scholarly journals Maleimide Self-Reaction in Furan/Maleimide-Based Reversibly Crosslinked Polyketones: Processing Limitation or Potential Advantage?

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2230
Author(s):  
Felipe Orozco ◽  
Zafarjon Niyazov ◽  
Timon Garnier ◽  
Nicola Migliore ◽  
Alexander Zdvizhkov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymer System ◽  
Side Reaction ◽  
The Self ◽  
The Other ◽  
Side Reactions ◽  
Thermal Treatments ◽  
Self Healing ◽  
Do So

Polymers crosslinked via furan/maleimide thermo-reversible chemistry have been extensively explored as reprocessable and self-healing thermosets and elastomers. For such applications, it is important that the thermo-reversible features are reproducible after many reprocessing and healing cycles. Therefore, side reactions are undesirable. However, we have noticed irreversible changes in the mechanical properties of such materials when exposing them to temperatures around 150 °C. In this work, we study whether these changes are due to the self-reaction of maleimide moieties that may take place at this rather low temperature. In order to do so, we prepared a furan-grafted polyketone crosslinked with the commonly used aromatic bismaleimide (1,1′-(methylenedi-4,1-phenylene)bismaleimide), and exposed it to isothermal treatments at 150 °C. The changes in the chemistry and thermo-mechanical properties were mainly studied by infrared spectroscopy, 1H-NMR, and rheology. Our results indicate that maleimide self-reaction does take place in the studied polymer system. This finding comes along with limitations over the reprocessing and self-healing procedures for furan/maleimide-based reversibly crosslinked polymers that present their softening (decrosslinking) point at relatively high temperatures. On the other hand, the side reaction can also be used to tune the properties of such polymer products via in situ thermal treatments.

scholarly journals The Effect of Superabsorbent Polymers on the Microstructure and Self-Healing Properties of Cementitious-Based Composite Materials

2021 ◽  
Vol 11 (2) ◽  
pp. 700
Author(s):  
Irene A. Kanellopoulou ◽  
Ioannis A. Kartsonakis ◽  
Costas A. Charitidis
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Hybrid Structure ◽  
The Self ◽  
Self Healing ◽  
Cementitious Composite ◽  
Superabsorbent Polymers ◽  
Porosity Reduction ◽  
Environment Control ◽  
The Impact

Cementitious structures have prevailed worldwide and are expected to exhibit further growth in the future. Nevertheless, cement cracking is an issue that needs to be addressed in order to enhance structure durability and sustainability especially when exposed to aggressive environments. The purpose of this work was to examine the impact of the Superabsorbent Polymers (SAPs) incorporation into cementitious composite materials (mortars) with respect to their structure (hybrid structure consisting of organic core—inorganic shell) and evaluate the microstructure and self-healing properties of the obtained mortars. The applied SAPs were tailored to maintain their functionality in the cementitious environment. Control and mortar/SAPs specimens with two different SAPs concentrations (1 and 2% bwoc) were molded and their mechanical properties were determined according to EN 196-1, while their microstructure and self-healing behavior were evaluated via microCT. Compressive strength, a key property for mortars, which often degrades with SAPs incorporation, in this work, practically remained intact for all specimens. This is coherent with the porosity reduction and the narrower range of pore size distribution for the mortar/SAPs specimens as determined via microCT. Moreover, the self-healing behavior of mortar-SAPs specimens was enhanced up to 60% compared to control specimens. Conclusively, the overall SAPs functionality in cementitious-based materials was optimized.

scholarly journals EFFECT OF THERMO-MECHANICAL TREATMENT ON PROPERTIES OF PARICA PLYWOODS (Schizolobium amazonicum Huber ex Ducke)

2017 ◽  
Vol 41 (1) ◽  
Author(s):  
Mírian de Almeida Costa ◽  
Cláudio Henrique Soares Del Menezzi
Keyword(s):  
Mechanical Properties ◽  
Mechanical Treatment ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Modulus Of Rupture ◽  
Thermal Treatments ◽  
Mechanical Compression ◽  
Specific Mass ◽  
Thermo Mechanical Treatment ◽  
Temperature And Pressure

