Thermal degradation of ceramic slurry-coated polyurethane foam used in making reticulated porous SiC ceramics

Abstract

A 25-μm-thick ceramic slurry-coated 12 ppi (pores per linear inch) polyurethane foam suitable for synthesis of oxide-bonded reticulated porous SiC ceramics was analysed by the thermal analysis techniques (thermogravimetry and differential thermal analysis) up to 700 °C in air to investigate the polymer degradation reactions associated with the pyrolysis stage of the fabrication process. The kinetic parameters of the polymer degradation reactions were determined using the non-isothermal thermogravimetric data, and the degradation mechanism was evaluated. The effects of slurry coating on the foam degradation process were discussed, and slurry coating on foam was found to have insignificant effects on PUF degradation reactions.

Appendix

Determination of loss in mass in slurry-coated PUF sample

Let X _sp is the initial mass of the slurry-coated PUF sample (in mg), F _sp is the final mass retention (in %), and t _sp is the mass retention (in %) at any time t. Let for the ceramic powder obtained by drying the slurry, the corresponding figures are X _s , F _s and t _s.

$${\text{Final mass }}\left( {\text{in mg}} \right){\text{ of the slurry-coated PUF sample }} = \, \left( {X_{\text{sp}} \times F_{\text{sp}} } \right)/100$$

(7)

Let us suppose that the entire sample of the slurry-coated PUF contains only slurry. In this case,

$${\text{Final mass }}\left( {\text{in mg}} \right) \, = \, \left( {X_{\text{sp}} \times F_{\text{s}} } \right)/100$$

(8)

$${\text{Then, the mass }}\% {\text{ of slurry in the slurry-coated PUF }} = \, \left[ {\left( {X_{\text{sp}} \times F_{\text{s}} } \right)/ \, \left( {X_{\text{sp}} \times F_{\text{sp}} } \right)} \right] \, \times \, 100 = \, \left[ {F_{\text{s}} /F_{\text{sp}} } \right] \, \times \, 100$$

(9)

$${\text{The mass }}\% {\text{ of PUF in the slurry-coated PUF }} = \, \left[ {1 \, {-} \, \left( {F_{\text{s}} /F_{\text{sp}} } \right)} \right] \, \times \, 100$$

(10)

$${\text{Initial mass }}\left( {\text{in mg}} \right){\text{ of PUF in the slurry-coated PUF or }}m_{\text{i}} = X_{\text{sp}} \times \, \left[ {1 \, {-} \, \left( {F_{\text{s}} /F_{\text{sp}} } \right)} \right]$$

(11)

$$\begin{aligned} {\text{Final mass }}\left( {\text{in mg}} \right){\text{ of PUF in the slurry-coated PUF or }}m_{\text{f}} \hfill \\ = \, \left( {X_{\text{sp}} \times F_{\text{sp}} } \right)/100 \, {-} \, \left[ {X_{\text{sp}} \times \, \left( {F_{\text{s}} /F_{\text{sp}} } \right) \, \times F_{\text{s}} } \right]/100 \hfill \\ = \, \left( {X_{\text{sp}} /100} \right) \, \left[ {F_{\text{sp}} {-}F_{\text{s}}^{2} /F_{\text{sp}} } \right] \hfill \\ \end{aligned}$$

(12)

$$\begin{aligned} {\text{Mass }}\left( {\text{in mg}} \right){\text{ of PUF in the slurry-coated PUF at any time }}t{\text{ or }}m_{t} \hfill \\ = \, \left( {X_{\text{sp}} \times t_{\text{sp}} } \right)/100 \, {-} \, \left[ {X_{\text{sp}} \times \, \left( {F_{\text{s}} /F_{\text{sp}} } \right) \, \times t_{\text{s}} } \right]/100 \, \hfill \\ = \, \left( {X_{\text{sp}} /100} \right) \, \left[ {t_{\text{sp}} {-} \, \left( {F_{\text{s}} /F_{\text{sp}} } \right) \, \times t_{\text{s}} } \right] \hfill \\ \end{aligned}$$

(13)

Thus, the degree of conversion for PUF in the slurry-coated PUF at time t or,

$$\alpha = \frac{{m_{\text{i}} - m_{\text{t}} }}{{m_{\text{i}} - m_{\text{f}} }}$$

(14)

can be determined by Eqs. (11)–(14).