Chemistry Reference
In-Depth Information
1.2
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02468
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0246810
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02468 0
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(a)
11.1
Profiles of absorption rate of cobalt in PAN fibres as a function of
precipitation bath parameters: (a) NaCNS concentration being
(1) 6%, (2) 8% and (3) 10%; (b) temperature being (1) 273 K,
(2) 283 K and (3) 293 K; and (c) plasticisation drawing being
(1) 500%, (2) 700%, (3) 900% and (4) 1100%. (Reprinted by
permission of
Textile Research Journal
.)
The metal ion uptake profiles are shown in Fig. 11.1 for variations of
NaCNS concentration (Fig. 11.1a), temperature (Fig. 11.1b) and plasticisa-
tion drawing (Fig. 11.1c) of the precipitation bath for Co uptake. Similar
curves were obtained with Ni. Table 11.2 shows the data for different para-
meters related to a fully metallised fibre obtained after metallisation of
PAN fibres, produced under different experimental conditions of the pre-
cipitation bath. Despite the fact that the uptake profiles are considerably
different and the data obtained (diffusion coefficient) confirms this, no
remarkable changes are observed in the total amount of metal absorbed by
the fibre. This means that saturation for metal uptake is obtained indepen-
dently of the precipitation bath parameters. The role of these parameters is
limited to the rate of metal uptake, and a choice for the optimal value of
these parameters should be based on economic reasons; first the consump-
tion of chemicals and energy and, secondly, the processing time. Taking
these two criteria into account, a NaCNS concentration of about 12%, a
temperature of 283 K and a plasticisation drawing of 500% are further used.
11.2.4 Physico-mechanical properties of the metallised
PAN fibres
Freshly produced PAN fibres, obtained under optimal conditions for met-
allisation, were treated with NiCl
2
and CoCl
2
solutions for different immer-
sion times. After treatment, an excess of liquor was removed and the fibres
were dried, thermofixated at 413 K for 20 min and washed until negative
reaction against Ni and Co ions was observed. Finally, the physico-
mechanical properties of the fibres were determined and are shown in Table
