What is the difference between a shape memory polymer and a shape memory alloy?
Shape-memory polymers differ from shape memory alloys (SMAs) by their glass transition or melting transition from a hard to a soft phase which is responsible for the shape-memory effect. In shape-memory alloys martensitic/austenitic transitions are responsible for the shape-memory effect.
What is the structure of the shape memory polymer?
The shape-memory polymer network consists of covalent netpoints and switching segments based on a physical interaction. To display shape-memory functionality, the polymer network has to be temporarily fixed in a deformed state under environmental conditions relevant to the particular application.
What are the different shapes of memory materials?
Overview. The two most prevalent shape-memory alloys are copper-aluminium-nickel and nickel-titanium (NiTi), but SMAs can also be created by alloying zinc, copper, gold and iron.
How are shape memory alloys different from regular alloys and metals?
Shape-memory alloys are metals that, even if they become deformed at below a given temperature, they will return to their original shape before deformation simply by being heated. Alloys with this unusual characteristic are used as functional materials in temperature sensors, actuators, and clamping fixtures.
Are shape memory alloys metals?
Shape-memory alloys are metals that, even if they become deformed at below a given temperature, they will return to their original shape before deformation simply by being heated.
What is the main properties of shape memory alloys?
Shape memory alloys are a unique class of alloys that have ability to ‘remember’ their shape and are able to return to that shape even after being bent. At a low temperature, a SMA can be seemingly plastically deformed, but this ‘plastic’ strain can be recovered by increasing the temperature.
How does metal have shape memory?
When a SMA is in martensite form at lower temperatures, the metal can easily be deformed into any shape. When the alloy is heated, it goes through transformation from martensite to austenite. In the austenite phase, the memory metal “remembers” the shape it had before it was deformed.
What are shape memory polymers used for?
These polymers have been used to produce, among other things, medical devices such as stents and catheters. Typical examples of polymers which can exhibit this shape memory effect include (meth)acrylates, polyurethanes, and blends of polyurethane and polyvinylchloride.
What is special about shape memory alloy?
How are shape memory alloys used in different products?
What is memory metal made of?
The most common memory metal is called NiTinol, consisting of equal parts of nickel and titanium. The table below displays alloys having shape memory effects. The memory transfer temperature is the temperature that the memory metal or alloy changes back to the original shape that it was before deformation.
What are shape memory alloys made of?
We call these “austenite” and “martensite,” the same words used for steel, although these phases share nothing in common with steel. Current shape memory alloys are: NiTi, or nitinol. This is the most developed SMA, with excellent mechanical properties.
What is shape memory material?
Shape memory materials return to a predetermined form above a given transition temperature. Shape memory materials exist in the form of metal alloys and polymers. Although shape memory polymers are cheaper, they exhibit lower performance in terms of magnitude of deformations, forces and durability.
What are the disadvantages of shape memory polymers?
Although shape memory polymers are cheaper, they exhibit lower performance in terms of magnitude of deformations, forces and durability. On the other hand, their reaction to temperature can be modified quite easily; with one set of monomers, it is possible to have a whole set of shape memory materials.
Why are elastic polymers used in shape memory textiles?
Obviously, elastic polymers are useful when developing shape memory textiles. When designing thermally responsive SMPs, several temperatures are important: Ttrans is the shape memory transition temperature where the shape change takes place Tm is the melting temperature and if Ttrans = Tm then the shape change takes place at the melting point
What are shape memory coatings?
Shape memory (SM) coatings can be defined as coatings that have the capacity to store a new shape when damage occurs to the original shape when they are exposed to heat, light, or other external damage. Shape memory materials are elastic polymer networks that are equipped with suitable stimuli-sensitive switches (Fig. 8.9 ).