Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Flexible epoxy resin curing agent

RIKACIDTM HF‐08
RIKACIDTM HF-08 is a flexible epoxy resin curing agent developed by ourcompany. The epoxy cured product exhibits excellent flexibility and transparency
when used with our acid anhydrides such as RIKACIDTM MH-700.
Feature








It is a compound having a carboxyl group at both ends of the flexible
structure.
The formulation of HF-08 gives the epoxy cure flexibility while
maintaining a relatively high Tg, and can improve impact resistance.
The epoxy cured product with excellent transparency is obtained, and
it is excellent in yellowing resistance during heat aging.
It does not cause a large decrease in moisture resistance of epoxy
cured products.
It exhibits its characteristics in combination with various epoxy resins
such as bisphenol A epoxy resin and alicyclic epoxy resin.

Typical properties
Table 1. Typical properties of HF-08
Appearance

Clear viscous liquid

Color (Hazen)＜100Equivalent of carboxyl group

310～360

Viscosity [mPa･s] (100℃)

150～210CAS RN®

60806-75-9※These values are not guaranteed.

＜Calculation of equivalent amount when HF-08 is blended.＞In this technical data, the equivalent calculation was performed assuming that one epoxy groupand one acid anhydride group or one carboxyl group react.

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Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Temperature dependence of viscosity of HF-08
Figure 1 shows the temperature dependence of the viscosity of HF-08.
106

Viscosity [mPa･s]

105

104

103

102

204060Temperature [℃]80100Fig 1. Temperature dependence of viscosity of HF-08

Foaming suppression effect at curing
Table 2 shows the foam suppression effect by the addition of HF-08.
The addition of HF-08 has the effect of suppressing foaming during curing.
Table 2. Foam suppression effect by the addition of HF-08
Formulation No.

1

23Remarks※12021P

100

100

100

Epoxy equivalent = 130

RIKACIDTM MH-700※2126

120112Equivalent of acid anhydride = 164

TM-1328

Carboxyl group equivalent = 336

11

1Accelerator

Blending ratio of HF-08(wt% / curing agent)

0

1020

Curing agent =MH-700＋HF-08

Foamed state at curing×△○-TM

CELLOXIDE

Formulation[p.b.w]
Equivalentratio = 1.0

RIKACID

HF-08

TPP-PB※3

CELLOXIDETM 2021P： Alicyclic epoxy resin （Daicel Corporation）※1※2 RIKACIDTM MH-700： 4-methyl cyclohexane-dicarboxylic anhydryde/cyclohexane-dicarboxylic anhydryde= 70/30 (wt%) (New Japan Chemical Co., Ltd.)※3 TPP-PB： Tetraphenyl phosphonium bromide （HOKKO CHEMICAL INDUSTRY CO., LTD.）
Curing condition： 120℃/1h ＋ 150℃/2h
Equivalent ratio = (Acid anhydride group + carboxyl group) / epoxy group＜Foaming state evaluation conditions＞
7 g of the epoxy composition was weighed in a test tube of φ 15 mm, and after hardening, the rise height from theinitial liquid level due to foaming was measured, and the foamed state was visually observed.
○: no foam, no interface rise, Δ: slightly foam, interface rise ≦ 5 mm, ×: foam, interface rise> 5 mm

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Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Impact resistance improvement
The relationship between the equivalent ratio and the impact resistance when
HF-08 is added according to the composition shown in Table 3 is shown in Figure
2. Impact resistance can be greatly improved by adding HF-08. In particular, theeffect is maximum around the equivalent ratio of 0.8.
400
HF-08：No formulation
HF-08：20wt%/Curing agent
HF-08：40wt%/Curing agent

300

Drop height [mm]

200

100

00.5

0.7

0.9

1.1

1.3

Equivalent ratio

Fig 2. Relationship between impact resistance and equivalent ratio＜ Impact resistance test conditions＞
・JIS K5600： According to drop impact test
・Drop load： 100g・Sample： Cured 2.5mm thick, see Table 3 for compounding and curing conditions.
・Measure the drop height where no crack occurs when the weight is dropped.

Table 3. Formulation [p.b.w] (Equivalent ratio = 1.0)
Formulation No.

1

23Remarks

CELLOXIDETM 2021P※1

100

100

100

Epoxy equivalent = 130

RIKACIDTM MH-700※2

126

112

96

Equivalent of acid anhydride = 164

RIKACIDTM HF-08

－28

63

Carboxyl group equivalent = 336

TPP-PB※3

1

1

1Accelerator

Blending ratio of HF-08(wt% / curing agent)

020

40

Curing agent =MH-700＋HF-08※1 CELLOXIDETM 2021P： Alicyclic epoxy resin （Daicel Corporation）※2 RIKACIDTM MH-700： 4-methyl cyclohexane-dicarboxylic anhydryde/cyclohexane-dicarboxylic anhydryde= 70/30 (wt%) (New Japan Chemical Co., Ltd.)※3 TPP-PB： Tetraphenyl phosphonium bromide （HOKKO CHEMICAL INDUSTRY CO., LTD.）
Curing condition： 120℃/1h ＋ 150℃/2h

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Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Influence on heat resistanceThe relationship between the Tg of the epoxy cured product and the equivalentratio when HF-08 is added is shown in Figure 3. When the addition amount of HF08 is 20wt%, almost no decrease of Tg occurs at the equivalent ratio of 0.8 to 1.2.
250
HF-08：No formulation
HF-08：20wt%/Curing agent
HF-08：40wt%/Curing agent

200

Tg [℃]

150
100
50
00.5

0.7

0.9

1.1

1.3

Equivalent ratio＜Heat resistance measurement condition＞
・Measure glass transition point (Tg) with DSC.
・Compounding and curing conditions are
the same as in Table 3.
・Heating rate： 20℃/min

Fig 3. The relationship of Tg and equivalent ratio

Impact on moisture resistanceFigure 4 shows the relationship between boiling water absorption and equivalentratio when HF-08 is added. When the amount of HF-08 added is 20 wt%, themoisture resistance hardly decreases at an equivalent ratio of 0.8 to 1.0.

