Elastomeric polyolefin foams with
excellent mechanical properties,
environmentally friendly performance, and cost effectiveness are highly
promising. Nevertheless, it is a huge challenge to obtain these advantages
in elastomeric polyolefin foams using chemical or common physical
blowing agents. Therefore, a strategy was applied to the ethylene–vinyl
acetate copolymer (EVA)/low-density polyethylene (LDPE) (EVA/LDPE)
system by combining crosslinking, microphase separation, crystallization,
and supercritical CO2 (scCO2) solid foaming.
Consequently, environmentally friendly EVA/LDPE foams of zero formamide
with the desired uniform cellular structure of expansion ratio over
8, average cell size less than 50 μm, and cell density over
109 #/cm3 were obtained. The lightweight EVA/LDPE
foams show excellent tensile strength and compression strength, much
higher than those of other elastomeric polyolefin foams. The reasons
for this are that (1) the introduction of crosslinking and entanglement
structures in EVA enhances the viscoelasticity, which is beneficial
to bubble nucleation and bubble stability in the foam, and simultaneously
improves the mechanical properties of the foam; (2) the existence
of LDPE segments in EVA leads to microphase separation, which is beneficial
to bubble nucleation; (3) low-temperature solid foaming enhances the
mechanical properties of the foam due to the uniform microcellular
structure; and (4) scCO2 foaming has zero formamide, which
meets the safety requirements and specifications of children’s
floor mats (T/CTJPA 005-2018).
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