Nanocomposites made from cellulose nanocrystals and tailored segmented polyurethanes

Abstract

The effect of the addition of microcrystalline cellulose nanofibers into linear segmented polyurethanes (SPU) was investigated. The polymers were synthesized with 4,4-methylene-bisphenyldiisocyanate (MDI) and poly (tetramethyleneglycol) (PTMG) with 1,4-butanediol (BD) as chain extender. The nanocrystals were introduced during the PU polymerization, which resulted in cellulose nanofibrils covalently linked to the polymer. The interactions between the cellulose nanofibrils and the matrix lead to interesting changes in the behavior of the PU, with the hard segment (HS) phase being more affected by these interactions. SPUs with different contents of HS were synthesized to better understand these effects (23 to 45 wt %). Thermal, thermo-mechanical and mechanical characterization of the nanocomposites were performed. In general, the nanocellulose favored the phase separation between the soft and hard domains generating an upward shift in the melting temperatures of the crystalline phases, an increase in the Young's modulus and a decrease in deformation at break.Comparison of the unfilled polymer responses and that of the nanocomposites showed that by increasing cellulose content, increased dynamic storage and tensile modulus as well as melting temperatures and enthalpy of melting of the soft domains can be achieved. Addition of cellulose during the polymerization essentially erased the potential shape memory behavior originally displayed by some of the SPU. However, a sample prepared by adding the cellulose nanocrystals after the reaction showed that the mechanical properties were still improved, while the shape memory behavior of the polymer was preserved.

Optimal Conditions for Isolation of Nanocrystalline Cellulose Particles

“…Due to these features, NCP can be used as a high-quality reinforcing filler for polymers and biodegradable materials, strengthening additive for papers, thickener for dispersions, as well as drug carrier and implant, etc. [4][5][6][7][8][9][10][11][12]. These particles can be made by treatment of initial cellulose samples with concentrated sulfuric acid (SA) at various temperatures and following mechanical or ultrasound disintegration of the acid-treated cellulose in water [2,[13][14][15][16][17][18][19][20][21].…”

Cellulose Nano Whiskers as a Reinforcing Filler in Polyurethanes

“…Softwood (SW) kraft pulp (Revol et al, 1994;Araki et al, 1998;Araki et al, 1999;Pu et al, 2007), SW sulfite pulp (Beck-Candanedo et al, 2005), hardwood (HW) ECF (elemental chlorine free) pulp (Beck-Candanedo et al, 2005), recycle pulp (Filson et al, 2009), cotton fiber (Revol et al, 1994;Dong et al, 1996;Dong et al, 1998;Araki et al, 2000;Hasani et al, 2008;Cao et al, 2009;Pei et al, 2010;Tang & Weder, 2010;Wang et al, 2010), sisal fiber (de Rodriguez et al, 2006;Tang & Weder, 2010), flax fiber (Cao et al, 2007), ramie fiber (Habibi et al, 2007;Habibi & Dufresne, 2008;Zoppe et al, 2009), wheat straw (Helbert et al, 1996), bamboo residue , bacterial microfibrils (Grunert & Winter, 2002), grass fiber (Pandey et al, 2009), tunicate cellulose (Favier et al, 1995;Angles & Dufresne, 2000;Sturcova et al, 2005;Ljungberg et al, 2006;Habibi et al, 2007;Siqueira et al, 2010;Tang & Weder, 2010), microcrystalline cellulose (MCC) Bondeson et al, 2006;Oksman et al, 2006;Bondeson & Oksman, 2007;Bai et al, 2009;Auad et al, 2010; have all been utilized as cellulose sources for whiskers. The most common preparation method employed is acid hydrolysis, including acid sulfuric and hydrochloric acid.…”

“…These drawbacks have continued to spur research into PU composites, especially nanocomposites, considering the superior properties that can be acquired by the introduction of nano particles into a PU product. In recent years, cellulose nano whiskers have been used as a reinforcing filler in PU synthesis, and improvements of both thermal and mechanical properties have been reported (Marcovich et al, 2006;Cao et al, 2007;Auad et al, 2008;Cao et al, 2009;Auad et al, 2010;Li et al, 2010a;Wang et al, 2010). Since different types of PU have been investigated through various preparation methods and characterization techniques, a summary and comparation with regard to the PU nanocomposite synthesis and a detailed discussion of the properties, mechanisms and other associated issues will facilitate future applications of cellulose nano whiskers in PU and other related polymers.…”

Preparation and Characterization of Waterborne Polyurethane Modified by Nanocrystalline Cellulose

“…The explanation for this fact is that the synergistic effect between the NCC and the waterborne polyurethane was significantly enhanced (Cao et al 2007). The addition of microcrystalline cellulose nanofibers into linear segmented polyurethanes (SPU) resulted in an increase in the Young's modulus and a decrease in the deformation at the break (Auad et al 2010).…”

“…The explanation for this fact is that the synergistic effect between the NCC and the waterborne polyurethane was significantly enhanced (Cao et al 2007). The addition of microcrystalline cellulose nanofibers into linear segmented polyurethanes (SPU) resulted in an increase in the Young's modulus and a decrease in the deformation at the break (Auad et al 2010). Recently, nanocrystalline cellulose (NCC) has been extensively studied because it exhibits many unique characteristics, such as high tensile strength and Young's modulus, polar groups (-OH), an enriched surface (Eyley and Thielemans 2011), and a high specific surface area (Cranston and Gray 2006;Zaman et al 2012) in addition to its biodegradable and environmentally benign nature (Wegner and Jones 2006).…”