Carbon foam with channel like pores prepared from reactive blended allyl novolac with bismaleimide using different cross-linking initiators

Abstract

Carbon foams with channel like pores have been prepared by pyrolysis of a thermosetting resin system; bismaleimide (BMI) modified allyl novolac (BAN) as carbon precursor and polyvinyl acetyl fibers (PVAF) as an organic sacrificial template. For improving the cross-linking density and glass transition temperature, dicumyl peroxide (DCP) was chosen as a curing initiator and compared the results with that of the most commonly used Hexamethylenetetramine (HTMA). After pyrolysis at 1000°C, the resulting PVAF/HTMA/BAN carbon foam developed excessive voids with linear lengths and widths up to 3 and 0.25mm respectively. Excessive bubbling of discrete self-curable BMI resin molecular chains surrounded by phenolic hydroxyl groups created such excessive voids and gaps. The PVAF/DCP/BAN carbon foam exhibited no such voids and the shape of the pores replicated the shape of PVAF template. Channel like pores were orientated at random with a non-cylindrical, flat, or kidney bean shape cross section with a maximum dimension of 25–50μm. Moreover, general characteristics were studied including density, porosity, open cell, pore-size distribution, thermal conductivity and flexural strength. Results have showed that the PVAF/DCP/BAN carbon foam possessed improved properties including density, thermal conductivity and flexural strength of 0.53gcm−3, 0.87 Wm−1K−1 and 19.12 MPa respectively.