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Journal ArticleDOI

Heterogeneous dynamics in the curing process of epoxy resins.

17 May 2021-Scientific Reports (Nature Publishing Group)-Vol. 11, Iss: 1, pp 9767-9767
TL;DR: In this article, the microscopic dynamics in the curing process of a catalytic epoxy resin were investigated under different temperature conditions utilizing X-ray photon correlation spectroscopy, which revealed that the temperature conditions greatly affected the dynamical heterogeneity and cross-linking density of the cured materials.
Abstract: Epoxy resin is indispensable for modern industry because of its excellent mechanical properties, chemical resistance, and excellent moldability. To date, various methods have been used to investigate the physical properties of the cured product and the kinetics of the curing process, but its microscopic dynamics have been insufficiently studied. In this study, the microscopic dynamics in the curing process of a catalytic epoxy resin were investigated under different temperature conditions utilizing X-ray photon correlation spectroscopy. Our results revealed that the temperature conditions greatly affected the dynamical heterogeneity and cross-linking density of the cured materials. An overview of the microscopic mechanism of the curing process was clearly presented through comparison with the measurement results of other methods, such as 1H-pulse nuclear magnetic resonance spectroscopy. The quantification of such heterogeneous dynamics is particularly useful for optimizing the curing conditions of various materials to improve their physical properties.

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Citations
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Journal ArticleDOI
TL;DR: In this paper , the authors reviewed the recent approaches and important characteristics of EVO-based epoxy vitrimer, including the selection of EvO, classification of covalent adaptable network (CANs) and material properties.

5 citations

Journal ArticleDOI
16 Aug 2021-Polymer
TL;DR: In this paper, the authors used X-ray photon correlation spectroscopy (XPCS) to analyze the dynamics of a matrix-free nanocomposite consisting of poly(methyl methacrylate)-b-poly(butyl acrylate)g-silica nanoparticles (PMMA-b-PBA-g-SiNPs).

4 citations

Journal ArticleDOI
TL;DR: In this article , a denoising autoencoder model is integrated into workflows for the analysis of nonequilibrium two-time intensity-intensity correlation functions for X-ray photon correlation spectroscopy (XPCS) experiments.
Abstract: X-ray photon correlation spectroscopy (XPCS) provides an understanding of complex dynamics in materials that are tied to their synthesis, properties, and behaviors. Analysis of XPCS data for dynamics that are far from equilibrium is labor intense and often can impede the discovery process, especially in experiments with high collection rates. Moreover, binning and averaging, involved in the analysis for alleviating poor signal-to-noise ratio, leads to a loss of temporal resolution and the accumulation of systematic error for the parameters quantifying the dynamics. Here, we integrate a denoising autoencoder model into workflows for the analysis of nonequilibrium two-time intensity-intensity correlation functions. Noise reduction allows for extracting the parameters that characterize the sample's dynamics with the temporal resolution limited only by frame rates. Not only does it improve the quantitative usage of the data, but it also creates the potential for automating the analytical workflow, which is a key to high-throughput or autonomous XPCS experiments. Various approaches for the uncertainty quantification and extension of the model for anomalies' detection are discussed.

3 citations

Journal ArticleDOI
TL;DR: An autofluorescence technique to characterize polymerization progress in real time/in line was developed, which functioned in the absence of typical fluorogenic groups on the monomer or polymer as discussed by the authors .
Abstract: An autofluorescence technique to characterize polymerization progress in real time/in line was developed, which functioned in the absence of typical fluorogenic groups on the monomer or polymer. The monomer dicyclopentadiene and polymer polydicyclopentadiene are hydrocarbons that lack traditional functional groups for fluorescence spectroscopy. Here, the autofluorescence of formulations containing this monomer and polymer during ruthenium-catalyzed ring-opening metathesis polymerization (ROMP) was harnessed for reaction monitoring. The methods fluorescence recovery after photobleaching (FRAP) and here-developed fluorescence lifetime recovery after photobleaching (FLRAP) characterized polymerization progress in these native systems—without requiring exogenous fluorophore. (Auto)fluorescence lifetime recovery changes during polymerization correlated linearly to degree of cure, providing a quantitative link with reaction progress. These changing signals also provided relative rates of background polymerization, enabling comparison of 10 different catalyst-inhibitor-stabilized formulations. Multiple-well analysis demonstrated suitability for future high-throughput evaluation of formulations for thermosets. The central concept of the combined autofluorescence and FLRAP/FRAP method may be extendable to monitoring other polymerization reactions previously overlooked for lack of an obvious fluorescence handle.
References
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Journal ArticleDOI
TL;DR: In this article, a theoretical perspective is provided on the glass transition in molecular liquids at thermal equilibrium, on the spatially heterogeneous and aging dynamics of disordered materials, and on the rheology of soft glassy materials.
Abstract: A theoretical perspective is provided on the glass transition in molecular liquids at thermal equilibrium, on the spatially heterogeneous and aging dynamics of disordered materials, and on the rheology of soft glassy materials. We start with a broad introduction to the field and emphasize its connections with other subjects and its relevance. The important role played by computer simulations in studying and understanding the dynamics of systems close to the glass transition at the molecular level is given. The recent progress on the subject of the spatially heterogeneous dynamics that characterizes structural relaxation in materials with slow dynamics is reviewed. The main theoretical approaches are presented describing the glass transition in supercooled liquids, focusing on theories that have a microscopic, statistical mechanics basis. We describe both successes and failures and critically assess the current status of each of these approaches. The physics of aging dynamics in disordered materials and the rheology of soft glassy materials are then discussed, and recent theoretical progress is described. For each section, an extensive overview is given of the most recent advances, but we also describe in some detail the important open problems that will occupy a central place in this field in the coming years.

