ORGANOCATALYTIC DEPOLYMERIZATION OF ANHYDRIDE CURED EPOXYRESIN AT MILD CONDITIONS
J. Liu1,*, Y. Liu1, Z.Q. Yu1 and T. Tang1,*
1 State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy ofSciences, Changchun, PR Chinae-mail: liujie@ciac.jl.cn; 86-431-85262683

Abstract
Alkaline catalyst is usually used as catalyst for decomposition of thermoplastic and thermoset polymer containing ester
bond. However, inorganic catalyst is difficult to remove from decomposition products. Here, we report an efficient andmild depolymerization method using organic base as catalyst to decompose anhydride cured epoxy resin. The yield ofeliminated resin was compared for different organic base in the ethylene glycol. N-methyl-piperidine was an appropriate
catalyst because it can be recycled with ethylene glycol by distillation. The approach provides a new potential way todecompose the polymer containing ester bond.
Keywords: Epoxy resin, Depolymerization, Organic base

1. Introduction

3. Results and Discussion

Epoxy resins are the most commonly used thermosets in
producing fiber reinforced polymer composites andprinted circuit boards because of their combination ofchemical resistance, heat resistance and goodmechanical properties. Currently, waste epoxy resinmaterials are decomposed mainly using thermal
processing and solvolysis [1, 2]. Solvolysis process
recovers not only inorganic reinforced materials but also
useful organic products by breaking of chemical bonds of
epoxy resins [3-5]. However, the high pressure nature ofmany solvents at high temperatures brings a lot oftrouble for processing speed and cost control. On theother hand, the inorganic catalyst can increase thedepolymerization efficiency but is difficult to remove fromdecomposition products. Here, we describe an efficientand mild depolymerization method using ethylene glycol(EG) and organic catalysts, which can be simultaneously
recycled by distillation after depolymerization.

Table 1 shows the results of experiments conducted tocompare the degradation efficiency of eight different
organic catalysts in EG. Reaction temperature was fixedat 180 oC and the reaction time was 4 h. 2, 2’-dipyridyl
shows no activity in decomposition of anhydride curedepoxy resin. The yield of eliminated resin for 2(Methylamino)ethanol and piperidine was 29.1% and42.5%, respectively. And the yield of eliminated resin for
N, N-dimethylethanolamine and N-methyl-piperidine was
39.1% and 100%, respectively. This result indicated thattertiary amine shows better activity than secondaryamine. DMAP also shows high activity in decompositionof epoxy resin. However, the boiling point of DMAP is
162 oC at 50 mmHg. So it is difficult to remove it from thedecomposition products. The boiling point of N-methylpiperidine is 106 oC and is lower than that of EG. We
distillated EG and N-methyl-piperidine at 180 oC torecycle solvent and catalyst at the same time.

2. Materials and Methods
The matrix resin used in this study was diglycidyl ether ofbisphenol A (DGEBA) with the average epoxide value of0.53 purchased from Sigma-Aldrich. Anhydride cured
samples were prepared by mixing the DGEBA, methyl
tetrahydrophthalic anhydride (MeTHPA) and curing
accelerator N, N′-dimethyl benzyl amine (BDMA) at room
temperature and then heating at 100 oC for 2 h, 150 oC
for 5 h. The weight ratio of DGEBA/MeTHPA/BDMA is100/78/1. The epoxy resin chips, EG and catalyst wereintroduced into a glass flask equipped with a reflux
condenser. The system was kept in an inert atmosphereat designated temperature. EG was distillated after thereaction is over. The distillated solvent and catalyst werecharacterized by H1-NMR.

Table 1. Degradation efficiency of different organic basein EG.
Organic base
Molecular
Yield offormulaeliminatedresin (%)
02,2’-dipyridylNNNN
4,4’-dipyridyl8.0
OH
29.1
2-(Methylamino)ethanol
NHOH
39.1
N,N-dimethylethanolamine
NN
1,5,7-triazabicyclo[4.4.0]
84.5
NN
H
dec-5-ene (TBD)
NH
42.5
PiperidineNN-methyl-piperidine
100
4-Dimethylaminopyridine
100
NN

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

Fig. 2. H1-NMR of N-methyl-piperidine and distillatedproducts.
Fig. 3 shows H1-NMR of N-methyl-piperidine anddistillated products. It can be seen that EG and N-methylpiperidine were found in the distillation products.

4. Conclusions
In summary, the depolymerization of anhydride cured
epoxy resin by the organic base catalyst in the ethylene
glycol in good decomposition efficiency at 180 oC. Nmethyl-piperidine shows high yield of eliminated resin.
Most importantly, the solvent and catalyst can berecycled simultaneously by distillation to save separation
step. This method provides an attractive option forchemical recycling comparable to inorganic-based
approaches.

References[1] S. Pickering. Composites: Part A 37 (2006) 1206–1215.
[2] M. Goto. J. Supercrit. Fluids 47 (2009) 500–507.
[3] R. Pinero-Hernanza and E. Lester. J. of Supercritical
Fluids 46 (2008) 83–92.
[4] K. El Gersifi and G. Tersac. Polym. Degrad. Stab. 91(2006) 690-702.
[5] Y. Liu and T. Tang. Polym. Degrad. Stab. 97 (2012)
214-220.

Acknowledgements
We thank the financial supports from the National Natural
Science Foundation of China for the projects (51103154)
and the Main Direction Program of Knowledge Innovationof Chinese Academy of Sciences (KGCX2-YW-230 andKGCX2-EW-211).

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013