A team of researchers from Zhengzhou University, China, and University of Toronto, Canada, 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 suppressed 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.
Title
Foaming with CO2 and water as co-blowing agents
VATIS UPDATE Part
Article body