ON THE INFLUENCE OF POLYOL COMPOSITION FUNCTIONALITY ON CONCENTRATION GRADIENTS IN POLYURETHANE-POLYISOCYANURATE FOAMS
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
OOO «Dau Izolan»
2.
KNITU
Type:
Article
Pages:
from 54
to 59
Status:
Published
Received:
31.01.2026
Accepted:
31.01.2026
Published:
31.01.2026
Language:
Russian
Keywords:
POLYURETHANE-POLYISOCYANURATE FOAMS, CONCENTRATION GRADIENTS, FUNCTIONALITY, POLYOL, ISOCYANURATE, RESIDUAL ISOCYANATE, COMPRESSIVE STRENGTH
Abstract:
The influence of the number-average functionality of the polyol composition (fn) on the formation of concentration gradients of residual isocyanate and isocyanurate groups and the anisotropy of the mechanical properties of polyurethane-polyisocyanurate (PIR) foams was studied. The aim of the study was to establish a correlation between the degree of crosslinking of the polyurethane matrix and the spatial distribution of triisocyanurate and free isocyanate along the foam height at a constant isocyanate index. Quantitative determination of isocyanurate and residual isocyanate groups in the synthesized polyurethane-polyisocyanurate foams was performed using Fourier transform infrared spectroscopy with an attenuated total internal reflection (ATR) configuration. Significant concentration gradients were found in the resulting PIR foams: isocyanate-to-isocyanurate conversion reached higher values in the upper layers of the foam, and the concentration of residual isocyanate groups was significantly lower than in the lower layers. It was shown that increasing the polyol's number-average functionality, which leads to the formation of denser urethane crosslinks, increases steric constraints, complicating the diffusion-controlled isocyanate trimerization reaction and, consequently, exacerbating the heterogeneity of the chemical composition across the material's height. This heterogeneity directly determines the anisotropy of the mechanical properties: the relative compressive strength of the foam increases consistently from the lower layers to the upper ones. Thus, it has been proven that reducing the functionality of the polyol component allows to produce polyurethane-polyisocyanurate materials with a more uniform distribution of isocyanurate cycles and residual isocyanate throughout the volume, which ensures increased isotropy of the material's properties. The obtained results represent a practical tool that can be applied in the development and optimization of formulations used to produce PIR foams.
The influence of the number-average functionality of the polyol composition (fn) on the formation of concentration gradients of residual isocyanate and isocyanurate groups and the anisotropy of the mechanical properties of polyurethane-polyisocyanurate (PIR) foams was studied. The aim of the study was to establish a correlation between the degree of crosslinking of the polyurethane matrix and the spatial distribution of triisocyanurate and free isocyanate along the foam height at a constant isocyanate index. Quantitative determination of isocyanurate and residual isocyanate groups in the synthesized polyurethane-polyisocyanurate foams was performed using Fourier transform infrared spectroscopy with an attenuated total internal reflection (ATR) configuration. Significant concentration gradients were found in the resulting PIR foams: isocyanate-to-isocyanurate conversion reached higher values in the upper layers of the foam, and the concentration of residual isocyanate groups was significantly lower than in the lower layers. It was shown that increasing the polyol's number-average functionality, which leads to the formation of denser urethane crosslinks, increases steric constraints, complicating the diffusion-controlled isocyanate trimerization reaction and, consequently, exacerbating the heterogeneity of the chemical composition across the material's height. This heterogeneity directly determines the anisotropy of the mechanical properties: the relative compressive strength of the foam increases consistently from the lower layers to the upper ones. Thus, it has been proven that reducing the functionality of the polyol component allows to produce polyurethane-polyisocyanurate materials with a more uniform distribution of isocyanurate cycles and residual isocyanate throughout the volume, which ensures increased isotropy of the material's properties. The obtained results represent a practical tool that can be applied in the development and optimization of formulations used to produce PIR foams.
Keywords:
POLYURETHANE-POLYISOCYANURATE FOAMS, CONCENTRATION GRADIENTS, FUNCTIONALITY, POLYOL, ISOCYANURATE, RESIDUAL ISOCYANATE, COMPRESSIVE STRENGTH
POLYURETHANE-POLYISOCYANURATE FOAMS, CONCENTRATION GRADIENTS, FUNCTIONALITY, POLYOL, ISOCYANURATE, RESIDUAL ISOCYANATE, COMPRESSIVE STRENGTH