ABSTRACT Thermo-mechanical treatment is a technique for wood modification in which samples are densified by means of heat and mechanical compression, applied perpendicularly to fibers, which under different combinations of time, temperature, and pressure increases wood density and thus improve some of its properties. This study aimed to treat thermo-mechanically parica plywood and observe the effects on its physical and mechanical properties. Specimens were submitted to two treatments, 120 and 150 ºC, remaining under pressure for seven minutes and, subsequently, under zero pressure for 15 minutes. Results showed a significant increase in specific mass from 0.48 g cm-3 to an average of 0.56 g cm-3, and a compression ratio of about 31.7% on average. Physical properties also varied significantly and results showed that treated samples swelled and absorbed more water than those untreated, leading to a greater thickness non-return rate. This indicates the proposed thermal treatments did not release the internal compressive stress generated during panel pressing, not improving its dimensional stability as a result. On the other hand, mechanical properties were positively affected, leading to an increase of 27.5% and 51.8% in modulus of rupture after treatments at 120 and 150 ºC, respectively. Modulus of elasticity and glue-line shear strength did not vary statistically and Janka hardness was 29.7% higher after treatment at 150 ºC.

scholarly journals Nanoparticle-Hydrogel Composites: From Molecular Interactions to Macroscopic Behavior

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 275 ◽  
Author(s):  
Corinna Dannert ◽  
Bjørn Torger Stokke ◽  
Rita S. Dias
Keyword(s):  
Mechanical Properties ◽  
Molecular Design ◽  
The Self ◽  
Self Healing ◽  
Sensor Applications ◽  
Composite Gels ◽  
Equilibrium Swelling ◽  
Hydrogel Composites ◽  
Materials Used ◽  
Network Component

Hydrogels are materials used in a variety of applications, ranging from tissue engineering to drug delivery. The incorporation of nanoparticles to yield composite hydrogels has gained substantial momentum over the years since these afford tailor-making and extend material mechanical properties far beyond those achievable through molecular design of the network component. Here, we review different procedures that have been used to integrate nanoparticles into hydrogels; the types of interactions acting between polymers and nanoparticles; and how these underpin the improved mechanical and optical properties of the gels, including the self-healing ability of these composite gels, as well as serving as the basis for future development. In a less explored approach, hydrogels have been used as dispersants of nanomaterials, allowing a larger exposure of the surface of the nanomaterial and thus a better performance in catalytic and sensor applications. Furthermore, the reporting capacity of integrated nanoparticles in hydrogels to assess hydrogel properties, such as equilibrium swelling and elasticity, is highlighted.

Microstructure and Mechanical Properties of Mg-Based Composites Reinforced with TiB2 Particles

2014 ◽  
Vol 900 ◽  
pp. 141-145 ◽  
Author(s):  
Can Feng Fang ◽  
Guang Xu Liu ◽  
Ling Gang Meng ◽  
Xing Guo Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Composite Material ◽  
High Temperature ◽  
The Self ◽  
Al Alloy ◽  
Temperature Synthesis ◽  
Microstructure And Mechanical Properties ◽  
High Temperature Synthesis

The effects of in-situ TiB2 particle fabricated from Al-Ti-B system via the self-propagating high-temperature synthesis (SHS) reaction technology on microstructure and mechanical properties of Mg-Sn-Zn-Al alloy were investigated. The results indicate that the size of the Mg2Sn and α-Mg+Mg32(Al,Zn)49 phase becomes coarser with the increasing content of Al-Ti-B preform, meanwhile the amount of eutectic α-Mg+Mg32(Al,Zn)49 phase increases too. The addition of Al-Ti-B is favorable toward promoting the strength of composites, but deteriorates elongation. The resulting as-extruded composite material with 4 wt.% Al-Ti-B preform exhibits good overall mechanical properties with an ultimate tensile strength of 291 MPa and an elongation over 2 %.

scholarly journals Metafore sebstva u autobiografskom diskursu Vesne Parun

2016 ◽  
Vol XIV (2) ◽  
pp. 184-184
Author(s):  
Kornelija Kuvač-Levačić
Keyword(s):  
Narrative Identity ◽  
The Self ◽  
The Other ◽  
Factual Information ◽  
Human Personality ◽  
The World ◽  
Literary Device ◽  
The Relationship ◽  
Symbolic Number ◽  
Do So

