Reinforced Smart Foams Produced with Time-Profiled Magnetic Fields

Abstract

Polymeric smart foams are lightweight and multifunctional porous materials that are sensitive to the magnetic field due to the presence of magnetic particles embedded in the matrix. Recently, a constant magnetic field has been exploited to align the particles along the magnetic field lines during the formation of the porous structure. In this paper, a new field-structuring process was developed that makes use of a time-profiled magnetic field during the foaming process to control the geometrical features of the particles aggregates. The effects of magnetic field strength as well as the switch-on and switch-off times on the magnetoelastic behavior of the smart foams were investigated. It was proven that the alignment of the particles results in both a strong relative sensitivity to the magnetic field and a positive stress change, whose extent depends on the geometrical features of the developed aggregates.

Chemically Functionalized Cellulose Nanocrystals as Reactive Filler in Bio-Based Polyurethane Foams

“…It is well-known that pristine CNC consists of chains that are arranged parallel to one another and are held together by strong H bonds, forming fibrils. These fibrils are locally orderly, to the extent of having a crystalline structure (namely type IV 1 ) [ 41 ] observed by analyzing the diffractogram in Figure 4 a which shows a typical pattern of cellulose I, with two main peaks at 2θ around 15.3° correlating to the overlapping of the reflection planes (1 0) and (110), and 2θ equal to 22.1° due to the reflection plane (200) [ 42 ]. However, a shoulder at 2θ equal to 20.3° on the lower side of the (200) plane is also evident.…”

Assembly and manipulation of responsive and flexible colloidal structures by magnetic and capillary interactions

“…One simple way to make field-responsive foams is the introduction of the inorganic magnetically responsive particles to foams which can stabilize the foams and allow their manipulation by an external magnetic field. [152][153][154][155] Similarly, Pickering emulsions containing paramagnetic particles can be reversibly switched between biphasic dispersions and fully phase-separated fluids upon application of a magnetic field. 60,156 Magnetically responsive particles can also be used to tune the shape and stabilities of the bubbles in the foams using an external magnetic field.…”

Correlation Between Temperature Changes and Magnetostrictions in Magnetorheological Foam

“…Besides, nucleation of pores in the matrix phase of MR foam causes a decrease in the resultant Young's modulus, which is in return result the MPC to be more susceptible to elongation [7], thus suitable for magnetostrictive application that require changeable dimensions easily and reversibly. This improved property of MR foam can be further utilized in applications of semi-active adaptive variable-stiffness devices, soft actuators, sensors and arti cial muscles [2,11].…”