1404 M C. Paina et al. / Carbon 41(2003)1399-1409 molten state for a sufficiently long duration( I h)below the order of the reaction was obtained from Eqs. (3)and 240C to allow further melt spinning (4), where a and b were estimated as described in Fig 4 From the dsc thermograms obtained at different heat- ing rates(5-20C/min), Fig. 3, it was observed that the maximum of the reaction peak was dependent on heating In k=In p +In rate. Based on these data, the Kissinger method [14 was used to estimate reaction kinetics parameters. The activa- tion energy was derived from the temperature dependence S=b of the peak maximum on the heating rate, as described by q(1) n=126√S The results for kinetic parameters, summarized in Table 2, suggest that the activation energy is smaller for the Vt (1) polymer than that of M polymer. This would be expected because the Vt polymer has a higher methyl acrylate content, and methyl acrylate is known to act as an initiator The frequency factors were calculated using Eq (2), and for the cyclization reaction [6]. However, the frequency M Fibers,lCN川H(CH2) spun VT Fibers, I(C N)/(CH2) A∈6pun Uv25h uv ht Fig. 6. Nitrile ratio for samples treated at various conditions, as determined by FT-IR-ATR spectroscopy1404 M.C. Paiva et al. / Carbon 41 (2003) 1399–1409 molten state for a sufficiently long duration (| 1 h) below the order of the reaction was obtained from Eqs. (3) and 240 8C to allow further melt spinning. (4), where a and b were estimated as described in Fig. 4. From the DSC thermograms obtained at different heat￾ing rates (5–20 8C/min), Fig. 3, it was observed that the E f E maximum of the reaction peak was dependent on heating ln k 5 ln ] 1 ln ]1 ]] (2) 2 R RT T m m rate. Based on these data, the Kissinger method [14] was used to estimate reaction kinetics parameters. The activa- a S 5 ] (3) tion energy was derived from the temperature dependence b of the peak maximum on the heating rate, as described by ] Eq. (1): n 5 1.26ŒS (4) ] f The results for kinetic parameters, summarized in Table d ln S D2 T m E 2, suggest that the activation energy is smaller for the VT ]]]5 2 ] (1) 1 R polymer than that of M polymer. This would be expected dS D ] because the VT polymer has a higher methyl acrylate Tm content, and methyl acrylate is known to act as an initiator The frequency factors were calculated using Eq. (2), and for the cyclization reaction [6]. However, the frequency Fig. 6. Nitrile ratio for samples treated at various conditions, as determined by FT-IR-ATR spectroscopy