The flexural, shear and tensile modulus of high density polyethylene structural foams were measured in order to determine the effect of skin thickness on their response under load. Data for foam density between 424 and 725 kg/m3 and skin thickness between 3 and 57% are compared with different models taken from the literature. It is found that the I-beam model of Hobbs and the simple square power-law of Moore are the best models for the flexural and tensile modulus, respectively. For the shear modulus, all the models tested performed equally well.

Irrevereible first-and eieeond-order reactions are studied for combinations of tubular and CST reactors when endothermal or exothermal adiabatic conditions prevail.Typical results presented for itf T and, Tr)i models show the variation of either the conversion or the relative residence time as a function of the mixing level of the system.

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The financial support from the Avco Corporation is gratefully acknowledged for making possible the construction of the experimental apparatus and especially the sampling probes used in this study at high temperatures.

Chemical flow reactors studied include models in which partial mixing and piston flow are present and others which involve partial mixing and short‐circuit. Mixing levels considered extend all the way between the extreme cases of tubular and continuous‐stirred tank reactors. Various orders of reaction are taken into account. The curves presented, obtained through analytical methods, show either the variation of conversion with mixing level at given values of residence time, or relative residence times for a given conversion. Graphical methods of solution are proposed. They involve, in part, a means of computation whereby the overall conversion for a number of reactors in series is obtained from the individual conversions. While isothermal conditions only have been considered, more interesting results are expected when other conditions are applicable, whether isothermal or not.