The effect of moisture on the creation of a physical/ chemical network in polyurethane/halloysite nanotube nanocomposites with shape memory behavior

Polyurethane is an engineering polymer that has different applications such as adhesives, foams, coatings, fibers, and so on. This polymer is produced by a step‐growth polymerization reaction between isocyanate and diol. Polyurethane is composed of covalent bonding of two hard and soft segments with different glass transition temperatures.1 Shape memory behavior caused by this structure, which is why this polymer is considered in the field of smart materials. Smart materials are capable of responding to external stimuli such as temperature, light, pH, electricity, solvent and magnetic fields. Moisture is one of the environmental factors affecting the synthesis of polyurethane.2 In this study, two samples were designed and tested to determine the effect of presenting moisture during synthesis on the polyurethane structure. The materials used were Hexamethylene diisocyanate (hard segment procreator), 1,4-butanediol and Poly (tetramethylene ether) glycol (soft segment procreator) and Dimethylacetamide (solvent) for synthesis. One weight percent of Halloysite nanotube was also added for improving shape memory and other mechanical properties. The first sample of polyurethane / Halloysite nanotube nanocomposite was synthesized in a moist environment. The second sample was synthesized in a moist environment. To investigation of the type of physical or chemical network in nanocomposite, a frequency sweep of rheological test was performed. The Dynamic mechanical analysis was used to study shape memory behavior. The results showed that the synthesis of polyurethane/ Halloysite nanotube nanocomposite in the presence of moisture, produced a chemical network in the polymer and had a more shape memory than the synthesized sample without moisture conditions. It was also noticeable that, the second specimen had physical network. From these tests it can be concluded that the presence of moisture in the synthesis environment is effective on the type of network and the behavior of shape memory. Considering that each of these types of polymer can have a special application in the industry, further research in this field and the examination of such effects on other properties of polyurethane is recommended.

کلیدواژه ها:

Polyurethane ، Shape memory ، network ، synthesis ، Halloysite nanotube