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Advantages and Characteristics of Cycloaliphatic Epoxy Resins TTA21 Applied to Electrical Casting Materials

Date:2023年03月13日Views:

Electrical casting materials refer to a kind of epoxy insulating materials used for casting insulating parts, transformers or dry transformers. Its formula adopts thermal curing system of epoxy resin anhydride, in which the bisphenol A epoxy resin is used most, and it enjoys many advantages such as excellent manufacturability, high strength of cured product, corrosion resistance and electrical properties. However, problems such as high viscosity, limited powder addition ratio, insufficient heat resistance and weather resistance always occur due to technological restrictions and use environment of terminal products. The epoxy bond of the cycloaliphatic epoxy resins is directly connected to alicyclic structure, which could improve the crosslinking density of the cured substance significantly, thereby improving heat and weather resistance and electrical insulation. In addition, the viscosity of the cycloaliphatic epoxy resins is extremely low, which contributes to the significant dilution effect. Therefore, cycloaliphatic epoxy resins can make up for the deficiency of bisphenol A epoxy resins applied in the electrical casting materials system. The combination of both materials can improve manufacturability, as well as making terminal electrical insulation products safer.

1. Basic information and specifications & parameters of cycloaliphatic epoxy resins TTA21

1.1 Basic information

Chinese name

3,4-环氧环己基甲酸-3',4'-环氧环己基甲酯

English name

3,4-Epoxycyclohexylmethyl- 3',4'-Epoxycyclohexane Carboxylate

CAS No.

2386-87-0

Structural formula

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Molecular weight

252.31

Molecular formula

C14H20O4

1.2 Specifications and parameters

Designation

TTA21S

TTA21L

TTA21P

Appearance

Colorless and transparent liquid

Content

90% min

95% min

97% min

Epoxide equivalent

128-145 g/mol

126-135 g/mol

126-135 g/mol

Chromaticity

100 APHA max

50 APHA max

50 APHA max

Viscosity

180-450 cP

220-300 cP

220-300 cP

Moisture content

0.05% max

0.05% max

0.05% max

Acid value

0.1% max

\

\

Total chlorine

\

\

100 ppm max

Specific Gravity

1.150-1.180

2. Basic performance data of TTA21P before and after thermal curing with methylhexahydrophthalic anhydride

Cycloaliphatic epoxy resin

TTA21P

Parts

100

Anhydride curing agent

MHHPA

Parts

130

Accelerant

AO-4

Parts

2

Viscosity

25

mPa·s

160

Thermal properties

Tg-DSC

226

H

J/g

350

Peak temperature

195

Tg-TMA

225

α1

μm/(m·℃)

56

α2

μm/(m·℃)

174

Tg-DMA E'

189

E“

208

tan?

231

Mechanical properties

Impact strength

KJ/m2

5.95

Bending strength

MPa

125

Flexural modulus

MPa

3120

Tensile strength

MPa

57

Tensile modulus

MPa

3205

Elongation at break

%

2.8

KIC

Mpa*m?

0.45

Electrical property

Volume resistivity

Ω*cm

1.168×1016

Surface resistivity

Ω

1.191×1015

Dielectric constant

C2/(N*M2)

3.0752

Dielectric loss

\

0.0042

Hardness

Shore D

\

89

Water absorption

25/24hr

%

1.05

Curing conditions

100℃×2hr + 140℃×2hr + 180℃×1hr

3. Effect of TTA21P addition ratio on system viscosity

3.1 Test materials: TTA21P/128

3.2 Conclusion: As shown in Figure 1, with the increase of TTA21P addition ratio, the system viscosity decreases rapidly, which reflects the obvious dilution effect of TTA21P.

4. Effect of TTA21P addition ratio on Tg of cured products

4.1 Test materials and curing conditions: TTA21P/128/ MHHPA/ BDMA and 100℃×2h+140℃×2h+180℃×1h.

4.2 Conclusion: As shown in Figure 2, with the increase of TTA21P addition ratio, Tg value of the cured product increases significantly, which reflects that TTA21P can improve the heat resistance of the material significantly.

5. Effect of addition ratio of TTA21P on mechanical properties of materials

5.1 Test materials and curing conditions: TTA21P/128/ MHHPA/ BDMA and 100℃×2h+140℃×2h+180℃×1h.

5.2 Conclusion: When the addition ratio of TTA21P increases gradually within the range of 0%~30%, the impact strength and tensile strength of the material increase continuously, while the bending strength increases first and then decreases (peaking at about 20%).

In conclusion, the optimal comprehensive performance can be obtained when the addition ratio of cycloaliphatic epoxy resins TTA21P is within the range of 10%~30%. The specific ratio should be determined based on various indicators and requirements of the complete formula.



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