Emulsion Stabilization Strategies for Tailored Isocyanate Microcapsules

Loureiro, Mónica V.; Mariquito, António; Vale, Mário; Bordado, João; Pinho, Isabel; Marques, Ana C.

doi:10.3390/polym15020403

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…Indeed, as shown elsewhere [38], the NCO content of I-Ac MCs decreases rapidly when the microcapsules are dispersed in aqueous solution, as compared with the respective behavior when they are stored at room conditions. In fact, the decrease in NCO content due to reaction with humidity has been reported for other similar MCs after long-time storing [39,40].…”

Section: Study Of Hdi-or Ipdi-loaded Organic Phasesupporting

confidence: 69%

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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Section: Study Of Hdi-or Ipdi-loaded Organic Phasesupporting

confidence: 69%

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

Avdeliodi,

Tsioli,

Bokias

et al. 2024

Polymers

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“…However, the use of isocyanates at lower concentrations does not guarantee an adhesive with the same final properties. To tackle this, our research group proposed to develop new PU and PCP adhesive formulations for the footwear industry, in which the crosslinkers would be polymeric microcapsules (MCs) containing isocyanate species [ 5 , 6 , 7 , 8 , 9 ]. By protecting the isocyanate inside polymeric MCs, direct contact with the operator is avoided.…”

Section: Introductionmentioning

confidence: 99%

“…We previously reported on the encapsulation of isocyanate species with the commonly used interfacial polymerization technique, in polyurethane/polyurea (PU/PUa) shelled MCs, and the solvent evaporation method, in biodegradable shelled MCs [ 5 , 6 , 7 , 8 , 9 ]. Isocyanate microencapsulation is typically reported to be achieved using an oil-in-water (O/W) micro-emulsion system combined with the interfacial polymerization technique [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

Design of Experiment for Optimizing Microencapsulation by the Solvent Evaporation Technique

Loureiro,

Aguiar,

Santos

et al. 2023

Polymers

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We employed microemulsion combined with the solvent evaporation technique to produce biodegradable polycaprolactone (PCL) MCs, containing encapsulated isophorone diisocyanate (IPDI), to act as crosslinkers in high-performance adhesive formulations. The MC production process was optimized by applying a design of experiment (DoE) statistical approach, aimed at decreasing the MCs’ average size. For that, three different factors were considered, namely the concentration of two emulsifiers, polyvinyl alcohol (PVA) and gum arabic (GA); and the oil-to-water phase ratio of the emulsion. The significance of each factor was evaluated, and a predictive model was developed. We were able to decrease the average MC size from 326 μm to 70 µm, maintaining a high encapsulation yield of approximately 60% of the MCs’ weight, and a very satisfactory shelf life. The MCs’ average size optimization enabled us to obtain an improved distributive and dispersive mixture of isocyanate-loaded MCs at the adhesive bond. The MCs’ suitability as crosslinkers for footwear adhesives was assessed following industry standards. Peel tests revealed peel strength values above the minimum required for casual footwear, while the creep test results indicated an effective crosslinking of the adhesive. These results confirm the ability of the MCs to release IPDI during the adhesion process and act as crosslinkers for new adhesive formulations.

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Environmental assessment of an innovative adhesive for the footwear industry: road map for product development

Simões,

Aguiar,

Marques

et al. 2024

Int J Life Cycle Assess

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Purpose This work presents an environmental assessment of two adhesives to evaluate the replacement of the traditional adhesive (PU) used in the footwear industry by a novel adhesive based on a microencapsulation approach (PUMC) which is more favorable from the safety and technical perspectives. The PU adhesive is polyurethane-based, while the PUMC adhesive is polyurethane-based but with its isocyanate compounds microencapsulated, increasing storage life and reducing risks related to the exposure of workers with the adhesives. Methods The potential environmental impact of the adhesives was evaluated using the life cycle assessment (LCA) methodology. A detailed process model was developed (both for laboratory and for a pilot-scale implementation) to investigate the environmental impacts associated with these processes. The functional unit was one kilogram of adhesive (PU and PUMC adhesives) produced. A cradle-to-customers’ gate approach was defined. The system boundary starts from extraction of resources, through material production, until adhesive use. This includes microcapsule production in the case of the PUMC adhesive. This study investigates the important drivers behind the environmental impacts to help guide commercialization efforts. A scenarios study/sensitivity analysis was conducted to determine the response of the PUMC adhesive system to the variability of the model, scenarios, and parameters. Results The results show that the PU adhesive environmental impact is due to acetone and polyol consumption in the production stage. In the PUMC adhesive system, acetone consumption and microcapsule production are the major factors responsible for the environmental impact. Polybutylene adipate terephthalate (PBAT), dichloromethane (DCM), and isophorone diisocyanate (IPDI) consumption are the major factors responsible for the environmental impact of the microcapsules’ production. A sensitivity analysis was conducted using three alternative scenarios focused on the reduction in material consumption and increase in material recuperation, as well as using an alternative renewable energy source. Although the traditional PU adhesive has a lower impact, it was found that the three alternative PUMC adhesive systems can become comparable to the traditional PU adhesive. Conclusions This study shows the advance and development of a new technology for microencapsulation of isocyanate in adhesives and its environmental advantages and disadvantages with respect to a traditional product that uses non-encapsulated isocyanate. Finally, it was shown that there is significant potential for minimizing some environmental impacts of the PUMC adhesive, such as optimizing the microcapsules’ production stage, increasing the production efficiency to decrease the required material consumption.

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Emulsion Stabilization Strategies for Tailored Isocyanate Microcapsules

Cited by 5 publications

References 39 publications

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

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

Design of Experiment for Optimizing Microencapsulation by the Solvent Evaporation Technique

Environmental assessment of an innovative adhesive for the footwear industry: road map for product development

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