Viscoelastic Polyurethane Foams for Use in Seals of Respiratory Protective Devices

• Published in: Materials Vol. 14; no. 7; p. 1600
• Main Authors: Okrasa, Małgorzata, Leszczyńska, Milena, Sałasińska, Kamila, Szczepkowski, Leonard, Kozikowski, Paweł, Majchrzycka, Katarzyna, Ryszkowska, Joanna
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 25.03.2021; MDPI
• Subjects: Blowing agents; Bulk density; COVID-19; Design; Differential scanning calorimetry; Elastic recovery; Fourier transforms; Glass transition temperature; Isocyanates; leak tightness; Masks; Moisture content; Permeability; personalization; Plastic foam; Polyurethane foam; Recovery time; Resilience; respiratory protective devices; Solvents; Sweat; Thermal degradation; Thermogravimetry; viscoelastic polyurethane foams; Viscoelasticity; Viscosity; Poland; respiratory protective devices; personalization; leak tightness; viscoelastic polyurethane foams
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma14071600

A key factor in effective protection against airborne hazards, i.e., biological and nonbiological aerosols, vapors, and gases, is a good face fit of respiratory protective devices (RPDs). Equally important is the comfort of use, which may encourage or discourage users from donning RPDs. The objective of the work was to develop viscoelastic polyurethane foams for use in RPD seals. The obtained foams were characterized using scanning electron microscopy, infrared spectroscopy, thermogravimetry, and differential scanning calorimetry. Measurements also involved gel fraction, apparent density, air permeability, elastic recovery time, compression set, rebound resilience, and sweat uptake. The results were discussed in the context of modifications to the foam formulation: the isocyanate index (I ) in the range of 0.6-0.9 and the blowing agent content in the range of 1.2-3.0 php. FTIR analysis revealed a higher level of urea groups with increasing water content in the formulation. Higher I and water content levels also led to lower onset temperatures of thermal degradation and higher glass-transition temperatures of the soft phase. A decrease in apparent density and an increase in mean pore sizes of the foams with increasing I and water content levels was observed. Functional parameters (air permeability, elastic recovery time, compression set, rebound resilience, and sweat uptake) were also found to be satisfactory at lower I and water content levels.