By using the concept of the Self as the human personality in its totality, as defined by Carl Gustav Jung and furthered by P. Ricoeur (the theory of narrative identity, the Self defined as an identity constructed by narrative configuration, the dialectics of the discovery of the other in one’s own Self and one’s own Self in the Other), this work will focus in the analysis of metaphors which express the Self of the auto-diegetic narrator as can be found in the autobiographical discourse of Vesna Parun. The corpus of this research is to be found in selected texts from her volume Noć za pakost. Moj život u 40 vreća (2001). From the first chapter of this volume [which consists of the following works of autobiography and essays: Poljubac života (1993), Do zalaska sunca hodajući za kamilicom (1958), Pod muškim kišobranom (1986)] the reader comes to realise that, for this author, the writing of autobiography is itself a problem of self-expression and that she had constantly deferred it, while, on the other hand, feeling a great compulsion from within to do so. This sense of paradox finds its reflection in some of the constitutive elements which can be found in her autobiographical discourse. In the relationship between literature and reality, which is something which the genre of autobiography questions in its own way, the author noticeably distances herself from the mere documentary transmission of factual information from her life. A reflection of this can be seen in the negation of a strict chronology of events and confessions, as she makes recourse to a technique which uses collage and appears fragmentary; furthermore, here prose here has a lyrical quality, negating "metaphor as a literary device" and transforming it into "literature as metaphor". The autobiographical prose of Vesna Parun is especially dense with metaphor, and it can be concluded that it expresses her Self. Attention is directed here to three metaphors in particular – the umbrella, which can be both "masculine" and "feminine", a map of the world, on the wall of every house in Vesna’s community, as well the sack, which is followed by the symbolic number 40, as many in which she could fill her life in. Besides the metaphors mentioned here, what will be proposed here is that in the autobiographical discourse of Vesna Parun literature itself is presented as metaphor of her Self, appearing to the reader as significantly (auto)meta-textual.

scholarly journals Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1918 ◽  
Author(s):  
Hyeong-Jun Jeoung ◽  
Kun Won Kim ◽  
Yong Jun Chang ◽  
Yong Chae Jung ◽  
Hyunchul Ku ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
In Situ Polymerization ◽  
Urea Formaldehyde ◽  
Testing Machine ◽  
Optical Microscope ◽  
The Self ◽  
Self Healing ◽  
Grubbs Catalyst ◽  
Healing Efficiency

The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 μm in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs’ catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs’ catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.

Exiles on Main Street

2017 ◽  
Author(s):  
Robin Whelan
Keyword(s):  
The Self ◽  
The Other ◽  
Main Street ◽  
Mutual Antagonism ◽  
Authority Figures ◽  
The Relationship ◽  
Do So

This chapter reconsiders the relationship between the Vandal kings and the Nicene Church, which has often been seen as an obstacle to effective Vandal rule. The self-portrayal of Nicene bishops as martyrs suffering in an age of heretical persecution—and the self-portrayal of Hasding dynasts as pious defenders of true (Homoian) Christianity—seems to commit them to mutual antagonism. Yet both parties also had interests in compromises, which are revealed by recurrent interactions between bishops and the court at Carthage. Even as they decried heretical Vandal tyranny, Nicene bishops petitioned their rulers to improve their church’s lot, using obsequious courtly language and the appropriate bureaucratic channels to do so. Vandal kings sometimes granted these petitions; even when refused, the possibility of compromise was retained for as long as possible. The result was tacit or even explicit acknowledgment of the legitimacy of the other parties, whether as rulers or Christian authority figures.

Saying No and Saying Yes

2019 ◽  
pp. 141-170
Author(s):  
Wendy Beth Hyman
Keyword(s):  
Thought Experiment ◽  
The Self ◽  
The Other ◽  
Faerie Queene ◽  
Other Hand ◽  
The Faerie Queene ◽  
Do So ◽  
The Erotic

“Saying No and Saying Yes” turns at last from the speaker of the erotic invitation to its imagined auditor: the figure being invited to “seize the day.” Persuasion poets, of course, never expect acquiescence—the motif would hardly exist if ladies were easily seduced. However, Spenser’s The Faerie Queene and Milton’s A Maske are among those longer works that make room for very demonstrable acts of refusal, and both do so within an explicitly moral, Protestant context: Spenser via his knight Guyon (hearing Acrasia’s song in the Bower of Bliss), and Milton through his virginal and unnamed Lady responding to the libertine Comus. Despite some obvious similarities between these encounters, the two poets imagine remarkably different responses to the voluptuous invitations they feature. Spenser’s Guyon responds not with his putative virtue, Temperance, but vehement rage to Acrasia’s invitation in the Bower—becoming an agent of the very materialist forces he repudiates. Milton, on the other hand, imagines a place for chastity that is not built upon a sequestration of the self, but a willingness to seek, and find, trial. He thereby provides a model for perhaps the most “impossible” thought experiment of all, one in which a woman participates as an intellectual and rhetorical equal, and in whom eloquence, chastity, and desire can coexist. Milton thereby utilizes the trope to turn it on its head, constructing within it a forum for a proto-feminist articulation of agency and voice.

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