Influence of MMT content on the microstructure and miscibility for PU/EP IPN nanocomposites by positron

Zhu, Yuchan; Zhou, Wei; Wang, Junjun; Wang, Bo; Kong, Lingbao; Jia, Qingming

doi:10.1002/pssc.200675853

Cited by 5 publications

(6 citation statements)

References 8 publications

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“…Meanwhile, it should be noted that in the 4% MBPF spectra, the shift of the peak from 3315 (O–H stretching vibration) to 3279 cm −1 was more obvious compared with other spectra, indicating stronger hydrogen bonding between the BPR chains and MMT. In addition, as reported in the literature [44,45], the strong interaction between the BPR chains and MMT corresponded to the good dispersion of MMT in the materials. In other word, the well dispersed MMT with a larger surface area of dispersed phase is beneficial to form hydrogen bonding [45].…”

Section: Resultssupporting

confidence: 74%

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Preparation and Characterization of Bio-oil Phenolic Foam Reinforced with Montmorillonite

Chang

et al. 2019

Polymers

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Introducing bio-oil into phenolic foam (PF) can effectively improve the toughness of PF, but its flame retardant performance will be adversely affected and show a decrease. To offset the decrease in flame retardant performance, montmorillonite (MMT) can be added as a promising alternative to enhance the flame resistance of foams. The present work reported the effects of MMT on the chemical structure, morphological property, mechanical performance, flame resistance, and thermal stability of bio-oil phenolic foam (BPF). The Fourier transform infrared spectroscopy (FT-IR) result showed that the –OH group peaks shifted to a lower frequency after adding MMT, indicating strong hydrogen bonding between MMT and bio-oil phenolic resin (BPR) molecular chains. Additionally, when a small content of MMT (2–4 wt %) was added in the foamed composites, the microcellular structures of bio-oil phenolic foam modified by MMT (MBPFs) were more uniform and compact than that of BPF. As a result, the best performance of MBPF was obtained with the addition of 4 wt % MMT, where compressive strength and limited oxygen index (LOI) increased by 31.0% and 33.2%, respectively, and the pulverization ratio decreased by 40.6% in comparison to BPF. These tests proved that MMT can blend well with bio-oil to effectively improve the flame resistance of PF while enhancing toughness.

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Section: Resultssupporting

confidence: 74%

“…In addition, as reported in the literature [44,45], the strong interaction between the BPR chains and MMT corresponded to the good dispersion of MMT in the materials. In other word, the well dispersed MMT with a larger surface area of dispersed phase is beneficial to form hydrogen bonding [45].…”

Section: Resultssupporting

confidence: 74%

Preparation and Characterization of Bio-oil Phenolic Foam Reinforced with Montmorillonite

Chang

et al. 2019

Polymers

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“…In epoxies, the o-Ps lifetime shows strong variations with the hardening and cross-linking process (69,99,(108)(109)(110). Systematic changes of the hole volume with the composition were detected for copolymers (76,89,111), blends (112)(113)(114)(115), and composites filled with carbon black (116,117), silica (118), nanoclays (119,120), or fullerenes (121). For α-olefin copolymers, for example, the hole volume shows a systematic variation with the number and length of branches and with the value of T g (122).…”

Section: The Influence Of Other Structural Properties On Palsmentioning

confidence: 99%

Positron Annihilation Spectroscopy

Dlubek

2008

Encyclopedia of Polymer Science and Technology

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FundamentalsThe positron is the antiparticle of the electron, ie, it has the opposite charge but otherwise the same properties. In matter, a positron may be created either by the β + decay of an unstable nucleus or from a high-energy γ-photon via e + -e − pair production. If the positron encounters an electron, both particles annihilate, ie, they are transformed into photons of an energy, which is given by the famous Einstein equation, E = 2mc 2 . Here, m is the mass of the electron, c the speed of light in vacuum, and for particles at rest E = 2 × 0.511 MeV. The selection rules for the γ-photon emission are derived from the conservation laws of energy and momentum and parity considerations. Free positrons annihilate mainly into two γ-photons of energy 0.511 MeV emitted in almost collinear directions, or with much less probability into three photons of an overall energy of 1.022 MeV (16,24,25).In nonconducting materials, such as polymers, positrons can exist as free particles (e + ) or as positronium (Ps, e + e − ), which is a positron-electron bound state. Ps was experimentally discovered by DeBenedetti and Richings in 1952 (26). The "chemical" symbol Ps for positronium appears to have been introduced by McGervey and DeBenedetti in 1959 (27). Its properties and interaction with matter were reviewed in several articles (25-30). Ps is a particle of the size of a hydrogen atom, r Ps = 0.53Å, but only the mass of two electrons, and a binding energy of 6.8 eV, that is half of the ionization energy of hydrogen. The lifetime of a Ps atom depends on the relative spin orientation of positron and electron. The para-Ps (p-Ps, singlet state, spins antiparallel) decays into two photons with a mean intrinsic lifetime (self-annihilation in a vacuum) of τ pPs 0 = 0.125 ns. The ortho-Ps (o-Ps, triplet state, spins parallel) can decay only into three photons, a much slower process than two-photon emission. Therefore, o-Ps has an intrinsic lifetime of τ oPs 0 = 142 ns. The formation probabilities of the p-Ps and o-Ps states are 0.25 and 0.75 of the total Ps yield (16,25).In condensed matter studies, 22 Na is usually used as the positron source. This isotope has a half-life of 2.6 years and emits positrons with an energy distribution that has its maximum at 0.20 MeV and ranges up to 0.54 MeV (10,16). The stopping profile of positrons is a decreasing exponential function. In materials with a density of 1 g/cm 3 50%, 90%, and 99% of positrons are stopped within a thickness of 0.170, 0.60, and 1.20 mm, respectively. The energetic positrons lose their energy rapidly via ionization and excitation of electrons and finally phonons. After a few picoseconds, the positrons are in thermal equilibrium with the ambient material. In defect-free molecular crystals, positrons migrate over a mean distance of typically 100 nm before annihilating. In defected crystals and in amorphous matter, positrons may annihilate from local free volumes. The mean positron lifetimes are typically τ e+ = 200-400 ps.

