A previous post described the tensile testing of polymers. The tensile test typically measures the load extension curve (stress-strain as seen above) until the sample breaks.  The toughness of the polymer can be estimated by the area under the stress strain curve.  The curves for the thermosets have a high modulus (steep slope in the initial linear region), but have little ... [Click to Continue...]

Over the years there have been many posts on the characterization of polymers that were focused mainly on thermosets.  In the next series of posts, we will discuss various types of mechanical testing that can be used to characterize the mechanical properties of both thermosets and thermoplastics.  In this post, we will discuss tensile testing for polymers. ASTM D638 ... [Click to Continue...]

The last post described the experimental procedure for the heat deflection temperature (HDT).  A lot of technical data sheets show the HDT to aid in the material selection process.  The HDT represents the upper use temperature for a particular polymer, formulation or composite.  Recall from the last post that the HDT is defined as the temperature at which a standard dimension ... [Click to Continue...]

A question that often arises when looking at technical data sheets is what is the difference between the glass transition temperature (Tg) and the heat deflection (or heat distortion) temperature (HDT).  To be clear, they are not the same and there is some confusion around the comparison.  Many factors can influence the HDT.  Let’s first begin by describing the heat deflection ... [Click to Continue...]