Reinforcing mechanisms in compression of LDPE/HDPE foams by the incorporation of ethylene plasma-treated B₄C

The role of the incorporation and ethylene plasma surface modification of B4C to reinforce foams based on low-density (LDPE) and high-density (HDPE) polyethylene blends, under compression, is investigated herein. Characterization of B4C was achieved through scanning electron microscopy (SEM), X-ray diffraction, and X-ray photoelectron spectroscopy. Composite foams, containing 0.5, 1.0, and 2.0 wt% of B4C, were characterized by SEM, differential scanning calorimetry, and compression testing. The increase of C-C bonds and the disappearance of oxygen-containing functional groups upon surface treatment confirmed that ethylene polymerizes on B4C forming strong chemical interactions. Both pristine and plasma-treated B4C in LDPE/HDPE foams act as nucleation agents yielding smaller cell size (d), higher cell density (N-c), and higher crystallinity (X-c). The reinforcing mechanisms were analyzed considering N-c, X-c,X- and the B4C-matrix interactions. The foams reinforced with 2.0 wt% of plasma-treated B4C exhibited the highest improvements, with increments of similar to 190% in the elastic modulus, 200% in the yielding strength, and 150% in the toughness at 50% of deformation, retaining the lightweight of the foams without B4C. This study presents valuable insights for developing advanced lightweight foams with improved mechanical properties, particularly for applications in cushioning automotive components, consumer goods, and biomedical devices.