Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Abstract

Self-nucleation (SN) is a special nucleation process triggered by selfseeds or self-nuclei that are generated in a given polymeric material by specific thermal protocols or by inducing chain orientation in the molten or partially molten state. SN increases the nucleation density of polymers by several orders of magnitude, producing significant modifications to their morphology and overall crystallization kinetics. In fact, SN can be used as a tool for investigating the overall isothermal crystallization kinetics of slow-crystallizing materials by accelerating the primary nucleation stage in a previous SN step. Additionally, SN can facilitate the formation of one particular crystalline phase in polymorphic materials. The SN behavior of a given polymer is influenced by its molecular weight, molecular topology, and chemical structure, among other intrinsic and extrinsic characteristics. This review paper focuses on the applications of DSC-based SN techniques to study the nucleation, crystallization, and morphology of different types of polymers, blends, copolymers, and nanocomposites.

Differential scanning calorimetry study of cross‐nucleation between polymorphs in isotactic poly(1‐butene)

“…With this aim, a standard self‐nucleation procedure was followed. The standard crystalline state was created by annealing the sample at 140 °C (or 120 °C for Form I seeded samples) for 3 min before cooling to 30 °C at 10 °C min −1 .…”

“…At this stage, the sample was heated to a selected self‐nucleation temperature (holding time of 5 min), and the subsequent crystallization temperature upon cooling at 10 °C min −1 was recorded. An extensive description of the self‐nucleation thermal protocol can be found elsewhere …”

“…In domain I a constant recrystallization temperature is found, while the crystallization process is enhanced for self‐nucleation within domain II. At lower temperatures the sample is not completely molten, and traces of annealed crystals with higher melting point are found in the heating scan after recrystallization …”

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

“…Hence, often in industrial settings, external nucleating agents are added to decrease the nucleation barrier in order to accelerate crystallization. It has also been demonstrated that self‐nucleation can be highly effective in increasing crystallization rate . The number of nuclei induced by self‐nucleation can overcome, by several orders of magnitude, the number of commonly found heterogeneous nuclei in a bulk polymer.…”

Fast Scanning Calorimetry

“…The melting of crystals at low temperatures near T g retains nuclei that can enhance cold-crystallization. For high melting temperatures such nucleus retention has in the past been called selfnucleation and the nuclei were found to survive heating above the equilibrium melting temperature [226][227][228][229][230][231]. This research has, thus, opened a new direction of inquiry to gather quantitative information about nucleation and growth of polymer crystals as it affects the amorphous and crystalline phases and their interrelationship.…”