Structures and physical properties of rigid polyurethane foams with water as the sole blowing agent

Abstract

Rigid polyurethane foams blown by varying water level were prepared in this study. The structures and physical properties of rigid polyurethane foams blown by water were measured with FT-IR, universal testing machine (Instron3365), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). The results show that polyurea and polybiuret were the typical characteristics, and the cream time and gel time were shorter for the fully water blown rigid foams than that for the fully cyclopentane blown foams. The density of foam samples decreased from 45.0 kg/m 3 to 27.4 kg/m 3 with the increase of water level from 3 pph to 7 pph. Compressive strength exhibited the similar behavior with density. The average cell size of foam samples ranged from 241 µm to 356 µm with the increase of water level from 3 pph to 7 pph, respectively. At the same time, poorer dimensional stability was encountered with the increase of average cell size due to fast diffusion rate of CO 2 out of the foam. The results of thermal analysis show that the glass transition temperature (T g ) shifted to a higher temperature with the increase of isocyanate level when more water was used as chemical blowing agent.

Preparation and characterization of water‐blown polyurethane foams from liquefied cornstalk polyol

“…The density of PUFs was measured according to GB 6343, which referred to ISO 845 15. At first, the polyurethane foams were cut into the dimension of 50 × 50 × 50 mm 3 (length × width × height).…”

“…Stress–strain measurement of PUFs was performed under ambient conditions on CMT 7503 electronic tensile tester in accordance with GB8813, which was equal to ISO 844 15. The size of the specimens was 50 × 50 × 50 mm 3 (length × width × height), and the compression speed was fixed at 5.0 mm/min in the direction parallel to the foam rising direction.…”

“…Dimensional stability measurement was performed according to GB8811, which was equal to ISO 2796 15. The foam samples, whose size was 100 × 100 × 25 mm 3 (length × width × height), were heated at 100°C in an oven and frozen at −20°C in a refrigerator for 48 h, respectively.…”

Preparation and Characterization of Sustainable Polyurethane Foams from Soybean Oils

“…The thermal degradation temperatures observed from TGA are reported in Table 5. Urea formation was found to be a dominant factor in the water-blown PU foam, especially during the initial stages of foam rise, according to Li et al [36] and Grünbauer et al [37]. Urethane structures were broken down at lower temperatures (first stage) with the evolution of isocyanate and alcohol, and resulted in the collapse of the cellular structure.…”

Properties of water blown rigid polyurethane foams with different functionality

“…Since water is a nonozone depleting, non-toxic and cheap blowing agent, some researches on water blown rigid foams and their applications have been performed [4][5][6] . However, compared to the CFCs blown rigid foams, water blown rigid foams encounter some problems such as dimensional stability, foam flow-ability, formulation viscosity, friability, substrate adhesion, insulation performance, K-factor aging and blowing agent solubility [7,8] . A broad study of different effects of polyol, blowing agent, MDI and catalyst on foam properties is very necessary to address these issues.…”