Effect of Cellulose Nanofiber (CNF) Surface Treatment on Cellular Structures and Mechanical Properties of Polypropylene/CNF Nanocomposite Foams via Core-Back Foam Injection Molding

Abstract

Herein, lightweight nanocomposite foams with expansion ratios ranging from 2–10-fold were fabricated using an isotactic polypropylene (iPP) matrix and cellulose nanofiber (CNF) as the reinforcing agent via core-back foam injection molding (FIM). Both the native and modified CNFs, including the different degrees of substitution (DS) of 0.2 and 0.4, were melt-prepared and used for producing the polypropylene (PP)/CNF composites. Foaming results revealed that the addition of CNF greatly improved the foamability of PP, reaching 2–3 orders of magnitude increases in cell density, in comparison to those of the neat iPP foams. Moreover, tensile test results showed that the incorporation of CNF increased the tensile modulus and yield stress of both solid and 2-fold foamed PP, and a greater reinforcing effect was achieved in composites containing modified CNF. In the compression test, PP/CNF composite foams prepared with a DS of 0.4 exhibited dramatic improvements in mechanical performance for 10-fold foams, in comparison to iPP, with increases in the elastic modulus and collapse stress of PP foams of 486% and 468%, respectively. These results demonstrate that CNF is extraordinarily helpful in enhancing the foamability of PP and reinforcing PP foams, which has importance for the development of lightweight polymer composite foams containing a natural nanofiber.

3D Printing of UV-Curable Polyurethane Incorporated with Surface-Grafted Nanocellulose

“…As a side note, the mixture of PU-based commercial resin with CNF exhibits a thick agglomeration with the inhomogeneous composition. The water moisture present in unmodified CNF on account of the hygroscopic nature of cellulose intervenes in the interface polymerization with hydrophobic polymers matrix such as PU [8,36]. In the addition of PEG and rGO as a compatibilizer, modified CNF was able to distribute well in the PU matrix.…”

“…In the addition of CNF, the oxygen composition increased owing to the rich hydroxyl groups of cellulose [26]. The mixture of PU and unmodified CNF shows a visible void of interfacial polymerization due to the large hydrophilic surface at the sites of cellulose chain and hydrophobic polymers matrix of PU (see Figure 6b) [8,36]. On the other hand, the modified CNF provided better dispersibility between PU and CNF/PEG and CNF/rGO.…”

Microstructure and Properties of Glass Fiber-Reinforced Polyamide/Nylon Microcellular Foamed Composites

“…The fracture in the GF/PA changes from a single-matrix fracture to a combined of matrix fracture, fiber pullout, and fiber broken, which helps increase the mechanical toughness [ 17 , 18 , 19 ]. GF/PA microcellular foamed composites have the characteristics of high strength and the advantages of being lightweight as well as having a low production cost and high product dimensional accuracy, because the addition of fibers could promote nucleation, refining the cell structure [ 20 ]. Therefore, GF/PA has gradually expanded from the initial interior parts to structural parts such as engines, bodies, and bumpers for vehicle application.…”

Reinforcement of polypropylene by cellulose microfibers modified with polydopamine and octadecylamine

“…These mechanical properties depended on the degree of substitution (DS) and were maximized at the optimal DS value of 0.44. Wang et al studied the foaming of ASA‐CNF/isotactic polypropylene (iPP) composites 18–22 . They confirmed the formation of a network‐like structure of CNFs in the iPP matrix by rheological measurements and achieved an 18‐fold expansion ratio by combining the materials with a core‐back injection molding process.…”