Abstract
The mass transport behavior of buffer in hydroxyethyl methacrylate copolymer (HEMA) at the temperature of 35℃-55℃ was investigated. The HEMA was irradiated with gamma-ray at radiation doses of 86-344 kGy in air. The buffer was prepared by citric acid anhydrous and sodium phosphate dibasic anhydrous. The pH values of buffer are 3.2~7.2.The transport behavior was studied by Harmon’s model. When the pH value of buffer is lower than 5.6, the experimental data are in excellent agreement with the Harmon’s model. If the pH value of buffer is larger than 5.6, the experimental data was divided into two stages. The first stage is pure Case I and the second stage is anomalous diffusion. The activation energies for diffusion (ED) and relaxation processes (Ev) were calculated from the Arrhenius plots of D and v.When the specimen, absorbed in buffer, is saturation, the solubility (S) of solvent in the specimen was determined. If the pH value of buffer increased, the solubility increased, too. For pH 3.2 and 4.1, the solubility decreased with increasing gamma-ray dosage. However, the sequence is opposite for pH 6.5 and 7.2.Compared the transition time when stage I switch to stage II and the time when the sharp front meet, we can find that the mechanisms changed due to the sharp front.The FTIR spectrum of HEMA showed a new peak at 1565cm-1 after the mass transport if the buffer of pH≧5.6. The peak was induced by C6H7O7- in HEMA.