Polypropylene foams: production, structure and properties

Abstract

It is well known the relevance given to the study of heat transfer in polymer foams, as one of the main applications is as lightweight thermal insulating elements. Alongside some of the possible strategies for improving the thermal insulating characteristics of polymer foams, there is also a tremendous interest in further extending the applications of these materials, mainly focusing on improving their poor mechanical properties. Although there is a great deal of interest in preparing and studying polypropylene foams, largely due to their good balance of properties and reduced cost, there is still lack of information regarding their mechanical and thermal conduction characterizations. With that in mind, this chapter considers the preparation, structure and properties of different polypropylene and polypropylene-based nanocomposite foams, focusing on the importance of the foam’s cellular structure and microstructure characteristics and/or filler’s orientation and dispersion in the mechanical and mainly thermal conduction properties, with the main objective of developing new multifunctional thermal insulating lightweight materials for diverse applications. A great deal of importance is given to some of the different strategies used towards the development of rigid polypropylene-based foams to be used as structural elements with improved thermal insulation characteristics. Particularly, we have focused on reducing the value of thermal conductivity via cellular structure control, as it is known to strongly depend on cellular structure characteristics such as cell size, cell density and cell anisotropy. First of all we have addressed the importance of the foaming process and foaming parameters in establishing a certain cellular structure, and secondly in the possibilities of adding high aspect ratio nano-sized fillers, that act as cell nucleating sites, promoting the formation of finer closed-cell foams.