a)      Shape memory materials

  
These types of materials are those that can revert from the current shape to a previously held shape, usually due to the action of heat. The UK Defence Clothing and Textiles Agency have extensively pioneered this technology. When these shape memory materials are activated in garments, the air gaps between adjacent layers of clothing are increased, in order to give better insulation. The incorporation of shape memory materials into garments thus confers greater versatility in the protection that the garment provides against extremes of heat or cold.

There are shape memory alloys and polymers. A shape memory alloy is usually in the shape of a spring. The spring is flat below the activation temperature but becomes extended above the activation temperature. By incorporating these alloys between the layers of a garment, the gap between the layers can be substantially increased above the activation temperature, which considerably improves protection against external heat. Shape Memory Polymers have the same effect as the alloys but, being polymers, are potentially more compatible with textiles. They could also be employed as flame retardants. The shape memory effect is observed when a plastic conforming to one shape returns, at a particular temperature, to a previously adopted shape.

For clothing applications, Polyurethane films have been made which can be incorporated between adjacent layers of clothing. When the temperature of the outer layer of clothing has fallen sufficiently, the polyurethane film responds so the air gap between the layers of clothing by becoming broader. This broadening is achieved if, on cooling, the film develops an out-of-plane deformation, which must be strong enough to resist the weight of the clothing and the forces induced by the movements of the wearer. The deformation must be capable of reversal if the outer layer of clothing subsequently becomes warmer.

Based on methods first developed by Mitsubishi Heavy Industries, for manufacturing polyurethane-based shape memory polymers, a unique, new, high performance material that features temperature sensitivity has been developed. Called DiAPLEX, this novel material can be used to make comfortable garments that are watertight without clamminess. To maintain a comfortable environment within garments DiAPLEX is designed to react at a transition temperature, which adapts the state of the material to variations in the internal and external environment. When, following strenuous activity or changes in the external environment, the temperature inside the garment reaches the transition temperature, the material automatically becomes either more waterproof or more permeable to water vapor.

Diaplex has Self-Control through which it Memorizes Conditions of Comfort and Responds to Changes in Environmental Temperature