Deeper insights into the thermal properties of epoxy thermoset resins using torsion measurements

Abstract

The glass transition temperature (T g ) of epoxy thermosets is a critical material property that depends on the component chemistry, the final cross-link density, and processing conditions. This study incorporates dynamic mechanical analysis (DMA) testing with a torsion clamp geometry on a TA Instruments DHR-2 and differential scanning calorimetry (DSC) to characterize five different two-component epoxy-amine systems. Investigation of the T g dependence on DMA frequency and heating shows that lowering the frequency from 1 to 0.01 Hz results in a T g very similar to that measured using DSC, while a heating rate of 0.3 C/min using DMA gives a T g comparable to the DSC measured value at 30 C/min. The DMA technique reveals secondary relaxation transitions and peak broadening in the tan(δ) plots of poorly mixed epoxy blends, quantified using full width at half maximum (FWHM) of tan(δ) peaks, and are indicative of a non-homogeneous cross-linked network and off-ratio blending, respectively. The increase in the FWHM due to poor mixing ranges from 8% to 96%. These parameters are easily measurable and quantifiable in DMA, but are not observed in DSC. The additional DMA insights are valuable for process development and failure analysis, and can improve the understanding of epoxies.

Thermo-curable and photo-patternable polysiloxanes and polycarbosiloxanes by a facile Piers–Rubinsztajn polycondensation and post-modification

“…Moreover, the maximum value of the tan δ peak was merely 0.14, indicating that a secondary relaxation of the cured network existed upon heating. 25,34 At the same time, the DSC results (Fig. S14, ESI †) showed no evidence of glass transition from −10 to 400 °C, proving that the glass transition of the fully cured resins may occur at higher temperatures (above 325 °C by DMA).…”

Effect of Plasticization on Stretching Stability of Poly(Vinyl Alcohol) Films: A Case Study Using Glycerol and Water

“…The DMA spectra of tan δ versus temperature for both of the PVA/GLY and PVA/H 2 O films are shown as Figure S6 (Supporting Information). It is worthy to note that the loss peak of tan δ refers to the occurrence of glass transition, [ 27 ] thus the glass transition temperature ( T g ) of PVA film can be determined from the tan δ versus temperature spectrum. The plasticizer‐content dependences of T g are plotted in Figure 3b.…”