Reinforcing mechanisms in compression of LDPE/HDPE foams by the incorporation of ethylene plasma-treated B 4 C

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, and the B₄C-matrix interactions. The foams reinforced with 2.0 wt% of plasma-treated B₄C exhibited the highest improvements, with increments of ∼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.

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