So different degrees of thermal expansivity
are generated in different components of the machine tool, and the original relative positions between the components are altered.
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.
This means that thermal expansivity
will drive the phase separation process.
The isobaric linear thermal expansivity
is defined as [[alpha].
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.
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).
Thus the two functions currently available for comparisons of any kind are the thermal expansivity
and the bulk modulus.
Figure 5 shows how the molecular composite model accounts for the variation of the amorphous phase thermal expansivity
with the orientation parameter.