The significant influence of graphene oxide (GO) on the unidirectional foaming of poly(lactic acid) (PLA) using supercritical CO 2 as blowing agent was investigated in this study for the first time. Highly oriented and elongated cell structures were obtained from the PLA/GO nanocomposites foams. The thermal, rheological, and CO 2 absorption properties of the PLA/ GO nanocomposites were studied to investigate the effect of GO on PLA unidirectional foaming. It was found that the incorporation of GO improved the storage modulus, loss modulus, and complex viscosity of the PLA/GO nanocomposites significantly. The addition of GO improved the CO 2 absorption ability of the nanocomposites, which caused high expansion ratio and increased average cell size during foaming process. The high expansion force by enhanced CO 2 absorption, high matrix viscosity of PLA/GO nanocomposites, and restriction of the mold in three directions together caused the formation of the highly elongated cell structure during foaming.

Biodegradable poly(lactic acid) (PLA) based poly(butylenes succinate) (PBS) foams with open cell structure were prepared via batch foaming method using supercritical carbon dioxide as blowing agent. It was found that PLA was immiscible with PBS, and PBS phase was dispersed as tiny spheres or large domains at various concentrations. The addition of PBS reduced the viscosity of the blends. During the foaming process, the PLA/PBS interfaces acted as cell nucleation sites and the low melt strength PBS contributed to the formation of cell connection channels, which resulted in open cell structure. The investigation of PBS content and foaming temperature found that PLA/PBS (80/20) foamed at 100 °C, obtaining the highest cell opening rate (96%). Two-step depressurization foaming experiments proved that bimodal cell structure PLA/PBS foams with high cell opening rate (97%) were able to be fabricated.

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Fe 3 O 4 -based magnetic rubbers are desirable because they take advantage of high elasticity, large elongations, and high magnetic saturation intensity of each component. However, direct compounding of rubbers and Fe 3 O 4 usually resulted in low mechanical properties which made the magnetic rubbers unable to satisfy practical applications. In this paper, we prepared nitrile butadiene rubber (NBR)/Fe 3 O 4 -based magnetic rubbers with good mechanical properties by means of in situ compatibilization using zinc dimethacrylate (ZDMA). Our strategy was based on the polymerization of ZDMA during a peroxide-induced vulcanization, in which the polymerized ZDMA (PZDMA) brought massive Zn 2+ ion pairs into NBR. Zn 2+ ion pairs not only increased the polarity of NBR but also strongly interacted with Fe 3 O 4 nanoparticles. Because of the graf t-PZDMA, the Zn 2+ ion pairs finally strengthened interactions between Fe 3 O 4 nanoparticles and NBR molecules. We hope this report laid an applied foundation for design of high performance magnetic rubbers to satisfy the various potential applications.

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