The mechanism of mass transport and the related crystallization in poly(ethylene terephthalate) (PET) were studied. Solvent-induced crystallization can occur during the transport process in PET at low temperature. The important effect of changing the surrounding medium to solvent molecules is to reduce the glass transition temperature. This phenomenon is called “plasticization”. The extent of plasticization relies on the amount of solvent around the polymer molecules, i.e., the concentration of solvent which will depend on the mass transport before saturation. Evidences for the transport mechanism in the first stage of crystallization were revealed. The distinct diffusion front was determined from the measurements of optical microscope and microhardness. The differential scanning calorimeter (DSC) curves displayed crystallization exothermic peaks whose areas decreased with the amounts of amorphous regions, representing the solvent-induced crystallization (SINC) process. The observed phenomenon of multiple-stage crystallizations is associated with the variation of boundary conditions during mass transport, which was ignored in most theoretical analyses.

Solvent transport in poly(ethylene terephthalate) (PET) and related phase transformation were investigated. The data of mass sorption were analyzed according to Harmon's model for Case I (Fickian), Case II (swelling), and anomalous transport. This transport process in PET is accompanied by the induced crystallization of the original amorphous state. The transformation was examined by wide‐angle X‐ray scattering, small‐angle X‐ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy. During this process, the matrix is under a strain state that causes different kinetic paths of crystallization as compared with that by thermal annealing. This state of strain assists the development of the solvent‐induced crystallization. The model regarding crystallization was proposed in terms of the study of long period L, the crystal thickness lc, and the thickness of amorphous layer la obtained from the one‐dimensional correlation function and interface distribution function. Different kinetic paths were discovered for different crystallization processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1444–1453, 2002

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When ammonia is added in methane to form carbon films using thermal chemical vapor deposition, effects of the ammonia/methane ratio on the deposition rate and microstructures of carbon films are investigated. Meanwhile, effects of the deposition temperature, working pressure, and residence time on the deposition rate are also considered. Experimental results indicate that as the ammonia/methane rate increases, the deposition rate of carbon films decreases, and also, the ordered degree, nano-crystallite size, and sp2 carbon atoms of carbon films increase. Nevertheless, if the deposition temperature, working pressure, and residence time increase, the deposition rate of carbon films increases. The relationship between the deposition rate and deposition process parameters is formulated. The deposition process is controlled by the process to create mono-carbon and bi-carbon species in carbon films. Moreover, one mono-nitrogen will suppress about three mono-carbons to form carbon films. Few nitrogen and hydrogen atoms are incorporated into carbon films. The activation energy (507 kJ/mole) of carbon deposition is related to the activation energies of methane and ammonia dissociation. If the working pressure is smaller than a threshold value (30 kPa) or the residence time is shorter than a threshold value (1.5 s), no film is formed