SYNOPSISThe present study deals with the investigation of the desorption of vinyl chloride from various commercial and experimental suspension PVC resins in a laboratory fluidized bed drier simulating an industrial drier. The results show that PVC resins may differ widely in the rate a t which the monomer is desorbed. The rate of diffusion of the monomer is a function of the drying time, the fluidization air temperature, the porosity, and the amount of glassy particles in the PVC. The residual monomer content decreases with increasing air temperature, drying time, and resin porosity. After 105 min of drying with hot air at 80°C, the residual monomer content in the grade with the highest porosity is reduced from 3400 to 2 ppm, whereas for the grade with the lowest porosity, it is reduced from 4300 to 172 ppm on a dry basis. It appears that the resins of the high molecular weight grades are more porous and the low molecular weight grades contain a high proportion of nonporous or glassy particles and, hence, the desorption rate is smaller in these grades. The proportion of glassy particles and the size of glassy domains are estimated in this study by applying the experimental desorption data at long times to a desorption model. The model is useful in differentiating the interior structure of various PVC grades.