Effects of heating rate on the foaming behavior and pore structure of carbon foams derived from phenol-formaldehyde resin
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摘要: 结合热塑性酚醛树脂的热失重和粘-温特性，研究了升温速率对其发泡行为及泡沫炭力学性能的影响。结果表明，热塑性酚醛树脂的发泡温区在200～300℃，并遵循热点成核发泡机制；300～600℃温区中产生的裂解气主要影响气泡的膨胀速度，进而影响泡沫炭的孔径及孔结构的均一性；以0.5℃/min升至240℃，再以3℃/min升至600℃，所制泡沫炭孔结构较为均一，其平均孔径、密度及压缩强度分别为300 μm、0.51 g/cm3和12.5 MPa。Abstract: The effect of heating rate on the foaming behavior of phenol-formaldehyde resin and the pore structure and compressive strength of the carbon foams produced were investigated. Results indicate that the viscosity of the resin changes little with temperature between 135 and 225℃, but increases abruptly above 225℃. The foams are formed between 200 and 300℃ by gas released during pyrolysis and the foaming behavior follows the hot-spot nucleation mechanism. By increasing the heating rate from 0.5 to 3℃/min the average pore size decreases from 304 to 267 μm, and the density and compressive strength increase from 0.34 to 0.51 g/cm3 and 6.1 to 12.5 MPa, respectively. The heating rate affects the expansion velocity of the bubbles formed, and the average size and homogeneity of the pores in the foams.
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Key words:
- Carbon foam /
- Phenol-formaldehyde resin /
- Pore structures
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