Polyurethanes Reinforced with Cellulose

Maria L. Auad, Mima A. Mosiewicki Norma E. Marcovich  

Keywords Polyurethane, nanocellulose, cellulose whiskers, nanofibrillated cellulose, shape-memory polymers, waterborne polyurethanes 

Vijay Kumar Thakur, Nanocellulose Polymer Nanocomposites, (65 8S) 2015 Scrivener Publishing LLC 

On the other hand, native cellulose is an abundant and inexpensive macromolecular compound that reinforces most plant cell walls. During recent years, attention has been devoted to the use of cellulose (nanocellulose or nanofibrillated cellulose), and important studies have been published [13-22]. The outstanding mechanical properties of nanocellulose or nanofibrillated cellulose, linked to its wide availability, biodegradability, and extensive number of alternatives for chemical modification, have been the driving force for its utilization as reinforcement in polymers. These cellulosic materials are composed of nanosized cellulose fibrils with a high aspect ratio (length-to-width 

Therefore, this chapter summarizes the recent investigations on polyurethanes reinforced with cellulose fibers, stressing the effect of using nano-sized cellulose particles to control the final performance of the composite materials. 

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Lin S, Huang J, Chang PR, Wei S, Xu Y, Zhang Q. Structure and mechanical properties of new biomass-based nanocomposite castor oil-based polyurethane reinforced with acetylated cellulose nanocrystal. Carbohydr Polym 2013 95 (1, 5) 91-99. 

Figure 6.7 presents TGA curves of polyurethane, cellulose, lignin and composites reinforced with cellulose and lignin. The decomposition of the polyurethane takes place in one step, while the composites decompose in two steps. In the first stage, decomposition occurs after the decomposition of the fiber and matrix alone. The small weight loss up to 100°C is related to the moisture content of the material. Above this temperature, some water molecules that are tightly bound to the fibers become volatile [21]. Thus, reinforcement decreases the thermal stability of the composite. 

Zhang, 2006), silk fibroin (Noishiki, Nishiyama, Wada, Kuga, Magoshi, 2002) reinforced with cellulose whiskers were reported. Meanwhile, Poly-(styrene-co-butylacrylate) (poly(S-co-BuA)) (Helbert, Cavaille, Dufresne, 1996), poly (vinyl chlo-ride) (PVC) (Chazeau, Cavaille, Canova, Dendievel, Boutherin, 1999), polypropylene (Ljungberg et al., 2005), waterborne polyurethane (Cao, Dong, Li, 2007), were also used as synthetic matrixes. 

One of the first reports on polyurethanes reinforced with nanocellulose crystals was the paper published by Marcovich and co-workers [22]. In this report, nanocrystals were obtained from synthetic microcrystalline cellulose by acid hydrolysis and re-dispersion into dimethyl formamide (DMF) by ultrasonication to obtain a stable suspension. The suspension was an effective means for incorporating the cellulose crystals into the unreacted polyol-isocyanate mixture, utilized to produce polyurethane composite films. The rheology of the uncured liquid suspensions revealed the formation of a filler... 

Li, Y., H. F. Ren, and A. J. Ragauskas. 2010. Rigid polyurethane foam reinforced with cellulose whiskers Synthesis and characterization. Nano-Micro Lett. 2 89-94. 

Zhu et al. studied polyurethane foams from soy reinforced with cellulose microfibers. They found an increase on the onset degradation temperature of the thermal degradation of polyurethane with the addition of 2 wt % cellulose fibers. They attributed this fact to the insulator effect of cellulose fibers [52]. Navarro-Baena et al. studied shape memory PU based on PLA-PCL-PLA block copolymer and reinforced with both CNCs and PLA grafted CNCs [72]. Aside the increment on the shape memory behavior of the polyurethane-based nanocomposites, they reported an increase on the thermal stability of the PU matrix in particular, they reported that, although CNCs improved the thermal stability of both PCL and PLEA blocks, in particular the thermal stability of the PCL block was improved in the nanocomposites increasing the maximum degradation temperature of about 40 with respect to the PCL block of the neat PU-matrix [72]. 

Mileo PC, Oliveira MF, Luz SM, Rocha GJM, Gonsalves AR. Evaluation of castor oil polyurethane reinforced with hgnin and cellulose from sugarcane straw. Adv Mater Res 2010 123-125 1143—6. 

Pei, A H., Malho, J. M., Ruokolainen, J., Zhou, Q., and Berglund, L. A (2011). Strong nanocomposite reinforcement effects in polyurethane elastomer with low volume fraction of cellulose nanocrystals. Macromolecules. 44,4422-4427. 

Cao X, Dong H, Li CM (2007) New nanocomposite materials reinforced with flax cellulose nanocrystals in waterborne polyurethane. Biomacromolecules 8 899-904 Cao X, Habibi Y, Lucia LA (2009) One-pot polymerization, surface grafting, and processing of waterborne polyurethane-cellulose nanocrystal nanocomposites. J Mater Chem 19 ... 

Linear Elastic and Rubber Elastic Behavior. Although stiffening is quite noticeable in the glassy regime of the amorphous phase, the most spectacular effect is seen in the rubber elastic regime phase, as already evoked in the case of reinforcement by cellulose whiskers (2). The PA6-clay hybrids example presented in Table 3 is quite representative of the situation encoimtered with semi crystalline thermoplastics, but elastomeric networks benefit as well of clay layer dispersion with a two- to threefold increase in modulus for polyurethane or epoxy networks... 

A. Pei, J. M. Malho, J. Ruokolainen, Q. Zhou, and L. A. Berglund, Strong Nanocomposite Reinforcement Effects in Polyurethane Elastomer with Low Volume Fraction of Cellulose Nanocrystals. Macromolecules 44, 4422-4427 (2011). 

Different core materials are used. They include foam, honeycomb core (plastic, paper, aluminum, etc.), ribs, balsa wood, filler spacers, corrugated sheet spacers, etc. Materials such as polyurethane foam, cellulosic foams, and polystyrene foams are widely used as core materials. Plastics, such as glass-reinforced polyester, are frequently used as the skins for panels. Different skin materials are used such as metallic skins alone or in conjunction with plastic skins. 

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