Analysis of the formulation of heat-resistant epoxy powder coatings (for performance)

Heat-resistant powder coating refers to a protective powder coating that can withstand high temperatures above 200 degrees C for a long time, apply the film unchanged color, do not destroy, and still maintain appropriate physical and aesthetic properties. The heat resistance of silicone powder coating is relatively high, but its high price, the initial appearance and mechanical performance is not very good, the curing temperature is high, and it is very difficult to obtain long-term resistance to high temperatures above 400 degrees.
the heat resistance of the epoxy resin itself is worse than that of silicone resin, but its performance is more comprehensive, and by changing and adding appropriate curing agents and pigments, better heat resistance performance can also be obtained . As a result, heat-resistant epoxy powder coatings are widely used.
1, heat-resistant epoxy powder coating performance requirements
1.1 heat resistance
heat resistance is the most important performance indicators, some products may not be long-term use at a certain high temperature, therefore, heat resistance can be divided into long-term and short-term two. According to the performance requirements of the object of use and other aspects, select the appropriate modified epoxy resin, curing agent and pigment filler, in order to achieve the goal of cheap and beautiful.
1.2 mechanical properties
including initial and late mechanical properties. Due to certain restrictions on the selection of curing agents and pigments, its mechanical properties can be slightly reduced compared to the requirements of general powder coatings, but the mechanical properties of the later stage can not be reduced too much, which is important.
1.3 anti-corrosion properties (including chemical resistance)
epoxy resin corrosion resistance is better, therefore, epoxy powder coatings can fully meet this requirement.
1.4 appearance
including flatness, gloss, color and other performance. Flatness can vary depending on the object being used. Slight orange peels should generally be allowed. Gloss mostly requires flat and light, which is perfectly achievable. As for color, especially light color, it is difficult to do a little unchanged. It can be solved by the appropriate addition of antioxidants and blocked amines.
1.5 storage stability
because it is not high temperature fast solidification, and the choice of resin Tg is high, so storage stability should be no problem.
2, heat-resistant epoxy powder coating raw materials
2.1 epoxy resin type selection
generally using BPA epoxy resin. Other good heat-resistant epoxy resins are:
(1) bisphenol A phenolic epoxy
:
solution point 65 degrees C, epoxy equivalent 201, Tg -224 degrees C; The structure is:
(2) cyclophenol-type epoxy
melting point 110 to 115 degrees C, epoxy equivalent 240 to 275 degrees C, Tg s 300 degrees C. Melting viscosity is low and bonding force is strong. Structured as:
cyclophenol epoxy structure (3) dibenzene epoxy
(YX-4020H (Japanese oiling シエ/C))
structure:
(4)) 4-4'-diamethane four-shrink glyceride
(TGDDM) (ELM434 (Japan's Myuma Chemical)
epoxy equivalent 117 to 134, up to Tg s 240 degrees C. The structure is:
2.2 epoxy resin modified
2.2.1 silicone resin modified
polysilicae modified epoxy resin, not only can reduce the internal stress of epoxy resin, but also increase the flexibility of epoxy resin and high temperature resistance. The active end-base (Si-OH, NH2, alkygen, etc.) of polysilicon and epoxy resin epoxy and hydroxyl reactions are used to generate segmented polymers. For example, the epoxy resin cyclosterone solution and the active silicone xylene solution into a three-mouth flavonoid, add the catalyst triacetylacetone aluminum, heat up to the reflow temperature, after the reaction is completed, decompression steamed out of the solvent, that is, silicone modified epoxy resin. The mechanical mixing of epoxy resin with methyl benzene silicone resin can also achieve the purpose of change.
example:
methyl benzene silicone powder (100 to 250 items) 100 parts
epoxy resin (100 to 250 eyes) 45 parts
lead glass powder (melting point) 450 degrees C, 200 to 400 eyes) 150
Fe2O3 (1 m) 3 parts
the powder coating can withstand 500 to 700 degrees C high temperature without peeling off.
2.2.2 appleamide compound modified
appleamide compound structure:appleamide modified epoxy powder coating formulation and performance as follows:
appleamide compound 30 parts
epoxy resin 70
-line formaldehyde resin
dimethyl methamphetumazole 2 parts
good block resistance
initial shearing follow-up force / (kg.cm-2) 150
heat resistance rate x /%80
: the test piece after 200 degrees C placed 1000h after the determination of the shearing follow force and the initial cut follow-up force ratio.
