Differential scanning calorimetry

About: Differential scanning calorimetry is a research topic. Over the lifetime, 50315 publications have been published within this topic receiving 1152335 citations. The topic is also known as: DSC.

How does “phase transformation toughening” work in semicrystalline polymers?

Abstract: The possibility of phase transformation toughening is demonstrated by the example of the β-modification of isotactic polypropylene (β-iPP), which undergoes βα-transformation (i.e., from hexagonal to monoclinic) during mechanical loading. The resulting α-iPP exhibits a higher crystalline density than the initial β-modification. That, along with the exothermic character of the βα-recrystallization, is responsible for the improvement in toughness that occurs. The occurrence of this βα-transformation is evidenced by differential scanning calorimetry (DSC). Toughness of the α- and β-iPP is studied and compared with the “essential work of fracture” concept by using static-loaded deeply double-edge-notched tensile (DDEN-T) specimens. The main effect of the βα-transformation is a large increase in the specific plastic work consumed in the necked zone. Light microscopic (LM) and infrared thermographic (IT) pictures reveal that the plastic zone becomes larger and its shape more circular when βα-transformation takes place. It is suggested that the principle of mechanical stress-induced phase transformation from a less toward a more dense crystalline state may be a universal tool for toughness upgrading in semicrystalline polymers.

Nucleation and Crystallization in Double Crystalline Poly(p-dioxanone)-b-poly(ε-caprolactone) Diblock Copolymers

Abstract: The crystallization behavior of three double crystalline diblock copolymers containing poly(e-caprolactone) and poly(p-dioxanone) has been studied via differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray scattering (WAXS). Crystallization and melting temperatures and enthalpies are compared among copolymers and to those of the corresponding homopolymers. Only one crystallization exotherm was observed for the diblocks. DSC and WAXS indicated that during isothermal crystallization PPDX crystallized first, followed by PCL. POM revealed a transformation of crystalline morphologies at around 50 °C, from granular aggregates at high temperature (where only PPDX is crystalline) to banded spherulites at lower temperature, where both blocks were crystalline. The kinetics of crystallization were studied in detail via spherulite growth rates obtained from POM, and it was found that PPDX crystallization in the diblocks occurred much more slowly than in the homopolymers, thi...

Crystallization of very low density copolymers of ethylene with α-olefins

Abstract: Differential scanning calorimetry (DSC) was used to analyze the crystal distribution in homogeneous ethylene–octene copolymers polymerized by the constrained geometry catalyst technology (CGCT). To minimize ambiguities from thermal history effects, copolymers were isothermally annealed at temperatures within the melting range. The cumulative crystallinity was related to the crystal distribution by the Gibbs–Thomson equation. The results provided a clear distinction between Type I copolymers (density less than 0.89 g/cc) and Type II copolymers (densities between 0.89 and 0.91 g/cc). The former had a singlecrystal population that was identified with the bundled crystals seen in transmission electron micrographs. In comparison, the latter had two crystal populations that correlated with lamellar crystals and bundled crystals. © 1995 John Wiley & Sons, Inc.