Polymer mold

By the addition of glass fibers, textile fibers, or chopped fabrics to crosslinkable polymers molding materials are produced with increased tensile strength, stiffness, and thermal stability compared to the filler-free polymers. The so-called reinforcing fillers, like carbon black, have good adhesion to the matrix due to their nonpolar structure and their characteristic geometry. 

Figure 7.76 Schematic illustration of molding area for a given polymer/mold combination. From Z. Tadmor and C. G. Gogos, Principles of Polymer Processing. Copyright 1979 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

The polymer molds may or may not be filled. The filling material can be a metal such as iron shot or silica particles. 

Nass, B., Hoerold, S., and Schacker, O. 2007. Polymer molding compositions based on thermoplastic polyamides. U.S. Patent Appl. 2007072967. 

In amorphous state, solid polymers retain the disorder characteristic for liquids, except that the molecular movement in amorphous solid state is restrained. The movement of one molecule versus the other is absent, and some typical liquid properties such as flow are absent. At low stress, polymers display elastic properties, reverting to a certain extent to the initial shape in a relaxation process. However, they can be irreversibly deformed upon application of appropriate force. The deformation and flow of polymers is very important for practical purposes and is studied by a branch of science known as rheology (see e.g. [1]). The combination of mechanical force and increased temperature are commonly applied for polymer molding for their practical applications. The polymers that can be made to soften and take a desired shape by the application of heat and pressure are known as thermoplasts, and most linear polymers have thermoplastic properties. 

In conventional amorphous polymers, molded part shrinkage can usually be predicted using a single measured coefficient of thermal expansion since the CTE values for the flow, transverse, and thickness directions are very similar. Knowledge of CTE or actual shrinkage behavior in the flow and width directions for a... 

This paper attempts to treat LCP molded part shrinkage first from a theoretical viewpoint related to directional and volumetric CTE s, and then from a more empirical perspective, where both actual shrinkage and CTE data are examined. Differences between LCP and conventional amorphous polymer molded part shrinkages are highlighted. A method is suggested for predicting potential shrinkage in a molded LCP article. 

Problem 4-8. Pressure-Driven Radial Flow Between Parallel Disks. The flow of a viscous fluid radially outward between two circular disks is a useful model problem for certain types of polymer mold-filling operations, as well as lubrication systems. We consider such a system, as sketched here ... 

Polymers having broad MW distributions not only exhibit improved polymer molding, but the MW breadth can also increase some of the polymer physical characteristics, including impact and tear resistance, toughness, creep and hoop stress resistance in pipe, and especially resistance to chemical attack, or stress crack (ESCR). These improved properties result because a broad MW distribution usually contains more of the long chains that can act as tie molecules to connect the crystalline lamellae (Figure 42). 

Unmodified PBT is a fairly ductile material exhibiting high elongation at break, even after crystallization. However, as to be expected of all rigid semi-crystalline polymers, molded parts of PBT show low notched Izod impact strength indicating that under conditions of stress concentration, the... 

Applications other than the use in synthesis also have been noted. Fluorocarbon polymer moldings have improved blocking and friction resistance when the surface is modified by the addition of [ (Ph2PhCH2) jPjjN X (X=C1, OH) . Fungicidal activity without concomitant plant damage has been noted for Ph2P(E)N=P(R)Ph2 (E=0 , s ) and (XC HJ2 )2 (X=H, halo, alkyl R=alkyl, substituted benzyl, Y=NOj, halide,... 

Flow photolysis experiments are carried out in microfluidic channels see Note 7). We use soft lithography (14, 19), a well-established polymer molding procedure, to build our microdevices. The following steps are carried out in the clean and dry environment of a laminar flow bench. 

Y. S. Kim, N. Y. L, J. R. Lim, M. J. Lee, S. Park, Nanofeature-pattemed polymer mold fabrication toward precisely defined nanostructure replication. Chem. Mater. 2005,17,5867. 

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