Polymers characteristics

Processes that are essentially modifications of laboratory methods and that allow operation on a larger scale are used for commercial preparation of vinyhdene chloride polymers. The intended use dictates the polymer characteristics and, to some extent, the method of manufacture. Emulsion polymerization and suspension polymerization are the preferred industrial processes. Either process is carried out in a closed, stirred reactor, which should be glass-lined and jacketed for heating and cooling. The reactor must be purged of oxygen, and the water and monomer must be free of metallic impurities to prevent an adverse effect on the thermal stabiUty of the polymer. 

The next major commodity plastic worth discussing is polypropylene. Polypropylene is a thermoplastic, crystalline resin. Its production technology is based on Ziegler s discovery in 1953 of metal alkyl-transition metal halide olefin polymerization catalysts. These are heterogeneous coordination systems that produce resin by stereo specific polymerization of propylene. Stereoregular polymers characteristically have monomeric units arranged in orderly periodic steric configuration. 

Polymers are suspended as microparticles in the latex and interactions between these microparticles are prevented by the presence of adsorbed suspending agent and soap molecules. Blending results in a random suspension of dissimilar particles in the mixture of latexes, each unaffected by the other. Rate of flocculation depends entirely on the stabilizer and not on the polymer characteristics as such. Coagulated mass contains an intimate mixture of the polymers. Acrylonitrile butadiene styrene (ABS) polymers [23-25] may be prepared by this method. 

How does average molar mass affect each of the following polymer characteristics (a) softening point ... 

Approximate values of Tg are included in Table II for the purpose of indicating the temperature region in which the polymer characteristically changes from a hard, more or less brittle glass to a rubbery or viscous polymer within which motions of portions of the chains, usually called segments, are comparatively unhampered by the interactions... 

The polymer characteristics addressed within these clusters are presented below in Table 1. Table 1 presents an overview of the many analytical/ characterisation techniques and methods used for the molecular characterisation... 

Because of the ubiquitous nature of polymers and plastics (synthetic rubbers, nylon, polyesters, polyethylene, etc.) in everyday life, we should consider the kinetics of their formation (the focus here is on kinetics the significance of some features of kinetics in relation to polymer characteristics for reactor selection is treated in Chapter 18). 

Quantities useful for predicting phase continuity and inversion in a stirred, sheared, or mechanically blended two-phased system include the viscosities of phases 1 and 2, and and the volume fractions of phases 1 and 2, and ij. (Note These are phase characteristics, not necessarily polymer characteristics.) A theory was developed predicated on the assumption that the phase with the lower viscosity or higher volume fraction will tend to be the continuous phase and vice versa (23,27). An idealized line or region of dual phase continuity must be crossed if phase inversion occurs. Omitted from this theory are interfacial tension and shear rate. Actually, low shear rates are implicitly assumed. 

Table 2.6. Important polymer characteristics and analytical methods for their determination...

This article studies some of the polymer characteristics influencing the slurry dispersion and describes a new class of acrylic based polymer showing promising dispersing properties for ultra fine calcium carbonate slurries. 

Figure 5.15 Examples of linker cross-linked polymer networks exhibiting liquid crystalline polymer characteristics.

The thermodynamics of weakly charged polyelectrolyte solutions have been the subjects of several recent investigations [110-112]. In these systems, the properties are intermediate between nonionic polymers and fully charged polyelectrolytes and both electrostatic and nonionic interactions can be important in determining the polymer characteristics. 

As was mentioned above, four main factors determine the properties of particulate filled polymers characteristics of the components, composition, structure and component interactions. All four are equally important and must be adjusted to achieve optimum properties and economics. 

The following polymer characteristics were obtained on the variously irradiated test specimens melt index (ASTM 1238-62T), Vicat softening temperature (modified ASTM 1525-58T) heat distortion (ASTM D 1220-63T) physical strength yield strength ultimate tensile strength percent elongation at break (ASTM D 412-64T) chemical resistance to boiling toluene. 

Amorphous polymers characteristically possess excellent optical properties. Unlike all the other commercially available fluoropolymers, which are semicrystalline, Teflon AF is quite clear and has optical transmission greater than 90% throughout most of the UV, visible, and near-IR spectrum. A spectrum of a 2.77-mm-thick slab of AF-1600 is shown in Figure 2.5. Note the absence of any absorption peak. Thin films of Teflon AF have UV transmission greater Ilian 95% at 200 mm and are unaffected by radiation from UV lasers. The refractive indexes of Teflon AF copolymers are shown in Figure 2.6 and decrease with increasing FDD content. These are the lowest refractive indexes of any polymer family. It should be noted that the abscissa could also be labeled as glass transition temperature, Tg, since Tg is a function of the FDD content of the AF copolymer. Abbe numbers are low 92 and 113 for AF-1600 and AF-2400. 

Coacervation Is a very complicated physical phenomenon. And, many factors affect the properties of the resulting microcapsules. Coacervation and phase separation from organic and aqueous media Involve many properties, materials and processes such as phase Inducing agents, stirring rates, core to wall ratios, polymer characteristics, core characteristics (wettability, solubility), cooling rates and rates of addition. 

Molecular weight between entanglements in undiluted polymer. Characteristic molecular weight from t]0 vs M behavior of undiluted polymers. 

In the IR spectrum of the polymer characteristic bands due to the carbonyl group have been observed. 

In many of the above polymers characteristic temperature drifts of the calorimeter were observed above and below Tg depending upon the previous thermal history of the sample. In the case of the synthetic rubber, GR-S, Rands,... 

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