Foams compressive properties

Density and polymer composition have a large effect on compressive strength and modulus (Fig. 3). The dependence of compressive properties on cell size has been discussed (22). The cell shape or geometry has also been shown important in determining the compressive properties (22,59,60,153,154). In fact, the foam cell stmcture is controlled in some cases to optimize certain physical properties of rigid cellular polymers. 

Good compression properties for cores made of honeycombs, wood and plywood. Low compression properties for foamed cores. The compression strength and modulus of a lOOkg/m foam are roughly as low as 2 MPa and 0.1 GPa, respectively. On the other hand, pinpoint impact is distributed across the whole surface facing, provided it is sufficiently resistant. 

We also need to discnss these factors in the resnltant foam, bnt that discnssion is complicated by density and to a degree the quality of the foam. This discussion will focus on the properties of the polymer. It is not unreasonable to assume that as we affect the polymer strength, we also affect the properties of the foam and elastomers that are produced from the polymer. Although more problematic, it also reflects on the compressive properties of the foam. 

Abstract— The use of organosilanes as adhesion promoters for surface coatings, adhesives and syntactic foams is described and reviewed in the light of published work. Data are presented on the beneficial effect of silanes, when used as pretreatment primers and additives, on the bond strength of two pack epoxide and polyurethane paints applied to aluminium and mild steel. It is shown that silanes when used as additives to structural epoxide and polyurethane adhesives are less effective than when used as pretreatment primers on metals but are highly effective on glass substrates. The compressive properties of glass microballoon/epoxide syntactic foams are shown to be markedly improved by the addition of silanes. 

Reference to Table 14 will show the effect of increasing levels of APES on the compressive properties of an anhydride cured epoxide/silica microballoon foam, the APES being added on the resin content. The notation w/r (wt% resin) has been used in the tables. Both the yield stress and strain to failure increased steadily with increased silane content, with a corresponding increase in compressive modulus. At the 5 wt% level there was no real increase in yield stress but a marked increase in strain to failure, resulting in a lower modulus. However, at the 4% level the compressive strength was more than double that of the nonsilane control. 

Effect of silane addition level on the compressive properties of an anhydride cured epoxide silica microballoon syntactic foam (APES, cured at 100 C for 4 h, nominal density 0.35 g/cm )... 

Uniaxial compressive properties are important to the design engineer who can utilize the foams inherent high compressive strength in reinforcing other structural members. Sandwich construction is a typical example of such a use, as in submarine-hull construction. Syntactic-foam prepregs have been developed for this application (7). 

Yosomiya and Morimoto (38) studied the compressive properties of continuous-glass-fiber-strand mat with different fiber lengths, different fiber-volume fractions, and different densities of the matrix foam. 

Mechanical properties of the foams are characterised by compressive and tensile testing. In compression, the foams deform extensively, producing smooth ascending compression curves, free of irregularities observed with... 

In foamed products, the blown-cell volume displaces resin to make consumer products less costly and less wasteful when discarded. A foam s shockabsorbing, heat-insulating, and compression properties are key added benefits for certain packaging applications (see Case 13.1). 

Storage at relatively high temperatures tends to further cure the foam and increases the number of polymer crosslinkages. The effect of storage at 275 F for 2 weeks was found to increase the ambient temperature compressive properties by 5%, and after 9 months the increase was 10 to 15%. Dimensional stability can be severely affected by low temperature aging, particularly at lower densities. 

The compression properties of amorphous PLA foamed in a continuous extrusion process using CO2 as a blowing agent are summarized in Table 17.12. Correlations were found by plotting the compressive modulus E) and stress at yield (tr) as a function of CO2 content. The decreased modulus and strength with the CO2 content is due to the high level of plasticization induced by the residual CO2 for specimens foamed at higher CO2 content [73, 74]. 

Chen, Schadler, and Ozisik (2011) investigated the compressive properties of PMMA/MWCNT nanocomposite foams. As shown in Figure 1.16, nanocomposite foams have greater modulus and collapse strength than the neat PMMA foam across the foam density range studied, and the effects were more prominent for nanotubes with higher aspect ratios. The addition of only 1% of MWCNTs (F-ClOO with an aspect ratio 100) led to 82% increase in the Young s modulus and 104% increase in the collapse... 

Chen L., Schadler L. S., and Ozisik R. An experimental and theoretical investigation of the compressive properties of multi-walled carbon nanotnbe/poly(methyl methacrylate) nanocomposite foams. Polymer 2011, 52, 2899-2909. 

Yan et al. (2011) prepared rigid PU nanocomposite foams reinforced with variable concentrations of carbon nanotubes for long-term use electrical conductive components. Particularly, for a 2 wt% CNT content, rigid PU foams presented around a 30% increase in compression properties and a 50% increase in storage modulus, both measured at room temperature, when compared to the unfilled PU foam, thus demonstrating the effective mechanical reinforcement effect that low amounts of carbon nanotubes have on PU foams. 

Poly(8-caprolactone) (PCL)/organomodified MMT nanocomposite foams prepared by chemical foaming with azodiformamide were reported in the literature. In comparison with the pristine foam, the nanocomposites presented an enhanced compressive property. By increasing clay content, the pore size decreased and the pore wall thickness ranained almost the same at low clay contents. However, at high clay contents, both parameters increased due to the change in the melt viscosity of nanocomposites and the heterogeneous nucleation behavior of the clay at low contents (Liu et al., 2009). 

Nakamura, K., Morck, R., Reimann, A., Kringstad, K., and Hatakeyama, H., 1989, Compression Properties of Polyurethane Foam Derived from Kraft Lignin. In Wood Processing and Utilization (J. F. Kennedy, P. A. Williams and G. O. Phillips, eds.), Ellis Horwood, Chichester, pp. 175-180. 

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