Curing agent, also known as hardener, curing agent or stabilizer, is a type of substance or mixture that promotes or controls the curing reaction. Resin curing is an irreversible change process in thermosetting resin through chemical reactions such as condensation, ring closing, addition or catalysis. Curing is accomplished by adding a curing (cross-linking) agent. Curing agent is an essential additive. Whether it is used as an adhesive, coating, or castable, a curing agent must be added, otherwise the epoxy resin cannot be cured. The type of curing agent has a great influence on the mechanical properties, heat resistance, water resistance, corrosion resistance, etc. of the cured product.

Classification by use

Curing agents can be divided into normal temperature curing agents and heating curing agents according to their uses. Epoxy resins generally have excellent properties when cured at high temperatures. However, coatings and adhesives used in civil construction need to be cured at room temperature due to difficulty in heating. Therefore, fatty amines, cycloaliphatic agents, polyamides, etc. are mostly used, especially in winter. Coatings and adhesives have to be used together with polyisocyanates, or polyethyl alcohols with a foul odor.

As for the medium-temperature curing agent and high-temperature curing agent, they should be selected based on the heat resistance of the substrate and the heat resistance, adhesiveness and chemical resistance of the cured product. The selection focuses on polyamines and acid anhydrides. Since the acid anhydride cured product has excellent electrical properties, it is widely used in electronics and electrical appliances.

The aliphatic polyamine cured product has excellent adhesiveness, alkali resistance, and water resistance. Aromatic polyamines are also excellent in chemical resistance. Since the nitrogen element of the amino group forms hydrogen bonds with the metal, it has excellent anti-rust effect. The higher the amine mass concentration, the better the anti-rust effect. The acid anhydride curing agent forms an ester bond with the epoxy resin, showing high resistance to organic and inorganic acids, and its electrical properties generally exceed those of polyamines.

Classification by chemical composition

1. Aliphatic amines

Different ranges of products have different properties; high reactivity, rapid reaction at room temperature or low temperature Cure; relatively insensitive to moisture. It has certain color stability; good chemical resistance, especially solvent resistance; good high temperature performance when used for thermal curing; good chemical resistance and good electrical and mechanical properties.

Ethylenetriamine DETA

Aminoethylpiperazine AE

Cure at low temperature under humid conditions; good film properties (such as excellent surface gloss) ; Can prevent amine blooming and water spots; good color stability; good bonding performance and chemical corrosion resistance; wide range of curing time and storage time; when used for thermal curing, it has Good high temperature performance; good chemical resistance and good electrical and mechanical properties.

Diaminocyclohexane DACH

Isophorone diamine IPDA

Methylenebiscyclohexaneamine 4,4'-PACM

Ethylenediamine EDA

H2NCH2CH2NH2 molecular weight is 60, active hydrogen equivalent is 15, colorless liquid, use 6-8 parts for every 100 parts of standard resin. Performance: Toxic, irritating odor, high volatility, low viscosity, rapid curing at room temperature. Used for bonding, pouring and coating. As the molecular weight of this type of amine increases, the viscosity increases, the volatility decreases, the toxicity decreases, and the performance improves. But they release a lot of heat and have a short shelf life. Generally speaking, the larger their molecular weight, the less affected they are by the blending amount. Long-term exposure to fatty polyamines can cause dermatitis. Their vapors are highly toxic, so care must be taken when handling them.

Diethylenetriamine DETA

H2NC2H4NHC2H4NH2, molecular weight 103, active hydrogen equivalent 20.6, colorless liquid, use 8-11 parts for every 100 parts of standard resin. Curing: 2 hours at 20°C + 30 minutes at 100°C or 4 days at 20°C. Performance: Pot life is 50 grams at 25°C for 45 minutes, heat distortion temperature 95-124°C, bending strength 1000-1160kg/cm2, compressive strength 1120kg/cm2, tensile strength 780kg/cm2, elongation 5.5%, impact strength

0.4 foot-pounds/inch Rockwell hardness 99-108. Dielectric constant (50 Hz, 23°C) 4.1 Power factor (50 Hz, 23°C) 0.009 Volume resistance 2x1016 Ω-cm Curing at room temperature, high toxicity, large heat dissipation, short pot life.