Water absorption rate [%]

1.2
10.8
0.6
0.4

HF-08：No formulation
HF-08：20wt%/Curing agent
HF-08：40wt%/Curing agent

0.2
00.5

0.7

0.9

1.1

Equivalent ratio

1.3＜Heat resistance measurement condition＞
・Based on JIS K6911
・Sample： Cured 3mm thick・Compounding and curing conditions are
the same as in Table 3.

Fig 4. Relationship between boiling water absorption and equivalent ratio
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Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Effect on heat resistant yellowing

Figures 5 to 7 show the relationship between thermal yellowing and equivalentratio when HF-08 is added. By optimizing the equivalent ratio, clear and colorlessepoxy cured products can be obtained.
100

Light transmittance [%]8060
After curing
After 150℃/3days aging
After 150℃/5days aging

402000.5

0.7

0.9
1.1
Equivalent ratio

1.3Fig 5. Relationship between heat resistant yellowing and equivalent ratio（HF-08 not included）

Light transmittance [%]100806040

After curing
After 150℃/3days aging
After 150℃/5days aging

2000.5

0.7

0.9
1.1
Equivalent ratio

1.3Fig 6. Relationship between heat resistance yellowing and equivalent ratio (HF-08: 20wt% / curing agent)Light transmittance [%]1008060＜Thermal yellowing measurement condition＞
・Evaluate the light transmittance of wavelength
400nm with UV-visible spectrophotometer.
・Sample： Cured 5mm thick・Compounding and curing conditions are
the same as in Table 3.
・Heat aging process： Use 150 ℃ gear oven40
After curing
After 150℃/3days aging
After 150℃/5days aging

2000.5

0.7

0.9
1.1
Equivalent ratio

1.3Fig 7. Relationship between heat resistance yellowing and equivalent ratio (HF-08: 40wt% / curing agent)
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Technical Bulletin No. A06-114-2007
New Japan Chemical Co., Ltd.

Physical properties of bisphenol A epoxy resin at curing

Table 4 shows the curing properties when using bisphenol A epoxy resin. By
adding HF-08, significant improvement in flexibility is possible.
Table 4. Curing properties of bisphenol A type epoxy resin
Formulation No.

1234Remarks

jERTM 828※1100100100100Epoxy equivalent = 185

RIKACIDTM MH-700※28680

7050

Equivalent of acid anhydride = 164

RIKACIDTM HF-08

01535

65

Carboxyl group equivalent = 336

LUVEAKTM DMP-30※3

0.5

0.5

0.5

0.5Accelerator

Blending ratio of HF-08(wt% / curing agent)

016

33

57

Curing agent = MH-700＋HF-08

Thermal shock value (point)

01310C-shaped washer method

Heat distortion temperature [℃]1391088455

Bending strength [MPa]122115

10697

Volume resistivity (25℃) [Ω･cm]

1×1016

1×1016

1×1016

1×1016

Boiling water absorption rate [%]

0.23

0.42

0.59

0.82

Formulation[p.b.w]
Equivalentratio = 1.0

Based on JIS K5600-5-4※1 jERTM 828： Bisphenol A epoxy resin (Mitsubishi Chemical Corporation)※2 RIKACIDTM MH-700： 4-methyl cyclohexane-dicarboxylic anhydryde/cyclohexane-dicarboxylic anhydryde= 70/30 (wt%) (New Japan Chemical Co., Ltd.)※3 LUVEAKTM DMP-30： 2,4,6-Tris(dimethylaminomethyl)phenol (NACALAI TESQUE, INC.）
Curing condition： 120℃/1h ＋ 150℃/2h＜C-shaped washer method evaluation method＞
A steel washer of φ 27 mm was embedded, and the points until the occurrence of a crack when heat cycles weregiven in the following table were compared. However, when a crack was generated in the step of producing a cured
product, it was regarded as point 0.
Point

12

34

5678

910

11

Temperature [℃]25525－1525－35

25－55

25130－55

Time [min]

－1030

1030

1030

1030

30

10

Inquiry
Please contact us at the following address, if you want to ask about these Technical Bulletin.
New Japan Chemical Co., Ltd. （http://www.nj-chem.co.jp/en/ )Osaka head office Polymer Materials Marketing ＆ Sales Dept. Marketing ＆ Sales Division
Bingomachi Nomura BLDG., 2-1-8, Bingomachi, Chuo-ku, Osaka 541-0051
TEL. ＋81-(0)6-6203-3962 FAX. ＋81-(0)6-6202-7784
Tokyo office Polymer Materials Marketing ＆ Sales Dept. Marketing ＆ Sales Division
GREEN OAK KAYABACHO., 1-3-3, Sinkawa, Chuo-ku, Tokyo 104-0033
TEL. ＋81-(0)3-5540-8106 FAX. ＋81-(0)-3-3297-1251

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