If density is independent of pressure, and therefore volume expansivity
is also independent of pressure (that is, the fluid is "incompressible"), Equation (9) simplifies to
Furthermore, it appears that thermal expansivity
effects dictate the phase separation process in polybutadienes of varying microstructure.
The reason is that functionally gradient materials can develop and relax the extra stress which caused by the different thermal expansivity
and are supposed to improve the welding strength and constant capacity.
Because the physical constraint of the material by the mold will convert thermal contraction strain into thermal stress, both the Young's Modulus and the expansivity
of the material are important to characterize.
The anisotropic expansivity
of the blends shows a strong dependence on PLC concentration and orientation direction.
In the range of purely elastic strains, both W and Q of each FRP component in stretching (+) and contraction (-) cycles should behave reversibly, the sign of Q being determined by that of the linear expansivity
In addition to the obvious significance of the time dependence of the volume following various thermal treatments, the thermal expansivity
as such represents one of the key variables in this context.
The thermal expansivity
and compressibility could be related to the free volume fraction and positive deviations from linearity were noticed in the former.
Compared with engineering plastics (EPs), PLCs have greater mechanical strength and thermal stability, frequently lower melt viscosity, exhibit lower flammability and thermal expansivity
, are more stable in vacuum, and resist chemical and radiational degradation (18-20).
Both aspects will affect the thermal expansivity
and mechanical properties of the film, which in turn are related to the stress in the film after curing.
Thus the two functions currently available for comparisons of any kind are the thermal expansivity
and the bulk modulus.
Roth, "Unpublished Observations of Density and Expansivity
," in J.
This conclusion is consistent with our previous thermal conductivity and expansivity
measurements on the same series of blends .