SL10

SL11

YIELDING AND FRACTURE IN CROSSLINKED EPOXIES

A. TCHARKHTCHI, J.-P. TROTIGNON, J. VERDU

ENSAM/SERAM, 151 Bd de l´Hôpital, F-75013 Paris, France

SL12

SL13

LOAD SEPARATION PRINCIPLE IN R-CURVE DERERMINATION FOR DUCTILE POLYMERS

P.M. FRONTINI

Institute of Materials Science and Technology (INTEMA), J.B. Justo 4302, 7600 Mar del Plata, Argentina

SL14

FRACTURE OF NOTCHED PP SPECIMENS UNDER CREEP CONDITIONS
J. KUČERA, E. NEZBEDOVÁ

Polymer Institute Brno, spol.s r.o., Tkalcovská 2, CZ-656 49 Brno, Czech Republic

SL15

COMPARATIVE STUDY OF MECHANICAL AND DIELECTRIC PROPERTIES OF ACRYLIC POLYMERS CONTAINING 1,3-DIOXACYCLOALIPHATIC STRUCTURES

R. Díaz-CALLEJA^a, E. RIANDE^b

^aDepartamento de Termodinámica Aplicada, ETSII, UPV, Valencia, Spain

^bInstituto de Ciencia Y Tecnología de Polímeros (CSIC), 28006 Madrid, Spain

SL16

DYNAMIC MECHANICAL AND DIELECTRIC BEHAVIOUR OF LIQUID-CRYSTALLINE POLYURETHANES

M. ILAVSKÝ^1,2, H. VALENTOVÁ¹, K. BOUCHAL², AND J. NEDBAL¹

¹Faculty of Mathematics and Physics, Charles University, 180 00 Praha 8, Czech Republic

²Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic,
Heyrovského nám. 2, 162 06 Praha 6, Czech Republic

Liquid-crystalline polyurethane networks were prepared from LC diol (D) – 6,6c -[ethylenebis(1,4-phenyleneoxy)]dihexanol, 2(4)-methyl-1,3-phenylene diisocyanate (DI) and poly(oxypropylene)triol (T) with initial mole ratios of hydroxy (OH) and isocyanate (NCO) groups r = [OH]_T/[NCO]_DI/[OH]_D, ranging from 1/2/1 to 1/40/39. For comparison, a linear polymer with r = 0/1/1 was prepared, which shows a complex mechanical and dielectric thermal and frequency behaviour. On cooling, the polymer forms nematic phase at 80 °C which freezes into the liquid-crystalline glassy state. On heating, the mesophase melts and a better ordered, smectic phase is formed at 95 °C, which melts at 120 °C. Introduction of chemical crosslinks reduces the flexibility of network chains and inhibits conformational arrangement required for liquid-crystalline ordering; the network with r = 1/2/1 shows only isotropic thermal behaviour. Increasing the amount of LC diol in networks (increasing the length of network chains) enhances both the thermal liquid-crystalline behaviour and the connectivity of the structure. Dynamic mechanical measurements during the curing reaction in the liquid-crystalline and isotropic states showed that the critical gel structure at the sol/gel transition exhibits a power-law mechanical behaviour; the relaxation exponent in the liquid-crystalline state is always higher than that in the isotropic state. As the physical and chemical gelation in the liquid-crystalline state proceed simultaneously, aggregation of mesogens enhances the connectivity of the structure in this state.

SL17

TENSILE DEFORMATION BEHAVIOUR OF THE POLYMER PHASE OF FLEXIBLE POLYURETHANE FOAMS AND POLYURETHANE ELASTOMERS

E. VAN DER HEIDE, O.L.J. VAN ASSELEN, G.W.H. INGENBLEEK, C.A.J. PUTMAN

Shell Research and Technology Centre, Amsterdam, P.O. Box 38000, 1030 BN, Amsterdam, Schell International Chemicals B.V.

SL18

MECHANICAL BEHAVIOR OF POLYMER MICROLAYERED COMPOSITES

ANNE HILTNER AND ERIC BAER

Department of Macromolecular Science and Center for Applied Polymer Research

Case Western Reserve University, Cleveland, OH 44106-7202

Lessons from biology have revealed that natural materials systems have architectures that are specifically designed to accommodate a unique spectrum of required properties. These architectures always have many scale levels that are bound together by interfacial coupling or adhesion. Recently, new synthetic approaches have been used to develop macromolecular materials that "self-assemble" into nano-scale morphologies. This lecture addresses another approach - the "forced-assembly" of synthetic polymers at the nano-scale. These less complex materials are currently available in commercial quantities.

Numerous examples illustrate how the coextrusion of film with three or more polymeric layers is used economically to achieve a desirable mix of end-use characteristics. More recently, layer-multiplying devices permit up to three polymers with dissimilar solid state structures and properties to be combined into unique microlayer and nanolayer laminates with thousands of layers. Studies of polymer microlayers with hundreds or thousands of alternating layers down to the nano-scale have revealed unique properties which are achievable when the layers are thin enough to produce synergistic combinations of key properties of the constituent components.

The applications of microlayer and nanolayer coextrusion technology can be separated into two broad areas that are illustrated with specific examples. In the first area, new materials with very thin layers are created that exhibit improved and unique physical properties. The improved properties include mechanical, optical, barrier and electronic, and combinations of these properties. The second area emphasizes the use of microlayer technology to generate large specific surface areas for fundamental studies of adhesion, diffusion and crystallization which can lead to the development of unique systems with gradient structures.

SL19

INVESTIGATION OF THE MECHANICAL BEHAVIOUR OF HETEROGENEOUS
POLYMERIC SYSTEMS AND FIBRE REINFORCED COMPOSITES USING
MICRO INDENTATION AND SCANNING FORCE MICROSCOPY

E. SCHULZ, G. KALINKA, H. STURM, M. MUNZ*

Federal Institute for Materials Research and Testing, Unter den Eichen 87, D-12205 Berlin, Germany, e-mail: eckhard.schulz@bam.de

*Technical University Berlin,Institute for Non-Metallic Materials, Polymer Physics, Englische Str. 20, D-10587 Berlin, Germany