2.3 nanometer filler modified epoxy resin
with silicone coupled agent through the in-place dispersion polymerization of nano SiO2 epoxy resin composite material, the epoxy resin played a good role in enhancing toughening, and improve the heat resistance of epoxy resin.
nometer SiO2 modified epoxy resin preparation method: in the mixing state of the dried nano SiO2 added to the acetone solution with an even agent, and then with ultrasonic treatment of 30min, the solution and epoxy resin stirred evenly after removing the solvent, heating up to 130 degrees C reaction 1h, after cooling can be. Nano-masked modified epoxy resins can also improve the heat resistance and flame retardant properties of epoxy resins.
of 2.4 curing agents
type of curing agent also has a significant impact on the heat resistance of epoxy resins. Generally speaking, the heat resistance of acidic curing agent is good. The more common curing agents are as follows:
(1) diabenzene (PMDA), melting point 280 degrees C, thermal deformation temperature of 290 degrees C.
(2) phenylconone tetlucodes (BTDA), melting point 227 degrees C, thermal deformation temperature greater than 280 degrees C.
(3) partial benzene triamcinolone, its structure is:
type: R1 - benzene- base, R2 - cyanide ethyl. The chemical name is: pythyl cyanide-2-benzodiamethyl one benzoic acid (commodity nameキュゾ one ル2MZ-CNS, Japan's four-country plant).
(4) boricol resin (FB phenolic resin), based on boric acid, borax, bisphenol A and formaldehyde aqueous solutions, is reduced under NaOH catalysis. Its structure is:
commercialized F-Series curing agent can make epoxy resin resistant to 300 to 400 degrees C high temperature, but still maintain a high bonding strength.
2.5 pigment selection
pigments have a great effect on the heat resistance of epoxy powder coatings, the selection of appropriate pigments, can significantly improve the heat resistance of epoxy powder coatings.
2.5.1 pigments
general inorgeable pigments have better heat resistance, most of which can be used. Black pigments can be made from chromium copper pigments (produced by Sheperd Color). Aluminum powder heat resistance is also very good, but the high temperature is easy to change color;
2.5.2 filler selection
General inorgeable fillers have better heat resistance, which is more suitable for silicon ash powder (calcium silicate) and mica powder. The two can be used alone or in a certain proportion. Models such as: Silicon Ash Powder NyadM400 (Nyco Corporation), Golden Mica Surface325HK (parent company of Surorite Cloud, Canada). Potassium hettanate can also be used, in addition to good heat resistance, but also improve the hardness of the coating, wear resistance, chemical stability and weather resistance, dosing 5% to 30%.
2.5.3 low melting point glass powder
low melting point (400 to 500 degrees C) glass powder is made of silicon oxide, sodium oxide, potassium oxide, boron oxide as raw materials; Usage is 10% to 50%. A small amount of glass fuse can also be added. Low melting point glass powder can also be replaced by pyrethloric acid (BaZr2F10).
3, heat-resistant epoxy powder coating formulation example
(1) coil epoxy powder formulation and performance as follows:
epoxy resin (Epikote1001) 15 parts

epoxy resin (Epikote1002) 15 parts
epoxy resin (Epikote 1007) 30 parts
formaldehyde epoxy resin 40
Calcium silicate 35
CaCO335
leveling agent 0.3 parts
butylehyde resin 3 parts
dibenzone tetramine 24.5 parts
formaldol resin (OCN-120) 9 parts
thyrene 0.5 parts
solidification condition: 180 degrees C, 30%.
Tg147 degrees C
gelding time (200 degrees C)/s25
thermal resistance (450 degrees C, 5min) no change (variable color)
(2) formula for curing epoxy powder with parabens-mide And the performance is as follows:
epoxy resin (Epikote1007) 20 parts
epoxy resin (Epikote 1004) 20 parts
-line phenolic epoxy resin (EPPN201) 40 parts
-line formaldehyde ring Oxygen resin (EPCN104) 20 servings
silica ash powder (or mica powder) 30 parts
CaCO330 parts
leveling agent 0.3 parts
double cyanide 2 parts
partial benzene-methane curing agent 6
good appearance gel time (200 degrees C) / s10 to 11, gelding time (after storage) / s8 to 9, heat resistance / c450 to 480, storage stability (40 degrees C, 7d) is good.
4, the study conclusion
there are many varieties of polymers resistant to high temperature, but there are still some difficulties and problems in preparing powder coatings that meet the requirements for all aspects of performance. Powder coatings with different high temperature requirements (200 to 600 degrees C) can be made with epoxy resin modified and selected with appropriate curing agents and pigments. Heat-resistant epoxy powder coatings can be widely used in home appliances: such as barbecue ovens, heaters, high-power lighting, as well as high-temperature parts of machinery and equipment, such as smoke pipes, high-temperature furnaces, petrochemical devices, aircraft, missiles, aerospace equipment and other coating protection. Heat-resistant epoxy powder coatings can also be used for coating electrical insulation materials. It can also be used as a flame retardant powder coating using brominated epoxy resins or by adding appropriate flame retardants.