Glassy polymers, oriented

Considering a fiber or thread of nylon-66, which is an unoriented glassy polymer, its modulus of elasticity is about 2,000 MPa (300,000 psi). Above the Tg its elastic modulus drops even lower, because small stresses will readily straighten the kinked molecular chains. However, once it is extended and has its molecules oriented in the direction of the stress, larger stresses are required to produce added strain. The elastic modulus increases. 

Farid 88) did not report on the excimer lifetime of the pyrene compound in the systems that were studied. Nevertheless, they proposed that the blue shift of the excimer emission peak in glassy polymers relative to solution was due to improper orientation of the excimer components in the polymer matrix 88). This proposal is supported by the observation 88) that the blue shift of the excimer peak for the pyrene... 

With these properties a wide field of application is revealed As the l.c. side chain polymers can be orientated in the l.c. state by an electric or magnetic field, it is possible to store any information obtained in the l.c. state by cooling the liquid crystalline polymer down to the glassy state. Obvious applications are e.g. optical filters or reflectors, prepared for linearly or circularly polarized light by cholesteric polymers. Furthermore the glassy polymers can serve as anisotropic matrices for dissolved molecules. 

S. The diffusion coefficients of gases in glassy polymer membranes are strong functions of the penetrant gas concentration in the membranes (or of the gas pressure), and depend also on polymer morphology (crystallinity, orientation), crosslinking, and chain mobility. The chain mobility depends, in turn, on the polymer free volume, the... 

Solid polymers may contain various stress concentration sources (hereafter referred to as flaws) which are either continuum defects (such as cracks, holes, inclusions, and the like) or quasimolecular flaws (such as regions of orientation, packing defect, crystallinity, or excess free energy) in an otherwise homogeneous and ostensibly structureless glassy polymer. 

There is much evidence that the intrinsic crazing of PC is related to the existence of a general mode of cavitational plasticity in glassy polymers. Examples have been given for polymers which behave very similar to PC. In particular PMMA and pre-oriented PS exhibit an almost identical behavior when stretched at high stresses and strains in a temperature region close to Tg. 

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