High thermal insulation and compressive strength polypropylene microcellular foams with honeycomb structure

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Global energy issues are becoming increasingly prominent, and have caused widespread attention. Lightweight, thermal insulation, environmentally friendly and recyclable polymeric foam materials exhibit a great application prospects in reducing energy consumption, saving resources and improving utilization. However, there are huge challenges in preparation of such high thermal insulation materials. Herein, recyclable, high mechanical strength and thermal insulation polypropylene (PP) foams were achieved by supercritical CO2 foaming in the presence of β nucleating agent (β-NAs). The obtained PP-β foam exhibited a variety of advantages, including high expansion ratio, continuous honeycomb polygonal cells, a very low thermal conductivity of 26.4 mW/m•K, strong tensile and compressive strength, as well as recyclable property. The accelerated crystallization process, decreased crystal size, and enhanced viscoelasticity caused by the β-NAs contributed to the formation of the multifunctional PP foams. The honeycomb polygonal cells greatly increased the curved path of heat propagation and reduced heat transfer efficiency, as well as enhanced the mechanical properties. Moreover, the compressed PP-β foam still possessed excellent thermal insulation property, as low as 37.1 mW/m•K. The recyclable multifunctional PP foam materials achieved by using physical foaming technology provided a potential solution for the preparation of multifunctional thermal insulation materials, which offered a big application prospect for polymer foam materials in the fields of reducing energy loss.