Heat Deflection VS Coefficient of Thermal Expansion?

Question

I was looking at a spec sheet for a photopolymer and saw these two different subsections under the "Thermal" section. I tried Googling around as I usually do, but no site could give me the clear difference between the two and some simply defined the two as the same. I have a hard time believing that since there are two distinct test methods indicated by the ASTM. Could someone please clarify what the difference is?
PS - To further clarify, I mean the difference between the two results, not the ASTM test methods.

Pete W · Accepted Answer

CTE characterizes dimensional change, with no load. It corresponds to a relatively fundamental physical principle, making it easy to use in a design calculation
Heat Deflection test characterizes the deformation under heat AND load, which includes a variety of phenomena happening at the same time. The result is dependent on the particular geometry and loading conditions specified by the test, in a way that makes it hard to extrapolate for design purposes. On the other hand, it is more useful when "shopping" for a material, by making it possible to compare them in standard conditions for applications that are limited by both heat and load at the same time.
For the two different lines of the heat deflection test, they correspond to different standard loads.
Annoyingly, the actual standards are not made freely available, but a general description can usually be found with a little searching. (e.g. here is one for ASTM-D648 )

Solar Mike · Answer

The coefficient of thermal expansion is the change in size of the material as the temperature changes, which is obvious when looking at the units: a length change per metre per degree.
Heat deflection is not about a change in length.

Heat Deflection VS Coefficient of Thermal Expansion?

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