Abstract
The mass transport behavior of nitrobenzene in PET with different treatments was investigated in this study. The specimens were divided into three types. If the sample was annealed at 70℃, and it is usually amorphous state. This is called "standard specimen". When it is annealed at 140℃, the amorphous state was changed to the crystalline state. On the other hand, the specimen was underwent tensile test and its morphology is partial oriented crystalline structure. The mass transport behavior consists of CaseⅠtransport (diffusion controlled), Case Ⅱ transport (swelling relaxation controlled), and anomalous transport (mixed of Case Ⅰ and Case Ⅱ transport). The plots of D and V versus 1/T is followed the Arrhenius equation, and then activation energies Ed and Ev were obtained in the plot. The sharp front was observed by microscopy during the nitrobenzene absorption in crystalline PET for different periods. The various kinds of crystallization kinetics may be seen in this study. Comparing the Ev of three various specimens, it is found that the value is largest in crystalline specimen and the lowest in virgin specimen. Moreover, the mass transport behavior of nitrobenzene in crystalline PET is pure Case Ⅱ transport for each stage and divided into three stages. The distance of sharp front of nitrobenzene in crystalline PET is proportional to time belongs to Case Ⅱ transport for each stage. Ev and Evsp are obtained by Arrhenius plot from mass transport and sharp front observation. The mass transport behavior of standard and drawn PET were obeyed the Harmon's equation. During nitrobenzene transport, the solvent-induced crystallization was occurred. This result caused the change of morphology of standard PET. The solubility of specimens with three kind treatments is different. The solubility in standard PET is the largest one and that in crystalline PET is the smallest one. Finally, mass transport may cause swelling and softening. For tensile test with nitrobenzene, the tensile strength of specimen is significantly decreased after the specimen underwent nitrobenzene absorption. From the stress - strain curve, Yield strength (MPa), Young's modulus (MPa) and initial slope (N/mm) are quickly decreased with increasing immersion time. The necking propagation is almost disappears after the specific period about 129 hours in this study. For the necking propagation observation, both the necking propagation displacement and the necking propagation time are slowly decreased with increasing immersion time. But the necking propagation rate almost maintained constant value.