“Nanocellulose Reinforced Smart Polyurethanes

N. MARCOVICH; M.L. AUAD; S. NUTT; M. I. ARANGUREN

Cracow, Poland

Conferencia; IX internacional Conference on Frontiers of Polymers and Advanced Materials; 2007

In this work, the capacity of nanocellulose to reinforce smart polyurethanes is investigated. The commercial segmented polyurethane (PU) utilized displays shape memory features; the polymer is capable of “remembering” their original shape after having been deformed. By a further application of an external stimulus, which in this case is the temperature, the original shape is recovered. The incorporation of nanofillers at small loadings (in the range of 1-5 wt %) into these polymers can produce performance enhancements, in particular the elastic modulus. The addition of these nanofillers allows producing stiffer materials, but maintaining a large capacity of deformation, comparable to that of the unfilled polymer. In particular, in the present work, the performance of shape memory polyurethanes reinforced with nanocellulose crystals has been investigated. Cellulose is one of the most abundant materials in nature, where it constitutes the primary structural material in a wide variety of plant life, as well as some animals1. In addition, the attributes of low cost, low density, high stiffness, consumable nature and biodegradability2 constitute major incentives for exploring new uses. Additionally, cellulose has polar groups that can interact with polar polymers, such as polyurethanes, leading to a composite material with good interfacial adhesion3. This is essential to obtain a material with enhanced properties. The nanocellulose was prepared by acidolysis of microcrystalline cellulose, which was further re-dispersed in an organic solvent to be incorporated into the PU. Interestingly, the addition of nanocellulose improved the separation of soft and hard segments (DSC and X-ray). On the other hand, the addition of cellulose at concentrations as low as 1% by weight increased the rigidity of the film as much as 70%. The shape memory behavior was investigated by subjecting the film to cyclic tensile loads and temperatures. The nanocomposite response was highly repeatable after the second cycle with shape recovery on the order of 80%.