Polymerized liquids, partially

The casting method has mostly been employed to fabricate poly(dimethylsi-loxane) (PDMS) chips, but has also been used with partially polymerized PS liquid preparations [85],... 

One of the prominent features of polymeric liquids is the property to recover partially the pre-deformation state. Such behaviour is analogous to a rubber band snapping back when released after stretching. This is a consequence of the relaxation of macromolecular coils in the system every deformed macro-molecular coil tends to recover its pre-deformed equilibrium form. In the considered theory, the form and dimensions of the deformed macromolecular coil are connected with the internal variables which have to be considered when the tensor of recoverable strain is to be calculated. Further on, we shall consider the simplest case, when the form and dimensions of macromolecular coils are determined by the only internal tensor. In this case, the behaviour of the polymer liquid is considered to describe by one of the constitutive equations (9.48)-(9.49) or (9.58). 

To insert a product it can be just immersed in a plastic liquid prior to the plastic hardening. The product could have fixed spider type supports or retractable pins or other features to support it when molten plastic is poured or injected around it. Another approach is to place the product on a layer of plastic that is partially polymerized in a mold cavity followed by applying a final layer that physically encloses it. For certain plastics and/or products a vacuum system can be used if air pockets or voids are to be eliminated. 

The value given is for a liquid —> liquid reaction corrected for Aso,n//. Separate measurements were made in ethanol and acetic acid. Hydrogen uptake was abnormal indicating the possibility of partial polymerization... 

In thermosetting resins the reactive groups of the molecules from cross-Knks between the molecules during the fabrication process. The cross-linked or cured material cannot be softened by heating. Thermoset materials are usually supplied as a partially polymerized molding compound or as a liquid monomer-polymer misture. In this uncured condition they can be shaped with or without pressure and polymerized to the cured state with chemicals or heat. 

The discovery of polystyrene is generally attributed to E. Simon in 1839 who believed he had made an oxidation product of styrene, but it is likely to have been discovered earlier (Kaufman, 1963). Bulk polymerization technique is the most widely used today to produce commercial PS. Styrene is partially polymerized at 80° C before being run into a tower fitted both with heating and cooling facilities. The top of the tower is maintained at around 100°C while the bottom is heated to 180°C. The higher temperatures at the base of the tower boil off any unreacted styrene from the polymer. Freshly made, liquid PS is directed into an extruder where it is shaped and allowed to cool. 

Casting syrup (casting resin) n. Liquid monomers or partially polymerized polymers, usually containing catalysts or curing agents, capable of polymerizing to the solid state after they have been cast in molds. The materials most generally used as the acrylics, styrenes, polyesters, epoxies, silicones, and nylons. 

Liquid crystals do not lend themselves to electron microscopy, as a liquid phase cannot be easily handled within a vacuum column unless cumbersome wet stages are employed. However, the fact that polymeric liquid crystals can be quenched to the glassy or partially crystalline states without any apparent disturbance of the local orientation characteristic of the liquid mesophase means that the electron microscope becomes a most useful tool. It is now providing new insights into the local molecular orientation in some liquid crystal polymer systems. 

In conclusion, the molecules of a polymeric liquid in flow, depending on the gradient rate, can be oriented and deformed significantly, compared to the isotropic structure, which prevails in the stationary liquid. If the macromolecules have already been partially oriented into liquid state, the change of the entropy is reduced and the crystals are easily formed. The kinetics of the crystallization process is considerably accelerated and the structure of the crystals that are produced is affected. 

Shear thinning (thixotropy) is one of the most common manifestations of non-Newtonian behavior in polymeric liquids [61], Increased shear can lead to partial alignment of polymers or colloid particles with the flow, thus decreasing viscosity. Examples include latex paint, blood, and syrups. Shear thickening is the opposite phenomenon (antithixotropy) whereby the material becomes more viscous or stiffer with increasing shear, often due to shear-induced organization, such as partial crystallization. Quicksand and aqueous solutions of cornstarch are examples of shear-thickening materials. 

Application of PMMA as fixative for bone was first demonstrated by Charnley [52]. The PMMA bone cement is composed of the liquid monomer MMA, a partially polymerized PMMA powder, an initiator (commonly used dibenzoyl peroxide), an activator (N, A-dimethyl-p-toluidine), a radiopacifier (visible to X-rays) such as barium sulfate or zirconium oxide, and a copolymer to influence the mixing and handling of the cement [53]. In some cases, an antibiotic (e.g., gentamicin) is included in the formulation to minimize infection during implantation. The polymerization is initiated by the interaction between the activator and the initiator, yielding a free radical... 

Ion-exchange methods are based essentially on a reversible exchange of ions between an external liquid phase and an ionic solid phase. The solid phase consists of a polymeric matrix, insoluble, but permeable, which contains fixed charge groups and mobile counter ions of opposite charge. These counter ions can be exchanged for other ions in the external liquid phase. Enrichment of one or several of the components is obtained if selective exchange forces are operative. The method is limited to substances at least partially in ionized form. 

Vinyl acetate -8 CH3C00CH CH2 427 2.6-13.4 1.1 3.0 72 Colourless, partially water soluble liquid Faint odour Polymerizes with heat or organic peroxides... 

Process in whicli continuous strands of roving or roving tape are wound, at a specified pitch and tension, onto the outside surface of a mandrel. Roving is saturated with liquid resin or is preimpregnated with partially cured resin. Application of heat may be required to promote polymerization. 

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