Foaming behavior, cellular structure and physical properties of polybenzoxazine foams

Abstract

In this paper, polymer foams based on a benzoxazine resin have been successfully prepared using azodicarbonamide (ADC) as a chemical blowing agent and have been characterized regarding their foaming behavior, cellular structure, and physical properties. The effect of the ADC on the curing process of the resin was analyzed using differential scanning calorimetry and blowing agent decomposition was followed by thermogravitmetric analysis (TGA). The characterization of the cellular structure of the foamed samples was done using scanning electron microscopy. The mechanical properties of the foams were determined using compression tests and the thermal conductivity was assessed using the transient plane source method. The results indicated that the curing process and gas release took place in a similar time interval. The foams showed an isotropic cellular structure with relative densities in the range 0.35–0.60, and showed compressive strengths and compressive moduli in the range of 10–70 MPa and 400–1100 MPa, respectively. Thermal conductivities were in the range of 0.06–0.12 W m−1K−1. The findings in this paper demonstrate the possibility of producing polybenzoxazine foams using a simple process in which curing and foaming take place simultaneously. In addition, the mechanical characterization of these materials indicates that they are suitable for structural applications.Peer ReviewedPostprint (published version

Facile Preparation of Lightweight and Robust Polybenzoxazine Foams

“…Lorjai et al , prepared polybenzoxazine foams by both the sol–gel method and using azodicarbonamide as a foaming agent, and the highest compressive strength of 12.4 MPa was reached. Ardanuy et al also used azodicarbonamide as a foaming agent to prepare polybenzoxazine foams, and good mechanical strength was achieved. Zúñiga et alsynthesized benzoxazine from diphenolic acid and found that it could self-foam through decarboxylation during curing.…”

Preparation and characterization of polybenzoxazine foam with flame retardancy

“…[18,19] In addition, polybenzoxazine is compatible with various thermosetting resins and can be stored at room temperature, which makes it a potential candidate to replace phenolic resins in many fields. [20] In view of these valuable properties of polybenzoxazine and in order to address the issue mentioned above on the brittlenes of the phenolic foam, we consider that polybenzoxazine foam may be an appropriate material for polymeric foams with good mechanical and thermal properties and fire resistance. [21] However, the research of polybenzoxazine foams is far from adequate and only few reports are disclosed.…”

“…[ 21 ] However, the research of polybenzoxazine foams is far from adequate and only few reports are disclosed. Ardanuy et al [ 20 ] prepared and characterized polybenzoxazine foams using azodicarboxylamine (ADC) as a chemical blowing agent. The results revealed that the curing process and gas release took place in a similar time interval.…”

The preparation and thermomechanical properties of high‐temperature foams based on thermoplastic poly(phthalazinone ether ketone)

“…9 Research has also been conducted on high-temperature foams based on other polymers such as polysulfone, polyethersulfone, or polyetheretherketone although to our knowledge, some of these are not commercially-available at present. [10][11][12][13][14][15][16][17][18][19] All of these foams share one or more of the following key characteristics: high glass transition temperature (T g ), high melting point, chemically-stable at high temperature. In contrast to these examples of high-temperature foams, the more common foams cannot survive high temperatures because their T g is too low (e.g., polystyrene foam), melting point is too low (e.g., polyethylene foams), or they have poor chemical stability (e.g., polyurethane foams, which also often have a low melting or T g ).…”