STEFANI Pablo Marcelo
congresos y reuniones científicas
Alicante, España
Congreso; I International Conference on Biodegradable Polymers and Sustainable Composites; 2007
Institución organizadora:
Dep. of Analytical Chemistry, Nutrition and Food Sciences, University of Alicante
Syntactic epoxy foams are two-phase closed cell foams which are usually made by dispersing low density hollow particles (microballoons) in a matrix material. The presence of strong but lightweight particles leads syntactic foams to higher strength compared to single-phase closed cell foams [1]. It is possible to tailor properties of syntactic foams by changing a wide variety of parameters, which include the matrix and microballoon materials, and microballoon size, size distribution, wall thickness and volume fraction [2]. Nowadays, the increasing concern about the environmental protection have rise to the search of epoxidized substitutes derived from renewable resources. In this sense, functionalized vegetable oils (FVO) such as epoxidized soybean oil (ESO), are considered attractive candidates to replace at least a proportion of the traditional epoxy resins in thermosetting formulations. ESO may be copolymerized with epoxy resin using amine or anhydride as crosslinking agent [3-5]. The control on epoxy resin/ESO ratio allows one to obtain foams with tailored properties according to the application purpose. In the present work, we report the synthesis and characterization of epoxy-ESO copolymers intended to be used in the fabrication of syntactic foams. The epoxy resin used was diglycidyl ether of bisphenol A (DGEBA, epoxide equivalent weight of 182), epoxidized soybean oil (ESO, epoxide equivalent weight of 244), methylhexahydrophthalic anhydride (MHHPA, equivalent weight of 168) as crosslinking agent and benzyldimethylamine (BDMA) as initiator and glass hollow microspheres (3M, average diameter 40mm, density 0.17 g/cm3). Copolymers with different DGEBA:ESO weight ratio (100:0 to 0:100) were synthesized using a stoichiometry amount of anhydride and 15% (weight basis) of microballons. Syntactic foams were obtained by curing the reactive mixture at 120 ºC during 3 h, followed by 190ºC for 2 h. The void content in the matrix was estimated according to the procedure described in ASTM D-2734. The experimental density of matrix and foams were determined by picnometry. The glass transition temperature (Tg) was measured by calorimetry in dynamic mode (10ºC/min) under inert amotmosphere. The density of the matrix decreases from 1.23 g/cm3 to 1.10 g/ cm3 for DGEBA:ESO ratio from 100:0 to  0:100 respectively, while the foam density (about 0.54 g/cm3) and void content (about 15%) remains almost constant with ESO content. The Tg of the copolymers decrease with the ESO content from 119ºC (neat matrix) to 26ºC for DGEBA:ESO 0:100. As expected, this decrease in Tg conducts to an increase in flexibility of the foam, as was seen in preliminary dynamical-mechanical (DMA) and flexural mechanical tests. References 1) Maharsia R.R., Jerro H. D., Mater. Sci. Eng., A 454–455 (2007) 416–422 2) Shutov FA. Adv Polym Sci 73/74 (1986) 63–123. 3)N.Gupta, N.Kishore, E. Woldesenbet, S. Sankaran, J Mater Sci 36 (2001) 4485–4491. 4)H. Miyagawa, A.K. Mohanty, M.Misra, L.T.Drzal, Macromol. Mater. Eng. 289 (2004) 629–635 5) D. Ratna, Polym Int 50 (2001) 179-184.