Batch foaming poly(vinyl alcohol)/microfibrillated cellulose composites with CO2 and water as co‐blowing agents. Issue 48 (16th July 2015) - Zhao, Na
ABSTRACT We studied the foaming behavior of poly(vinyl alcohol) (PVOH) and microfibrillated cellulose (MFC) composites in a batch process using supercritical carbon dioxide (scCO2) and water as co‐blowing agents. In PVOH/MFC composites, water is an economical plasticizer. It not only suppresses the potential thermal degradation of PVOH but also extends the processing window. A uniform cell structure and a high cell density were achieved in the PVOH/MFC foams. The results showed that cell density was increased by increased water content. Further, the MFC contained both micro‐ and nano‐sized fibers. These created numerous heterogeneous nucleation sites and caused local pressure variations. However, cell density decreased when the MFC was overdosed. Due to the high crystallinity that then developed around the MFC, the gas content was too low, and the stiffness was too high. The experimental results also showed that the cell morphology and density could both be controlled by the water and the MFC content. The effects of the foaming temperature and pressure on the cellular morphology of the PVOH/MFC composite foams were examined systematically. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42551.