**5. References**

14 Mass Transfer in Chemical Engineering Processes

first step for the study of diffusion issue. The molecular diffusion coefficient tested in the paper is under static condition; nevertheless, how to evaluate the molecular diffusion under

> 20.1 19.6 19.4 19.2 19.0 18.9 18.7 pressure(MPa)

Fig. 7. Relationship of N2 mole fraction in liquid phase and its diffusion coefficient in N2-oil

20.1 18.4 17.6 17.0 16.5 16.0 15.5 pressure(MPa)

Fig. 8. Relationship of CH4 mole fraction in liquid phase and its diffusion coefficient in CH4-

the relation between P and D the relation between P and content

the relation between P and D the relation between P and content

0.00

0.00

0.05

0.10

0.15

0.20

content(f)

0.25

0.30

0.35

0.40

0.02

0.04

0.06

0.08

content (f)

0.10

0.12

0.14

dynamic condition needs to develop new theories and testing method further.

5.536

2.22

2.23

2.24

2.25

2.26

diffusion coeficient (10-12

oil diffusion experiment

m2/s)

2.27

2.28

2.29

2.30

5.54

5.544

diffusion coeficient (10-12

diffusion experiment

m2/s)

5.548

5.552

5.556


**2** 

*Iran* 

Mohammad Karimi

**Diffusion in Polymer Solids and Solutions** 

The industrial importance of penetrable and/or impenetrable polymer systems is evident when one faces with a huge number of publications considering various aspects of diffusion phenomenon. Strong worldwide interest to realize more details about the fundamental of the process, generalize the governed laws to new findings, and find fast and reliable

Polymers are penetrable, whilst ceramics, metals, and glasses are generally impenetrable. Diffusion of small molecules through the polymers has significant importance in different scientific and engineering fields such as medicine, textile industry, membrane separations, packaging in food industry, extraction of solvents and of contaminants, and etc. Mass transfer through the polymeric membranes including dense and porous membranes depends on the factors included solubility and diffusivity of the penetrant into the polymer, morphology, fillers, and plasticization. For instance, polymers with high crystallinity usually are less penetrable because the crystallites ordered has fewer holes through which gases may pass (Hedenqvist and Gedde, 1996, Sperling, 2006). Such a story can be applied for impenetrable fillers. In the case of nanocomposites, the penetrants cannot diffuse through the structure

In the present chapter the author has goals of updating the theory and methodology of diffusion process on recent advances in the field and of providing a framework from which the aspects of this process can be more clarified. It is the intent that this chapter be useful to

An enormous number of scientific attempts related to various applications of diffusion equation are presented for describing the transport of penetrant molecules through the polymeric membranes or kinetic of sorption/desorption of penetrant in/from the polymer bulk. The mass transfer in the former systems, after a short time, goes to be steady-state, and in the later systems, in all the time, is doing under unsteady-state situation. The first and the second Fick's laws are the basic formula to model both kinds of systems, respectively (Crank

Diffusion is the process by which penetrant is moved from one part of the system to another as results of random molecular motion. The fundamental concepts of the mass transfer are

techniques of measurement, makes motivation to follow in this field of science.

directly; they are restricted to take a detour (Neway, 2001, Sridhar, 2006).

**1. Introduction**

scientific and industrial activities.

**2. Diffusion process** 

and Park, 1975).

**2.1 Fick's laws of diffusion** 

*Amirkabir University of Technology, Department of Textile Chemistry* 