Triethylenetetramine

TETA H2NC2H4NHC2H4NHC2H4NH2, molecular weight 146, active hydrogen equivalent 24.3, colorless viscous liquid, use 10-13 parts for every 100 parts of standard resin. Curing: 2 hours at 20°C + 30 minutes at 100°C or 7 days at 20°C. Performance: Pot life is 50 grams at 25℃ for 45 minutes, heat distortion temperature 98-124℃, bending strength 950-1200kg/cm2, compressive strength 1100kg/cm2, tensile strength 780kg/cm2, elongation 4.4%, impact strength

0.4 foot-pounds/inch, Rockwell hardness 99-106. It cures at room temperature, has slightly lower toxicity than diethylenetriamine, has large heat dissipation, and has a short pot life.

Tetraethylenepentamine TEPA

H2NC2H4 (NHC2H4)3NH2, molecular weight 189, active hydrogen equivalent 27, brown liquid, use 11-15 parts per 100 parts of standard resin. Same performance as above.

Polyethylene polyamine PEPA

H2NC2H4 (NHC2H4)nNH2, light yellow liquid, use 14-15 parts per 100 parts of standard resin. Performance: less toxic, low volatility, long pot life, cheap.

Dipropylenetriamine DPTA

H2N (CH2)3 NH (CH2)3NH2, molecular weight 131, active hydrogen equivalent 26, light yellow liquid, use 12-100 parts of standard resin 15 servings. Performance is the same as TETA.

Dimethylaminopropylamine DMAPA

(CH3)2N (CH2)3NH2, low viscosity transparent liquid, use 4-7 parts per 100 parts of standard resin.

It is highly toxic and has two reactions: curing and catalysis. It has good adhesion properties, good flexibility and long pot life.

Diethylaminopropylamine DEAPA

(C2H5)2N (CH2)3NH2 Molecular weight 130 Active hydrogen equivalent 65 Low viscosity transparent liquid Use 4-8 parts for every 100 parts of standard resin. Curing: 60-70℃ for 4 hours. Performance: Pot life is 50 grams at 25°C for 4 hours, heat distortion temperature 78-94°C, compressive strength 920-1050kg/cm2, tensile strength 480-640kg/cm2, impact strength 0.2 foot-pounds/inch, Rockwell hardness 90 -98. The dielectric constant (50 Hz, 23°C) is 3.75, and the power factor (50 Hz, 23°C) is 0.007.

Medium temperature curing and good low temperature performance.

Trimethylhexamethylenediamine TMD

(H2N)2(C6H9)(CH3)3 colorless liquid, cold solidified, long pot life and low toxicity. Use 21 parts per 100 parts of standard resin. Curing: 80℃ for 1 hour + 150℃ for 2 hours. Performance: Applicable period is 400 grams at 25℃ for 50 minutes or 50℃ for 10 minutes. Martin heat resistance is 92℃, bending strength is 1150kg/cm2, impact strength is 20Kg-cm/cm2 tg δ 0.0009 (23℃, 100C/S).

Surface resistance 5.4x1011Ω (300V) Volume resistance 9x1015Ω.cm (300V) Medium temperature curing, low temperature performance.

Dihexyltriamine

H2N (CH2)6 NH (CH2)6NH2

Hexanediamine modified product AMINE248

The molecular formula is unknown. It is a transparent liquid with a viscosity of 1000-3000cps at 25℃. Use 4-8 parts for every 100 parts of standard resin. Curing at room temperature -100℃. Less toxic and good flexibility.

Hexanediamine adduct

CH-2, L2505, unknown molecular formula, amine value 160-210, low viscosity transparent liquid, 65 parts for every 100 parts of standard resin.

CH3 amine value 400-500, low viscosity transparent liquid, use 60 parts for every 100 parts of standard resin.

Hexanediamine HDA

H2N (CH2) 6NH2, molecular weight 116, active hydrogen equivalent 29, colorless flaky crystals, melting point 42°C, 12-100 parts of standard resin 15 servings. It is highly toxic and can be cured at room temperature but not well. The applicable period is short.

Trimethylhexanediamine

Molecular weight 158, 20-25 parts per 100 parts of standard resin. Curing: 2 hours at 20°C + 30 minutes at 100°C or 7 days at 20°C. Performance: During the pot life of 50 grams at 25℃ for 45 minutes, the heat distortion temperature is 105℃, the bending strength is 1150kg/cm2, the tensile strength is 650kg/cm2, the elongation is 4.4%, and the impact strength is 0.4 feet-pounds/inch. Dielectric constant (50 Hz, 23°C) 4.0 Power factor (50 Hz, 23°C) 0.001 Volume resistance 9x1015 Ω-cm.

