Can epoxy resin be used to make paint without hardener and can it cure naturally?

Introduction of materials

Epoxy resin is a generalized reference to organic polymer compounds containing two or more epoxy groups in the molecule, with the exception of a few, their relative molecular mass is not high. The molecular structure of epoxy resin is characterized by the presence of active epoxy groups in the molecular chain, which can be located at the end of the molecular chain, in the middle, or in a cyclic structure. Due to the molecular structure contains active epoxy groups, so that they can be with a variety of types of curing agent crosslinking reaction and the formation of insoluble, non-melting with three-way network structure of the polymer.

[Edit paragraph]Application characteristics

1, a variety of forms. A variety of resins, curing agents, modifiers, systems can be adapted to almost all kinds of applications on the form of requirements, which can range from very low viscosity to high melting point solid.

2, easy curing. Choose a variety of different curing agents, epoxy resin system can be almost in the temperature range of 0 ~ 180 ℃ curing.

3, strong adhesion. Epoxy resin molecular chain inherent in the polar hydroxyl and ether bonding, so that it has a high adhesion to a variety of substances. Epoxy resin curing low shrinkage, resulting in low internal stress, which also helps to improve the adhesion strength.

4, low shrinkage. Epoxy resin and the reaction of the curing agent used is through a direct addition reaction or epoxy resin molecule in the ring-opening polymerization reaction to carry out, there is no water or other volatile by-products released. They and unsaturated polyester resins, phenolic resins, compared to the curing process shows very low shrinkage (less than 2%).

5, mechanical properties. Cured epoxy resin system has excellent mechanical properties.

6, electrical properties. Cured epoxy resin system is a high dielectric properties, resistance to surface leakage, arc-resistant insulation material.

7, chemical stability. Usually, the cured epoxy resin system has excellent alkali resistance, acid resistance and solvent resistance. Like other properties of cured epoxy system, chemical stability also depends on the selected resin and curing agent. Appropriate selection of epoxy resins and curing agents can be made to have special chemical stability properties.

8, dimensional stability. The combination of many of the above properties, so that the epoxy resin system has outstanding dimensional stability and durability.

9, mold resistance. The cured epoxy resin system is resistant to most molds and can be used in harsh tropical conditions.

[edit]Classification of types

According to the molecular structure, epoxy resins can be broadly divided into five categories:

1. Glycidyl ether epoxy resins

2. Glycidyl ester epoxy resins

3. Glycidyl amine epoxy resins

4. Linear aliphatic epoxy resins

5, Alicyclic epoxy resins

The most used epoxy resins in the composite materials industry are the first type of glycidyl ether epoxy resins, which are mainly bisphenol propane epoxy resins (referred to as bisphenol A-type epoxy resins). The second is glycidylamine epoxy resin.

1. Glycidyl ether epoxy resins

Glycidyl ether epoxy resins are made by polycondensation of phenols or alcohols with epichlorohydrin containing active hydrogen.

(1) Diphenolpropane-type epoxy resins Diphenolpropane-type epoxy resins are made by polycondensation of diphenolpropane and epichlorohydrin.

Industrial diphenol propane epoxy resin is actually a mixture of molecules with different degrees of polymerization. Most of these molecules are linear structures containing two epoxy group ends. A few molecules may be branched and very few terminate with a chlorohydrin group rather than an epoxy group. Therefore, the epoxy group content and chlorine content of epoxy resins have a great influence on the curing of the resin and the properties of the cured product. Industry as a resin control indicators are as follows:

① Epoxy value. Epoxy value is to identify the nature of the epoxy resin is the most important indicators, industrial epoxy resin model is different according to the epoxy value to distinguish. Epoxy value is the amount of epoxy group contained in each 100g resin. The reciprocal of the epoxy value multiplied by 100 is called the epoxy equivalent. The meaning of the epoxy equivalent is: containing 1 mol epoxy group of epoxy resin grams.

② Inorganic chlorine content. Chlorine ions in the resin can be complexed with amine curing agent and affect the curing of the resin, but also affect the electrical properties of the cured resin, so the chlorine content is also an important indicator of epoxy resin.

③ Organic chlorine content. Organic chlorine content in the resin marks the molecule does not play a closed-loop reaction of the part of the chlorohydrin group content, its content should be reduced as far as possible, otherwise it also affects the curing of the resin and the performance of the cured material.

④ Volatile fraction.

⑤ Viscosity or softening point.

