Abstract
The intercalation degree of nanoclays in polymeric foamed nanocomposites containing clays is a key parameter determining the final properties of the material, but how intercalation occurs is not fully understood. In this work, energy dispersive X-ray diffraction (ED-XRD) of synchrotron radiation was used as an in-situ technique to deepen into the intercalation process of polymer/nanoclay nanocomposites during foaming. Foamable nanocomposites were prepared by the melt blending route using low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) with surface treated nanoclays and azodicarbonamide (ADC) as the blowing agent. Foaming was induced by heating at atmospheric pressure. The time and temperature evolution of the interlamellar distance of the clay platelets in the expanding nanocomposites was followed. Upon foaming, interlamellar distances of the nanocomposites based on LDPE and PP increase by 18% and 16% compared to the bulk foamable nanocomposite. Therefore, the foaming process enhances the nanoclay intercalation degree in these systems. This effect is not strongly affected by the type of nanoclay used in LDPE, but by the type of polymer used. Besides, the addition of nanoclays to PP and PS has a catalytic effect on the decomposition of ADC, i.e., the decomposition temperature is reduced, and the amount of gas released increases. This effect was previously proved for LDPE.
Highlights
Polymeric foams are light-weight materials with an excellent strength-to-weight ratio and good thermal and sound insulation properties, having many applications in the insulating, packaging, construction, and automotive industries [1,2]
Few works focus on the intercalation/exfoliation induced by the foaming process itself
The effect of the surface modification of the nanoclays in the intercalation of the clay platelets during foaming was investigated using three low-density polyethylene (LDPE)-based nanocomposites with different types of clays. In these systems, the intercalation during the foaming phenomenon is not associated with the type of clay, but with the foaming process of polyethylene itself
Summary
Polymeric foams are light-weight materials with an excellent strength-to-weight ratio and good thermal and sound insulation properties, having many applications in the insulating, packaging, construction, and automotive industries [1,2]. Foamed polymer/clay nanocomposites are attractive for applications requiring high strength and lightweight and enhanced flammability resistance, among other properties [3,4,5]. There is extensive research on the effect of nanoclays’ addition in the properties of foams [11,12,13,14,15,16,17,18,19]. These works relate the properties with the state of dispersion/aggregation of the nanoclays in the nanocomposite bulk precursors before foaming. Few works focus on the intercalation/exfoliation induced by the foaming process itself
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