Improving the Insulating Capacity of Polyurethane Foams through Polyurethane Aerogel Inclusion: From Insulation to Superinsulation

Abstract

A novel synthesis of polyurethane foam/polyurethane aerogel (PUF–PUA) composites is presented. Three different polyurethane reticulated foams which present the same density but different pore sizes (named S for small, M for medium, and L for large) have been used. After the characterization of the reference materials (either, foams, and pure aerogel), the obtained composites have been characterized in order to study the effect of the foam pore size on the final properties, so that density, shrinkage, porous structure, mechanical properties, and thermal conductivity are determined. A clear influence of the pore size on the density and shrinkage was found, and the lowest densities are those obtained from L composites (123 kg/m3). Moreover, the aerogel density and shrinkage have been significantly reduced through the employment of the polyurethane (PU) foam skeleton. Due to the enhanced mechanical properties of polyurethane aerogels, the inclusion of polyurethane aerogel into the foam skeleton helps to increase the elastic modulus of the foams from 0.03 and 0.08 MPa to 0.85 MPa, while keeping great flexibility and recovery ratios. Moreover, the synthesized PUF–PUA composites show an excellent insulating performance, reducing the initial thermal conductivity values from 34.1, 40.3, and 50.6 mW/(m K) at 10 °C for the foams S, M, and L, to 15.8, 16.6, and 16.1 mW/(m K), respectively. Additionally, the effect of the different heat transfer mechanisms to the total thermal conductivity is herein analyzed by using a theoretical model as well as the influence of the measurement temperature.

Effect of the shape and the distribution of cells on the effective thermal conductivity of polyurethane foam

“…However, the type of PU foam roughly affects the radiation. It can be explained by the cell size as reported in Merillas et al's study 61 . Moreover, the effect of the shape affects the radiation, this effect is greater in the case of Gibson and Ashby cell.…”

“…It can be explained by the cell size as reported in Merillas et al's study. 61 Moreover, the effect of the shape affects the radiation, this effect is greater in the case of Gibson and Ashby cell. The mean variation of the radiativity between the two shapes is about 33%.…”

Identification of Hybrid Polymer Material STERED and Basic Material Properties Used in Road Substructures or Pavements

“…The open structure is permeated with moisture and vapor and has low water absorption [ 18 ]. According to their mechanical strength, foams are divided into flexible or rigid [ 19 ].…”

Preventing the Collapse Behavior of Polyurethane Foams with the Addition of Cellulose Nanofiber

“…This phenomenon is a critical issue in industrial product manufacturing. Previous studies have identified several causes of this issue, such as an insufficient temperature during the foaming, rapid gelation, and the absence of surfactant [ 3 , 10 , 11 , 12 , 13 ].…”