Polyvinylidene Chloride PVDC

Polyvinylidene chloride is manufactured under the tradename Saran by Dow Chemical. It is a variant of PVC, having both chlorine atoms at the same end of the monomer instead of at the opposite ends as shown below  

Saron has improved strength, hardness, and chemical resistance over that of PVC. The operating temperature range is from 0 to 175°F (—18 to 80°C). 

Saran is resistant to oxidants, mineral acids, and solvents. In applications such as plating solutions, chlorides and certain other chemicals, polyvinylidene chloride is superior to pol)rpropylene and finds many applications in the handling of municipal water supplies and waste waters. Saran is also resistant to weathering and UV degradation. Refer to Table 2.33 for the compatibility of PVDC with selected corrodents. Reference [1] provides a more comprehensive listing. 

Saran has found wide application in the plating industry and for handling deionized water, pharmaceuticals, food processing, and other applications where stream purity protection is critical. It also finds application as a lined piping system. Refer to Reference [2]. 

Saran is also used to manufacture auto seat covers, film, bristles, and prepared coatings. 

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The storage capacity of an ANG storage system is always greater than its delivered capacity, usually by about fifteen percent. For some carbons, however, it can be as high as thirty percent because of the large amount of methane which is held by the adsorbent at less than one bar, (0.1 MPa). Carbons which are very microporous, such as polyvinylidene chloride (PVDC) carbons, tend to have very steep initial slopes to their methane isotherm, and as much as thirty percent of their overall uptake occurs at less than 0.1 MPa. These carbons have a high storage capacity but a much lower deliverable VfV. 

Cellophane is an old and respected packaging material which has been improved over the years. The two general types are coated with nitrocellulose (N/C) and polyvinylidene chloride (PVDC), respectively. Nitrocellulose-coated cellophane is moisture proof and useful for packaging dry products. It does not exclude oxygen or moisture completely, but for noncritical products it is entirely satisfactory. Baked goods are often packaged in this breathing type film. It is often used for cookies, candies, and rolls because its lack of taste and odor makes it very compatible with these products. 

MIR techniques have simplified obtaining infrared spectra of many materials important in packaging. These include rubber, plastics, laminations, and components of these materials that find use in pumps, sample packages, and devices. The combination of MIR and computerized pattern recognition techniques can be used for differentiating and classification of flexible packaging polymers such as polyvinyl chloride (PVC), polyvinylidene chloride (PVdC), acrylonitrile (Barex), and CTFE (Aclar) [22]. 

Vinyl chloride polymers and copolymers are often referred to as vinyl resins. PVC is the most important member of the vinyl resin family, which includes polyvinyl acetate (PVAC), polyvinyl alcohol (PVA), polyvinylidene chloride (PVdC) and polyvinyl acetal. Almost always the term PVC includes polymers of VCM as well as copolymers that are mostly VCM. 

Polyvinylidene chloride (PVDC), polyethylene (LDPE and HDPE), polypropylene (PP), PVC, and polystyrene all have excellent resistance to oxygen permeation. Polyethylene also has relatively good resistance to the permeation of water, which makes it an excellent choice for bread bags. 

Linear polymers prepared by step reaction polymerization, such as nylon 66, and linear, ordered polymers prepared by the chain polymerization of symmetrical vinylidene monomers, such as polyvinylidene chloride (PVDC), can usually be crystallized because of symmetry and secondary-bonding. Isotactic polymers, such as isotactic polypropylene (PP), usually crystallize as helices. 

Polyvinyl acetate (PVAc) loses acetic acid, and polybutyl methacrylate loses butene at high temperatures. Both PVC and polyvinylidene chloride (PVDC) lose chlorine as hydrogen chloride and other halogenated species when heated above 200 °C. 

The values of D, P, and S of a polymer, such as polyethylene, are a function of the polymer structure and may be altered by the introduction of pendant groups. The values of D and P, and to some extent S, are reduced when a chlorine pendant group is inserted in polyethylene, as in PVC. These values are reduced further by the introduction of a second chlorine pendant group (as in polyvinylidene chloride, PVDC). 

Halogenated aliphatic polymers such as polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) are moderately resistant to attack by reactants. The fluorinated polymers, such as ptfe, are exceptionally resistant to attack by acids and alkalis even at elevated temperatures because of their tight packing and high C—F bond energy. 

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). 

BMs commonly include from two to seven layers, although more are also used. The construction usually includes one or more barrier layers. These are plastics with a particular resistance to the transmission of water vapor or gases such as oxygen or carbon dioxide. Examples are ethylene vinyl alcohol (EVOH), nylons, and polyvinylidene chloride (PVDC). Their presence greatly enhances the performance of the BM as a package for foodstuffs, beverages, and other critical products. The barrier materials are all deficient in some respect such as price, mechanical strength, and moisture resistance. Thus not used as a material of sole construction for BM. Their use is in thin layers shielded by other more robust and economical body plastics. 

Films made with barrier polymers, e.g., polyamide (PA)/polyethylene (PE) laminates, ethylene vinyl acetate (EVA) copolymer/polyvinyl chloride (PVC)-polyvinylidene chloride (PVDC) copolymer laminates, and ionomer/ PA/EVA laminate films are used for vacuum packaging, particularly products like red meat. 

Early models used to describe the structure of ACs included the Franklin model itself (Fig. 2.5), and a ribbon-hke structure [89] somewhat similar to the Jenkins and Kawamura model for glass-like carbon (Fig. 2.17). Interestingly, these models were based on results obtained with polyvinylidene chloride (PVDC) (or Saran) char, a typical nongraphitizable material (unlike the well-known graphitizability of polyvinyl chloride [PVC] char). Various arguments have been used to criticize these and other models based on the occurrence of sp carbon besides sp carbon in nongraphitizable materials [10, 75]. 

Ban, L.L., Crawford, D., and Marsh, H. (1975). Lattice-resolution electron-microscopy in structural studies of non-graphitizing carbons from polyvinylidene chloride (PVDC). J. Appl. Cryst., 8, 415-20. 

This group covers polyvinyl chloride (PVC), polyvinylidene chloride (PVdC), polyvinyl acetate and polyvinyl alcohol, each of which has packaging applications. 

Polyvinylidene chloride (PVdC) (trade name Saran)... 

Polyvinylchloride (PVC) is commercially the most signihcant member of the family of vinyl resins. The other important members of this group are chlorinated-PVC (CPVC) and polyvinylidene chloride (PVDC). PVC is one of the most widely used, commodity type thermoplastics with an annual consumption of over 5 Mton/y in the USA. The excellent versatility of PVC is attributed to its blending capability with a variety of plasticizers, additives and fillers to yield products ranging from very flexible to very rigid types. In addition, PVC has a low cost advantage and a reasonably good balance of properties, which... 

Polyvinylidene chloride PVDC -CH2-CCI2- Ixan, Saran... 

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