Plasticizers, PVC

When blended with phthalate ester plasticizers, PVC becomes soft and pliable. 

PVC copolymers PVC foams P V C formulation PVC plasticizers PVC plastisols PVC resins... 

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. 

Poly(vinyl chloride). To be converted into film, poly(viayl chloride) [9002-86-22] (PVC) must be modified with heat stabilizers and plasticizers, which increase costs. Plasticized PVC film is highly transparent and soft, with a very high gas-permeation rate. Water-vapor transmission rate is relatively low. At present, PVC film is produced by blown-film extmsion, although casting and calendering are employed for heavier gauges (see Vinyl POLYAffiRS). 

Internal Plasticizers. There has been much dedicated work on the possibiUty of internally plasticized PVC. However, in achieving this by copolymerization significant problems exist (/) the affinity of the growing polymer chain for vinyl chloride rather than a comonomer implies that the incorporation of a comonomer into the chain requites significant pressure (2) since the use of recovered monomer in PVC production is standard practice, contamination of vinyl chloride with comonomer in this respect creates additional problems and (J) the increasing complexity of the reaction can lead to longer reaction times and hence increased costs. Thus, since standard external plasticizers are relatively cheap they are normally preferred. 

The role of specific interactions in the plasticization of PVC has been proposed from work on specific interactions of esters in solvents (eg, hydrogenated chlorocarbons) (13), work on blends of polyesters with PVC (14—19), and work on plasticized PVC itself (20—23). Modes of iateraction between the carbonyl functionaHty of the plasticizer ester or polyester were proposed, mostly on the basis of results from Fourier transform infrared spectroscopy (ftir). Shifts in the absorption frequency of the carbonyl group of the plasticizer ester to lower wave number, indicative of a reduction in polarity (ie, some iateraction between this functionaHty and the polymer) have been reported (20—22). Work performed with dibutyl phthalate (22) suggests an optimum concentration at which such iateractions are maximized. Spectral shifts are in the range 3—8 cm . Similar shifts have also been reported in blends of PVC with polyesters (14—20), again showing a concentration dependence of the shift to lower wave number of the ester carbonyl absorption frequency. 

Low Temperature Performance. The abihty of plasticized PVC to remain flexible at low temperatures is of great importance in certain apphcations, eg, external tarpaulins or underground cables. Eor this property the choice of the acid constituent of the plasticizer ester is also important. The linear aUphatic adipic, sebacic, and azeleic acids give excellent low temperature flexibiUty compared to the corresponding phthalates and trimeUitates (Pig. 3). 

Migration and Extraction. When plasticized PVC comes into contact with other materials, plasticizer may migrate from the plasticized PVC into the other material. The rate of migration depends not only on the plasticizer employed but also on the nature of the contact material. 

Emissions During Disposal and Incineration. The increasing use of modem incinerators to dispose of domestic waste results in complete combustion of plasticizers to carbon dioxide and water. The preponderance of plasticizer going into landfiUs is as plasticized PVC. Once a landfiU has been capped anaerobic conditions prevail and it is biologically relatively inactive. Under these conditions the main route by which organic components are removed from the landfiU contents is by ingress of water, extraction, and subsequent loss of water from the site to the environment. 

In plasticized PVC, Hquid plasticizers first fill the voids or pores in the PVC grains fairly rapidly during powder mixing. If a large amount of plasticizer is added, the excess plasticizer beyond the capacity of the pores initially remains on the surface of the grains, making the powder somewhat wet and sticky. Continued heating increases the diffusion rate of plasticizer into the PVC mass where the excess Hquid is eventually absorbed and the powder dries. 

Calcium—zinc stabilizers are used in both plasticized PVC and rigid PVC for food contact where it is desired to minimize taste and odor characteristics. AppHcations include meat wrap, water botdes, and medical uses. 

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

Electrical Applications. Plastics are used for electrical insulation, conduit and enclosures, lighting fixtures, and mechanical devices. The most widely used plastic for wire and cable insulation is flexible, plasticized PVC, which constitutes well over half the market in insulating wires for buildings, automobiles, appHances, and power and control lines. Polyethylene is also a factor. Higher performance plastics such as nylon and fluoropolymers also play a smaller role in this area. 

