DGEBA/MDA/PGE 계의 열분해 특성

송영욱·이홍기．·돈윤승．．·김상욱

서울시립대학교 화학공학과·．우석대학교 화학공학과

．．제일모직 화성연구소

Thermal Decomposition Characteristics of DGEBA/MDA/PGE System

Y. W. Song, H. K. Lee．, Y. S. Don．．, and S. W. Kim

Dept. of Chem. Eng., The Univ. of Seoul

．Dept. of Chem. Eng., Woosuk Univ.

．．R & D Center, Cheil Industries Inc.

Introduction

Though epoxy resin has good mechanical and electrical properties, it was readily degraded by thermal and electrical stresses. Because thermal and electrical stresses concentrated to epoxy resin for long-term, the epoxy resin would be deteriorated during its service life[1,2]. From this view point, preventing for epoxy system large accident by thermal and electrical degradation from occurring, it is very important to resist against thermal and electrical stresses. In this study, the thermal decomposition properties of the epoxy system with diluent was investigated by Kissinger equation[3∼5].

Experiment

Used epoxy resin was commercial resin, diglycidyl ether of bisphenol A(DGEBA, Epon 828) by Shell Co. Curing agent was 4,4□-methylene dianiline(MDA) and diluent was phenyl glycidyl ether(PGE).

DGEBA

MDA

PGE

Fig. 1  The structure of DGEBA, MDA and PGE

These chemicals were provided by Fluka Chemie AG. MDA was fixed to the system(30 phr) and PGE was introduced to the system(5∼25 phr). DGEBA/MDA/PGE system was cured for 1 hr at 150℃, after curing for 1.5 hr at 80℃. The sample of DGEBA/MDA/PGE system was decomposed by TGA. Heating rate of TGA was 5, 10, 15 and 20 ℃/min. To prevent the sample from oxidizing, inert gas(N2) was flowed with the rate of 100 ml/min. Thermal decomposition activation energy of DGEBA/MDA/PGE was studied by Kissinger equation.

Fig.   TG thermograms of the DGEBA/MDA/PGE(20 phr) system by TGA analyzer at various heating rates.

Results and Discussion

The patterns of decomposition thermograms for DGEBA/MDA/PGE system were similar to other epoxy system. Also, the graphs of DGEBA/MDA/PGE system were similar when the heating rates of TGA were different. In Fig. 2, the shapes of decomposition graphs for DGEBA/MDA/PGE(20 phr) system were shown.

Decomposition temperature(Td) of the system were found about 350∼380℃, which is respectively stable values for epoxy/diluent system. Td of the system with various PGE contents and heating rates were listed in Table 1.

Table   Td of DGEBA/MDA/PGE System with Various PGE Contents and Heating Rates.

Heating rate	System
	D/M/PGE(5)	D/M/PGE(10)	D/M/PGE(15)	D/M/PGE(20)	D/M/PGE(25)
5 ℃/min	359.5℃	357.3℃	352.6℃	352.9℃	353.1℃
10 ℃/min	368.4℃	366.5℃	362.8℃	365.7℃	363.7℃
15 ℃/min	375.5℃	374.1℃	372.0℃	372.8℃	368.8℃
20 ℃/min	377.3℃	380.1℃	374.9℃	372.4℃	374.2℃

Though these values were different, it seemed that the decomposition temperature (Td) for DGEBA/MDA/PGE system decreased with the increment of PGE contents and decrement of heating rates.

Fig.   DTG thermograms of DGEBA/MDA/PGE(20 phr) system at various heating rates.

To use Kissinger equation, it was required to know the temperature of the maximum peak of DTG graph. They obtained from DTG curves, as shown Fig. 3. The maximum peak temperature of DTG graph increased with the increment of heating rates. From Fig. 3, thermal decomposition activation energy of DGEBA/MDA/PGE system were calculated by Kissinger equation. These data were listed in Table 2.

Table   Thermal Decomposition Activation Energy(Ead) of DGEBA/MDA/PGE System by Kissinger Equation.

System	D/M/PGE(5)	D/M/PGE(10)	D/M/PGE(15)	D/M/PGE(20)	D/M/PGE(25)
Ead (kJ/mol)	213.27	170.05	153.10	188.18	194.88

From the results, it was found that the thermal decomposition activation energy(Ead) of DGEBA/MDA/PGE(15) system has lowest value. So, it is considered that PGE reduced the thermal decomposition energy of system till 15 phr by reaction with MDA. However, it seemed that excess of PGE in cure reaction increased the thermal decomposition energy as an inert. To explain these results, it is necessary to study mechanism of DGEBA/MDA/PGE system.

References

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