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“…In addition, river-line markings and smoother fractured surface morphology (compared to the neat EP/PU g-IPN) for g-IPN nanocomposites could be due to the formation of hydrogen bonding of epoxy and urethane chains with silicate layers. The hydrogen bonding enhances the compatibility of the components and promotes effective crosslinking density; consequently, the size of the PU dispersed phase is reduced and smoother fractured surface morphology is observed 3,15,21,22 .…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…These entanglements of multiple crosslinked polymers bring about forced miscibility compared to simple blends and the resulting IPN materials exhibit excellent size stability and a possibly synergistic combination of the properties of their components [12][13][14] . These make IPNs interesting in innumerable applications 15,16 . The properties of IPN materials are determined by the kinetics of formation of the growing networks and by the thermodynamics of mixing of the constituent polymers 18 .…”

Section: Introductionmentioning

confidence: 99%

Preparation, Characterization and Study of the Morphological, Mechanical and Thermal Properties of Epoxy/Urethane Interpenetrating Polymer Networks Nanocomposites

Ghafghazi

Esfandeh

Morshedian

et al. 2012

Polymers and Polymer Composites

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In this study epoxy/urethane (EP/PU) graft interpenetrating polymer networks (g-IPNs) nanocomposites were prepared by a simultaneous polymerization method and the effects of organophilic montmorillonite (Cloisite 30B) content on the mechanical, morphological and thermal properties of the nanocomposites were investigated. Cloisite 30B was dispersed in epoxy resin via a sonication method, after which g-IPN nanocomposites were prepared by thorough mixing of a synthesized isocyanate-terminated urethane pre-polymer with this epoxy resin (EP/PU weight ratio=75/25) followed by simultaneous curing of the resins. Polytetramethylene ether glycol (PTMEG) with molecular weight (Mw) of 3000 g/mol was used to prepare urethane prepolymers. Curing reactions were followed by Fourier Transform Infrared spectroscopy (FT–IR). Wide Angle X-ray diffraction (WAXD) was used to investigate the dispersion of Cloisite 30B in g-IPN nanocomposite specimens. Based on these results, an exfoliated morphology has been suggested for nano IPN specimens containing 1 and 3 wt.% of Cloisite 30B and an intercalated morphology for that with 5 wt.% of Cloisite 30B. Dynamic Mechanical Thermal Analysis (DMTA) was used to determine the glass transition temperature (Tg) of the IPNs. The maximum Tg was observed for the nanocomposite with 3 wt.% of Cloisite 30B. The storage modulus (E′) of nanocomposites increased with increasing clay content. Thermogravimetric Analysis (TGA), tensile measurements and Scanning Electron Microscopy (SEM) were used to study the thermal, mechanical and morphological properties of the prepared specimens. The maximum tensile properties were obtained at 3 wt.% of Cloisite 30B. Furthermore, with increasing clay content, the onset of the thermal degradation temperature was delayed.

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Influence of MMT content on the microstructure and miscibility for PU/EP IPN nanocomposites by positron

Cited by 5 publications

References 8 publications

Preparation and Characterization of Bio-oil Phenolic Foam Reinforced with Montmorillonite

Preparation and Characterization of Bio-oil Phenolic Foam Reinforced with Montmorillonite

Positron Annihilation Spectroscopy

Preparation, Characterization and Study of the Morphological, Mechanical and Thermal Properties of Epoxy/Urethane Interpenetrating Polymer Networks Nanocomposites

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