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300μm、0.51 g/cm3和12.5 MPa。
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 tempera-ture 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 av-erage size and homogeneity of the pores in the foams.
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