Storage modulus and foaming ability

How does frequency affect specific storage modulus?

Fig. 5 shows the specific storage modulus (E’/ρ) and the specific loss factor (tanδ/ρ) as a function of frequency, in the measuring range of 1 Hz–100 Hz. With increasing EMS content, the specific storage modulus decreases, regardless of d -lactide content.

Why does the storage modulus decrease at 25 °C?

The storage modulus decreases at 25 °C due to the foaming agent. In the case of foamed samples, the decrease in the initial modulus is smaller and it decreases above T g + 10 °C to the order of magnitude of the storage modulus of the unfoamed sample (5.7 MPa).

What is the difference between storage modulus and loss factor?

The storage modulus is maximal; the loss factor is minimal ( Fig. 4 .). As the temperature gradually rises, the smallest segments begin to move first, as the energy required for this is lower. As the temperature increases, both the loss modulus and the loss factor increase.

What are the properties of polylactic acid based foam?

One of the main properties of foams is their energy absorbing and damping ability, therefore it is important to study and develop these properties in polylactic acid-based foams as well. Foaming with thermally expandable microspheres (EMS) is a very promising method among continuous foaming technologies.

Why is TPU a good foaming material?

The melt strength and viscosity of TPU and cross-linked TPU in the foaming process are of great importance on the foam behavior. Higher complex viscosity and elastic modulus increase the ability of the polymer to support cell growth, which means better foamability .

Does PBAT increase the damping properties of closed-cell foam sheets?

We extruded closed-cell foam sheets from PLA with different d -lactide content. We extended the frequency-dependent properties of amorphous PLA foams to 20 000 Hz. The damping properties increase with an increasing foaming agent content. We increased the damping property of unfoamed PLA with the use of PBAT.