Plasticized PVC. Chlorinated paraffins are employed as secondary plasticizers with fire-retardant properties in PVC and can be used as partial replacements for primary plasticizers (qv) such as phthalates (1) and phosphate esters (2). 

The largest single market is the United States at approximately 40,000 t. Europe as a whole is approximately two and a half times greater than the United States mainly because of the extensive use of chlorinated paraffins as secondary plasticizers in plasticized PVC, which is virtually absent in the United States. 

Almost all PVC powder coatings are appHed by the fluidized-bed coating process. Although some electrostatic spray-grade formulations are available, they are very erratic in their appHcation characteristics. The resistivity of plasticized PVC powders is low compared to other powder coating materials and the appHed powder quickly loses its electrostatic charge. For the same reason, PVC powders show poor appHcation characteristics in an electrostatic fluidized bed and are seldom used in this process. 

Dry-Blending. Most plasticized PVC powders are prepared by a dry-blend process in which the plasticizers, stabilizers, pigments, and additives are absorbed on the porous PVC particles at elevated temperatures while they are being agitated in a high speed mixer. Thermosetting powders are almost never prepared by this process. 

Medium 20,000-50,000 4 Acrylic resins, plastics, PVC, ammonium chloride, DMT, copper compounds, lead Ferroalloys, fluorspar, nickel Iron, potash, glass-making mixtures... 

Vinyl chloride Power stations Chimneys Vehicle exhausts Plastic PVC pipes... 

In some cases, plasticization of a PSA may be detrimental to its performance. A well-known example is the deterioration of the performance of an adhesive applied to plasticized PVC. Migration of the plasticizer from the flexible vinyl into the PSA often softens the adhesive to the point where it fails cohesively from the vinyl, leaving sticky residue behind during removal of the adhesive-coated article from the substrate. One way to address this detrimental effect of plasticizer migration is to formulate an already plasticized PSA, perhaps because a better balance exists between the plasticizer in the PVC substrate and the PSA in contact with it [101]. 

Chlorinated rubber is also used to promote the adhesion of solvent-borne CR adhesives to metals and plasticized PVC. Addition of a low molecular weight chlorinated rubber (containing about 65 wt% chlorine) improves the shear strength and creep resistance of polychloroprene adhesives [75] but a reduction in open time is also produced. A heat reactivation (process in which the surface of the adhesive film is raised to 90-100°C to destroy the crystallinity of the film and allowing diffusion to produce polymer chain interlocking more rapidly) restores tack to the polychloroprene adhesives. 

Shoe adhesives. CR adhesives are used for the permanent attachment of shoe soles. For difficult-to-bond sole materials (plasticized PVC, EVA foaming soles, thermoplastic rubber, SBR) graft polymer solutions of Neoprene AD-G combined with a polyisocyanate provide a good adhesion. Another major area for CR contact adhesives is the manufacture of leather goods, particularly leather shoe sole bonding and belt lamination. 

The use of SPME for CE has not (yet) been studied widely. Li and Weber (170) reported an off-line SPME-CE approach for the determination of barbiturates in urine and serum, utilizing a sorbent of plasticized PVC coated around a stainless steel rod. Eor extraction, the coated rod was inserted for 4 min in a Teflon tube containing 50 p.1 of sample, and next the rod was repeatedly desorbed in another Teflon tube which each time contained 5 p.1 of desorption solution. This solution was transferred to an injection vial and an aliquot was injected into the CE system (Eigure 11.19). The extraction procedure appeared to be selective and effectively allowed the handling of very small samples. 

Extruded composites of plasticized PVC and short cellulose fibers have been investigated by Goettler [103]. Pronounced increases in tensile modulus, yield, and ultimate tensile strength are observed. Single step processing of reinforcement and polymer with good product performance are key characteristics of the material whose field of application lies in the vinyl hose industry. 

Such an experience with one plastic, PVC, makes it doubly important to carefully examine any plastic to be used with a food product. The basic question to be answered is Does the plastic container provide adequate protection to the food product during the entire life cycle of the container Adequate protection of a food product in a polyethylene container implies that there is no undesirable change in the chemical content of the food during storage in the container. Thus, our study is concerned with the ways in which food products can change when stored in polyethylene containers. 

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