Diethylamine DEA

HN (C2H5)2, molecular weight 73, active hydrogen equivalent 73, colorless liquid, use 12 parts for every 100 parts of standard resin. It has both curing and catalytic reactions.

Polyetherdiamine H2N (CH2)nO (CH2CH2O) mNH2

2. Aromatic amines

Metaphenylenediamine m-PDA MPD

(NH2)2C6H4, molecular weight 107, active hydrogen equivalent 26.7, white crystal (black solid?), melting point 62°C, 14-16 parts per 100 parts of standard resin. Curing at 60℃ for 2 hours +150℃ for 2 hours. The pot life is 500 grams at 50℃ for 2.5 hours, the heat distortion temperature is 150℃, the bending strength is 1050kg/cm2, the compressive strength is 710kg/cm2, the tensile strength is 540kg/cm2, the elongation is 3.0%, and the impact strength is 0.2-0.3 feet-pounds. /inch, Rockwell hardness 108. The dielectric constant (50 Hz 23℃) is 3.3, the power factor (50 Hz 23℃) is 0.007, it has excellent heat resistance and corrosion resistance, good electrical properties and low toxicity. Because it is a solid, it is inconvenient to use. Care must be taken to prevent gelation when heated and mixed with resin.

Metaxylylenediamine MXDA

(NH2CH2)C6H4, molecular weight 135, active hydrogen equivalent 33.2, colorless liquid, use 16-18 parts per 100 parts of standard resin. Curing takes 24 hours at room temperature + 1 hour at 70°C or 4 days at room temperature. The pot life is 100 grams at 25℃ for 50 minutes, the heat distortion temperature is 130-150℃, the bending strength is 1200kg/cm2, the compressive strength is 1030kg/cm2, the tensile strength is 720kg/cm2, the elongation is 6.7%, the dielectric constant (50 Hz 23℃) 4.0, power factor (50 Hz 23℃) 0.005, volume resistance greater than 2x1016Ω.cm, can be cured at room temperature, has excellent heat resistance and corrosion resistance, good electrical properties, and low toxicity. It has low curing temperature, low viscosity, low toxicity, long pot life and good solvent resistance. It easily absorbs carbon dioxide in the air, which causes bubbles in the product.

Diaminodiphenylmethane DDM HT-972 DEH-50

[(NH2)(CH3)C6H4]2CH2, molecular weight 196, active hydrogen equivalent 49, white crystal, long-term It turns brown when exposed to sunlight, with a melting point of 89°C. Use 25-30 parts per 100 parts of standard resin. Curing at 60℃ for 2 hours +150℃ for 2 hours. The pot life is 500 grams at 50℃ for 3 hours, the heat distortion temperature is 145-150℃, the bending strength is 1190kg/cm2, the compressive strength is 710kg/cm2, the tensile strength is 550kg/cm2, the elongation is 4.4%, and the impact strength is 0.3-0.5 feet. - lbs/in Rockwell hardness 106. The dielectric constant (50 Hz 23℃) is 4.4, the power factor (50 Hz 23℃) is 0.004, the volume resistance is greater than 1015Ω.cm, it has excellent heat resistance and corrosion resistance, good electrical properties and low toxicity. Heat resistance and high mechanical strength. Because it is a solid, it is inconvenient to use. Care must be taken to prevent gelation when heated and mixed with resin.

Diaminodiphenyl sulfone DDS HT-976

[(NH2)C6H4]2SO2, molecular weight 248, active hydrogen equivalent 62, melting point 175°C, per 100 parts of standard resin 35-40 servings. Curing 130-150℃ 3 days-2 hours.

The pot life is 500 grams at 130℃ for 1.5 hours, usually using BF3-amine complex as accelerator (the dosage is 0.5-2%), the heat distortion temperature is 175-190℃, the bending strength is 1220kg/cm2, and the compressive strength is 710kg/cm2 , tensile strength 580kg/cm2, elongation 3.3%, impact strength 0.3-0.5 feet-pounds/inch, Rockwell hardness 110. It has excellent heat resistance and corrosion resistance, good electrical properties and low toxicity. Slow response. Heat resistant 175℃.

