The first edition was produced at a time when the advantages of studying oriented polymers were just becoming apparent. From a sci entific stand point it had been demonstrated that greater insight into both structure and properties could be obtained if an oriented polymer was prepared. From a technological viewpoint, major advances were under way, especially in high modulus and high strength fibres. Twenty years later, it is possible to review the scientific advances which have been made in this area and to provide much wider perspectives for the technology. As in the case of the first edition, the emphasis is on the methodologies available for characterizing oriented polymers and their mechanical behaviour. It is a particular pleasure to thank the contributing authors for their cooperation and Dr Philip Hastings of Chapman & Hall for his support and encouragement. I am also indebted to Professors A. H. Windle and D. C. Bassett for their respective contributions to sections 1. 3. 1 and 1. 3. 4. Although this chapter has been extensively revised, the contribution of the late Leslie Holliday to the first edition of this book is also acknowledged. Introduction 1 I. M. Ward 1. 1 THE PHENOMENON OF ORIENTATION Orientation in polymers is a phenomenon of great technical and theo retical importance. The word orientation itself conveys a number of ideas."

The first edition was produced at a time when the advantages of studying oriented polymers were just becoming apparent. From a sci entific stand point it had been demonstrated that greater insight into both structure and properties could be obtained if an oriented polymer was prepared. From a technological viewpoint, major advances were under way, especially in high modulus and high strength fibres. Twenty years later, it is possible to review the scientific advances which have been made in this area and to provide much wider perspectives for the technology. As in the case of the first edition, the emphasis is on the methodologies available for characterizing oriented polymers and their mechanical behaviour. It is a particular pleasure to thank the contributing authors for their cooperation and Dr Philip Hastings of Chapman & Hall for his support and encouragement. I am also indebted to Professors A. H. Windle and D. C. Bassett for their respective contributions to sections 1. 3. 1 and 1. 3. 4. Although this chapter has been extensively revised, the contribution of the late Leslie Holliday to the first edition of this book is also acknowledged. Introduction 1 I. M. Ward 1. 1 THE PHENOMENON OF ORIENTATION Orientation in polymers is a phenomenon of great technical and theo retical importance. The word orientation itself conveys a number of ideas."

Advances in industrial technologies and improved performance of constructional materials are interdependent and have become of increasing concern in recent years. This Conference aimed to - provoke discussion of the limits towards which high temperature alloys properties can, ultimately, be developed, identify the resulting R&D requirements and design developments. Following a key-note paper concerning the relation of current capabilities to requirements for gas turbines the conference was structured into 3 sessions which examined: * the theoretical?ldpracticallimits for HT Alloys, * the potential for development in alloys and processing, * engineering considerations. Finally, feeling perhaps the approaching "wind of change"??1s Conference on remaining alloy potential was wound up with a paper entit1ed "The potential?ld problems ofEngineering Ceramics". The different sessions each included a number of invited papers followed by a series of posters and were concluded by a presentation of a "synthesis" by a sess10n rapporteur and general discussion. This structure is retained in the proceedings, including the discussion points in those cases where?le authors have provided written answers to questions raised.

The last four years since the publication of the first of this series have seen further striking developments in both the science and technology of oriented polymers. In particular, polymers possessing very high degrees of molecular orientation are now quite commonplace, and this is reflected by the inclusion of five chapters dealing with ultra-high modulus polyethylene fibres, oriented liquid crystalline polymers (both lyotropics and thermo tropics) and polydiacetylene single crystal fibres. At the same time there is continuing interest in the structure and properties of less highly oriented polymers and in the mechanisms of deformation in polymers. It is therefore good to have these themes represented also. I should like to thank the contributors for adhering to a rather tight time schedule, and the publishers for their cooperation, so that this book can provide up-to-date reviews of the state of the art in a rapidly moving area of polymer science. I. M. WARD v CONTENTS Preface.... . . . .. . . . . .. ... . . . . . . . . . .. . . .. . . . . . . ... ... v List of Contributors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX 1. Polymer Single Crystal Fibres ........................ .