(2) Phenolic multi-epoxy resins Phenolic multi-epoxy resins include phenol formaldehyde-type, o-cresol formaldehyde-type multi-epoxy resins, which, compared with di-phenol-based propane-type epoxy resins, contain more than two epoxy groups in the linear molecule, and therefore have a high cross-linking density of the cured product, which has excellent thermal stability, mechanical properties, electrical insulation, water resistance and corrosion resistance. They are made by polycondensation of linear phenolic resin with epichlorohydrin.

(3) other polyhydroxyphenolic glycidyl ether epoxy resins This type of resin has a practical representative of: resorcinol epoxy resins, resorcinol-formaldehyde epoxy resins, tetraphenol ethylene-based epoxy resins and tris(hydroxyphenyl)methane-type epoxy resins, these multifunctional glycidyl ether resins have a high heat distortion temperature and rigidity after curing, and can be used individually

or mixed with the general E-type resin ***. These polyfunctional glycidyl ether resins have high heat distortion temperature and rigidity after curing, and can be mixed with general-purpose E-type resins*** for high performance composites (ACM), printed wiring boards and other matrix materials.

(4) aliphatic polyol glycidyl ether epoxy resin aliphatic polyol glycidyl ether molecules containing two or more epoxy groups, the majority of these resins are very low viscosity; most of the long-chain linear molecules, and therefore flexible.

2, other types of epoxy resins

(1) Glycidyl ester epoxy resins Glycidyl ester epoxy resins and diphenol propane epoxide resin comparison, it has a low viscosity, the use of good workmanship; high reactivity; bonding force is higher than the general-purpose epoxy resins, curing material mechanical properties; good electrical insulation; good weather resistance, and good resistance to ultra-low temperatures in the ultra-low temperature conditions, still has a good performance. Under the condition of ultra-low temperature, it still has higher bonding strength than other types of epoxy resin. Good surface gloss, light transmission, good weather resistance.

(2) Glycidylamine epoxy resin The advantages of this type of resin is multi-functionality, high epoxy equivalent, crosslinking density, heat resistance significantly improved. On the previous domestic and foreign has used glycidylamine epoxy resin superior adhesion and heat resistance, to manufacture carbon fiber reinforced composite materials (CFRP) for aircraft secondary structure materials.

(3) alicyclic epoxy resin This type of epoxy resin is made by the double bond of alicyclic olefin by epoxidation, their molecular structure and bisphenol propane-type epoxy resins and other epoxy resins have a big difference, the former epoxy group are directly connected to the alicyclic ring, and the latter's epoxy group are epoxy propyl ether connected to the core of benzene or aliphatic hydrocarbons. The cured alicyclic epoxy resin has the following characteristics: ① high compression and tensile strength; ② long-term exposure to high temperatures can still maintain good mechanical properties; ③ arc resistance, UV aging resistance and weather resistance is good.

(4) aliphatic epoxy resin This type of epoxy resin molecular structure is not only no benzene nucleus, there is no aliphatic ring structure. There is only a fatty chain, the epoxy group is connected to the fatty chain. Epoxy polybutadiene resin cured strength, toughness, adhesion, resistance to positive and negative temperature performance are good.

[Edit]Guidelines

Epoxy resin and epoxy resin adhesive itself is non-toxic, but due to the solvents and other poisons added in the preparation process, so many epoxy resins are "toxic", in recent years, the domestic epoxy resin industry is through the waterborne modification to avoid the addition of other ways to keep the epoxy resin "non-toxic". Epoxy resin "non-toxic" color. At present, the vast majority of epoxy resin coatings for solvent-based coatings, containing a large number of volatile organic compounds (VOC), toxic, flammable, and therefore harmful to the environment and human body.

Epoxy resin and additives are generally used at the same time, in order to obtain the value of the application. Additives can be selected according to different purposes, commonly used additives have the following categories: (1) curing agent; (2) modifier; (3) filler; (4) diluent; (5) other.

One of the curing agent is essential additives, whether for adhesives, coatings, casting materials need to add curing agent, otherwise the epoxy resin can not be cured.

Due to the use of different performance requirements, the epoxy resin and curing agent, modifier, filler, diluent and other additives also have different requirements. Now their selection methods are outlined below:

(a) the selection of epoxy resins

1, from the use of choice

As a bonding agent, it is best to choose a medium value of epoxy (0.25-0.45) of the resin, such as 6101, 634; as a casting material, it is best to choose a high value of epoxy (> 0.40) of the resin, such as 618, 6101; as a coating for the general selection of low epoxy value (> 0.40) of the resin, such as 618, 6101; as a coating for the general selection of low epoxy value (>) of the resin, such as 618, 6101. For coating, generally use low epoxy value (<0.25) of the resin, such as 601, 604, 607, 609, etc..

