Vinylidene Chloride Copolymers PVDC

Poiyvinyiidene chioride, PVDC, is an addition poiymer of vinyiidene chioride with the foiiowing structure  

Incorporation of a comonomer reduces crystallinity and the crystalline melting point, permitting processing at lower temperatures or imparting solubility in organic solvents. Vinyl chloride and methyl acrylate are commonly used as comonomers for extrudable resins, typically in amounts from 6 to 28%. Vinylidene chloride copolymers with methyl acrylate and methyl methacrylate are commonly used for latex (water-based) coatings. Copolymers with acrylonitrile, methacryloni-trile, and methyl methacrylate are common for solvent-based coatings. All commercially available PVDC resins are copolymers. 

PVDC resins can be processed in a variety of ways, including extrusion, coextrusion, laminating, latex coating, and injection molding, to meet specific packaging requirements. Both blown and cast films are also produced. 

The main applications of PVDC resins are in food packaging as barrier materials to moisture, gases, flavors, and odors. Monolayer films are used in household wrap. 

Typical properties of PVDC resins are shown in Table 4.9. 

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To illustrate the compaction process that occurs in an extruder, a Maddock solidification [1] experiment (described in detail in Section 10.3.1) was performed using a 63.5 mm diameter machine [2]. The extruder was operated at a screw speed of 60 rpm with a poly(vinylidene chloride) copolymer (PVDC) powder. After the extruder reached a steady-state operation, screw rotation was stopped and full cooling was applied to the extruder. After several hours of cooling, the screw and PVDC resin were removed from the extruder and the density of the bed was measured using Archimedes s principle. The compaction phenomenon in the extruder is shown by the density measurements of the solid bed in Fig. 4.1. As shown in this figure, the density of the solid bed increased from the feedstock bulk density of 0.73 g/cm to nearly the solid density of 1.7 g/cmT... 

Vilit Poly(vinylidene chloride) copolymers, PVDC Hiils A.-G... 

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. 

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... 

Oriented, heat shrinkable, poly(vinylidene chloride) (PVDC) films are widely used for packaging purposes, particularly for packaging food. However, vinylidene chloride copolymers need to be plasticized so that they can be extruded and stretched into oriented films at commercial rates. The greater the proportion of plasticizer, the lower the viscosity and the easier the polymer is to extrude and orient, as well as better the abuse resistance of the final product. 

Abbreviations for plastics ABS, acrylonitrile-butadiene-styrene CPVC, chlorinated poly vinyl chloride ECTFE, ethylene-chlorotrifluoroethylene ETFE, ethylene-tetrafluoroethylene PB, polybutylene PE, polyethylene PEEK, poly ether ether ketone PFA, perfluoroalkoxy copolymer POP, poly phenylene oxide PP, polypropylene PVC, polyvinyl chloride PVDC, poly vinylidene chloride PVDF, poly vinylidene fluoride. 

Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometallic compounds. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinylidene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. Without the use of heat stabilizers, PVC could not be the widely used polymer that it is, with worldwide production of nearly 16 million metric tons in 1991 alone (see VlNYL polymers). 

Poly( vinylidene chloride) does not dissolve in most common solvents at ambient temperatures. Copolymers, particularly those of low crystallinity, are much more soluble. However, one of the outstanding characteristics of vinylidene chloride polymers is resistance to a wide range of solvents and chemical reagents. The insolubility of PVDC results less from its polarity than from its high melting temperature. It dissolves readily in a wide variety of solvents above 130°C. 

The infrared spectrum of PVdC is shown in Fig. 18 [Krimm and Liang (101)]. It is not possible to orient a PVdC film in order to obtain polarized spectra, but when a copolymer is made of vinylidene chloride... 

PS PSF PSU PTFE PU PUR PVA PVAL PVB PVC PVCA PVDA PVDC PVDF PVF PVOH SAN SB SBC SBR SMA SMC TA TDI TEFE TPA UF ULDPE UP UR VLDPE ZNC Polystyrene Polysulfone (also PSU) Polysulfone (also PSF) Polytetrafluoroethylene Polyurethane Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) poly(vinyl butyrate) Poly(vinyl chloride) Poly(vinyl chloride-acetate) Poly(vinylidene acetate) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl fluoride) Poly(vinyl alcohol) Styrene-acrylonitrile copolymer Styrene-butadiene copolymer Styrene block copolymer Styrene butadiene rubber Styrene-maleic anhydride (also SMC) Styrene-maleic anhydride (also SMA) Terephthalic acid (also TPA) Toluene diisocyanate Ethylene-tetrafluoroethylene copolymer Terephthalic acid (also TA) Urea formaldehyde Ultralow-density polyethylene Unsaturated polyester resin Urethane Very low-density polyethylene Ziegler-Natta catalyst... 

