Drying at room temperature of plasticized PVC previously immersed in liquids. Modelling and experiments
✍ Scribed by A. Aboutaybi; J. Bouzon; J.M. Vergnaud
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 518 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0014-3057
No coin nor oath required. For personal study only.
✦ Synopsis
Alrstract--For preparation of plasticized PVC sheets with low matter transfer when contacted with liquids, the process of drying of plasticized PVC previously immersed in the liquid is of interest. The complex process of drying for plasticized PVC has been elucidated with the help of experiments and a mathematical model. The model, based on a numerical method with finite differences, takes into account the diffusion of the liquid with a diffusivity depending on the concentrations of liquid and plasticizer, as well as the evaporation rate on the surface. At the end of the immersion of PVC in the liquid, two profiles of concentration are developed through the polymer for the liquid and for the plasticizer, with a high concentration of liquid and a low concentration of plasticizer on the PVC surface. Because of the evaporation of the liquid, another lower value of concentration is obtained for the liquid on the PVC surface. For these reasons, the liquid which has entered the PVC is trapped in the polymer; it can be evaporated only at high temperature. NOMENCLATURE CN,, = Concentration of the liquid at position n, at time (i + 1) At, CLE ~ C~ = concentration of liquid absorbed by thejPVC, at infinite time, Ci, = concentration of liquid absorbed by the PVC, after 15 min of immersion, Co = concentration of liquid on the PVC surface, Cpo = initial concentration of plasticizer in the sheet, D, = diffusivity (cm2/sec) at position n, h 0 = evaporation rate of pure liquid (g/cm2/sec), h = evaporation rate of liquid from the sheet, M, = dimensionless modulus at position n, M, = amount of liquid transferred at time t, M0 = initial weight of PVC sample, M~ = total amount of liquid absorbed by PVC, at infinite time, At = increment of time, L = thickness of PVC, Ax = thickness of a slice in PVC sheet, S = area of the sheet (2 × area of each face of the sheet). C~ = concentration of the liquid at position n, at time i. At.