Abstract
This paper focuses on the development of hybrid structures containing two different classes of porous materials, nanocomposite foams made of polyurethane combined with graphene-based materials, and aluminum open-cell foams (Al-OC). Prior to the hybrid structures preparation, the nanocomposite foam formulation was optimized. The optimization consisted of studying the effect of the addition of graphene oxide (GO) and graphene nanoplatelets (GNPs) at different loadings (1.0, 2.5 and 5.0 wt%) during the polyurethane foam (PUF) formation, and their effect on the final nanocomposite properties. Globally, the results showed enhanced mechanical, acoustic and fire-retardant properties of the PUF nanocomposites when compared with pristine PUF. In a later step, the hybrid structure was prepared by embedding the Al-OC foam with the optimized nanocomposite formulation (prepared with 2.5 wt% of GNPs (PUF/GNPs2.5)). The process of filling the pores of the Al-OC was successfully achieved, with the resulting hybrid structure retaining low thermal conductivity values, around 0.038 W∙m−1∙K−1, and presenting an improved sound absorption coefficient, especially for mid to high frequencies, with respect to the individual foams. Furthermore, the new hybrid structure also displayed better mechanical properties (the stress corresponding to 10% of deformation was improved in more than 10 and 1.3 times comparatively to PUF/GNPs2.5 and Al-OC, respectively).
Highlights
In recent years, porous materials have attracted a huge interest from both academia and industry because they may find applications in a variety of fields, such as energy storage [1], catalysis [2], drug release [3], sound and thermal insulation [4], environmental remediation [5] and others
The foams are hereafter referred as polyurethane foam (PUF), PUF/xGNPs and PUF/xGO, characterization, the samples were settled to rest for 24 h at room temperature to ensure complete where x refers to the carbon nanostructure content
The success of PUF and PUF nanocomposites preparation relies on the appropriate reaction between the precursors, namely the extinction of isocyanate groups through the reaction with hydroxyl groups of the polyol and urethane formation; this was confirmed by FTIR analysis (Figure S1)
Summary
Porous materials have attracted a huge interest from both academia and industry because they may find applications in a variety of fields, such as energy storage [1], catalysis [2], drug release [3], sound and thermal insulation [4], environmental remediation [5] and others. One interesting example of porous materials are aluminum open-cell foams (Al-OC) This type of foam is characterized by a low weight, high thermal and electrical conductivities, and high internal surface area. We reported the impregnation of a cellulose/graphene foam into an Al-OC foam, creating a hybrid structure with higher mechanical properties (increase in stress of 100 times) with respect to the cellulose foam This multifunctional hybrid foam presented high sound absorption coefficient (near 1 between 1000–4000 Hz) and low thermal conductivity. To further explore these types of structures, in the present work we considered the incorporation of polyurethane foams (PUF) into Al-OC ones. Graphene oxide (GO) (4 mg/mL aqueous dispersion) was purchased from Graphenea
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