Vinylidene chloride, copolymers properties

Vinylidene chloride copolymers were among the first synthetic polymers to be commercialized. Their most valuable property is low permeabiUty to a wide range of gases and vapors. From the beginning in 1939, the word Saran has been used for polymers with high vinylidene chloride content, and it is still a trademark of The Dow Chemical Company in some countries. Sometimes Saran and poly (vinylidene chloride) are used interchangeably in the Hterature. This can lead to confusion because, although Saran includes the homopolymer, only copolymers have commercial importance. The homopolymer, ie, poly (vinylidene chloride), is not commonly used because it is difficult to fabricate. 

Table 6. Mechanical Properties of High Vinylidene Chloride Copolymers...

Table 19. Film Properties of Vinylidene Chloride Copolymer Latex ...

Conversely, cling film (plasticised PVC/PVDC, (poly(vinyl chloride)/poly (vinylidene chloride), copolymer, which has very high gas-barrier properties) on peeling from a roll generates static electricity thus promoting adhesion to a surface, e.g., ceramics, but not metallic surfaces which conduct the static electricity away... 

Plasticizers are used in the polymer industry to improve flexibility, workability, and general handling properties. Dibutyl sebacate and phthalates, such as dibutyl phthalate, diethyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, and diphenyl-2-ethylhexyl phosphate, serve widely as plasticizers in vinylidene chloride copolymers, nitrocellulose-coated regenerated cellulose film, and cellulose acetate (Castle et ah, 1988a). In PVC, di(2-ethylhexyl)... 

TABLE 3. MECHANICAL PROPERTIES OF HIGH VINYLIDENE CHLORIDE COPOLYMERS... 

Humidity does not affect the permeability, diffusion coefficient, or solubility coefficient of flavor/aroma compounds in vinylidene chloride copolymer films. Studies based on /n /w-2-hexenal and D-limonene from 0 to 100% rh showed no difference in these transport properties (97,98). The permeabihties and diffusion coefficients of /n /w-2-hexenal in two barrier polymers are compared in Table 12. Humidity does not affect the vinylidene chloride copolymer. In contrast, transport in an EVOH film is strongly plasticized by humidity. 

The excellent adhesion to primed films of polyester combined with good dielectric properties and good surface properties makes the vinylidene chloride copolymers very suitable as binders for iron oxide pigmented coatings for magnetic tapes (168—170). They perform very well in audio, video, and... 

However, replacement strategies are not straightforward with compromises on either performance and cost having to be addressed. An excellent example of this centres around the chlorine issue. Chlorine imparts a unique set of properties to addition polymers, such as the ability to crystallise on film formation. Vinylidene chloride copolymers have exeellent gas, odour and moisture barrier properties impossible to achieve from non-chlorinated waterborne film forming materials. In the barrier packaging area it has a unique position, with proposed replacements being unable to fully match its overall... 

PAN Pancheshnikova, R.B., Brodko, L.S., Monakov, Yu.B., Petrenko, P.I., Yanovskii, D.M., and Minsker, K.S., Hydrodynamic and conformational properties of vinyl chloride-vinylidene chloride copolymers in solutions (Russ.), Vysokomol. Soed., Ser. 

Ethylene, 1,1-dichloro-, polymer with chloroethylene Poly (vinylidene chloride-co-vinyl chloride) Vinyl chloride copolymer with vinylidene chloride Vinyl chloride-1,1-dichloroethylene copolymer Vinyl chloride/vinylidene chloride copolymer Vinyl chloride/vinylidene chloride polymer Vinylidene chloride/vinyl chloride polymer Ciassification Vinyl/vinylidene chloride Empihcai (C2H3CI C2H2Cl2)x Formuia (CH2CCl2)x(CH2CHCI)y Properties Solid dens. 1.690-1.730 m.p. 163 C Toxicoiogy May be harmful by inh., ing., or skin absorption may cause irritation to eyes, skin, mucous membranes, upper respiratory tract TSCA listed... 

In order to confer such necessary properties as heat sealability and moistureproofness, the base cellulose film is topcoated with a lacquer of either modified nitrocellulose or vinylidene chloride copolymer. The former system was developed in the late 1920 s and is based on nitrocellulose plasticised with organic esters. In addition, paraffin wax and resins are added to confer moistureproofness. This type of coating can be modified to give only partial moistureproofness or, if necessary, can be made non-heat sealing. 

The nitrocellulose coated films were the only type available until the early 1950 s, when vinylidene chloride copolymer coatings were introduced. The method of coating is essentially the same as that used for the nitrocellulose type. This later type of coating has the advantage that subsequent conversion, eg printing and bag making, does not have as marked an effect on barrier properties as on the nitrocellulose coatings where the water vapour permeability can be increased quite appreciably. 

Vinylidene chloride copolymers (PVDC) This set of polymers includes resins for extrusion and molding, resins for solution coating, and latexes for eoating. A variety of eomonomers are used to aehieve different properties. The barrier properties are important for food paekaging. Typically, these polymers are used with other polymers sueh as polyethylene or polypropylene in multi-layer structures. 

Properties and Applications of Vinylidene Chloride-Vinyl Chloride Copolymers ... 

Since some properties of the vinylidene chloride-vinyl chloride copolymers are greatly dependent on crystallisation and orientation it is convenient to consider the applications of these copolymers and then to discuss the properties of the products. 

Table 17.1 General properties of vinylidene chloride-vinyl chloride (85 15) copolymer...

Vinyl chloride has gained worldwide importance because of its industrial use as the precursor to PVC. It is also used in a wide variety of copolymers. The inherent flame-retardant properties, wide range of plasticized compounds, and low cost of polymers from vinyl chloride have made it a significant industrial chemical. About 95% of current vinyl chloride production worldwide ends up in polymer or copolymer applications. Vinyl chloride also serves as a starling material for Uie synthesis of a variety of industrial compounds. The primary nonpolymeric uses of vinyl chloride are in the manufacture of vinylidene chloride and tri- and tetrachloroethylene. 

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