Polyolefinic nanocomposite foams: Review of microstructure-property relationships, applications, and processing considerations

Abstract

In this review, we survey the state of the art on polymeric foams incorporating nano-scale fillers. Particular focus of the review is on foams from polyolefinic nanocomposite formulations incorporating a wide variety of fillers. The nano-scale additives can influence the foam structure and properties in two ways: Firstly, they can act as composite reinforcement to enhance the mechanical properties and functionality of the matrix polymer; and secondly, they can act as foaming-processing aids through modification of the rheological, thermal and crystallization properties of the matrix as well as serving as heterogeneous nucleation sites. Through a combination of these influences, and using advanced processing techniques it is possible to achieve nanocomposite foams that have higher cell density, and more uniform cell size or controlled cell-size distribution. Such controlled foam morphologies, in turn, can yield better specific mechanical properties resulting in more effective light-weighting solutions. Further, the nano-scale additives can impart additional desired functionality resulting in multi-functional foams. In this article, we provide an overview of the mechanical, thermal and a few other relevant functional properties – such as piezoelectric sensitivity, acoustics, and filtration efficiency – of foams prepared using nanocomposite formulations, along with the processing considerations for achieving high quality foams using such materials.

Extrusion foaming of multiphasic polyethylene/ethylene-vinyl acetate copolymer/carbon nanotube mixtures: Tailoring foam properties by selective localization of nanoparticles

“…However, increasing the CNT content more than 2.5 phr led to inverse trends in the foam density, void fraction, cell density and bubble size, which most probably caused by poor dispersion of CNT nanoparticles. 16…”

“…In addition to the heterogeneous nucleation role, CNTs can also affect the rheological properties of the systems, which is crucially important at the growth stage of extrusion foaming process. 16 The rheological behavior of molten samples will be investigated in the following subsection.…”

“…14 It has been reported that the presence of nanofillers significantly affects the foamability and foaming properties of polymers. 15,16 The nanofillers can improve the foamability of a polymeric matrix by changing the rheological, thermal and crystallization behavior of the matrix as well as by providing the heterogeneous bubble nucleation sites. 16 The impacts of nanofiller characteristics on the performance of unfoamed polymeric nanocomposites have been extensively studied.…”

“…15,16 The nanofillers can improve the foamability of a polymeric matrix by changing the rheological, thermal and crystallization behavior of the matrix as well as by providing the heterogeneous bubble nucleation sites. 16 The impacts of nanofiller characteristics on the performance of unfoamed polymeric nanocomposites have been extensively studied. [17][18][19] However, the effects of nanofiller dispersion and localization state on the properties of polymer nanocomposite foams are more complex than that of solid polymer nanocomposites.…”

Preparing low-Density microcellular polystyrene foam by in-Situ fibrillated PTFE and supramolecular nucleator TMC-300 in the presence of sc-CO2

“…However, inorganic additives with nonuniform distribution and dispersion tend to agglomerate within a polymer melt which reduces the effective surface-to-volume ratio and leads to an inhomogeneous foam morphology. 12,17 In the foaming method, apart from conventional extrusion foaming, microwave-assisted foaming is also widely studied. Compared with the traditional process, microwave-assisted foaming can increase the sample surface and core temperatures, resulting in uniform foam products.…”