Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2024 May 2;6(10):5618-5629.
doi: 10.1021/acsapm.4c00033. eCollection 2024 May 24.

Microcapsules of Poly(butylene adipate- co-terephthalate) (PBAT) Loaded with Aliphatic Isocyanates for Adhesive Applications

António Aguiar  1 , Lucas P Marcelino  1 , António Mariquito  1 , Carla L Simões  2 , Ricardo Simoes  2   3 , Isabel Pinho  4 , Ana C Marques  1
Affiliations

Microcapsules of Poly(butylene adipate- co-terephthalate) (PBAT) Loaded with Aliphatic Isocyanates for Adhesive Applications

António Aguiar et al. ACS Appl Polym Mater. .

Abstract

This work introduces the encapsulation of hexamethylene diisocyanate derivatives (HDI, TriHDI, and PHDI) with the biodegradable polymer poly(butylene adipate-co-terephthalate) (PBAT) through a solvent evaporation method. These microcapsules (MCs) were then employed in adhesive formulations for footwear. Moreover, MCs containing PHDI were produced in a closed vessel, demonstrating the potential for recovering and reusing organic solvents for the first time. The MCs were achieved with an isocyanate payload reaching up to 68 wt %, displaying a spherical shape, a core-shell structure, and thin walls without holes or cracks. The application of MCs as cross-linking agents for adhesives was evaluated following industry standards. The adhesives' strength surpassed the minimum requirement by a significant margin. Creep tests demonstrated that the formulation with MCs exhibits superior thermostability. Furthermore, the formulation with MCs-PHDI presented the best results reported to date for this type of system, as no displacement was observed in the bonded substrates. Environmental assessment indicates that adhesives with MCs have higher global warming potential (+16.2%) and energy consumption (+10.8%) than the standard commercial adhesives, but under alternative realistic scenarios, the differences can be insignificant. Therefore, adhesive formulations incorporating MCs promise to be on par with traditional adhesive systems regarding environmental impacts while providing benefits such as improved and safe handling of isocyanates and excellent bonding effectiveness.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Production of microcapsules by open vessel: (1) addition of the organic phase to the aqueous phase; (2) emulsification and evaporation of DCM; (3) formation of solid MCs; and (4) filtration. Production of microcapsules by closed vessel. (1) addition of the organic phase to the aqueous phase; (2) emulsification and evaporation of DCM at 35 °C and a vacuum of 300 mbar; and (3) filtration.
Figure 2
Figure 2
Optical microscopy photographs (first line) and SEM images of the MCs.
Figure 3
Figure 3
1H NMR spectra of the raw material and MCs in CDCl3.
Figure 4
Figure 4
FTIR spectra of MCs (up). Thermograms of the raw material and MCs, obtained under a N2 atmosphere (down).
Figure 5
Figure 5
Viscosity of the adhesive formulations with nonencapsulated isocyanates (up) and encapsulated isocyanates (down), over 1 week.
Figure 6
Figure 6
Results of the peel tests (average of three adhesive joints).
Figure 7
Figure 7
Comparison of relative contributions for GWP and EC of the CA and MCA systems and the three alternative scenarios of the MCA system.
See this image and copyright information in PMC

References

    1. Eram S.; Fahmina Z.. Polyurethane: An Introduction. In Polyurethane; Fahmina Z.; Eram S., Eds.; IntechOpen: Rijeka, 2012; pp 1–14.
    1. Michael S.Structure–Property Relations in Polyurethanes. In Szycher’s Handbook of Polyurethanes; CRC Press, 2012; pp 87–135.
    1. Wright H. C.; Cameron D. D.; Ryan A. J. Rational Design of a Polyurethane Foam. Polymers 2022, 14 (23), 5111.10.3390/polym14235111. - DOI - PMC - PubMed
    1. Gonçalves D.; Bordado J. M.; Marques A. C.; Galhano dos Santos R. Non-Formaldehyde, Bio-Based Adhesives for Use in Wood-Based Panel Manufacturing Industry—A Review. Polymers 2021, 13 (23), 4086.10.3390/polym13234086. - DOI - PMC - PubMed
    1. Poljanšek I.; Fabjan E.; Moderc D.; Kukanja D. The effect of free isocyanate content on properties of one component urethane adhesive. Int. J. Adhes. Adhes. 2014, 51, 87–94. 10.1016/j.ijadhadh.2014.02.012. - DOI