Nanoporous polymer foams

Nanoporous polymer foams from nanostructured polymer blends preparation, characterization, and properties... 

Just as microporous foams present better properties than conventional foams, it is expected that nanoporous foams will present enhanced properties because of their lower pore size. For instance, they could have better mechanical properties, such as better toughness, higher impact energies, and strain to failure [26], In addition, they could present an improved thermal insulation behavior because of the Knudsen effect [27], More details about the expected properties of nanoporous polymer foams will be provided in the last section of this chapter. 

Once these mechanisms have been exposed, it can then be expected that this knowledge will lead to a new generation of nanoporous polymer foams, produced from optimal nanostructured polymer blends that can overcome the current limitations of this approach. 

Table 9.1 Micro and nanoporous polymer foams obtained from nanostnictured polymers reported in the literature, with process conditions as well as nanostructure and porous structure characteristics [pore size ( p) and porosity (Vf)]... 

Although it is commonly expected that nanoporous polymer foams will present improved properties over conventional or microporous foams, there are just a few experimental evidences about this behavior. The main limitation to characterize several properties of nanoporous foams is the production of sufficiently large samples that can be subjected to standard test protocols (with most of the results reported previously obtained in the form of thin films). 

Some evidences about the improvement of the mechanical properties of nanoporous PMMA/MAM blends have been reported [98]. However, up to date detailed studies about the mechanical properties or nanoporous polymer foams can only be found on neat polymers without nanostructuration. 

Most of the reported works are limited to the development of nanoporous structures in films or to particular processing parameters however, in the last years significant advances were performed in the production of bulk nanoporous polymer foams in a wide range of processing conditions, showing some of the best features reached, such as a nearly perfect correlation between the former nanostructure and the final porous structure. These advances are a promising step in the search of a continuous industrial process for the production of nanoporous polymer foams. 

The development of a continuous foaming production route able to produce nanoporous polymer foams with fine porous structures and medium-high porosities. 

Further study of the physical properties of nanoporous polymer foams. 

Modification of the foaming processes, polymer precursors, or inclusion or an additional production step that allows connecting the inner open porous structures of some of these materials with the exterior of the sample. By this way a wide set of apphcations could be fulfilled by these nanoporous polymer foams. 

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