Designing the foam structures in terms of density and morphology gives the chance to tune their mechanical and functional properties to the specific application. Nowadays, this design has been leveled up by the introduction of graded foams which are characterized by spatially nonuniform densities and/or morphologies. Graded foams have proved superior compared to uniform one in numerous examples and loading conditions but in pure compressive loading, where properties such as the Young's modulus of graded foams are always inferior to uniform ones. When using sintered beads foams, macroscopic pure compression may induce local bending on the single bead, which can be exploited to induce stiffening. This thesis was investigated on both polystyrene and thermoplastic polyurethane samples made by foamed beads sintered in a cylindrical mold. The response to compressive tests of graded foams made by sintering beads having nonuniform cells structures was compared to the uniform counterparts. The results evidenced that, at same average density, foams had up to a 30% ca. of increase of the Young's modulus when the beads are characterized by a denser outer layer.
No abstract
Polyphenyl sulfone (PPSU) is a highly stable and rigid polymer with good chemical and mechanical resistance used in automotive and aerospace industries in high‐temperature applications during long‐operating cycles. PPSU foams are applied as core materials in lightweight composites ensuring high strength, fire resistance, thermal and acoustic insulation. In this paper, PPSU slabs are foamed using CO2, N2, and He as blowing agents (BAs). An experimental campaign is carried out to estimate the BAs' diffusivity in the polymer. In details, CO2 diffusivity ranges from 8E‐11 to 1E‐09 m2/s at temperatures from 220 to 260°C; diffusivity of N2 ranges from 2E‐10 to 5E‐09 m2/s (220–260°C) and it is 4E‐09 m2/s for He at 220°C. Foaming tests reveal an expansion ratio as high as 400% for CO2, 130% for He, and 150% for N2.Scanning electron microscopy analysis is also performed on produced samples, obtaining a cell number density of 1.3E07, 2.6E05, and 1.8E06 cells/cm3 when saturating, respectively, with CO2 at 220°C and 100 bar, N2 at 220°C and 100 bar, and He at 230°C and 100 bar.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.