Novolac-based microcapsules containing isocyanate reagents for self-healing applications

Avdeliodi, Efterpi; Beobide, Amaia Soto; Voyiatzis, George A.; Bokias, Georgios; Kallitsis, Joannis K.

doi:10.1016/j.porgcoat.2022.107204

Cited by 8 publications

(11 citation statements)

References 37 publications

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“…The replenishment of micro-cracks that occur in PU materials after long-term use or environmental stimuli is one way to prevent macro-cracks from appearing, which often does not require exogenous initiation and is mainly of three types: microcapsules, liquid core fibers and microvascular. 28 As the first generation of polymer selfhealing methods, the earliest report dates back to the microcapsule system proposed by White in 2001. 29 The composite is usually prepared by mixing PU particles or powder with filler and other components.…”

Section: Substance Landfillmentioning

confidence: 99%

Self‐healing polyurethane based on a substance supplement and dynamic chemistry: Repair mechanisms and applications

Cao,

Zhang,

Zhang

et al. 2023

J of Applied Polymer Sci

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This review systematically summarizes the repair mechanisms and applications of self‐healing polyurethane (SHPU) materials aiming at energy conservation and safety under different repair methods. As of now, the repair methods that have emerged can be divided into two categories: substance landfill and bond repair. In terms of the repair mechanisms for both, the former involves the release of healing agents from micro‐carriers (microcapsules, hollow fibers, and microvascular) to fill the damaged area upon external impact. In contrast, bond repair combines physical and chemical changes triggered by light, heat, and other factors. To achieve efficient self‐healing in this mode, both the reorganization of broken chemical bonds and the high mobility of chain segments are crucial. Reversible covalent bonds and supramolecular interactions, as two branches of aforementioned reversible chemical bonds, share the responsibility for maintaining efficient self‐healing despite infinite cycling. Additionally, multiple synergistic crosslinked networks, special nanomaterials, and microphase separation are often used to solve the problem of incompatible healing efficiency and mechanical strength in bond repair. When the perspective is focused on the application, this gradually improved SHPU with strong potential and comprehensive performance has provided raw materials for many fields related to human development, such as road, architecture, healthcare, and electronic.

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Section: Substance Landfillmentioning

confidence: 99%

Self‐healing polyurethane based on a substance supplement and dynamic chemistry: Repair mechanisms and applications

Cao,

Zhang,

Zhang

et al. 2023

J of Applied Polymer Sci

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“…In our research group, we are currently focusing on the development of self-healing materials for waterborne polyurethane (WPUs) coatings [ 23 , 24 , 25 ]. One of our methodologies is based on the effective encapsulation of active compounds, which, when released, will impart additional functionalities, with the self-healing ability being a first target.…”

Section: Introductionmentioning

confidence: 99%

“…Isocyanate compounds, oils and functional polymers are investigated, among others, as encapsulated active compounds. Thus, in our previous work [ 25 ], MDI and IPDI were used to prepare core-shell microcapsules through interfacial polymerization in oil-in-water emulsion, using poly(vinyl alcohol) (PVA) as an emulsifier and diethylenetriamine (DETA) as a crosslinking reagent, reacting with MDI. The microcapsules are composed of a PVOH-polyurea composite shell and a liquid core containing IPDI.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds

Avdeliodi,

Tsioli,

Bokias

et al. 2024

Polymers

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The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance—Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI.

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“…With the increasing maturity of preparation technology, microencapsulated self-healing materials have developed rapidly and have obvious advantages, and become the main direction of research and development of self-healing polymer materials. [2][3][4][5] Through previous literature research, [6][7][8][9][10] the main disadvantage of microencapsulated self-healing materials in applications was shell strength. The low-strength microcapsules resulted in the problems of short storage time and low core fraction content.…”

Section: Introductionmentioning

confidence: 99%

“…Through previous literature research, 6–10 the main disadvantage of microencapsulated self‐healing materials in applications was shell strength. The low‐strength microcapsules resulted in the problems of short storage time and low core fraction content.…”

Section: Introductionmentioning

confidence: 99%

Compatibility of high strength silica‐modified microcapsules modified with polydopamine in elastomer substrates

Li,

Wang,

et al. 2023

Polymer Composites

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Microcapsules with polydopamine composite shell layer were successfully synthesized by functionalizing silica‐modified microcapsules containing isophorone diisocyanate. The components and micromorphology of silica‐modified microcapsules at different reaction periods were studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The structure of different microcapsules was characterized by FTIR, 1H nuclear magnetic resonance and x‐ray photoelectron spectroscopy. The mechanical performances of different microcapsules were analyzed by nanoindentation technique. The compatibility and self‐healing efficiency of different microcapsules with the substrate were also investigated by the tensile tests. The results showed that the density of the silica‐modified microcapsule shell gradually increased and the mechanical performances were enhanced with the silica source. The hardness and elastic modulus of silica‐modified microcapsules in suitable core fraction (76.5 wt%) were 139.9 MPa and 2.2 GPa, which are 2.3 times and 4.8 times higher than those of untreated microcapsules, respectively. The functionalized modified microcapsules had excellent compatibility with the elastomeric substrate (PU‐PPG2000). At the same time, the self‐healing efficiency of the functionalized modified microcapsules in PU‐PPG2000 was 69.8%, which was 48.9% higher than that of the untreated microcapsules prepared under the same conditions. Silicon modification improved the density of microcapsules, enhancing their mechanical strength. At the same time, functionalization modification improved the interfacial bonding strength of microcapsules, further improving the compatibility with the polymer matrix.Highlights Microcapsules with different silicon sources are characterized. Microcapsules are functionalized with polydopamine. Individual microcapsules are tested for mechanical strength by nanoindentation. The compatibility of the functionalized microcapsules is excellent. The self‐healing efficiency of modified microcapsules is greater than 70%.

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Novolac-based microcapsules containing isocyanate reagents for self-healing applications

Cited by 8 publications

References 37 publications

Self‐healing polyurethane based on a substance supplement and dynamic chemistry: Repair mechanisms and applications

Self‐healing polyurethane based on a substance supplement and dynamic chemistry: Repair mechanisms and applications

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds

Compatibility of high strength silica‐modified microcapsules modified with polydopamine in elastomer substrates

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