Splay pattern

Low-pressure SF products can have characteristic surface splay patterns. However, the utilization of increased mold temperatures, increased injection rates, or grained mold surfaces will serve to minimize or hide this surface streaking. Finishing systems like... 

These are usually self-adhesive, precut, printed patterns on a substrate that are simply adhered to the surface of a product. Decals generally use a transparent plastic film while labels are usually on an opaque plastic, metallic and multilayer sandwich base. Labels of sufficient thickness are useful for hiding unavoidable appearance problems such as gate and sprue removal areas, sink marks, blushes, splays, and weld lines. 

Splay or streaking Patterns around gating Material damped prior to injection... 

Preedericksz transition in planar geometry is uniform in the plane of the layer and varies only in the z direction. However, in some exceptional cases, when the splay elastic constant Ki is much larger than the twist elastic constant K2 (e.g., in liquid crystal polymers), a spatially periodic out-of-plane director distortion becomes energetically favourable. The resulting splay-twist (ST) Freedericksz state is manifested in experiments in the form of a longitudinal stripe pattern running parallel to the initial director alignment no x. 

A. Buka and L. Kramer, Theory of nonlinear transient patterns in the splay Preedericksz transition, Phys. Rev. A 45(8), 5624-5631, (1992). 

Fig. 6.9. Micromechanical model for the converse flexoeffect in a nematic liquid crystal. Cross section of a field-induced fiexoelectric domain pattern in a nematic between plane-parallel electrodes, containing alternating regions of splay (S) and bend (B) of the director field. The calculated period of this pattern is inversely proportional to the electric field (c/. Fig. 6.8). (Figure reprinted with kind permission of the author and the publisher from Meyer. ° Copyright 1969 by the American Physical Society.)...

Fig. 7.5. Increasing curvature in response to an increasing electric field the thresholdless field-induced periodic splay-bend deformation. The pattern in the director field is shown to the left (in any oblique cut perpendicular to the optic axis) and the optic axis deflection with increasing field is shown to the right. (From Rudquist et reproduced with kind permission of Taylor Francis, http //www.tandfonline.com.)...

Splay marks Circular pattern around gate High moisture in plastic, trapping of gas in rib... 

Twist relaxation of splay and bend is a general phenomenon in materials with small K2. Chiral structures can occur in defective nematic samples even when there is no azimuthal anchoring at all. Twisted brushes observed by Press and Arrott in textures of lens-shaped nematic droplets floating on the water surface are one example [15]. Another well-known illustration of twist relaxation is the periodic pattern of stripes that occur in the geometry of splay Frederiks transition in polymer nematics with a small (less than 0.33) ratio K2/K [16]. A field applied normally to the planar nematic cell causes stripe structures composed mostly of twist rather than the uniform splay response observed in regular materials. 

Fig. 5.16. The director-field patterns in volume elements subjected to splay, twist, and bend curvature strains.

A. Buka, L. Kramer Theory of transient patterns in the splay freedericksz transition of nematics, in S. Kai (ed.) Pattern formation in complex dissipative systems. World Scientific, Kitalqrushu,... 

The influences of nonunifoim strains on die electric polarization in materials with molecular dipoles and die possibly resulting piezoelectric effects were first considered for liquid crystalline (LC) materials (Meyer 1969 HeUrich 1971). The arrangements of the individual LC molecules are classified according to the orientation distribution of the so-called molecule director, a vector diat represents the main axis of the molecule in question, but not necessarily its dipole moment Basically, three nonunifoim deformation modes can be identified (1) Splay is a deformation, in which the directors of die individual LC molecules assume a radial fanUke pattern with their tips further away from each odier dian dieir ends. (2) Bend is a deformation, in which the LC directors are arranged like die rail cars of the trains on parallel tracks in a curve. (3) Twisf is an LC director arrangement, in which the directors of subsequent LC-molecule layers are rotated eidier all clockwise or all counterclockwise relative to each odier. Combinations of die diree fundamental deformation modes are also known. Many additional details and die state of the art may be found in the pertinent literature and on die Internet, e.g., in Andrienko (2006). 

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