A | B | C | D | E | F | G | H | CH | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
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| Names | |
|---|---|
| IUPAC name
poly(1-chloroethylene)[1]
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| Other names
Polychloroethene
| |
| Identifiers | |
| Abbreviations | PVC |
| ChEBI | |
| ChemSpider |
|
| ECHA InfoCard | 100.120.191 |
| KEGG | |
| MeSH | Polyvinyl+Chloride |
CompTox Dashboard (EPA)
|
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| Properties | |
| (C2H3Cl)n[2] | |
| Appearance | white, brittle solid |
| Odor | odorless |
| Density | 1.4 g/cm3 |
| insoluble | |
| Solubility in ethanol | insoluble |
| Solubility in tetrahydrofuran | slightly soluble |
| −10.71×10−6 (SI, 22 °C)[3] | |
| Hazards | |
| NFPA 704 (fire diamond) | |
Threshold limit value (TLV)
|
10 mg/m3 (inhalable), 3 mg/m3 (respirable) (TWA) |
| NIOSH (US health exposure limits):[4] | |
PEL (Permissible)
|
15 mg/m3 (inhalable), 5 mg/m3 (respirable) (TWA) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
| |
| Elongation at break | 20–40% |
|---|---|
| Notch test | 2–5 kJ/m2 |
| Glass Transition Temperature | 82 °C (180 °F)[5] |
| Melting point | 100 °C (212 °F) to 260 °C (500 °F)[5] |
| Effective heat of combustion | 17.95 MJ/kg |
| Specific heat (c) | 0.9 kJ/(kg·K) |
| Water absorption (ASTM) | 0.04–0.4 |
| Dielectric Breakdown Voltage | 40 MV/m |
Polyvinyl chloride (alternatively: poly(vinyl chloride),[6][7] colloquial: vinyl[8] or polyvinyl; abbreviated: PVC[8]) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons of PVC are produced each year.[9]
PVC comes in rigid (sometimes abbreviated as RPVC) and flexible forms. Rigid PVC is used in construction for pipes, doors and windows. It is also used in making plastic bottles, packaging, and bank or membership cards. Adding plasticizers makes PVC softer and more flexible. It is used in plumbing, electrical cable insulation, flooring, signage, phonograph records, inflatable products, and in rubber substitutes.[10] With cotton or linen, it is used in the production of canvas.
Polyvinyl chloride is a white, brittle solid. It is insoluble in all solvents but swells in its monomer and some chlorinated hydrocarbon solvents.
Discovery
PVC was synthesized in 1872 by German chemist Eugen Baumann after extended investigation and experimentation.[11] The polymer appeared as a white solid inside a flask of vinyl chloride that had been left on a shelf sheltered from sunlight for four weeks. In the early 20th century, the Russian chemist Ivan Ostromislensky and Fritz Klatte of the German chemical company Griesheim-Elektron both attempted to use PVC in commercial products, but difficulties in processing the rigid, sometimes brittle polymer thwarted their efforts. Waldo Semon and the B.F. Goodrich Company developed a method in 1926 to plasticize PVC by blending it with various additives,[12] including the use of dibutyl phthalate by 1933.[13]
Production
Polyvinyl chloride is produced by polymerization of the vinyl chloride monomer (VCM), as shown.[14]
|
About 80% of production involves suspension polymerization. Emulsion polymerization accounts for about 12%, and bulk polymerization accounts for 8%. Suspension polymerization produces particles with average diameters of 100–180 μm, whereas emulsion polymerization gives much smaller particles of average size around 0.2 μm. VCM and water are introduced into the reactor along with a polymerization initiator and other additives. The contents of the reaction vessel are pressurized and continually mixed to maintain the suspension and ensure a uniform particle size of the PVC resin. The reaction is exothermic and thus requires cooling. As the volume is reduced during the reaction (PVC is denser than VCM), water is continually added to the mixture to maintain the suspension.[9]
PVC may be manufactured from ethylene, which can be produced from either naphtha or ethane feedstock.[15]
Microstructure
The polymers are linear and are strong. The monomers are mainly arranged head-to-tail, meaning that chloride is located on alternating carbon centres. PVC has mainly an atactic stereochemistry, which means that the relative stereochemistry of the chloride centres are random. Some degree of syndiotacticity of the chain gives a few percent crystallinity that is influential on the properties of the material. About 57% of the mass of PVC is chlorine. The presence of chloride groups gives the polymer very different properties from the structurally related material polyethylene.[16] At 1.4 g/cm3, PVC's density is also higher than structurally related plastics such as polyethylene (0.88–0.96 g/cm3) and polymethylmethacrylate (1.18 g/cm3).
