[E014]
E-mail: garea@tsocm.pub.ro; calin@tsocm.pub.ro; iovu@tsocm.pub.ro;
University “POLITEHNICA” of Bucharest, Faculty of Industrial Chemistry, 149 Calea Victoriei, 71101-Bucharest, Romania
* ICEMENERG S.A., Bucharest, Romania
It is well known that the conventional crosslinking treatments of epoxy resins with different crosslinking agents exhibit high temperatures, long reaction times and also high energy consumption. Thus it is urgently required some alternative technology to energy saving.
An alternative method for the crosslinking process of epoxy resin with different crosslinking agents is microwave heating.
The mechanism of microwave heating is based on the fact that the microwave energy is absorbed by the polar groups from the matter [1,2]
Microwave tehnique exhibits some advantages such as energy saving, shorter time reaction and a rapid volumetric heating [3,4].
This paper present the crosslinking process of two epoxy resin under microwave (MW) treatment using three different amines as a curing agent (P 350, H10-30, H 043).
II. Experimental
II.1. Materials
Two liquid epoxy resin (MW1, MW2) supplied by ICEMENERG-Bucharest were used as received.
MW1 is a complex mixture of 30-60 % epoxy resin based on epiclorhydrine and bisphenol A with 365-380 molecular weight, epoxy equivalent = 182,195 g/eqv., 10-20 % polipropylenglycoladipate (molecular weight = 1000-1500) and 10-20 % diphenyl glycidil ether with an epoxy equivalent = 155-170 g/eqv.
MW2 is mixture of 50-100 % epoxy resin based on bisphenol A and epiclorhydrine, with a molecular weight = 700, 10-25 % epoxy resin based on bisphenol F and epiclorhydrine and 10-25 % 1,6 hexandioldiglycidilether
The hardeners used were P 350, H 043, H 1030.
P 350 is a polyamide diamines or amidopolyamines, derived from reaction of dimer fatty acids (e.g. linoleic dimer acid) with low molecular mass polyamines (e.g. DETA or TETA).These curing agents are actually complex mixtures and contain several reactive functional groups.
H 043 is a complex mixture between 25-50 % 3-aminomethyl-3,5,5-trimethylciclohexylamin, 2,5-10 % nonylphenol and 25-50 % benzoyl alchol.
H 10-30 is a complex mixture of 25-50 % 3-aminomethyl-3,5,5-trimethylciclohexylamin, 2,5-10 % nonylphenol ,25-50 % m-phenylenbis (methylamine) and 2,5 –10 % benzoyl alchol.
Mixtures (~15 g) of DGEBA with variable amounts of curing agent were introduced into a glass flask (25 ml), which was then placed into the reaction chamber of the microwave oven.
II.2. Equipments
The crosslinking reaction occurs into microwave reactor “PLAZMATRONIKA” which has the following characteristics:
- power consumption 1000 W
- maximum temperature 250oC;
- outside dimensions :heigt 450 mm, width 460 mm, depth 320 mm
- an IR sensor which measures the sample’s temperature during the crosslinking process.
It was possible to estabilish the enhancement of curing process as the temperature increases in time
III.1. The influence of the set temperature
Fig.1. The evolution of sample’s temperature against the reaction time for MW2- P 350 system. The tests were run at two different set temperatures.
As it was expected, if the set temperature is higher, the maximum temperature reaches a higher value for the same system (MW2-P350).
III.2. The influence of the resin type used
Fig. 2. The evolution of sample’s temperature against the reaction time for two different systems (MW1-H043 and MW2- H043). The tests were run at two different set temperatures.
One may notice that MW2-H043 system exhibits a higher reactivity than MW1-H043 system regardless of the set temperature used in the experiments.
Crosslinking tests of MW1 and MW2 were also performed with a different crosslinking agent, H10-30. The behaviour of this agent may be observed in Fig. 3. In this case a different behaviour in the reactivity of the two resins was noticed depending on the reaction time.
Fig. 3. The evolution of sample’s temperature against the reaction time for two systems with the same crosslinking agent (MW1-H10-30 and MW2- H10-30) at 40oC.
Fig. 4. The influence of the system’s composition against the dependence temperature vs. time at 50oC.
One may notice from Fig. 4 that the highest reactivity is obtained for the system MW1-H10-30.
IV. References
[1] J. Zhou, C. Shi, B. Mei, R. Yuan, Research on the technology and the mechanical properties of the microwave processing of polymer, Journal of Materials Processing Technology, 137 (1993), 156-158.
[2] F. Y. C. Boey, B. H. Yap, Microwave curing of an epoxy-amine system:effect of curing agent on the glass-transition temperature, Polymer Testing, 20 (2001), 837-845.
[3] J. Jayanthi, F. Boey, Rate enhancement in microwave curing. Am. Ceram. Soc.,Ceram. Trans. 57, 1997
[4] J. Jacob, L. H. L. Chia, F.Y.C. Boey, Review:thermal and non-thermal interaction of microwave radiation with materials, J. Mater. Sci. 30 (1995), 5321-5327.