Abstract
In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a compression test. The results showed that the introduction of CNF into the polyurethane matrix not only created stronger urethane bonding between the hydroxyl groups in the cellulose chain and isocyanate groups in polymethylene polyphenylisocyanate, but also developed an additional filler–matrix interaction between CNF and polyurethane. With the increase of the CNF replacement ratio, a higher glass transition temperature was obtained, and a higher amount of char residue was generated. In addition, an increase of up to 18-fold in compressive strength was achieved for CNF-PUF (polyurethane foam) nanocomposites with a 40% CNF replacement ratio. CNF has proved to be a promising substitute for traditional polyols in the preparation of polyurethane foams. This study provides an interesting method to synthesize highly green bio-oriented polyurethane foams.
Highlights
Polyurethane foam, first produced and commercialized in the 1950s, have attracted much attention due to their low density, high mechanical properties, and use in a wide variety of applications including the construction and automotive industries, depending on the type of foam [1,2,3]
With the introduction of cellulose nanofibrils (CNF), the open-cell structure was disrupted, and as the CNF replacement ratio increased, there were large amounts of CNF deposited on and dispersed among the open cells, providing a chance to interact with the PUF matrix
The CNF played an important role as fillers interacting with the PUF cells, which potentially resulted in improved mechanical properties
Summary
Polyurethane foam, first produced and commercialized in the 1950s, have attracted much attention due to their low density, high mechanical properties, and use in a wide variety of applications including the construction and automotive industries, depending on the type of foam [1,2,3]. CNFs have a diameter in the range of 5 to 50 nm and length of several μm, respectively [27] They exhibit a hierarchical order in the supramolecular structure and organization, high aspect ratio, high surface area, and reactive surfaces containing –OH groups. All these unique characteristics make CNF a promising candidate as a reinforcing material and may at least partially replace polyols [28,29,30,31,32,33,34,35]. Research has been conducted using up to 10% CNF as the additive to improve the mechanical properties of PUF. The morphology, thermal stability, and spectroscopic characterization of the foam composites were analyzed in this study
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