Biodegradable polymers, both synthetic and natural, often show poor foamability, in terms of the ability to form a fine-celled structure and to retain it. In fact, foams with high density and/or non uniform morphology are generally obtained with these materials. Poor rheological properties, poor solubility and inadequate diffusivity of the ordinary foaming agents, and insufficient setting mechanisms (e.g., crystallization kinetics), are the possible reasons. In this work different approaches, tuned to the different materials, have been investigated to improve the foamability of biodegradable materials, such as polyesters, polysaccharides, vegetal and animal proteins. This comprehensive analysis allows one to gain a wide and clear picture of the relevance and efficiency of the available strategies: process optimization, macromolecular design, choice of blowing agent, and use of additives.
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