Producers
About half of the world's PVC production capacity is in China, despite the closure of many Chinese PVC plants due to issues complying with environmental regulations and poor capacities of scale. The largest single producer of PVC as of 2018 is Shin-Etsu Chemical of Japan, with a global share of around 30%.[15]
Additives
The product of the polymerization process is unmodified PVC. Before PVC can be made into finished products, it always requires conversion into a compound by the incorporation of additives (but not necessarily all of the following) such as heat stabilizers, UV stabilizers, plasticizers, processing aids, impact modifiers, thermal modifiers, fillers, flame retardants, biocides, blowing agents and smoke suppressors, and, optionally, pigments.[17] The choice of additives used for the PVC finished product is controlled by the cost performance requirements of the end use specification (underground pipe, window frames, intravenous tubing and flooring all have very different ingredients to suit their performance requirements). Previously, polychlorinated biphenyls (PCBs) were added to certain PVC products as flame retardants and stabilizers.[18]
Plasticizers
Among the common plastics, PVC is unique in its acceptance of large amounts of plasticizer with gradual changes in physical properties from a rigid solid to a soft gel,[19] and almost 90% of all plasticizer production is used in making flexible PVC.[20][21] The majority is used in films and cable sheathing.[22] Flexible PVC can consist of over 85% plasticizer by mass, however unplasticized PVC (UPVC) should not contain any.[23]
| Plasticizer content (% DINP by weight) | Specific gravity (20 °C) | Shore hardness (type A, 15 s) |
Flexural stiffness (Mpa) | Tensile strength (Mpa) | Elongation at break (%) | Example applications | |
|---|---|---|---|---|---|---|---|
| Rigid | 0 | 1.4 | 900 | 41 | <15 | Unplasticized PVC (UPVC): window frames and sills, doors, rigid pipe | |
| Semi-rigid | 25 | 1.26 | 94 | 69 | 31 | 225 | Vinyl flooring, flexible pipe, thin films (stretch wrap), advertising banners |
| Flexible | 33 | 1.22 | 84 | 12 | 21 | 295 | Wire and cable insulation, flexible pipe |
| Very Flexible | 44 | 1.17 | 66 | 3.4 | 14 | 400 | Boots and clothing, inflatables, |
| Extremely Flexible | 86 | 1.02 | < 10 | Fishing lures (soft plastic bait), polymer clay, plastisol inks |
Phthalates
The most common class of plasticizers used in PVC is phthalates, which are diesters of phthalic acid. Phthalates can be categorized as high and low, depending on their molecular weight. Low phthalates such as Bis(2-ethylhexyl) phthalate (DEHP) and Dibutyl phthalate (DBP) have increased health risks and are generally being phased out. High-molecular-weight phthalates such as diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) are generally considered safer.[21]
While DEHP has been medically approved for many years for use in medical devices, it was permanently banned for use in children's products in the US in 2008 by US Congress;[24] the PVC-DEHP combination had proved to be very suitable for making blood bags because DEHP stabilizes red blood cells, minimizing hemolysis (red blood cell rupture). However, DEHP is coming under increasing pressure in Europe. The assessment of potential risks related to phthalates, and in particular the use of DEHP in PVC medical devices, was subject to scientific and policy review by the European Union authorities, and on 21 March 2010, a specific labeling requirement was introduced across the EU for all devices containing phthalates that are classified as CMR (carcinogenic, mutagenic or toxic to reproduction).[25] The label aims to enable healthcare professionals to use this equipment safely, and, where needed, take appropriate precautionary measures for patients at risk of over-exposure[26]
phthalate.svg)
Metal stabilizers
BaZn stabilisers have successfully replaced cadmium-based stabilisers in Europe in many PVC semi-rigid and flexible applications.[27]
In Europe, particularly Belgium, there has been a commitment to eliminate the use of cadmium (previously used as a part component of heat stabilizers in window profiles) and phase out lead-based heat stabilizers (as used in pipe and profile areas) such as liquid autodiachromate and calcium polyhydrocummate by 2015. According to the final report of Vinyl 2010,[28] cadmium was eliminated across Europe by 2007. The progressive substitution of lead-based stabilizers is also confirmed in the same document showing a reduction of 75% since 2000 and ongoing. This is confirmed by the corresponding growth in calcium-based stabilizers, used as an alternative to lead-based stabilizers, more and more, also outside Europe.[9]
Heat stabilizers
Some of the most crucial additives are heat stabilizers. These agents minimize loss of HCl, a degradation process that starts above 70 °C (158 °F) and is autocatalytic. Many diverse agents have been used including, traditionally, derivatives of heavy metals (lead, cadmium). Metallic soaps (metal "salts" of fatty acids such as calcium stearate) are common in flexible PVC applications.[9]
Properties
PVC is a thermoplastic polymer. Its properties are usually categorized based on rigid and flexible PVCs.[29]