1. The mechanism of absorption
The absorption isotherms of phenol and the resulting contraction of polyethylene terephthalate (PET) fibres were investigated in relation to their thermal history.
The phenol absorption in the drawn yarn heat-treated at 220°C without tension is of the Langmiur type. In the case of as-drawn or low temperature treated samples, the isotherms are not of the Langmiur type and is accompanied by the contractions of samples on absorption. In the IR spectra of absorbed phenol
v OH of phenol appears at 3, 468 cm
-1, indicating that phenol is absorbed in PET through hydrogen bonding. The results make us to conclude that the true isotherm of phenol on PET fibre should be of Langmiure type. Thus is due to the change of the fine structure with absorption of phenol, that isotherms other than the Langmiur type are observed for samples with certain thermal history. The structural properties of the absorption region are also discussed in relation to i) the total sites available for the absorption, ii) the fraction of gauche form of ethylenedioxy linkage and iii) the peak intensity of X-ray small angle scattering.
2. The estimation of the lateral order distribution
The weight fraction of the amorphous region, _??_, which is available for the absorption of phenol from the aqueous solution of a certain concentration
x is determined by the equation (2), assuming that the carbonyl groups in the amorphous region are only available for the absorption site and the Langmiur relation between the amount of phenol absorbed in the sample and the concentration in the solution is held at absorption equiribrium. Where
M is the number of total site in the unit weight of sample [in equation (2), mg phenol/g sample was used as the unit of
M.],
m the number of site occupied in the unit weight of sample and
K the equiribrium constant of the absorption-which was determined from a Langmiur isotherm of the sample heat-treated at 220°C without tension.
In the case of drawn or low temperature treated samples, _??_ has been observed to increase with increasing
x due to the fusion of low order region in the samples. The summative mass order curves can be drawn by plotting _??_ against
x, if
x is assumed to be a measure of order. The lateral order distribution curves are obtained by plotting the slope of the summative curves against the order function
x.
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