2, from the mechanical strength of the selection

Epoxy value is too high resin strength, but more brittle; epoxy value of high and low temperatures in the middle of the strength is good; epoxy value of low high temperature strength is poorer. Because the strength and the size of the cross-linking degree is related to the epoxy value of high curing degree of cross-linking is also high, epoxy value of low curing degree of cross-linking is also low, so it causes the difference in strength.

3, from the operation requirements on the choice

Do not need high temperature resistance, strength requirements are not great, hope that the epoxy resin can be fast drying, not easy to lose, you can choose epoxy value of the lower resin; such as hope that penetration is also better strength, you can choose epoxy value of the higher resin.

(B), the choice of curing agent

1, curing agent type:

Commonly used epoxy resin curing agent has fatty amine, alicyclic amine, aromatic amine, polyamide, anhydrides, resins, tertiary amine, and in the role of the photoinitiator, ultraviolet light or light can also make the epoxy resin curing. Room temperature or low temperature curing generally choose amine curing agent, heating curing is commonly used anhydride, aromatic curing agent.

Epoxy value is to identify the quality of the epoxy resin is the most important indicators, epoxy resin model division is based on the different epoxy value to distinguish. The epoxy value is the number of grams of epoxy group contained in 100 grams of resin.

2, the amount of curing agent

(1) amine crosslinking agent calculated according to the following formula:

Amine dosage = MG/Hn

where:

M = molecular weight of the amine

Hn = the number of active hydrogens contained in the number of

G = epoxy value (per 100 grams of epoxy resin contained in the number of epoxy equivalents)

The scope of change is not much.

The range of change is not more than 10-20%, if too much amine is used to cure, it will make the resin brittle. If too little is used, the curing is not perfect.

(2) When anhydride is used, it is calculated according to the following formula:

Anhydride dosage = MG (0.6~1)/100 where:

M=molecular weight of anhydride

G=Epoxy value (0.6~1) is the experimental coefficient

3. Principle of selecting curing agent: curing agent has a big impact on the performance of epoxy resin, and is generally selected according to the following points. The principle of selecting curing agent: the curing agent has great influence on the performance of epoxy resin, generally select according to the following points.

(1), from the performance requirements on the choice: some require high temperature resistance, some require good flexibility, some require good corrosion resistance, according to different requirements to choose the appropriate curing agent.

(2), from the curing method on the choice: some products can not be heated, you can not choose heat-curing curing agent.

(3), from the applicable period on the choice: the so-called applicable period, that is, refers to the epoxy resin to join the curing agent from the time until the end of the time can not be used. To be applicable to a long period of time, the general choice of anhydride or latent curing agent.

(4), from the safety of choice: the general requirements of small toxicity is good, to facilitate safe production.

(5), from the cost of choice.

(C), the choice of modifiers

The role of modifiers is to improve the epoxy resin tanning, shear, bending, impact resistance, improve insulation properties. Commonly used modifiers are:

(1), polysulfide rubber: can improve the impact strength and peeling resistance.

(2), polyamide resin: can improve the brittleness, improve adhesion.

(3), polyvinyl alcohol tert-butyl aldehyde: improve impact tanning resistance.

(4), nitrile rubber: improve impact tanning resistance.

(5), phenolic resins: can improve temperature and corrosion resistance.

(6), polyester resin: to improve the impact tanning resistance.

(7), urea-formaldehyde melamine resin: increase chemical resistance and strength.

(8) Furfural resin: improve static bending properties, improve acid resistance.

(9), vinyl resin: improve peeling resistance and impact strength.

(10), isocyanate: reduce moisture permeability and increase water resistance.

(11), silicone resin: improve heat resistance.

The amount of polysulfide rubber can be between 50-300%, need to add a curing agent; polyamide resin, phenolic resin dosage is generally 50-100%, polyester resin dosage is generally in the 20-30%, you can no longer add a curing agent, but also a small amount of curing agent to promote a faster reaction.

Generally speaking, the more modifier dosage, the greater the flexibility, but the heat distortion temperature of the resin product is correspondingly lower.

In order to improve the flexibility of the resin, it is also common to use toughening agents such as: dibutyl phthalate or dioctyl phthalate.

