating system requires long-term foam suppression, and the immersion coating process continuously introduces air. It is preferred to use compound or modified silicon defoamers, and cannot rely solely on instantaneous defoaming effects;
7. Special non silicone defoamer for digital inkjet ink adaptation, with extremely low levels of precipitates, will not cause nozzle clogging failure at all;
8. Ceramic and new energy powder water-based slurries (such as silicon nitride, zirconia, etc.) are adapted with low impurity modified polyether defoamers to avoid introducing silicon pollution that interferes with sintering performance. Organic silicon defoamers are prohibited from use in some application scenarios.
IV、 A crucial point to avoid pitfalls
1. Pay attention to the order of addition
It is recommended to add some defoamers during the pigment dispersion and grinding stage in water-based systems to achieve foam suppression. In the later stage of paint mixing, some defoamers should be added to eliminate the bubbles generated in the later stage. It is not advisable to leave them all at once and add them in large quantities.
2. The more defoamers added, the better
There is a clear critical addition amount: when it is below the critical value, the defoaming effect is insufficient, and when it exceeds the critical value, shrinkage fish eye defects immediately appear. The conventional addition amount is 0.1-0.5% of the total formula, and gradient small-scale tests must be conducted to verify it step by step according to gradients of 0.1%, 0.2%, and 0.3%
3. Special reminder for sintered powder slurries (silicon nitride, zirconia)
High temperature sintering of organic silicon defoamers will result in residual silicon dioxide impurities. If high-temperature sintering is required in the future, non silicon polyether defoamers should be preferred to prevent the introduction of silicon impurities that may affect product performance.
4. To determine whether the selection is qualified, 4 small tests need to be conducted for verification
① Instant defoaming effect;
② Durability of foam inhibition (repeated stirring to see if bubbles return);
③ Coating appearance: whether there are shrinkage pores, fish eyes, or loss of gloss;
④ Storage stability: Hot storage at 50 ℃ for 7 days, check for precipitation and delamination.
Even if the defoaming effect is good, once it causes shrinkage and loss of gloss defects in the system, this defoamer belongs to the category of unqualified system.
V、Common cases of incorrect selection
1. Directly adding water-based organosilicon defoamers to solvent systems can directly cause a large number of shrinkage pores and appearance defects in fish eye paint films;
2. The immersion coating system only uses defoamer products with strong instantaneous defoaming but poor foam suppression performance, which can lead to continuous foaming problems in the production process.
3. The use of mineral oil defoamers in the high gloss varnish system can directly cause appearance defects such as fogging and loss of gloss in the paint film;
4. The use of ordinary organic silicon defoamers in the sintered ceramic slurry system will result in residual silicon impurities after sintering, directly causing performance defects in the product;
