Lightweight conductive foam: An ultralight conductive nanocomposite foam with a density of 0.05 g cm−3 (see SEM image) was successfully prepared based on multi‐walled carbon nanotubes and rigid polyurethane. An interesting density‐dependent conductor–insulator transition was observed in this ultralight composite, which reveals the weight‐lightening limit of a conductive polymer composite.

Different density rigid polyurethane foams (RPUF) filled with various expandable graphite loadings were fabricated by cast molding. The flame retardant properties of these composites were assessed by limiting oxygen index and horizontal and vertical burning tests. The results showed that the flame retardant efficiency got better with increase in the foam density at the fixed EG weight percent or with increase in the EG weight percent at the fixed foam density. After burning, the low density (0.065 g/cm 3 ) pure burned RPUF produced the highly collapsed and carbonized material, while the high density (0.510 g/cm 3 ) pure RPUF had little change in size and had reduced destruction of the material. Moreover, the scanning electronic microscope (SEM) observation showed that the higher density EG/RPUF composites had a more compact outer layer (burned layer) after burned, in which more wormlike materials composed of expanded graphite particles appeared. In addition, higher foam density led to less plastic deformation in the interface layer between the burned and the inside layers. These results indicated that a weight percent of a flame retardant additive that achieves satisfactory flame retardancy for a certain density foam cannot effectively be applied for another density foam.

It is particularly difficult to prepare a foam CPC material because its porous structure makes it hard to form a conductive network. We utilized acetone‐assisted dispersion to disperse CNTs into PU foam and successfully prepared a lightweight conductive CNT/assembled PU foam composite. The NTC effect, which exclusively exists in the melt state CPC materials, has unexpectedly been observed in the solid‐state lightweight conductive CNT/sPU composite. Higher gas fraction and lower matrix modulus could result in stronger NTC effect. The mechanism that thermal expansion of gas wrapped in the cellular structure induces more perfect conductive paths has been proposed to satisfactorily elucidate the NTC effect and its gas fraction and matrix modulus dependence.magnified image

Rigid polyurethane foams (RPUF) filled with various loadings of expandable graphite (EG) or/and hollow glass microspheres (HGM) were prepared by cast molding. The flame retardant properties of these composites were investigated by limiting oxygen index (LOI), horizontal and vertical burning tests. The composite with 10 wt % HGM and 20 wt % EG had the best flame retardant properties, and its LOI value reached 30 vol %. The addition of an appropriate loading of HGM improved the compressive strength and modulus of RPUF and EG/RPUF. When the HGM content arrived at 10 wt %, the compressive strength and modulus of the composites reached the maximum value. The dynamical mechanical analysis (DMA) showed that the addition of EG and HGM made the glass transition temperature shift to a higher temperature, and 10 wt % EG and 10 wt % HGM filled RPUF had the highest storage modulus. The scanning electronic microscope (SEM) observation indicates that the additives led to the decrease in the cell size. In addition, the flame retardant mechanism, the thermal properties, the burned surfaces and the interface surfaces were elucidated.

An ionic liquid (IL), 1-ally-3-methylimidazolium chloride (AmimCl), was used as cosolvent for cellulose and soy protein isolate (SPI) to prepare different compositions of cellulose/SPI blend films, which were coagulated under a nonsolvent condition. The structures of the blend films were investigated by Fourier transform infrared (FTIR) spectrum, X-ray diffraction (XRD), scanning electron microscope (SEM), and transparence analysis, and the physical properties of the films such as mechanical properties, water resistance, water vapor permeability, gas permeability, and thermal stability were also examined. The results indicate that cellulose/SPI blends have excellent miscibility in all weight ratios of cellulose to SPI. With the increase of cellulose content in blend films, the tensile strength, elongation at break, water resistance, and thermal stability of the cellulose/SPI blend films all increase. The addition of the cellulose results in a decrease in the water vapor permeability values. In addition, all films have high gas barrier capacities. These films appear to have the potential as packing and/or coating materials, replacing synthetic polymer films.