Manufacturing and design issues in foamed materials processing. Solution and diffusion of gas in polymers. Sorption experiments for determining the solubility and diffusivity. Plasticizing effect of gas in a polymer. Bubble nucleation theories. Processing strategies for the production of high nucleation density foams. Mathematical model of bubble growth. Processing strategies for the bubble growth control. Effect of melt strength on bubble coalescence. Continuous processing of microcellular foamed polymers.