Hydration-induced reinforcement of rigid polyurethane–cement foams: mechanical and functional properties

Abstract

Mechanical and functional properties of a newly proposed hybrid foam based on rigid polyurethane foam and Portland cement for application in the building field are herein reported. The hybrid is characterized by the co-continuity of the two phases, hydrated cement and polyurethane, which cooperate in a synergistic way to the properties of the resulting material. Furthermore, the closed-cell foam structure gives the material properties typical of porous materials: in particular, the hybrid foam evidences thermal insulation, sound absorption and acoustic insulation, high impact energy and low density typical of polymeric foams. At the same time, the hybrid foam exhibits water vapor permeability, improvement of thermal stability, high compressive mechanical behavior, and adhesion to concrete and mortars typical of inorganic binders such as cement. The materials were obtained by mixing cement powder with polyurethane foam precursors, i.e., methylene di(phenyl-isocyanate), polyol polyether and catalysts, and silicone surfactants. Water was used as blowing reagent. The resulting compounds were foamed in flat closed molds. The cement phase was then allowed to hydrate in accelerated conditions, i.e., in water at 60 °C for 72 h. Mechanical, morphological, and functional charac- terization showed that the hydrated cement particles interacted with each other, forming an inorganic network within the polymeric matrix (co-continuity), thus ‘‘hydration-induced reinforcement of polymer–cement’’ hybrid foam, in contraposition with the term ‘‘composite foam.’

Recycling of polyurethane foam waste in the production of lightweight cement pastes and its irradiated polymer impregnated composites

“…It is clearly observed that typical behavior takes place for the hardened WCP0 specimens cured at 7 and 28 days with a slight change in weight loss percentage. The TGA/DrTGA thermal curves demonstrated three major stages: the first stage appeared in the temperature range between 80°C and 120°C, which represent the weight loss that can be attributed to the chemically bound water (i.e., water present in the chemical structure of cement hydrated phases [CSH and ettringite] that removed by heating in the temperature range 80°C–180°C) . The second stage can be seen around 420°C–475°C due to dehydroxylation of calcium hydroxide CH, as the Portlandite decomposed into free lime at 420°C–475°C.…”

Mechanical, acoustic, and thermal performances of shear thickening fluid–filled rigid polyurethane foam composites: Effects of content of shear thickening fluid and particle size of silica

“…The thermostability of materials indicates how well the material can protect itself from the damage of drastically changing heat, and is thus also a critical characteristic valued in material science . Therefore, studies on the effects of using various additives on the thermostability of PU foam have become popular in recent years.…”

“…Rigid PU foam material has good cushioning, thermal, insulation, and acoustic absorption properties, though these properties may conflict with others. Therefore, retaining all of the properties of rigid PU foam material has been an emphasis in many studies . In this study, STF is used to increase the mechanical properties, sound absorption efficacy, and thermal insulation of rigid PU foam.…”

“…7 The thermostability of materials indicates how well the material can protect itself from the damage of drastically changing heat, and is thus also a critical characteristic valued in material science. 8 Therefore, studies on the effects of using various additives on the thermostability of PU foam have become popular in recent years. Michałowski et al 9 applied polyhedral oligomer silsesquioxane (POSS) modifier to improve the thermostability and flammability of rigid polyurethane foams, and they found that the cellular structure of the foam was dependent on the addition of POSS modifier.…”

“…Therefore, retaining all of the properties of rigid PU foam material has been an emphasis in many studies. 19 In this study, STF is used to increase the mechanical properties, sound absorption efficacy, and thermal insulation of rigid PU foam. The pattern of changes in the porous structure of the rigid PU foam containing STF is analyzed in terms of the particle size of SiO 2 and the content of STF, examining the influence of the two parameters on the aforementioned characteristics.…”