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Characterization of rigid polypropylene‐based microcellular foams produced by batch foaming processes
Author(s) -
Velasco José Ignacio,
Antunes Marcelo,
Realinho Vera,
Ardanuy Mónica
Publication year - 2011
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.22048
Subject(s) - materials science , polypropylene , blowing agent , composite material , dissolution , foaming agent , dynamic mechanical analysis , polymer , organoclay , chemical engineering , polyurethane , porosity , engineering
The properties of polypropylene (PP) foams can be extended by controlling the cellular structure and adding functional fillers. PP‐based microcellular foams having an interesting combination of mechanical and transport properties were prepared by two different batch foaming processes. The batch processes employed were a semisolid state CO 2 dissolution physical foaming process and a chemical one based on the dissolution of the gases generated by the thermal decomposition of a chemical blowing agent in the molten state. The role of the cellular structure and nanofillers (5 wt% of organoclay and 10–20 wt% of cellulosic fibers) on the foam properties and CO 2 diffusion rate was discussed. Foams with expansion ratios around 3 but different cell structures were prepared and studied concerning their structural characteristics. For unfilled foams prepared by CO 2 dissolution, the microcellular structure resulted in the highest values of the specific storage modulus. A fraction of organically‐treated montmorillonite dispersed into the PP matrix resulted in superior mechanical properties due to the combined effect of a finer cell structure and inherent higher stiffness of the silicate layers. Despite displaying an open‐cell structure, foams reinforced with high contents of cellulosic fibers showed increased specific storage moduli with respect to the unfilled foams. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers