Innovative technique to fabricate nanocomposite bimodal foams containing expandable polymeric miroballoons: piezoelectric characteristics

One of the remarkable properties of special materials is the piezoelectric phenomenon. The piezoelectric effect is the ability of materials and crystals to convert mechanical energy into electrical energy and vice versa. One way to increase the piezoelectric effect of materials is foaming. The presence of cavities in a foamed material causes the accumulation of electric charge and improves the piezoelectric property of the material. In this paper, a new method is carried out to produce nanocomposite bimodal foams. Piezoelectric low density polyethylene syntactic foams containing expandable polymeric microballoons (EPM) were manufactured using injection molding, then the refoaming process was conducted via batch method. In order to investigate the piezoelectric properties of samples, the effect of microballoon weight% and nanoclay content were studied. The results showed that refoaming process significantly enhanced the piezoelectric properties of both composite and nanocomposite foam specimens. The data of peak-to-peak voltage revealed that the highest piezoelectric response was achieved for the bimodal sample containing the lowest weight% of microballoon (2.5 wt%) as well as highest level of nanoparticle (2 wt%).