Resin · EP

Epoxy Resin

Bisphenol A diglycidyl ether (DGEBA). Crosslinked with amines or anhydrides. Standard resin for anti-corrosion primers and floor coatings.

On This PageChemical Structure Curing Mechanism Curing Agent Selection Key Parameters Application Window Common Defects

Structure & Grades

Bisphenol A diglycidyl ether (DGEBA), average polymerization degree n=0~2. Industrial grades by epoxy value:

HO-C₆H₄-C(CH₃)₂-C₆H₄-O-CH₂-CH(OH)-CH₂-[O-C₆H₄-C(CH₃)₂-C₆H₄-O-CH₂-CH(OH)-CH₂]ₙ-O-

Grade	Epoxy value eq/100g	Viscosity Pa·s @25°C	Application
E-51 / 828	0.48-0.53	10-15	High-solids primer, casting
E-44 / 834	0.41-0.47	25-40	General anti-corrosion paint
E-20 / 1001	0.18-0.22	Solid	Powder coatings, coil

Curing Mechanism

Room temperature: aliphatic amine or modified amine. Amine nitrogen lone pair nucleophilically attacks epoxy ring, breaking C-O bond to form epoxy ester:

R-NH₂ + CH₂-CH-CH₂-O- → R-NH-CH₂-CH(OH)-CH₂-O-
(Epoxy ring opening → secondary amine + β-hydroxyl)

R-NH- + CH₂-CH-CH₂-O- → R-N(-CH₂-CH(OH)-CH₂-)₂
(Secondary amine continues reaction → 3D crosslinked network)

Anhydride Curing Agent (MeTHPA) requires 120-160°C baking. Better heat and chemical resistance.

β-Hydroxyl (-OH) further accelerates cure speed. This is the source of epoxy auto-catalysis effect, and also the reason for its short pot life.

Curing Agent Selection

Curing Agent	Type	Dosage phr	Pot Life	Characteristics
TETA Triethylenetetramine (TETA)	Aliphatic amine	11-13	30 min	Fast cure, greenish, short pot life
Polyamide 650	Modified amine	50-100	2-4 h	Flexible, good adhesion, moderate weathering
Modified amine 593	Adduct amine	25-35	1-2 h	Low toxicity, medium pot life
Phenalkamine T-31	Phenolic modified	25-35	30 min	Low-temperature humid cure (down to -5°C)
MeTHPA	Anhydride	80-90	Long	Requires baking, heat resistance 150°C

Key Process Parameters

Parameter	Typical Value	Description
Mixing Ratio	By active hydrogen equivalent ratio 1:1	Deviation >10% causes performance drop
Pot Life	30-60 min @25℃	Larger volume releases heat faster
Surface Dry	4-6 h @25°C	Tack-free to touch
Full Cure	7 days @25°C / 30 min @80°C	First 3 days strength only 70%
Application Temperature	10-35°C	Does not cure below 5°C
Relative Humidity	≤85%	High humidity causes blushing and Pinholes

Application Window

Spray Application

Airless spray pressure 15-20 MPa, nozzle 0.43-0.53 mm. Thinner xylene:butanol = 7:3, addition ≤10%.

Brush/Roller Application

Brush first coat on edges and welds, dry film 30-50μm. Recoat interval min 8h, max 72h (abrasive if exceeded).

Common Defects & Solutions

Defect	Cause	Solution
Pinholes	Cure too fast, solvent trapped	Reduce film thickness, slow down spray, add slow-drying solvent
Blushing	High humidity, amine exudation	Stop application when humidity >85%; add 5% butanol
Poor Adhesion	Incomplete degreasing	Sa2.5 blast, roughness 40-75μm
Short Pot Life	Mixed too much, high temperature	Small batches, frequent mixing, operate below 25°C

BASTAIN Corresponding Products

EP-ZR Epoxy Zinc-rich PrimerEP-MIO Epoxy MIO IntermediateSEAL Epoxy Sealer PrimerGR-ZR Graphene Epoxy Zinc-richMR-1590 Mirror Back Red Primer