What are the ingredients contained in the varnish `hardener` thinner?
Date：2024-04-11 Categories：News
Diluent is based on Cyclohexanone. Butyl acetate. Anhydrous xylene is a mixture of organic solvents.
Curing agents, also known as hardeners, curing agents or modifiers, are a class of substances or mixtures that enhance or control the curing reaction.
Resin curing is the process of irreversible changes in thermosetting resins through chemical reactions such as condensation, ring closure, addition or catalysis, and curing is accomplished by the addition of curing (cross-linking) agents.
Classification of epoxy resin curing agents
(1) Alkaline and acidic curing agents:
(1) alkaline curing agents, including aliphatic diamines and polyamines, aromatic polyamines, other nitrogen compounds and modified fatty amines.
② acidic curing agents, including organic acids, anhydrides, and boron trifluoride and its complexes.
(2) Forming and catalytic curing agents:
This kind of curing agent and epoxy group undergoes addition reaction to form part of the chain segment of the curing product, and makes the linear molecule crosslinked into the body structure molecule through gradual polymerisation reaction, and this kind of curing agent is also known as melon-type curing agent. Such as primary amines, polythiols, polyphenols, low molecular polyamides, organic acids and anhydrides and low condensate curing agent.
② catalytic curing agent This type of curing agent only on the epoxy resin to trigger the role of opening the epoxy group, catalytic epoxy resin itself polymerisation into a network structure, the generation of ether bond as the main structure of the homopolymer, and the curing agent itself does not produce crosslinking reaction. Such as tertiary amine, imidazole, dicyandiamine, boron trifluoride complex, stannous chloride, stannous isooctanoate and stannous octanoate.
Common epoxy resin curing agent introduction:
Epoxy resin curing material has excellent mechanical properties, electrical properties, chemical resistance, and therefore widely used. Curing agent is one of the necessary raw materials for epoxy resin curing material, otherwise the epoxy resin will not be cured. In order to meet the requirements of various applications, the corresponding curing agent should be used. There are many types of curing agents, which are introduced below:
Fatty polyamines
Ethylenediamine
EDA H2NCH2CH2NH2 Molecular Weight 60 Active Hydrogen Equivalent 15 Colourless Liquid 6-8 parts per 100 parts of Standard Resin
Properties: toxic, aggressive odour, high volatility, low viscosity, fast curing at room temperature. Used for bonding, casting and coating. This kind of amine increases with molecular weight, viscosity increases, volatility decreases, toxicity decreases and performance improves. However, they have high heat release and short application period. Generally speaking, the higher molecular weight they have, the less they are affected by the amount of coordination. Prolonged exposure to fatty polyamines can cause dermatitis, and their vapour toxicity is very strong, so they should be operated with great care.
Diethylenetriamine
DETA H2NC2H4NHC2H4NH2 Molecular Weight 103 Active Hydrogen Equivalent 20.6 Colourless Liquid
Use 8-11 parts per 100 parts of standard resin. Curing: 2 hours at 20°C + 30 minutes at 100°C or 4 days at 20°C. Properties: Applicable period 50g 25°C for 45 minutes, heat distortion temperature 95-124°C, flexural strength 1000-1160kg/cm2, compressive strength 1120kg/cm2, tensile strength 780kg/cm2, elongation 5.5%, impact strength
0.4 ft-lb/in Rockwell hardness 99-108. dielectric constant (50 Hz, 23°C) 4.1 power factor (50 Hz, 23°C) 0.009 bulk resistance 2×1016
Ω-cm Curing at room temperature, high toxicity, high heat release, short application period.
Triethylenetetramine TETA H2NC2H4NHC2H4NHC2H4NH2
Molecular weight 146 Active hydrogen equivalent 24.3 Colourless viscous liquid 10-13 parts per 100 parts of standard resin
Curing: 2 hours at 20°C + 30 minutes at 100°C or 7 days at 20°C. Properties: Applicable period 50g 25℃45 minutes, heat distortion temperature 98-124℃, flexural strength 950-1200kg/cm2, compressive strength 1100kg/cm2, tensile strength 780kg/cm2, elongation 4.4%, impact strength
0.4 ft-lb/in Rockwell hardness 99-106, room temperature curing, toxicity is slightly lower than diethylenetriamine, heat release, short application period.
Tetraethylenepentamine TEPA
H2NC2H4(NHC2H4)3NH2 Molecular Weight 189 Active Hydrogen Equivalent 27 Brown Liquid 11-15 parts per 100 parts of standard resin.
Properties as above.
PEPA H2NC2H4(NHC2H4)nNH2 Light Yellow Liquid 14-15 parts per 100 parts of standard resin.
Properties: low toxicity, low volatility, long application period, low price.
Dipropylenetriamine DPTA H2N(CH2)3 NH(CH2)3NH2
Molecular weight 131 Active hydrogen equivalent 2
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