Effects of Processing Temperature on ReCrete Polyurethane Foam

Abstract

Research is conducted to determine the effect of processing temperature on some of the physical and mechanical properties of a polyurethane foam called ReCrete. The polyurethane foaming process is manipulated to change the foam's density, chemistry, and mechanical properties. There is a 30-min period after ReCrete components are mixed when the materials are still undergoing significant chemical reaction. Researchers manipulate these chemical reactions by changing the environmental temperature during this process. This study investigates the effect of processing temperature on the chemistry and the resulting mechanical properties for a polyurethane foam system molded in aluminum cylinders and boxes. Processing temperature is varied from 25°C to 85°C. Researchers show that the processing temperature has a significant effect on ReCrete chemistry and density. The average density decreases by 19% over this temperature range. The chemistry, in turn, affects the static and dynamic mechanical properties. The axial compressive modulus and strength decrease by 24 and 16%, respectively. The chemistry changes that results from higher processing temperatures produce foam that is less rigid in compression, but tougher and more flexible. The dynamic flexural failure strength increases by 38% when the processing temperature is increased from 25°C to 85°C. Foam processed at 85°C has significantly greater resistance to brittle failure under impact.

A Review of Research on the Effect of Temperature on the Properties of Polyurethane Foams

“…Mold temperature affects the cell structure of polyurethane foams, and for the microstructure of polyurethane foams cast at different mold temperatures, Mohan et al [ 41 ] carried out a microscopic experiment for observation, and the results showed that polyurethane foams treated at low temperatures produced anisotropic cell content of uniform size toward the upward direction. The limited passage between the cells through the cell walls resulted in stiffness.…”

“…In addition, mold temperature can affect the density as well as the density gradient of polyurethane foam materials [ 43 ]. Researcher Mohan [ 41 ] foamed polyurethane foams materials at different mold temperatures and observed their density after foaming, finding that as the temperature increased, the foaming chemicals could not fill the cylinder due to the increase in viscosity during foaming. Voids are created where the foam cannot be filled, and the polyurethane foams density decreases to varying degrees.…”

“…The change in mold temperature caused the change in cell structure and therefore the change in mechanical properties of polyurethane foams. Scholars Mohan [ 41 ] and Dacia Jackovich [ 44 ] measured the mechanical properties of polyurethane foamed successfully at different mold temperatures. The general results show that with the increase in mold temperature, the mechanical properties of polyurethane foams materials such as compression, tensile, shear strength and elastic modulus have a significant decreasing trend.…”

Thermal volatilisation analysis of TDI-based flexible polyurethane foam

“…urethane, urea, biuret, allophonate) that lend the foams different physical properties and which can even vary across the crosssection of a foam as a result of temperature gradients during processing. [1][2][3] The thermal degradation of polyurethane is, therefore, unsurprisingly complex; it depends on the structure of the material, making it strongly dependent on the type of polyol or polyisocyanate from which it is synthesised. The presence of additives, such as fire retardants, can also significantly affect the degradation processes which occur.…”

The effect of molding conditions on product properties in the production of flexible polyurethane foam using a Box–Behnken design

“…The working or processing temperature of PU production affects its intensity, macroscopic and microscopic morphology, quasi-static pressure, mechanical properties, and dynamic fracture strength. Researchers have also reported that the average density, compressive modulus, yield strength, and collapse strength of PU foam decreased as the temperature increased between 25 and 80°C (Mohan et al 2008). Jackovich et al have examined the effect of mold temperature and size on the physical and mechanical properties of rigid PU foams.…”