The complete submitted paper forming the body of this report forms deliverable MU3 d in the VAM 2000-2003 programme.
The paper incorporates some basic material originally described in report LGC/VAM/2002/016 part 2, but includes very substantial additional work.
The basic work in the previous report described the implementation of full curve fitting of a spherical particle diffusion model to polymer extraction data obtained by pressurised fluid extraction. The additions included in the present paper are:
- A comparison of the numerical model with the three-point extrapolation reported in earlier published work, showing marked improvement on manually acquired data from Soxhlet extraction.
- Extension to include plane sheet and cylindrical particle shapes, allowing film and fibre modelling respectively.
- Implementation of an improved uncertainty estimation method which allows for correlation among residuals; failure to take this effect into account can result in substantial underestimation of uncertainty and also compromise parameter estimates.
- An approximate implementation of a model based on concentration-dependent diffusion coefficient. This model resulted in a very marked improvement in fit compared to any of the constant diffusion coefficient models.