(D), filler selection

The role of filler is to improve some of the properties of the product, and improve the heat dissipation conditions of the resin curing, with the filler can also reduce the amount of epoxy resin, reduce costs. Different fillers can be used for different purposes. The size of the best less than 100 mesh, depending on the use of dosage. Commonly used fillers are as follows:

Filler name function

Asbestos fiber, glass fiber to increase the toughness, impact resistance

Quartz powder, ceramic powder, iron powder, cement, adamantine to improve the hardness

Alumina, ceramic powder to increase the adhesion to increase the mechanical strength

Asbestos powder, silica powder, high-temperature cement to improve the thermal resistance

Asbestos powder, quartz powder, stone powder Reduce shrinkage

Aluminum powder, copper powder, iron powder and other metal powder Increase thermal and electrical conductivity

Graphite powder, talcum powder, quartz powder Improve anti-abrasive and lubricating properties

Diamond and other abrasive materials Improve anti-abrasive properties

Mica powder, porcelain powder, quartz powder Increase the insulating properties

Various kinds of pigments, graphite Color

In addition, according to the data reported that the appropriate amount (27-35%) of P, AS, Sb, Bi, Ge, Sn, Pb oxides added to the resin can be maintained under high heat and pressure adhesion.

(E), the choice of diluent

Its role is to reduce viscosity, improve the permeability of the resin. Diluent can be divided into two categories of inert and active, the amount generally does not exceed 30%. Commonly used diluents are as follows:

Active diluents

Name Brand Use Remarks

Diglycidyl ether 600 ~30% need to be added to the calculation of the amount of curing agent

Polyglycidyl ether 630 Ditto ditto ditto ditto

Butyl ether of propylene oxide 660 ~15% ditto ditto ditto

Phenyl ether of propylene oxide 690 ditto ditto ditto ditto ditto

Di-epoxypropylene ether 690 ditto ditto ditto ditto

Ethyl di-epoxypropane ether 669 Ditto Ditto

Propyl tri-epoxypropane ether 662 Ditto Ditto

Inert Diluent

Name Dosage Remarks

Xylene ~15% No more curing agent

Toluene Ditto Ditto

Benzene Ditto Ditto

Acetone Ditto Ditto

Before adding the curing agent, it is necessary to check all the materials used, such as resin, curing agent, filler, modifier, diluent, etc., and the following requirements should be met:

(1), no moisture: water-containing materials should be dried first, and solvents containing a small amount of water should be used as little as possible.

(2), purity: in addition to water impurities other than the content of the best in less than 1%, if the impurities in the 5-25% can be used although the right to use, but to increase the percentage of the formula. When used in small quantities, it is better to use reagent grade.

(3), to understand the failure of each material.

In the absence of acceptance conditions of the plant, it is best to do a small sample test before use according to the formula.

(F), the three stages of curing

1. Liquid - operating time

Operating time (also working time or period of use) is a part of the curing time, after mixing, the resin/hardener mixture is still liquid and can be worked and suitable for application. To ensure a reliable bond, all construction and positioning work should be done during the curing operation time.

2. Gel-into-cure

The mixture begins to enter the curing phase (also known as the ripening phase), when it begins to gel or "mutate". At this point the epoxy has no possibility of working for a long time and will lose its viscosity. It cannot be disturbed in any way at this stage. It will become a hard rubbery soft gel that you will be able to move with your thumb.

Because the mixture is only partially cured at this point, the newly applied epoxy can still be chemically linked to it, so the untreated surface can still be bonded or reacted to. In any case, the ability to do this diminishes as the mixture nears cure

3. Solid - final cure

The epoxy mixture reaches the stage of curing into a solid, which can then be sanded and shaped. At this point you can no longer press it with your thumb, at this point the epoxy has about 90% of its final reaction strength, so you can remove the retaining clips and leave it at room temperature for a number of days while it continues to cure.

At this point the newly used epoxy resin can not be chemically linked to it, so the epoxy surface must be properly pre-treated such as sanding, in order to get a good bonding mechanical strength.

[edit]Main domestic manufacturers

1, Baling Petrochemical Company (Epoxy Resin Division)

2, Bluestar New Materials Wuxi Resin Factory

3, Dalian Qihua Company

4, Jiangsu Sanyu Group Company

5, Nanya Epoxy Resin (Kunshan) Limited

6, Dow Zhangjiagang Company

7, Guangzhou Hongchang Electronic Materials Industry Co.

