Shape memory polymers are smart combined materials that canchange from a temporary deformed shape back to their original shape with anexternal stimulus such as temperature. Recent developments in material scienceindicated that there a strong worldwide interest in using shape memory polymersfor textile, medical and automotive manufacturing.
Shape memory polymers (SMPs) can be stimulated bytemperature, pH (the level of acidity or alkalinity), chemicals and light.They are able to sense and respond to external stimuli in a predetermined shape.
In terms of chemical structure, SMPs can be considered asphase segregated linear block copolymers having a hard segment and a softsegment. The hard segment acts as the frozen phase and the soft segment acts asthe reversible phase. The reversible phase transformation of the soft segmentis responsible for the shape memory effect.
The polymer materials have various elasticities such as fromhard glass to soft rubber. SMPs, however, have the characteristics of both ofthem, and their elasticity modulus show reversible change with the transitiontemperature.
Characteristics and Features
When applied with an external stimulus, shape memorypolymers have the capability of changing shape. Among these SMPs, the shape ofthe thermally responsive shape memory polymers can be readily changed aboveshape memory transition temperature (Ttrans), and the deformation can be fixedbelow this temperature. Then when they are heated above Ttrans, their originalshape can be recovered automatically.
Applications for Textile & Garment Products
Researchers and manufacturers have until recentlysynthesized several kinds of SMP and used them as the major components in shapememory fabrics. Major efforts are underway to develop smart products in the market.
Although shape memory alloys (smart combined metals, such asnickel-titanium) have been applied for the production of underwire bras andflame-retardant laminates, it is held that shape memory polymers have betterpotential for textiles and apparels. For instance, thermal insulating fabrics,various breathable fabrics with shape memory characteristics, shrink-resistantfinishing for apparel fabrics, and shoes. Processes for making these products include finishing, coating, laminating, blending, and other innovative structures.
Characteristics of Shape Memory Fabrics & Garments
When SMPs changes from glassy state to rubbery state, itselastic modulus, tensile and elastic properties would vary greatly, whichwould be useful for garments. When worn at body temperature or washed at a hightemperature, SMP-based garments recover from the deformed state to the originalstate with a good flat appearance and crease retention. They also have abagging recovery effect.
Shape-memory finishing fabrics have good temperaturesensitivity and different thermal triggering, including hot water washing,tumble drying, hot air simulated by normal travel hairdryer and steaming. Theyhave higher breaking and tearing strength compared with traditional finishingfabrics. They also have better performance and improved wrinkle resistanceafter drying.
Shape Memory Materials in Textiles
SMPs are increasingly popular in the fabric engineering asthey respond dynamically to changes in heat and moisture levels, ensuringgreater comfort for the wearer. They are thus often used to produce high-end functional garments. It is believed that SMPs can be activated in not onlyfunctional garments, but also fashion apparel, which will be characterized withnot only technological innovation, but also value-added aesthetic benefits tothe wearer.
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