Abstract
In this work, polypropylene (PP) was foamed via rotational molding using a chemical blowing agent (CBA) based on azodicarbonamide over a range of concentration (0 to 0.5% wt.). The samples were then analyzed in terms of morphological, thermal and mechanical properties. The morphological analysis showed a continuous increase in the average cell size and cell density with increasing CBA content. Increasing the CBA content also led to lower foam density and thermal conductivity. Similarly, all the mechanical properties (tension, flexion and impact) were found to decrease with increasing CBA content. Finally, the efficiency of the rotomolding process was assessed by producing neat PP samples via compression molding. The results showed negligible differences between the rotomolded and compression molded properties at low deformation and rate of deformation indicating that optimal rotomolding conditions were selected.
Highlights
Scientific and industrial research increasingly focused on foamed thermoplastic materials, which are composed of a cellular core structure generated by the expansion of a blowing agent inside a thermoplastic matrix
The results showed that PP foams produced using a high injection rate, a low melt temperature and a high melt pressure exhibited a more uniform and finer cellular core structure
Both parameters increase with increasing chemical blowing agent (CBA) content since more gas is available to blow the nucleated cells
Summary
Scientific and industrial research increasingly focused on foamed thermoplastic materials, which are composed of a cellular core structure generated by the expansion of a blowing agent inside a thermoplastic matrix. Foamed polystyrene (PS) and polyethylene (PE) products have been commercially available for decades Their usefulness is limited due to their low heat deflection temperature.[6] When PS foams are heated above their glass transition temperature (Tg) around 100C, they become soft and deform.[7] foamed PE is rarely used above 100C because of its low melting point (110–130C).[8] PS and PE foams are not suited for applications requiring elevated service temperature environments like contact with boiling water or sterilization processes. Some studies have been conducted on PP foams manufactured by injection molding,[13,14,15,16] compression molding[17,18,19] and extrusion molding.[20,21] For example, Ahmadi and Hornsby reported how the structure of PP foams was influenced by the injection molding processing conditions.[13]
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