Fabrication of Highly Interconnected Poly(ε-caprolactone)/cellulose Nanofiber Composite Foams by Microcellular Foaming and Leaching Processes

Abstract

In this study, microcellular polycaprolactone (PCL)/sodium bicarbonate (NaHCO3)/cellulose nanofiber (CNF) composite foams with highly interconnected porous structures were successfully fabricated by microcellular foaming and particle leaching processes. Supercritical CO2 (scCO2) served as a physical foaming agent, NaHCO3 was chosen as a chemical foaming agent and porogen, and CNF acted as a heterogeneous nucleating agent. The effect of scCO2, NaHCO3, and CNF on pore structures and the cofoaming mechanism were investigated. The results indicated that the addition of NaHCO3 and CNF increased the melt strength of the PCL matrix significantly. During the foaming process, the presence of CNF can form a rigid network due to the hydrogen bonding or mechanical entanglement between individual nanofibers, improving the nucleating efficiency but slowing down the cell growth rate. Additionally, due to the interaction of “soft” PCL matrix and “hard” domains in a PCL-based composite during the foaming process, together with the NaHCO3 leaching process, highly interconnected cell structures appeared. The obtained PCL/NaHCO3/CNF composite foams had a cell size of 15.8 μm and cell density of 6.3 × 107 cells/cm3, as well as an open-cell content of 82%. The reported strategy in this paper may provide the guidelines and data supports for the fabrication of a PCL-based porous scaffold.

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

“…They reported an increase in pore density and a decrease in the pore size as PEO content increased, and after the polymer leaching process, highly interconnected pore morphologies were obtained. Li et al [303] combined supercritical CO 2 foaming with particle leaching to produce PCL/cellulose nanofiber composite foams with highly interconnected pores. NaHCO 3 , used as a chemical blowing agent, as a heterogeneous nucleating agent, and as a porogen, provided more CO 2 for cell nucleation and growth.…”

Developing Fibrous Biomaterials to Modulate Epithelial to Mesenchymal Transition

“…Porogen leaching is also most effective in small batches; the process becomes far more difficult at high volumes [Janik and Marzec, 2015]. Recently, Li et al [2021] used porogen leaching in the development of nanofiber composite foams made up of cellulose nanofibers (CNFs). In this study, they were looking into greener methods for scaffold development and were able to use a a b Fig.…”

In Situ Nanofibrillar Polypropylene-Based Composite Microcellular Foams with Enhanced Mechanical and Flame-Retardant Performances

“…It is noteworthy that the incompatibility between the matrix and the dispersed phase reduces the interfacial adhesion. However, the weak interfacial interaction leads to the stripping of micro/nanoscale fibrils from the matrix at the interface due to the stress concentration effect, thus reducing the mechanical properties [ 25 ]. Therefore, the incorporation of functional third phase additives can not only endow the composite foams with functional properties, but also help to balance the conflicting requirements of in situ fibrillation and interfacial adhesion on compatibility demands.…”