Chlorine-containing vinyl polymers

Peak Notation Assignment of Main Peaks Molecular Weight Retention Index Relative Intensity 

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In the following data acquisition, the same 163 standard polymer samples used in the former edition were adopted as a set of representative ones utilized in versatile fields, which include representative synthetic polymers [a) polyolefins (homopolymers) (001— 007), b) vinyl polymers with ethylene units (copolymers) (008—015), c) vinyl polymers with styrene units (016—028), d) vinyl polymers with styrene derivatives (029—035), e) acrylate-type polymers (036—049), f) chlorine-containing vinyl polymers (050-059), g) fluorine-containing vinyl polymen (060—066), h) the other vinyl polymers (067—070), i) diene-type elastomers (071—081), j) polyamides (082-090), k) polyacetals and polyethers (091—095), 1) thermosetting polymers (096—106), m) polyimides and polyamide-type engineering plastics (107—114), n) polyesters (115—126), o) the other engineering plastics with phenylene skeletons (127—138), p) sificone polymers (139—143), and q) polyurethanes (144—147)] along with some natural polymers [r) cellulose-type polymers (148-155) and s) the other some natural polymers (156-163)]. 

Cblorina.ted Pa.ra.ffins, The term chlotinated paraffins covers a variety of compositions. The prime variables are molecular weight of the starting paraffin and the chlorine content of the final product. Typical products contain from 12—24 carbons and from 40—70 wt % chlorine. Liquid chlotinated paraffins are used as plasticizers (qv) and flame retardants ia paint (qv) and PVC formulations. The soHd materials are used as additive flame retardants ia a variety of thermoplastics. In this use, they are combiaed with antimony oxide which acts as a synergist. Thermal stabilizers, such as those used ia PVC (see vinyl polymers), must be used to overcome the inherent thermal iastabiUty. 

Widespread chlorine-containing polymers would include, 1) stable molding material for practical use such as polyvinyl chloride (PVC), polyvinylidene chloride and poly(epichlorohydrin)(PECH) and, 2) reactive polymers capable to introduce additional functional groups via their active chlorines such as chloromethyl polystyrene, poly (3-chloroethyl vinyl-ether) and poly (vinyl chloroacetate). While the latter, especially the chloromethyl polystyrene, has been widely used recently for the synthesis of variety of functional polymers, we should like to talk in this article about the chemical modification of the former, mainly of PVC and PECH, which was developed in our laboratory. 

Chlorine-containing polymers such as poly(vinyl chloride) PVC undergo an autocatalytic dehydrochlorination reaction under the influence of elevated temperature and UV radiation. Since the HCl originating from the dehydro chlorination of the PVC chains is believed to sustain this autocatalytic process, stabilizers that irreversibly bond HCl can thus inhibit the degradation. Heavy metal compounds such as cadmium stearate or lead stearate are currently used for this purpose. However, alternatives are required due to environmental problems associated with the use of heavy metals. Indeed, the largest current application of LDH materials is in the polymer industry, mainly to stabilize PVC [3,229-232]. 

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. 

Polymeric carbocations have been formed from a chlorine-containing polymer such as chlorinated SBR and polystyrene, poly(vinyl chloride), and polychloroprene, by reaction with (C2Hs)2A1C1, for example... 

The chlorine content of Polymer Fractions I, II, and III was determined by gravimetric analysis and found in all cases to be within 1% of the value for undegraded poly (vinyl chloride). (Since it was difficult to remove the last traces of solvent, the actual chlorine content of the polymers was probably even closer to the theoretical value.) The chlorine content of the insoluble residue was much lower. Thus, the insoluble residue of samples obtained from the experiments illustrated by Table III contained typically only 46-49% Cl. 

One example in this category is the case of one polymer in two stereoregular forms Other examples are of two polymers which are chemically very similar such as poly(methyl acrylate) with poly(vinyl acetate) A series of systems which have been studied in some detail are various mixtures of chlorine containing polymers. Blends of chlorinated PVC with PVC have been studied It has been suggested that at 65.2 % wt.- % chlorine they are miscible and at 67.5 wt.- % they are not. Chlorinated polyethylene with 45 wt.- % chlorine has also been found to be miscible with PVC In this case it was suggested that phase separation occurs on heating. 

