Preparation of Cross‐Linked Sponge With Piezoelectric Properties Based on Low Density Polyethylene/Poly(Ethylene‐ Co‐ Vinyl Acetate) and Barium Titanate: Relationship Between Mechanical Properties, and Cell Structure With Piezoelectric Coefficients

ABSTRACT In this study, cross‐linked foams were developed using a blend of ethylene‐vinyl acetate copolymer (EVA), and low‐density polyethylene (LDPE), incorporated with barium titanate (BaTiO 3 ), to explore their piezoelectric characteristics, as well as the various effective parameters, such as foam density, morphology and crystallization. In this regard, LDPE/EVA blends containing BaTiO 3 were prepared through the melt mixing method. In these mixtures, maleic anhydride‐grafted LDPE (LDPE‐ g ‐MAH) was used as the compatibilizer, followed by forming cross‐linked foams using dicumyl peroxide through the compression molding method. As observed, an increase in EVA content caused a higher rate of crosslinking, decreased cell size, as well as an increase in the gel content. The addition of BaTiO 3 to EVA‐dominant composites, due to improved interaction with vinyl acetate groups acting as nucleating agents, resulted in cells smaller than 100 μm in diameter and increased the modulus to 0.63 MPa. EVA‐dominant samples, in comparison to those LDPE dominant, exhibited less hysteresis, higher cell strength, and a faster response rate, leading to enhanced sensor performance and accuracy. The inclusion of the compatibilizer contributed to a higher modulus and finer cell size, attributed to the effective dispersion of BaTiO 3 particles within the matrix. Furthermore, the synergistic impact of the cellular structure and BaTiO 3 on piezoelectric properties yielded the highest piezoelectric coefficient (0.8 pC/N) in the LDPE‐dominant sample (LDPE/EVA: 70/30 w/w%) containing 20 wt.% BaTiO 3 , owing to its higher output voltage and lower modulus compared to the other samples.