Types of Weight-Gain Data

A qualitative correlation between temperature T, penetrant activity a, and the forms of fluid penetration into polymers is given in the map depicted in Fig. 4.1 (Hopfenberg and Frisch 1969). 

Upon reviewing a large amount of data, it became possible to relate fluid sorption in polymers and polymeric composites by means of six schematic curves relating weight gain to y/i as sketched in Fig. 4.2 below. The scales marked in that figure apply to the linear Fickian (LF) plot alone. 

Curves A and B accord with data collected for both polymers and composites. Of these, A corresponds to a case where weight-gain never attains equihbrium, such as for two phase diffusion, and B represents the circumstance of two-stage diffusion. Weight gain data compatible with those curves are associated with benign fluid effects that are essentially reversible upon drying. 

Data represented by curves C and D are recorded mostly for polymeric composites. Of these, C accounts for the case of rapidly increasing fluid content, which is usually accompanied by damage growth that leads to material break down, large deformations, as well as occasional failure. 

Curve D accords with weight loss that is attributable to chemical or physical break-down of the material. This break down occurs mostly in the form of separations between fibers and polymer, caused by leaching along the fiber/matrix interphase regions, as well as by hydrolysis, i.e. the detachment of side groups from the backbones of the polymeric chains followed by chain scissions. 

---

Material system Exposure Type of weight-gain data sketched in Fig. 4.2 Reference... 

---