Polyvinylidene chloride properties

Certain copolymers of this type have been found to have excellent gas barrier properties, with the dry polymer having an oxygen permeability only about 1/lOth that of polyvinylidene chloride. Unsurprisingly, the copolymer has a high moisture absorption and a high moisture vapour transmission rate. Where the material is swollen by water, gas permeability is also higher. 

Carbonized Resins. A special sorbent made by controlled thermal pyrolysis of polyvinylidene chloride (Dow developmental Adsorbent XF-4175L) (34) was shown to be three to five times more effective for the collection of highly volatile compounds, such as vinyl chloride (Figure 5) and methyl chloride, than the best available activated charcoal (31,36,37). Although this sorbent is not commercially available, Carbosive and Carbosive S show similar collection properties and they are available from gas chromatographic supply houses or may be obtained already packed in small collection tubes (SKC Inc., Eighty Four, PA). 

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). 

Barrier Plastics. When plastics replace metals and glass in packaging, their permeability is often a limiting property. Barrier performance generally increases with density and crystallinity. The most promising barrier plastics include ethylene/vinyl alcohol, polyvinylidene chloride, polyacrylonitrile, and polyethylene naphthoate. These are used most efficiently by laminating them to commodity plastics such as polyethylene and polyethylene terephthalate. 

This is made by the reaction of strong nitric acid with cellulose. Today it is mainly used as a coating to provide heatsealing with general barrier properties. It seals at a lower temperature than polyvinylidene chloride, but for the same coating weight offers a considerably inferior barrier. It is highly flammable. 

There are two polymers used in a maj ority ofhigh barrier food packages copolymers containing polyvinylidene chloride (Saran ) and ethylene-vinyl alcohol copolymer (Eval, Selar-OH ). Packages in which either polyvinylidene chloride or ethylene-vinyl alcohol copolymer (EvOH) provide the barrier are invariably multilayer since neither of these materials offers the properties required to make a good monolayer structure. There are advantages and disadvantages associated with each of these materials, and the... 

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... 

The development of hollow thermoplastic microspheres has offered the prospect of lower density plastisols with superior physical properties and appearance than have been attainable by other known techniques. Such microspheres have become available, having, for example, diameters on the order of 10 to 200 im, most often 20 to 100 pm, and densities of 0.06 to 0.02 g/cm, or even as low as 0.015 g/cm. The thermoplastic material of which the microspheres are formed is typically a polyvinylidene chloride or a copolymer of polyvinylidene chloride with other vinyl or acrylic monomers, such as acrylonitrile, butylene, and the like. The hollow microspheres contain a physical blowing agent, typically a lower alkane, most often a butane or pentane, or their mixtures. A variety of such materials are commercially available. 

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. 

Polyvinylidene Chloride Stereoregular thermoplastic polymer of vinylidene chloride has good abrasion and chemical resistance and barrier properties. Vinylidene chloride (VDC) content always exceeds 50%. Proeessed by molding and extrusion. Used in food paekaging films, bag liners, pipes, upholstery, fibers, and eoatings. Also called PVDC. 

More or less the same process as used for polyvinylidene chloride film can be applied to polypropylene, which also shows this self-stabilising property. In order to reduce the crystallinity of the unstretched film, internal cooling of the balloon by cold mandrels and (or) external cooling by water sprays is necessary. 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

High barrier polymers, such as polyvinylidene chloride (PVDC), polyacrylonitrile (PAN), polyester, acid copolymers and ionomers have been proposed and are under evaluation as a replacement for PE. However, they present some drawbacks in terms of scalability and/or mechanical properties and/or outgassing rates. Cost of these polymers is also generally higher. 

Regenerated cellulose film, cellophane, can be cast from the solution of cellulose xanthate formed through the viscose process after which the film is subsequently hydrolyzed back to cellulose. Since the end product is essentially cellulose, it is readily biodegradable [11], Cellophane is typically plasticized with ethylene glycol, propylene glycol, or glycerol. To improve the barrier properties, cellophane is often coated with polyvinylidene chloride, which would hinder the biodegradability. 