8, Guodu Chemical Kunshan Company

9, Huntsman Advanced Materials Corporation

10, Kingboard Chemical Group

11, Wuxi Diophthalmics Company

12, Changchun Chemical (Jiangsu) Co. Ltd

[Edit]Epoxy Resin Application Fields

1. In the field of coatings

Applied to automobiles: chassis primer, parts paint, tanker truck interior coating

Applied to containers: food tanks inner and outer wall coatings, tanks inside and outside the wall of the anticorrosive coating, pressure tanks anticorrosive

Applied to plant equipment: equipment, Pipeline anticorrosive coatings, refrigerator, washing machine outer coatings, electrical equipment insulation coatings

Application in civil engineering: bridge anticorrosive coatings, steel structure anticorrosive coatings, cement products seepage control coatings, floor coatings, decorative coatings, functional coatings, steel wire mesh cement gates

Application in ships: bottom cargo warehouse wall coatings, sea container coatings, anti-corrosive coatings for steel parts

Application in other: steel furniture powder coating, storage tanks inside and outside walls, pressure tanks anti-corrosion

Application in other: food tanks inside and outside walls, pressure tanks anti-corrosive coatings In other applications: powder coating for steel furniture, powder coating for resistive components, powder coating for steel parts, valve body anti-corrosion, heavy corrosion-resistant super wear-resistant ceramics, shielding vertical pipeline pumps, solar water heaters, solar panels, weapons

2. In the field of composites

In the automotive industry: fiberglass reinforced plastic (FRP) car shells, fiberglass reinforced plastic (FRP) floors, fiberglass reinforced plastic (FRP) tanker trucks, control systems, instrumentation and electrical parts, displays, automotive dry-type electrical parts, and other products. In the field of composite materials

Application in automobile: FRP car shell, FRP floor, FRP tank, control system instrument and electrical parts, display, automobile dry ignition coil, FRP parts, non-slip grain steering wheel cover, epoxy resin local reinforcement material,

Application in factory equipment: FRP oxygen cylinder, FRP storage tank, FRP container, pipeline, molds, propeller, weaving loom arrows, aircraft honeycomb structural parts, hood, rollers, shafts, mounted machine foundation leveling, self leveling flooring, solenoid coils, pilot valves, glass parts, glass fiber reinforced plastic pump valves, electric carbon products, construction engineering structural parts, machine transmission parts

Application to insulating materials: copper cladding board, fiberglass plate, tube, rod, transformers, relays, high-voltage switches, insulators, mutual inductors, impedance, cable head, sealing or encapsulation and molding of electronic devices, components, alarms, solid state power supply, FBT back-scanning transformer, focusing potentiometers, Motorcycles, automobiles and other motor vehicle ignition coils, electronic, electrical parts, light-emitting diodes, signal lamps, fully enclosed batteries, motor encapsulation, temperature transmitters, tape recorder heads, circuit boards closed, integrated circuits, diodes, transistors discrete devices, passive filters, structural encapsulation of LEDs, encapsulation of solar panels, power supply components, IC regulators and solid state relays, coal mine safety inspection systems, Intrinsically safe modules, automatic reclosers

Applications in sporting goods: fiberglass helmets, racquets, golf clubs, fishing poles, bowling balls, sledges, surfboards, fiberglass rowing boats, sailboats, racing cars, reclining chairs, hockey sticks

Applications in other: aircraft fuselage, helicopter propeller blades, wind turbine blades, medical instruments, scalpel handles, pacemakers, Crafts Jewelry, valve seals, hydraulic construction engineering, field luminescent screen, concrete wear layer, thermal insulation materials, animal models, space vehicles, marine tail shaft, rudder shaft, chemical wood, tower reinforcement, magnetic levitation train tracks, solar cells, musical instruments, epoxy decorations, fiberglass tent poles, knife handles, windows, furniture, pumps, crutches, graphics cards, infrared filters, digital displays, matrix emitter, light-emitting diodes and photodiodes, light-emitting diodes and photoelectric diodes, LEDs and photoelectric diodes, LEDs and photoelectric diodes. In the field of adhesives

Applications: room temperature fast curing toughness epoxy resin binder, conductive adhesive, room temperature curing static flocking adhesive, optical structural adhesive, shuffleboard adhesive, chemical anchoring adhesive, high functionality of silk, artificial flowers, magnetic writing boards, automotive repair adhesive, stone adhesive. Adhesive, stone adhesive