Dynamic Mechanical Analysis during polyurethane foaming: Relationship between modulus build-up and reaction kinetics

• Published in: Polymer testing 2021-11, Vol.103, p.107336, Article 107336
• Main Authors: Cimavilla-Román, Paula, Santiago-Calvo, Mercedes, Rodríguez-Pérez, Miguel Ángel
• Format: Article
• Language: English
• Subjects: Chemical reactions; Dynamic mechanical analysis; FTIR Spectroscopy; Rheokinetics; Rigid polyurethane foams
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2021.107336

The modulus build-up and relative density evolution during the reactive foaming of four standard polyurethane formulations was monitored in-situ by Dynamic Mechanical Analysis (DMA) with a customised set-up in parallel plate geometry. The modulus increased from 0.01 MPa in the first minutes to over 1.2 MPa within 20 min. The set-up also enabled the recording of vitrification followed by curing times. These typically occur within 3 min of each other. The results of DMA are corroborated by measurements of the reaction kinetics with Infrared Spectroscopy. This goes to show that the modulus remains nearly unchanged during the stage of swiftest isocyanate conversion, while the point of gel conversion is accompanied by their increase. •DMA was applied to in-situ measure the modulus development of Rigid Polyurethane foams during foaming.•Employing a customised fixture density evolution was monitored simultaneously during the DMA experiments.•The modulus build-up profiles recorded with DMA were corroborated by measurements of the reaction kinetics.•Vitrification times can be inferred from the temporal evolution of the Loss modulus of the foams.