In 2004, the Saran brand changed to using LDPE due to enviTonmental concerns with polyvinylidene chloride (PVDC) despite the excellent barrier properties of the latter, not matched by the LDPE film. Coltro et al., in a 2014 study, stdl found some commercial cling films containing phthalates. 

Latex adhesives, of which there are many types (Nitrile rubber adhesives (NBR), SBR, Ethylene-vinyl acetate copolymers, acrylics, polyvinylidene chloride, etc.), should ideally be cross-linkable (for wash and dry-clean resistance), preferably with a low cure (reaction) temperature (see Reaction setting adhesives), as some fibres, such as polypropylene, may be damaged by high temperatures. The binder (adhesive) type can markedly affect physical properties and performance the amount of hard and soft polymer in the binder controls the sofmess of the finished product. Most binders impart adequate dry-state adhesion and so the choice of adhesive is usually governed by secondary requirements such as the method and conditions of application and costs. 

Saran is the trademark of Dow Chemical for their proprietary polyvinylidene chloride resin. It has a maximum allowable operating temperature of 175°F/81°C. It is used to line piping as well as vessels. Refer to Table 3.13 for the physical and mechanical properties of Saran. 

Table 3.13 Physical and Mechanical Properties of Polyvinylidene Chloride...

Polyvinylidene chloride (PVDC), a polymer formed from CH2=CCl2, is diiScult to formulate and is not used for any type of product by itself. It is usually manufactured as a copolymer with various monomers, including acrylonitrile, vinyl chloride, acrylic esters, or methacrylic esters. A unique property of PVDC copolymers is to prevent water and gases from diffusing through the film. In this way, PVDC copolymer films provide a vapor barrier, and are commonly used to wrap foods for storage. The commercial name Saran refers to both the PVDC homopolymer and its copolymers. Reference Spectrum 22 provides the IR and Raman spectra of a vinylidene... 

Polymer electrolyte is composed of polymer substrate and metal salt. Possible polymer substrates include polyethylene oxide, poly vinylidene fluoride, poly(methyl methacrylate), polyvinylidene chloride, and polyacrylonitrile. Examples of cations of metal salt are li, Na, K, and Mg. Possible anions are BF, SCN, SO3CF3, AsF PF and NfCFjSOj). An inorganic modifier such as nanopartide Ti02 can be added to increase mechanical properties of supercapadtor. Mass is divided so that polymer substrate is 30 to 90 wt%, metal salt is to 2 to 30 wt%, and nanotube modifier is 3 to 30 wt%. 

The mechanical properties of protein-based materials are substantially lower than those of standard synthetic materials, such as polyvinylidene chloride (PVDC) or polyester (Table 11.11). The mechanical properties of protein-based materials were measured and modelled as a function of film characteristics [74, 131, 132]. For stronger materials (e.g., based on wheat gluten, corn gluten and myofibrillar proteins, critical deformation (DC) = 0.7 mm) and elastic modulus (K = 510 N/m) values are slightly lower than those of reference materials such as LDPE (DC = 2.3 mm, K = 135 N/m), cellulose (DC = 3.3 mm, K = 350 N/m) or even PVC films. The mechanical properties of corn gluten-based material are close to those of PVC. 

Among the additives used to modify the properties of polymeric packaging materials, plasticisers have raised much concern from the hygienic point of view. Butyl stearate, acetyltributyl citrate, alkyl sebacates and adipates are important because they are types of plasticisers that typically have low toxicities. Materials such as epoxidised soybean oil are widely used in polyvinyl chloride, polyvinylidene chloride and polystyrene as thermal stabilisers and lubricants at a level of 0.1-27%. Toxicity of epoxidised soybean oil is affected by the presence of oxirane, also known as ethylene oxide, which was upgraded to Group 1 as a carcinogenic agent to humans, based on mechanistic and other relevant data. 

---