Structure-property relationships of medium-density polypropylene foams

Abstract

This paper is focused on the production and characterization of a collection of polypropylene (PP) foams with relative densities ranging from 0.3 to 0.6. Samples were foamed using the improved compression moulding method. The process allows controlling density and cellular structure independently as well as obtaining PP foams without fillers, crosslinking or using special PP grades. The influence of blowing agent content, density, cellular structure and foaming conditions on the mechanical response measured in compression, tensile, bending and Charpy impact tests was determined. Results show that density, open cell content and blowing agent concentration have a significant influence on the mechanical performance of medium‐density PP foams. © 2013 Society of Chemical Industry

Effects of extrusion process, type and content of clays, and foaming process on the clay exfoliation in HMS PP composites

“…These foams are discs with a diameter of 180 mm and a height of 10 mm. A more detailed description of the ICM technique can be found elsewhere …”

“…Moreover, composites containing three different clay contents (2.5, 5, and 7.5 wt %) were generated in order to analyze the effect of the clay content. Finally, cellular materials were produced by the Improved Compression Moulding (ICM) route in order to analyze the effect of the foaming process . ICM was selected because in this foaming process the material is only subjected to temperature and pressure and hence, there are no other forces associated to the foaming process which could contribute to the clay exfoliation (such as shear forces in extrusion foaming).…”

Influence of the irradiation dose in the cellular structure of natural rubber foams cross-linked by electron beam irradiation

“…The N 0 values (density of cell nuclei) experienced a clear increment with the foaming time until 53 s. This fact is clearly connected with the blowing agent decomposition reaction, which gradually evolved during this period of time up to its completion (53-60 s.). As ADC is a self-nucleating blowing agent, the higher the amount of the decomposed blowing agent, the higher the number of cell nuclei can be formed (Saiz-Arroyo et al, 2013). In addition, the size of the cells that have already nucleated increases with time due to the increasing amount of gas generated which came from the surrounding polymer matrix to the interior of the cells.…”

Highly anisotropic crosslinked HDPE foams with a controlled anisotropy ratio: Production and characterization of the cellular structure and mechanical properties

“…On the other hand, mechanical properties are also influenced by the characteristics of the cellular structure. For instance, high open cell contents, that is, high interconnectivities between cells, are not desirable since both elastic modulus and collapse stress decrease as the open cell content increases [14,15]. The homogeneity of the cellular structure is also a factor to consider [16].…”

“…On the one hand, foam density is the main factor that determines the mechanical behavior of cellular materials [2,[12][13][14]. On the other hand, mechanical properties are also influenced by the characteristics of the cellular structure.…”