Vinyl chloride polymers description

The Smith-Ewart kinetic theory of emulsion polymerization is simple and provides a rational and accurate description of the polymerization process for monomers such as styrene, butadiene, and isoprene, which have very limited solubility in water (less than 0.1%). However, there are a number of exceptions. For example, as we indicated earlier, large particles (> 0.1 to 0.5 cm diameter) may and can contain more than one growing chain simultaneously for appreciable lengths of time. Some initiation in, followed by polymer precipitation from the aqueous phase may occur for monomers with appreciable water solubility (1 to 10%), such as vinyl chloride. The characteristic dependence of polymerization rate on emulsifier concentration and hence N may be altered quantitatively by the absorption of emulsifier by these particles. Polymerization may actually be taking place near the outer surface of a growing particle due to chain transfer to the emulsifier. 

General Description Polyvinylidene Chloride (PVDC) resin is a copolymer of vinylidene chloride (VDC) with vinyl chloride or other monomers Dow Plastics vinyl chloride and vinylidene chloride, Saran, is usually supplied as a white, free-flowing powder. Dow Saran polymers are known worldwide for their gas-moisture, and chemical-barrier properties, and for their ignition-resistant properties. 

The original DMA((t) technique and the relevant analytical description [91-94] allowed us to estimate experimentally the activation volumes of a- and p-relaxations in polymers. As an example, Fig. 17 shows the mechanical spectra of poly(vinyl chloride) (PVC) obtained without and under different static loading (maximal shear stresses Tgh). 

There can be many variations on this general description because the substituents bonded to the four carbons in the double bonds can be quite variable. For example, all four bonds may be to hydrogens (CH2 = CHj, ethene, or ethylene), there may be one methyl group attached (CH2 = CHCH3, propene, or propylene), there may be a chlorine attached (CH2 = CHCl, vinyl chloride), and so on. Polyethylene, polypropylene, polyvinyl chloride (PVC), and many other addition polymers have been manufactured in mass quantities by this approach and used for many consumer products. Figure 14.33 lists some of the addition polymers that have been manufactured. Also listed are the individual alkene units (monomers) that are in these polymers and some of the uses of each. 

More than 95 percent of all VCM is used to produce polyvinyl chloride (PVC), an important polymer for the housing and automotive industries. (A detailed description of PVC is included in Chapter 19 ) The rest of the vinyl chloride goes into the production of chlorinated solvents. 

While the situation with respect to simple vinyl polymers is straightforward, the tacticity and geometrical arguments are more complicated for more complex polymers. Here we will only briefly consider this situation. Before we move to an illustration of this let us view two related chloride-containing materials pictured below. We notice that by inserting a methylene between the two chlorine-containing carbons the description of the structure changes from racemic to meso. Thus, there exists difficulty between the historical connection of meso with isotactic and racemic with syndiotactic. 

---