“…A constant mixing ratio of 1:1.1 by volume for polyol:isocyanate has been maintained in the moulding of foam samples. It was found that this is the desirable mixing ratio that yields the highest mechanical properties 24 of the rigid PU foam considered for a given density. To vary the densities of foam samples, the amount of polyol and isocyanate mixture placed in a mould box of constant volume (50 × 50 × 50 mm 3 ) was altered for foam formation.…”
Section: Methodsmentioning
confidence: 94%
“…It is, however, noted that the parameters Pm and η are calculated here for 60% of foam compression as at 70% compression, corresponding stresses and strains shown in Figure 3 are quite high and are likely to be in densification phase.Figure 4.Comparison of stress–strain curves obtained for different mixing ratios. 24 …”
Density is an important parameter that influences the properties and performances of rigid polyurethane foam. In this study, a systematic engineering approach is presented for determining the effect of density on mechanical properties of rigid/crushable PU foam for design applications. To this end, several mechanical performance parameters, that is, mean load and strength, secant modulus, energy absorption efficiency and densification strain are at first identified for the PU foam. Foam samples of different densities are obtained by varying the amount of liquid polyol–isocyanate of a desired mixing ratio in a constant-volume cubical mould and letting the blow and gelation reactions progress to completion. By conducting compression tests on cubic specimens of foam obtained, it is shown that various mechanical parameters of interest increase monotonically with respect to density. An SEM-based study on the effect of density on foam microstructure has also been carried out.
“…A constant mixing ratio of 1:1.1 by volume for polyol:isocyanate has been maintained in the moulding of foam samples. It was found that this is the desirable mixing ratio that yields the highest mechanical properties 24 of the rigid PU foam considered for a given density. To vary the densities of foam samples, the amount of polyol and isocyanate mixture placed in a mould box of constant volume (50 × 50 × 50 mm 3 ) was altered for foam formation.…”
Section: Methodsmentioning
confidence: 94%
“…It is, however, noted that the parameters Pm and η are calculated here for 60% of foam compression as at 70% compression, corresponding stresses and strains shown in Figure 3 are quite high and are likely to be in densification phase.Figure 4.Comparison of stress–strain curves obtained for different mixing ratios. 24 …”
Density is an important parameter that influences the properties and performances of rigid polyurethane foam. In this study, a systematic engineering approach is presented for determining the effect of density on mechanical properties of rigid/crushable PU foam for design applications. To this end, several mechanical performance parameters, that is, mean load and strength, secant modulus, energy absorption efficiency and densification strain are at first identified for the PU foam. Foam samples of different densities are obtained by varying the amount of liquid polyol–isocyanate of a desired mixing ratio in a constant-volume cubical mould and letting the blow and gelation reactions progress to completion. By conducting compression tests on cubic specimens of foam obtained, it is shown that various mechanical parameters of interest increase monotonically with respect to density. An SEM-based study on the effect of density on foam microstructure has also been carried out.
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