Production and Analysis of Cellulose Nanowhisker Reinforced Thermo-water Responsive Polyurethane Nanocomposites

16. Tekstil Teknolojisi ve Kimyasındaki Son Gelişmeler Sempozyumu, Bursa, Turkey, 4 - 06 May 2017, (Full Text)

Publication Type: Conference Paper / Full Text
City: Bursa
Country: Turkey
Süleyman Demirel University Affiliated: Yes

Abstract

In this study, shape memory-polyurethane was reinforced with cellulose nanowhiskers (CNWs) to create heterogeneous-twin-switch shape memory effect (thermal and water responsiveness simultaneously) and chemical/mechanical characterization of the produced polymeric nanocomposite films were conducted. Shape memory polymers (SMPs) are among attractive smart materials having the capability to return their original (permanent) shapes from a temporary shape under appropriate external stimulus and the most common type of these materials are thermal induced SMPs. Among the thermal induced SMPs, segmented shape-memory-polyurethanes (SMPUs) have gained much popularity and they are mainly used in biomedical and tissue engineering applications. Recently, there are attempts to modify SMPUs to have a switching temperature within the range of body temperature and create dual responsive structure that can be stimulated by different stimuli such as temperature and moisture. This study covers modification of SMPUs which has a transition temperature suitable for body applications by CNWs to enhance its application areas in case of thermal comfort. SMPUs having thermal-induced shape memory effect will simultaneously possess water-induced shape memory effect by CNWs due to the percolation network of the CNWs whose hydrogen bonding can be regulated by water reversible. The disadvantages of thermal induced SMPU such as transition temperature not suitable for the body and disadvantages of water responsive SMPs such as low elastic modulus, stiffness strength properties and long shape recovery time are aimed to be decreased by producing nanocomposites consisting of SMPU and CNWs. This modification process is easier to have the determined function (thermo-water responsive) as synthesis of a dual function polymer matrix needs complex chemical molecular design. The CNW-SMPU nanocomposite films were produced by introducing CNWs as nanofiller into a SMPU matrix in this study. A series of nanocomposite films with varying CNW concentrations, ranging from 0-20 wt % was produced by solution blending CNWs and the SMPU. The nanocomposite films were subsequently prepared by solution casting method. Fourier transform infrared (FT-IR) analysis was performed to characterize nanocomposite films. The effects of CNW on the mechanical and shape memory performance of films were investigated by tensile and thermo-aqueous programming tests. According to FT-IR analysis results, the peaks belonging to cellulose became visible in films with the increase of the CNW amount. Strength and elongation at break increased for until 10% CNW with increasing CNW concentrations however a decrease was observed for 20% concentration. In thermal-aqueous test results, we obtained the least value of 48.5 % shape fixity of neat SMPU where as the nanocomposite containing 20% CNW had the maximum value of 69.3 %. The maximum total shape recovery of 91.45 % was also obtained for 20% CNW and 80.41 % of this recovery belongs to water-induced shape memory effect. Summing up, it was observed that produced nanocomposite maintained its thermal-induced shape switchable effect originally existing in SMPU and simultaneously it possessed water-induced shape memory effect due to the percolation network of the cellulose whiskers whose hydrogen bonding can be regulated by water reversibly.