Shape Memory Materials
The Shape Memory Alloys are characterized by their extraordinary ability to recover any shape pre-programmed, upon heating until reaching their Martensite-Austenite transformation temperature. Nitinol, in particular, is the name of a light weight alloy having a content of Titanium of 45% and, until today, it has been used in advanced sectors like aerospace and, recently, in medical applications. Biocompatibility of Ni-Ti alloys depends on the intrinsic strength of Ni intermetallic bond, that avoids the presence of its particles on the external surface of the wire, and on the inertness of superficial TiO2. Through the Technology Transfer Programme of the ESA, Grado Zero Espace has transferred this knowledge in traditional sectors, like, in this case, for textile applications. In this framework, Grado Zero Espace has used Shape Memory Alloys to obtain a fabric used for the manufacturing of a shirt with long sleeves. The sleeves could be programmed to shorten immediately as the room temperature heats up. The shirt can be screwed up, pleated and creased, then, just by a flux of hot air (even a hairdryer), it can pop back automatically to its former shape. Later, the name "Oricalco" was associated to the fabric Oricalco obtained by Grado Zero Espace and used to manufacture the first shape memory shirt. Besides, after Oricalco development, Grado Zero Espace continued its study on Shape Memory Materials and on other type of Ni-Ti Alloys accumulating a lot of experience in manufacturing different type of Smart Textile Structure (fabrics, knits, tubular, special yarn, hybrid yarn,...), and permitting, in some cases, to optimize the manufacturing processes also for serial production. Grado Zero Espace, in fact, had an important role within the Loose&Tight project, which aimed at developing a novel concept of elastic graduated compression hosiery based on the exploitation of the superelasticity of Nickel-Titanium based alloys integrated as thin wires in a properly designed textile structure. At present time, Grado Zero Espace is dealing with the development of a textile product (more in the specific an ortopaedic support) within the Avalon project, which has the principle objective to develop novel hybrid textile structures integrating multifunctional Shape Memory Alloys (SMAs) and the related processing techniques as well as design, simulation and organizational methodologies. (see Shape Memory Shirt made of Oricalco Fabric in Science Museum of Chicago)
Shape memory polymers have the capability of changing their shape in response to external stimuli, one of them is temperature. Thermo-responsive shape memory polymers consist of two polymer components and resulting two phases, one with a higher melting temperature than the other.
The shape-memory effect is not related to a specific material property of single polymers, but instead is realized from a combination of the polymer structures and their morphologies. The phase responsible for the highest thermal transition, such as highest melting point among all the phases, is the basis for the permanent shape. Above this temperature the polymer is completely in the melt state. While the glass transition temperature of the other phase can be used as a molecular switch for a temporary shape. This material, in fact, after processing into a form, assume a permanent shape which can be deformed to produce other shapes and then, by applying heat, is able to return to its initial shape.
Some of the shape memory polymers are bio-compatible and biodegradable and, currently, their main applications are in the medical field. Potential non-medical applications include carrier systems for cosmetic and beauty care products, optical, electronic and mechanical parts for control systems and special plastics for the repair of accident damage or cars. However, since shape memory polymers are not expensive to produce, their applications could be easily broadened to other areas, e.g., niche textiles, to take advantage of their unique properties.
This is, in fact, one of the objectives of Leapfrog project that is aiming at a technology breakthrough in the clothing industry. In ambit of this project Grado Zero Espace shared its competence in non-conventional textiles in order to solve, together with the other partners, some problems regarding shape memory polymer's synthesis, their extrusion, the physical and mechanical properties of the obtained yarn, its workability in current textile machines, design of the most suitable weaving structure to obtain a well valuable effect and, at the end, it was possible the realization of the first smart orthogonal hybrid fabric made of Shape Memory Polymer.
Only with consulting activities