Download or read book Effect of Silica Nanoparticles on Interfacial Tension and Crystallization of Poly(lactic Acid) in Supercritical Carbon Dioxide written by Kaveh Sarikhani and published by . This book was released on 2016 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the effect of silica nanoparticles on two of the most important parameters in the foaming of poly (lactic acid) (PLA) was studied: interfacial tension and crystallization. According to classical nucleation theory, the nucleation rate is inversely related to the exponential cubic power of interfacial tension, similarly the critical nucleation cell size to interfacial/surface tension. A decrease in surface tension decreases the energy barrier for cell nucleation and consequently increases the number of cells, leading to an exponential increase in cell density and smaller cell size. Solid nanoparticles, such as those made of silica, can be adsorbed at the interface and decrease the interfacial tension between polymer melt and surrounding fluid. They can also prevent coalescence through repulsion between two similar particles at the interface of two growing cells or increase in elasticity of the interface. Furthermore, nanoparticles can act as nucleating agents for the foaming of polymers by increasing local stress variations around the particles. In particular, nanoparticles can improve PLA crystallization, which is one of the approaches to address the low melt strength of PLA, one of the barriers for PLA foaming. In addition to melt strength, crystallization and crystallinity can further improve the mechanical properties of PLA.