Textiles come to life

A shirt that rolls up its sleeves when the temperature rises, protective wear that adjusts the level of insulation according to environmental requirements, and morphing clothes. This sounds futuristic, but is becoming a reality thanks to shape-memory polymers.

February 20, 2008

Andreas Lendlein, GKSS Institute of Polymer Research, Teltow, Germany

Jinlian Hu Shape Memory Polymers and Textiles Woodhead Publishing, CRC Press • 2007 • 360 pp ISBN: 978-1-23-84569-047-2

Shape-memory polymers (SMPs) are able to change their shape when exposed to an external stimulus, such as heat, light, or a magnetic field.

Shape Memory Polymers and Textiles outlines potential applications for thermally induced SMPs in clothing, covering a broad spectrum from fashion apparel to protective wear and technical textiles.

Jinlian Hu focuses primarily on polyurethanes. The data presented are mainly from the Institute of Textiles and Clothing at the Hong Kong Polytechnic University, where the author is a professor.

Besides macroscopic shape changes of filaments, fibers, and fabrics, another interesting ability of SMPs is explored for its benefit in textile applications: the temperature dependency of water vapor permeability through the material.

At low temperatures, the fabric is less permeable and retains body heat. At high temperature, moisture permeability increases and heat is released. While the shape change is a one-way effect, the variation in permeability is reversible.

The basic concept of shape memory capability is introduced at the beginning of the book and different potential applications in textiles are summarized. The design criteria for SMPs are essentially confined to polyurethanes and address specific aspects that are of importance for textile applications.

A comprehensive overview of characterization methods for the determination of thermal transition temperatures, polymer morphology, and permeability is given in Chapter 3. Here the emphasis is not on the introduction of the methodical principles, but on the specific application of these analytical methods to shape-memory polyurethanes. These descriptions and the data presented are valuable for those who are just entering the field of SMP research.

Of special interest is the chapter dedicated to the water vapor permeability of shape-memory polyurethanes. Structure-property relationships are explained in detail, especially how these are determined using the characterization methods introduced earlier.

Thermomechanical tests for the determination of shape-memory properties such as shape fixity, shape recovery rates, and switching temperatures are only superficially described. However, the following chapter gives an insight into different models that try to simulate the shape-memory process and predict shape-memory properties. Stimuli-sensitive gels and their applicability in textiles are briefly touched on in Chapter 8.

The final two chapters are the real highlight of the book. Here the tremendous application potential of SMPs in the area of textiles is impressively illustrated.

Examples include wrinkle-free clothing and intelligent waterproof, breathable fabrics. Shape-memory fibers, as well as membranes incorporated in laminates, are presented. Here the reader is fascinated by the technology and a future vision for intelligent textiles becomes obvious.

The focus of the book is clearly on the application of SMPs in textiles. It will be of great interest for textile engineers and designers, who like to introduce innovative material technologies. The active movement of fibers enables fascinating effects. The aesthetic look of a garment can change from static to dynamic and the tactile nature of the textile can be adjusted.

The strong focus on polyurethanes in the description of material properties, shape-memory functionality, fiber processing, and textile technology is a strength of the book.

At the same time, it is also a weakness. As a result, the book only offers limited insight into fundamental aspects of SMP research and does not cover important progress in this field within the last few years.

Readers more interested in the present status of fundamental research are referred to current reviews such as Liu, C., et al., J. Mater. Chem. (2007) 17, 1543 and Behl, M., and Lendlein, A., Soft Matter (2007) 1, 58. Shahinpoor, M. S., and Schneider, H.-J., Intelligent Materials, Royal Society of Chemistry, Cambridge, (2008) is also to be recommended as a source for complimentary information.