Flexible PVC

In 1965, Scientific Oil and Chemical Company Inc. introduced the first preservative designed specifically for plastics preservation, 10, lO -oxybisphenoxarsine (OBPA) [II, 19.1.]. The initial product was a 1% solution in epoxidized soybean oil. The early products were particularly designed for flexible PVC applications. Over the years additional products have been developed with up to 5% OBPA in liquid solutions. In 1976, solid resin concentrates of OBPA were introduced. These products have improved handling convenience. The first isothiazoline, 2-n-octyl-4-isothiazolin-3-one (OIT) [II, 15.4.], was registered for use as an antimicrobial for plastic in 1973. 

In recent years, the predominant antimicrobials for plastics include a wide variety of different chemical types. The leading antimicrobials currently being used in plastics include  

Other antimicrobial agents that find some use in specialty applications in plastics include  

Silver technologies (glass, zeolite, ceramic, inorganic carriers) 

Many types of plastics can benefit from antimicrobial treatment. Flexible PVC is the primary plastic that is treated with antimicrobial. Other polymer systems treated with biocides include polyurethanes, polyolefins, polyamides, polysulfones, and styrenics. 

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Flexible PVC Flexible wear lenses Flexicoker Flexicoking... 

Almost all of the OX that is recovered is used to produce phthaUc anhydride. PhthaUc anhydride is a basic building block for plasticizers used in flexible PVC resins, for polyester resins used in glass-reinforced plastics, and for alkyd resins used for surface coatings. OX is also used to manufacture phthalonitrile, which is converted to copper phthalocyanine, a pigment. 

Table 8. Flammability of Flame-Retardant-Treated Flexible PVC ...

Table 9. Oxygen Index of Flexible PVC Containing Antimony and Boron...

Molybdenum Oxide. Molybdenum compounds incorporated into flexible PVC not only increase flame resistance, but also decrease smoke evolution. In Table 10 the effect of molybdenum oxide on the oxygen index of a flexible PVC containing 50 parts of a plasticizer is compared with antimony oxide. Antimony oxide is the superior synergist for flame retardancy but has Httle or no effect on smoke evolution. However, combinations of molybdenum oxide and antimony oxide may be used to reduce the total inorganic flame-retardant additive package, and obtain improved flame resistance and reduced smoke. 

Zinc Sta.nna.tes, The zinc staimates are also effective synergists for flexible PVC however, as shown in Figure 4a, antimony oxide is more effective. If more chlorine such as in a chlorinated paraffin such as Cereclor is added, then the staimates become more effective and eventually outperform antimony oxide (Fig. 4b). 

Alumina Trihydrate. Alumina trihydrate is usually used as a secondary flame retardant in flexible PVC because of the high concentration needed to be effective. As a general rule the oxygen index of flexible poly(vinyl chloride) increases 1% for every 10% of alumina trihydrate added. The effect of alumina trihydrate on a flexible poly(vinyl chloride) formulation containing antimony oxide is shown in Figure 5. 

Fig. 5. Effect of alumina trihydrate on the oxygen index of flexible PVC (30) having 5 phr Tribase XL, 3 phr Sb202, 0.05 phr petroleum wax, and (—...

RigidPoly(vinylchloride) Foam. The techniques that have been used to produce rigid vinyl foams are similar to those for the manufacture of flexible PVC foams. The two processes that have reached commercial importance for the manufacture of rigid vinyl foams (246) are the Dynamit-Nobel extmsion process and the Kleber-Colombes Polyplastique process for producing cross-linked grafted PVC foams from isocyanate-modified PVC in a two-stage mol ding process. 

Economics. The price of mbber modified flexible PVC foam ranges between about 2.00 to 3.00 per board foot ( 800—1200/m ) and that of unmodified, plasticized PVC foam is about 0.70 to 2.50 per board foot ( 300— 1000/m ) depending on the volume, thickness, and density of the product. 

The basic metal salts and soaps tend to be less cosdy than the alkyl tin stabilizers for example, in the United States, the market price in 1993 for calcium stearate was about 1.30— 1.60, zinc stearate was 1.70— 2.00, and barium stearate was 2.40— 2.80/kg. Not all of the coadditives are necessary in every PVC compound. Typically, commercial mixed metal stabilizers contain most of the necessary coadditives and usually an epoxy compound and a phosphite are the only additional products that may be added by the processor. The requited costabilizers, however, significantly add to the stabilization costs. Typical phosphites, used in most flexible PVC formulations, are sold for 4.00— 7.50/kg. Typical antioxidants are bisphenol A, selling at 2.00/kg Nnonylphenol at 1.25/kg and BHT at 3.50/kg, respectively. Pricing for ESO is about 2.00— 2.50/kg. Polyols, such as pentaerythritol, used with the barium—cadmium systems, sells at 2.00, whereas the derivative dipentaerythritol costs over three times as much. The P-diketones and specialized dihydropyridines, which are powerful costabilizers for calcium—zinc and barium—zinc systems, are very cosdy. These additives are 10.00 and 20.00/kg, respectively, contributing significantly to the overall stabilizer costs. Hydrotalcites are sold for about 5.00— 7.00/kg. 