The maximum rates of crystallization of the more common crystalline copolymers occur at 80—120°C. In many cases, these copolymers have broad composition distributions containing both fractions of high VDC content that crystallize rapidly and other fractions that do not crystallize at all. Poly(vinylidene chloride) probably crystallizes at a maximum rate at 140—150°C, but the process is difficult to follow because of severe polymer degradation. The copolymers may remain amorphous for a considerable period of time if quenched to room temperature. The induction time before the onset of crystallization depends on both the type and amount of comonomer PVDC crystallizes within minutes at 25°C. 

Barrier Properties. Vinylidene chloride polymers are more impermeable to a wider variety of gases and liquids than other polymers. This is a consequence of the combination of high density and high crystallinity in the polymer. An increase in either tends to reduce permeability. A more subde factor maybe the symmetry of the polymer structure. It has been shown that both polyisobutylene and PVDC have unusually low permeabilities to water compared to their monosubstituted counterparts, polypropylene and PVC (88). The values listed in Table 8 include estimates for the completely amorphous polymers. The estimated value for highly crystalline PVDC was obtained by extrapolating data for copolymers. 

Homo and copolymers of vinylidene chloride (VDC) possess extremely high barrier properties to gases, water and aromas as well as good resistance to water and solvents. The barrier properties of polyvinylidene chloride (PVDC) come from the dense packing of its polymer chains (without voids or branching) which are crystalline in their stable form. The chlorine content of the high density polymer is 73 % (1.80-1.97 g/cm3, crystalline). 

The copolymers of vinylidene chloride (VDC) and BMA have high flexibility. Their tensile strength and toughness can be further improved by including proper amounts of VDC and BMA homopolymers. The melt mixing method cannot be used because the melting point of PVDC is high (nearly 200°C) [31]. The inclusion of the homopolymers via the concentrated emulsion method can, however, be easily achieved. Three preparation procedures were employed to... 

A number of copolymers of vinylidene chloride are used in practice. Copolymers with acrylonitrile are used in low flammability fibers (modacrylic fibers). These fibers begin to lose weight when heated at 285-308° C due to dehydrohalogenation [41] but do not ignite easily. A tercopolymer butadiene-styrene-vinylidene chloride is used in fabrics industry and in paper industry. Other copolymers include PVC/PVDC, used for fibers and for films with low permeability to gases and water vapors (barrier films), etc. 

In the present section, general comparisons will be presented between these two theories. Both theories will be utilized in a correlative mode. The parameters for barrier polymers will be defined for idealized completely amorphous poly(vinylidene chloride) (PVDC) and a VDC/VC copolymer. It will be shown that physically significant qualitatitive differences exist between the results calculated by the two theories. 

PVDC-VC with vinylidene chloride-methyl acrylate copolymer (PVDC-MeA)... 

Polyvinyl chloride (PVC), which belongs to the family of vinyl polymers, and its copolymers vjith vinylidene chloride (PVDC), polystyrene (PS) and its copolymers, polyvinyl acetate (PVA), polyvinyl alcohol (PVAL), ethylene copolymers with vinyl alcohol (CEVA) are also employed in anticorrosion films [3,18,20,22-24]. 

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. 

Poly(vinylidene chloride) (PVDC). The homopolymer is intractable in the conventional plastics processing techniques. For this reason, copolymers of vinylydene chloride with vinyl chloride or terpolymers with vinyl chloride and acrylonitrile are used. Due to its exceptionally low vapour, gas, and aroma permeability, PVDC films are used for packaging and for the barrier layer in composite films. Paper varnished by PVDC is a widespread packaging material. Trade names Diofan (FRG), Ixan (B), Saran (USA). 

This material has excellent barrier properties and is frequently used in food packaging applications. Films made from PVDC have good cling properties, which is an advantage for food wraps. Commercial polymers are all copolymers of vinylidene chloride with vinyl chloride, acrylates, or nitriles. Copolymerization of vinylidene chloride with other monomers reduces the melting point to allow easier processing. Corrosion-resistant materials should be considered for use when processing PVDC. 

Narrow and relatively narrow molecular weight distribution (MWD) homopolymers comprise an obvious group of products that can be produced from the FRRPP process. These materials would be used mainly for R D purposes. PS and PMAA homopolymers would be good examples of relatively narrow MWD homopolymers that can be produced in large scale through the FRRPP process. Recently, poly(vinylidene chloride) (PVDC) has been produced through the FRRPP process, including various related copolymers. 

Plasticizer studies were conducted in order to improve the foamability of the other monomeric constituents of the VDC-based copolymers. Table 4.5.2 shows the classes and formulations of the Scientific Polymer Products plasticizers used in this study. Also, water and V-methyl-2-pyrolidinone (NMP) were considered in the plasticizer studies. Studies of P(VDC-AN), poly(vinylidene chloride-co-vinyl chloride) (PVDC-VC), and poly(vinylidene chloride-co-acrylontirile-co methyl methacry-... 

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