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EXECUTIVE SUMMARY The unique feature of liquid crystalline polymers (LCPs) -high local (microscopic) orientational order, which is retained in the solid state - has significant implications in a range of DOD applications utilizing polymers. The remarkable mechanical properties and thermal stability of fibers from precursor liquid crystalline solutions (lyotropic spinning dopes) are the principal driving forces that launched these materials and encouraged efforts to place LCPs in structural applications where weight savings are critical. It would appear that advances in processing the lyotropic polymers could allow the incorporation of LCPs into other than uniaxial designs multiaxially oriented items. Moreover, novel processing might make thermotropic LCPs eligible for critical structural applications. However, the unique feature of LCPs is itself problematic the current understanding of processing with control of orientation falls short of permitting deliberate manipulation of macroscopic orientation (with the exception of unisexual fibers). Even carefully des igned applications that exploit other features of liquid crystallinity (an' sotropic thermal expansivity, transport anisotropy, optical characteristics, etc.) will be retarded until there is an in-depth understanding of how processing promotes morphology in conjunction with how molecular structure affects the mechanical and the unusual physical properties of these new classes of polymers. The principal conclusions of the committee are as follows: · New cost-ef~ective synthetic efforts and stabilization techniques are required to manipulate and maintain sequence distribution and thereby control polymer properties. · Theories of LOP behavior must address polymer flexibility to realistically predict blending, theological, and chain dynamical properties of ordered polymer phases. · Processing protocols must go beyond conventional methodologies, e.g., explore solid-state forming of LCPs in efforts to achieve multiaxial order and obviate macroscopic heterogeneity. 1
2 · Compressive failure mechanisms must be understood in order to suggest solutions to current mechanical limitations of LCP applications; ~of LCPs (e.g., as barrier simultaneously, new nonstructural applications materials) should be explored. · LCPs may find extensive applicability in blends and composites. However, the roles of LCPs as the dispersed phase or as the matrix phase, filler shape and adhesion (and self-adhes~on) are complex and poorly understood issues. · Lowering the cost of LCP in products through lower cost monomer, polymerization and fabrication processes will catalyze the overall acceptance and range of applications of LCPs by the user community. · An interdisciplinary effort is required to exploit the anisotropy of LCPs in nonlinear optical applications. · The current annual Federal funding level for LCP research is almost $10 million. · LCPs and the ir unique advantages as s tructural polymers were discovered and developed in U.S. industrial research laboratories in the 1960s and 1970s. A cursory glance at the following table suggests that current research and manufacturing effort has now become worldwide. Companies Engaged in LOP Development United States Western Europe Japan Allied-Signal Akzo Asahi Amoco (Dartco) BASE Denki Kagaku DuPont Bayer Idemitsu Eastman DSM Kuraray Hoechst Celanese Hoechst Mitsubishi Chemical Monsantoi ICI Mitsubishi Gas Montedison Mitsui Toatsu Rhone-Poulenc Nippon Petrochemical Polyplastics Sumitomo Teijin Toray Toyobo Unitika Has stopped research Source: Outlook for Advanced Engineering Materials: Plastics, Composites and Ceramics. November 1986, R861101. Cambridge, Mass .: Arthur D. Little Decision Resources .
3 Committee discussions frequently returned to economic and geopolitical topics, about which it was collectively agreed that members were ill-equipped to make meaningful recommendations. Nevertheless, two of these issues deserve attention: · There was a consensus that meaningful evaluation of new (and potential) LOP systems is severely hampered by a limited number of facilities in the United States wherein intermediate-scale monomer and polymer synthesis [between the lab-bench scale (-100 g) and pilot plant (100 to 1000 lb)] can be carried out. · Although many companies are market developing LCPs, large volume use awaits lower cost polymers. Therefore, LCPs are a fertile area warranting intensive study. The findings will have an impact on a wide range of problems that include mechanical and optical properties of polymers. Moreover, it is anticipated that the findings on LCPs will lead to a more comprehensive understanding of conventional polymers and their fabrication techniques.