In a flexible PVC compound, ingredients in the recipe are chosen based on cost and/or thein contribution to physical and other properties and performance. Typical ingredients (16,17) are stabilizers, fillers, plasticizers, colorants, and lubricants. 

Plasticizers. Monomeric (mol wt 250—450) plasticizers (qv) are predominantiy phthalate, adipate, sebacate, phosphate, or trimeUitate esters. Organic phthalate esters like dioctyl phthalate (DOP) are by far the most common plasticizers in flexible PVC. Phthalates are good general-purpose plasticizers which impart good physical and low temperature properties but lack permanence in hot or extractive service conditions and are therefore sometimes called migratory plasticizers. Polymeric plasticizers (mol wt up to 5000 or more) offer an improvement in nonmigratory permanence at a sacrifice in cost, low temperature properties, and processibiHty examples are ethylene vinyl acetate or nitrile polymers. 

Fillers. These are used to reduce cost in flexible PVC compounds. It is also possible to improve specific properties such as insulation resistance, yellowing in sunlight, scuff resistance, and heat deformation with the use of fillers (qv). Typical filler types used in PVC are calcium carbonate, clays, siHca, titanium dioxide, and carbon black. 

Secondary Plasticizers. Also known as extenders, secondary plasticizers continue to play a significant role ia flexible PVC formulations. They do not impart flexibiHty to the PVC resia alone, but when combiaed with a primary plasticizer act ia such a way as to add flexibiHty to the final product. 

The dry blend can also be extmded and the extmdate chipped to produce pellets of PVC compound which can then be subsequendy reprocessed to produce the final product. This has the benefit of ease of storage of raw materials since all the formulation ingredients are contained bound in the gelled compound. Many producers of flexible PVC only purchase PVC compound, and many companies exist solely to produce PVC compound rather than a tme end product such as sheet, flooring, or pipe. 

A change in plasticizer affects the properties of a flexible PVC article. Certain properties are more important for some apphcations than others and hence some plasticizers find more extensive use in some application areas than others. The PVC technologist must ascertain the most important properties for an application and then make the correct choice of plasticizer. 

Fig. 2. Volatile loss of plasticizers from flexible PVC (BSS 35) where M represents Cg [...

The widespread usage of phthalates in flexible PVC has resulted in many investigations being made of their concentration in the environment. Unfortunately the ubiquitous presence of phthalates in laboratory chemicals and equipment has caused problems in the analysis of very low concentrations of phthalates in environmental samples and has led to erroneously high levels being reported. 

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Emissions During Processing. During the production of flexible PVC products plasticizers are exposed for up to several minutes to temperatures of - ISO C. The exact conditions depend on the processing technique employed, but it is evident that the loss of plasticizer by evaporation and degradation can be significant. 

Table 6. Air Treatment in Flexible PVC Processing Plants in Western Europe, 1991...

Emissions During Exterior End Use. When flexible PVC is used in exterior appHcations plasticizer loss may occur due to a number of processes which include evaporation, microbial attack, hydrolysis, degradation, exudation, and extraction. It is not possible, due to this wide variety of contribution processes, to assess theoretically the rate of plasticizer loss by exposure outdoors. It is necessary, therefore, to carry out actual measurements over extended periods in real life situations. Litde suitable data have been pubHshed with the exception of some studies on roofing sheet (47). The data from roofing sheet has been used to estimate the plasticizer losses from all outdoor appHcations. This estimate may weU be too high because of the extrapolation involved. Much of this extracted plasticizer does not end up in the environment because considerable degradation takes place during the extraction process. 

Ref. 136. LDPE = low density polyethylene HDPE = high density polyethylene PP = polypropylene PS = polystyrene EPVC = flexible PVC ... 

The majority (92% in 1988) of the butyraldehyde produced in the United States is converted into 1-butanol and 2-ethyIhexanol (2-EH). 2-EH is most widely used as the di(2-ethylhexyl) phthalate [117-81-7] ester for the plasticisation of flexible PVC. Other uses for 2-EH include production of intermediates for acryflc surface coatings, diesel fuel, and lube oil additives (24). 

Plastics and Synthetic Products. To prevent degradation of plastics at elevated processing temperatures, it is necessary to use suitable heat stabilizers. Eor example, flexible poly(vinyl chloride) (PVC) manifests uncontroUed color development in the absence of stabilizers. Accordingly, cadmium salts of organic acids are typically used in a synergistic combination with corresponding barium salts, in about a 1 3 cadmium barium ratio, to provide a cost-competitive heat stabilizer for flexible PVC. 

Table 13.15 Current rating and technical data for 1100 V, single-core flexible, PVC insulated copper conductor cables for control and power wiring...

Figure 27.8. Typical load-deflection curves for (a) latex, (b) flexible PVC, (c) polyester polyurethane (curve C) and polyether polyurethane foams (curve D). Shell Chemical Co.)...

Membranes are applied directly to the metal or concrete surface to protect from corrosion by any liquor that penetrates the brick lining through pores and cracks. Membranes consist of sheet material bonded to the metal or concrete, e.g., flexible PVC sheet, or it may be formed in situ (e.g., polyester resin reinforced with glass fiber, or synthetic rubber sheet, lead, polyisobutylene, polyethylene and asphalt). 

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