Meta-aminomethylamine MAMA (NH2)

(CH2NH2)C6H4, molecular weight 123, active hydrogen equivalent 30.7, melting point 38°C, 14-18 parts per 100 parts of standard resin, Curing 130-150℃ 3 days-2 hours. High elongation at break.

Benzidine

(NH2)C6H4 C6H4 (NH2)

Chloro-o-phenylenediamine CPDA

(NH2)2C6H3 CL< /p>

Xylylenediamine trimer GY-51 CH-2

Viscosity 60℃ 2000-6000cps, 30-60 parts per 100 parts of standard resin, curing at room temperature -60℃ 7 Day - 1 hour. Low toxicity.

WA-060 CH-3 has a viscosity of 6000-10000cps at 60°C. Use 30-60 parts per 100 parts of standard resin. Curing takes 7 days to 1 hour at room temperature -60°C.

Xylylenediamine trimer derivatives

Viscosities are 5cps, 40cps and 100cps at 25℃, 25-30 parts per 100 parts of standard resin, curing at room temperature -60℃ for 7 days -1 hour. Low viscosity. Low toxicity.

Bisbenzylaminoether

(H2NCH2C6H4)2O, 30-60 parts for every 100 parts of standard resin, can be cured at room temperature, has a long pot life, low exotherm, and heat distortion temperature 68℃.

Mixture of m-phenylenediamine and diaminodiphenylmethane

60-75% MPDA and 40-25% DDM are mixed and melted, and are liquid at room temperature. The melting point of the 40:60 mixture of diaminodiphenylmethane and m-phenylenediamine is 25°C. Use 20 parts for every 100 parts of standard resin. The epoxy resin will be cured at 40°C for 5 hours. If a mixture of triphenyl phosphate and phenol is added, it will solidify in 9 hours at 20°C. Thermal deformation temperature 150℃, bending strength 1150kg/cm2, impact strength 17Kg-cm/cm2, tensile strength 560 kg/cm2, elongation at break 4.8, Rockwell hardness 105-110, dielectric constant (50 Hz 23℃) 4.5, power factor (50 Hz 23℃) 0.006, mixture of m-phenylenediamine, diaminodiphenylmethane and toluenediamine, m-phenylenediamine:diaminodiphenylmethane:toluenediamine=30-70:10 -50: The mixture of 5-35 is a stable liquid. Example: A liquid obtained by mixing 50 parts of meta-phenylenediamine, 30 parts of diaminodiphenylmethane, and 20 parts of toluenediamine (meta:para=80:20) at 100°C has a stable period of 9 months. Use 18.5 parts per 100 parts of standard resin. Curing at 80°C for 2 hours + 140°C for 2 hours. Impact strength 115Kg-cm/cm2, Rockwell hardness 105. The mixture of o-toluenediamine, m-toluenediamine and diaminodiphenylmethane, with a ratio of 26:14:60, does not precipitate at 23°C for 48 hours, and gels with epoxy resin in 45 minutes at 23°C. Diaminodiphenylmethane and isophoronediamine mixture: 40-30% DDM and 60-70% IPDA are mixed and melted, and are liquid at room temperature. When 40% DDM is mixed with 60% IPDA, 25 parts of the mixture are used for every 100 parts of the standard resin. The heat distortion temperature is 130-155°C, the rational bending strength is 1160kg/cm2, the dielectric constant (50Hz 23°C) is 3.4, and the power factor (50 (H23°C) 0.012.

Metaphenylenediamine (MPDA)

Methylenediphenylenediamine (MDA)

3. Amidoamines

Different amides have different reactivity. Low viscosity; good bonding performance; good curability under humid conditions; amide modification can achieve faster curing speed and chemical stability.

4. Latent curing amines

Dicyandiamide (DICY) is a latent curing agent with a stability of more than six months; the product comes in a variety of forms and particles size. Imidazole is a latent catalyst for epoxy systems, and its storage time can range from a few hours to 6 months. They can be used as good accelerators for other curing agents, such as dicyandiamide and anhydrides.

5. Urea substitute

In dicyandiamide accelerator, it can be used as a low-toxicity substitute for Monuron and Diuron.