1,774 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis, curing process, and application of epoxy resins are reviewed and a review of the final properties of cured epoxide resins is presented. But, the authors do not consider the type of epoxide resin, curing agent, and curing process.

1,132 citations

Book ChapterDOI
TL;DR: In this article, a wide variety of rheological observations of materials in the vicinity of an LST are discussed with respect to their universality, and a variety of applications for polymers near the liquid-solid transition are presented that either already exist or can be envisioned.
Abstract: Polymeric materials near the liquid-solid transition (LST) exhibit a very distinct relaxation pattern. The reference point for analyzing these patterns is the instant of LST at which relaxation becomes self-similar over wide ranges of the relaxation time. The universality of this transition and its consequences have been explored extensively during the past decade. This study will present an overview of rheological implications inherent in liquid-solid transitions of polymers. The LST can be most reliably detected in a dynamic mechanical experiment in which the frequency independence of the loss tangent marks the LST. A wide variety of rheological observations of materials in the vicinity of an LST are discussed with respect to their universality. It is shown that polymer chemistry, molecular weight, stoichiometry, temperature, inhomogeneities, etc. greatly influence the material behavior near the LST. However, the characteristic self-similar relaxation is shown by all investigated materials, independent of the nature of the LST (e.g., both, physically and chemically crosslinking polymers). Several theories predict chemical and rheological properties in the vicinity of an LST. They are briefly discussed and compared with experimental results. A variety of applications for polymers near LST are presented that either already exist or can be envisioned. The self-similar relaxation behavior which results in a power law relaxation spectrum and modulus is not restricted to materials near LST. Different classes of polymers are described that also show power law relaxation behavior. What makes the self-similar relaxation specific for materials at LST is its occurrence at long times with the longest relaxation time diverging to infinity.

669 citations

Journal ArticleDOI
TL;DR: In this article, the times to gelation and to vitrification for the isothermal cure of an amine-cured epoxy (Epon 828/PACM-20) have been measured on macroscopic and molecular levels by dynamic mechanical spectrometry, infrared spectroscopy, and gel fraction experiments.
Abstract: The times to gelation and to vitrification for the isothermal cure of an amine-cured epoxy (Epon 828/PACM-20) have been measured on macroscopic and molecular levels by dynamic mechanical spectrometry (torsional braid analysis and Rheometrics dynamic spectrometer), infrared spectroscopy, and gel fraction experiments. The relationships between the extents of conversion at gelation and at vitrification and the isothermal cure temperature form the basis of a theoretical model of the time–temperature–transformation (TTT) cure diagram, in which the times to gelation and to vitrification during isothermal cure versus temperature are predicted. The model demonstrates that the “S” shape of the vitrification curve depends on the reaction kinetics, as well as on the physical parameters of the system, i.e., the glass transition temperatures of the uncured resin (Tg0), the fully cured resin (Tg∞), and the gel (gelTg). The bulk viscosity of a reactive system prior to gelation and/or vitrification is also described.

467 citations

BookDOI
22 Sep 2011
TL;DR: In this paper, a review of the experimental techniques that focus on molecular and polymeric glass formers, the challenges involved, and the results obtained in this relatively new field is presented.
Abstract: Dynamic heterogeneity refers to the independence of fast and slow modes in a system displaying dispersive relaxation and is not an alternative model to the dynamics in complex materials, but rather a required approach for rationalizing an increasing number of experimental results on supercooled liquids. The last twenty years has seen the advent of numerous experimental techniques aimed at studying the heterogeneous nature of viscous liquids. The methods either demonstrate heterogeneity per se, or provide information on the time‐ and length scale involved in this concept. This chapter reviews the experimental techniques that focus on molecular and polymeric glass formers, the challenges involved, and the results obtained in this relatively new field. Most approaches have particular strengths and weaknesses, so that only the synergistic efforts of combining numerous approaches will advance our understanding of the heterogeneous nature of dynamics significantly.

437 citations

Trending Questions (1)
How does the density of epoxy resin change over time during curing?

The provided paper does not mention how the density of epoxy resin changes over time during curing.