Effects of starch nanocrystal‐graft‐polycaprolactone on mechanical properties of waterborne polyurethane‐based nanocomposites

Abstract

Based on a ''graft from'' strategy, the surface of starch nanocrystals (StN) were functionalized by grafting with polycaprolactone (PCL) chains via microwave assisted ring-opening polymerization (ROP). The modified natural nanoparticles were then compounded into a PCL-based waterborne polyurethane as matrix. The structural and mechanical properties of the WPU/StN-g-PCL nanocomposites were characterized by XRD, FTIR, SEM, DSC, DMA, and tensile testing. It was interesting to note that a loading-level of 5 wt % StN-g-PCL resulted in a simultaneous enhancement of tensile strength and elongation at break, both of which were higher than those of neat WPU. This enhancement was attributed to the uniform dispersion of StN-g-PCL because of its nano-scale size, the increased entanglements mediated with grafted PCL chains, and the reinforcing function of rigid StN. Increasing the StN-g-PCL content however caused the StN-g-PCL to self-aggregate as crystalline domains, which impeded improvement in tensile strength and elongation at break, but significantly enhanced Young's modulus.

Cellulose-reinforced composites: From micro-to nanoscale

“…Starch nanocrystals (StNs) were used to reinforce a soy protein isolate (SPI) [43] or cassava starch [44] or waterborne polyurethane [45] matrices, in order to produce a class of full-biodegradable nanocomposites. Soy protein isolate was found to be efficiently reinforced even with very low StNs loading level (<2 wt%).…”

Comparative properties of cellulose nano-crystals from native and mercerized cotton fibers

“…CNCs exhibit exceptional characteristics, such as high aspect ratio, large specific surface area, high specific strength and modulus, biodegradability and reactive surfaces that can facilitate chemical modification (Zivanovic et al 2007;Chang et al 2009;Wu et al 2010). Potential applications of CNCs are in various fields such as materials science, electronics, catalysis and biomedicine (Park et al 2008;Gatenholm and Klemm 2010).…”

Effect of adding a small amount of high molecular weight polyacrylamide on properties of oxidized cassava starch

“…Introducing a polymer containing functional groups for hydrogen bonding into starch blends has been proven to be an effective method for improving the mechanical properties of a variety of starch blends, such as chitosan/starch (Xu, Kim, Hanna, & Nag, 2005), plasticized starch/polyurethane (Lu, Tighzert, Berzin, & Rondot, 2005), thermoplastic starch/polycaprolactone (Shin, Lee, Shin, Balakrishnan, & Narayan, 2004), and the like. On the other hand, the chain entanglement between components of polymer blends is relative to the molecular weight of the polymers involved, and linear polymers with high molecular weight undergo long range interactions (Carlsson & Jonsson, 1996) which plays a major role in improving the elongation at break (Chang, Ai, Chen, Dufresne, & Huang, 2008;Follain, Joly, Dole, & Bliard, 2005). From the two respects of miscibility and chain entanglement, it appears that the mechanical properties of starch may be modified by adding a high molecular weight PAM into the system in small quantities.…”