Chlorine-containing Polymers. Polymers containing one chlorine atom in various environments (other sustituents) were studied by XPS poly(vinyl chloride) PVC, poly(chlorotrifluoro-ethylene) PCTFE, an (ethylene-chlorotrifluoroethylene) copolymer, and poly(epichlorohydrine) PEPI, were chosen because besides carbon atoms they contain chlorine in presence of hydrogen, fluorine, and oxygen atoms. The valence band spectra of these compounds (see Figure 9) show that features can be easily and unambiguously assigned to a contribution from the chlorine molecular orbitals. 

Whilst such stabilisers have found use in many chlorine-containing polymers their main application has been with poly (vinyl chloride). These additives will be considered in Chapter 12. 

Figure 9.2. The structures of three of the chlorine-containing polymers considered in developing the correlation for the dielectric constant e at room temperature, (a) Poly(vinyl chloride), (b) Poly(vinylidene chloride), (c) Poly(oxy-2,2-dichloromethyltrimethylene).

Copolymers of vinyl fluoride with such monomers as vinylidene fluoride or l-chloro-2-fluoroethylene were prepared in the presence of trichloroacetyl peroxide at 0 C in sealed tubes. The chlorine-containing copolymers were then reductively dechlorinated at 60 C in tetrahydrofuran with tri- -butyltin hydride in the presence of 2,2 -azobis(isobutyronitrile) for up to 40 hr. This general procedure led to the formation of polymers with a reasonable control of the level of head-to-head, tail-to-tail linkages in the product [27]. 

I. Organic carbochain polymers and copolymers of poly-4-methylpentene-l [4] PMMA or methyl methacrylate (MMA) copolymers with other alkyl-(meth)acrylates (AMA) [1-3, 5] poly(vinyl acetate) vinyl acetate copolymer with ethylene [4, 6-8] polymers of chlorine-containing olefins [9]. 

Poly(vinyl ethers) formed from methyl ethyl ether or isobutyl ether are used as soft plasticizing resins. Solubility and compatibility depend on the alkyl group. In the paint sector, poly(vinyl ethers) are used mainly as plasticizing and in some cases as adhesion-improving resins for chlorine-containing binders, styrene polymers, nitrocellulose, and brittle resins. An example of a commercial product is Lutonal (BASF). 

In addition to polyvinyl chloride (PVC), the chlorine-containing polymers and different copolymers of vinyl chloride are polyvinylidene chloride, chloro-rubber, rubber hydrochloride, chlorinated polyolefins, polychloro-prene, and polytrifluorochloroethylene. In addition to detecting chlorine with the Beilstein test (see Chapter 4), these polymers can be identified by using the color reaction with pyridine (see Table 6.2). 

Polyaniline (PANI) is a nonconductive polymer that could be rendered conductive by HCl doping. Several methods exist to accomplish such a doping. One of them is the incorporation of a chlorine-containing polymer into a polyaniline matrix and the irradiation of the resultant blend. Ionizing radiation (e-beam or y-irradiation) leads to the dehydrochlorination of the second polymer and the subsequent doping of the PANI (Figure 9.9). Several chlorine-containing polymers were tested in this approach, PVC, chlorinated polyisoprene, poly(vinylidene chloride-co-vinyl acetate), poly(vinylidene chloride-co-vinyl chloride). " ... 

The Gr value is defined as a measure of the production of free radicals R. The Gr value gives the number of free radicals formed per 100 eV (1 eV = 1.6 X 10 J) of energy absorbed. Resonance-stabilized molecules such as styrene can distribute the absorbed energy over the whole molecule, which causes relatively fewer bond to be broken than in nonresonance-stabilized molecules. Thus, the Gr value is low, for example, for both styrene and poly(styrene). Chlorine radicals that can start chain reactions can be formed by the action of radiation on chlorine-containing compounds. Consequently, the Gr value for vinyl chloride as well as for poly(vinyl chloride) is high (Table 21-2). Because of its double bonds, ethylene can absorb more energy than poly(ethylene) before free radicals are formed consequently, the Gr value for the polymer is higher. 

A copolymer of methyl methacrylate and vinyl chloride containing labelled chlorine ( "Cl) has been examined using thermovolatilization analysis and radiochemical assay. The yields of methyl chloride and hydrogen chloride agree with predictions made from sequence distribution calculations. The thermal degradation of a number of chlorine-containing polymers, poly(vinyl chloride), chlorinated polyethylene, chlorosulphonated polyethylene, polychloroprene, poly-epichlorhydrin, and co- and ter-polymers of epichlorhydrin has been compared and structural effects elucidated. ... 

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