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Polyvinyl chloride

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Polyvinyl chloride
Density1380 kg/m3
Young's modulus(E)2900-3400 MPa
Tensile strength(σt)50-80 MPa
Elongation @ break20-40%
notch test2-5 kJ/m2
Glass temperature87°C
melting point212°C
Vicat B185°C
heat transfer coefficient (λ)0.16 W/m.K
linear expansion coefficient (α)8 10-5 /K
Specific heat (c)0.9 kJ/kg.K
Water absorption (ASTM)0.04-0.4
Price0.5-1.25 €/kg
1 Deformation temperature at 10kN needle load
source: A.K. vam der Vegt & L.E. Govaert, Polymeren,
van keten tot kunstof, ISBN 90-407-2388-5

Polyvinyl chloride, (IUPAC Polychloroethane) commonly abbreviated PVC, is a widely-used plastic. In terms of revenue generated, it is one of the most valuable products of the chemical industry. Globally, over 50% of PVC manufactured is used in construction. As a building material, PVC is cheap and easy to assemble. In recent years, PVC has been replacing traditional building materials such as wood, concrete and clay in many areas. Despite appearing to be an ideal building material, concerns have been raised about the costs of PVC to the natural environment and human health (harmful chemical).

There are many uses for PVC including vinyl siding, magnetic stripe cards, window profiles, gramophone records, which is the source of the name for vinyl records, pipe, plumbing and conduit fixtures, bean bags; and, in its soft form, for clothing, upholstery, flooring, roofing membranes, electrical cables, and lightweight hobby artillery. The material is often used for pipelines in the water and sewer industries because of its inexpensive nature and flexibility.

Preparation

Polyvinyl chloride is produced by polymerization of the monomer vinyl chloride, as shown. PVC is a hard plastic that is made softer and more flexible by the addition of plasticizers, the most widely used being phthalates. 

    H        H                    H    H    H    H
     \      /                     |    |    |    |
      C == C          -->  ... -- C -- C -- C -- C -- ...
     /      \                     |    |    |    |
   Cl        H                    Cl   H    Cl   H

Vinyl chloride monomer       Polyvinyl chloride polymer

History

Polyvinyl chloride was accidentally discovered on at least two different occasions in the 19th century, first in 1835 by Henri Victor Regnault and in 1872 by Eugen Baumann. On both occasions, the polymer appeared as a white solid inside flasks of vinyl chloride that had been left exposed to sunlight. 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 blocked their efforts.

In 1926, Waldo Semon of B.F. Goodrich developed a method to plasticize PVC by blending it with various additives. The result was a more flexible and more easily processed material that soon achieved widespread commercial use.


Applications

Electric wires

PVC is commonly used as for the insulation on electric wires, the plastic used for this purpose needs to be plasticized. Sadly in a fire PVC coated wires can form HCl fumes.

Window frames

uPVC windows frames have been very popular in the UK. uPVC is Unplasticised PolyVinyl Chloride.

PVC pipes

Polyvinylchloride is also used for making pipes and other such uses.

Health and safety

Phthalate plasticizers

Many Vinyl products contain additional chemicals to change the chemical consistency of the product. Some of these additional chemicals called additives and plasticizers can leach out of vinyl products. Because soft PVC toys have been made for babies for years, there are concerns that these additives leach out of soft toys into the mouths of the children chewing on them. Vinyl IV bags used in neo-natal intensive care units have also been shown to leach DEHP (Bis(2-ethylhexyl) phthalate), a phthalate additive. In January 2006, the European Union placed a ban on six types of phthalate softeners in toys (See directive 2005/84/EC). In 2003, the US Consumer Product Safety Commission (CPSC) denied a petition for a similar ban in the United States[1]; however, in the USA most companies have voluntarily stopped manufacturing PVC toys for this age group or have eliminated the phthalates. In a draft guidance paper published in September 2002, the US FDA recognizes that many medical devices with PVC containing DEHP are not used in ways that result in significant human exposure to the chemical[2]. However, FDA is suggesting that manufacturers consider eliminating the use of DEHP in certain devices that can result in high aggregate exposures for sensitive patient populations such as neonates. However, alternative softeners have not been properly tested to determine whether they are more or less safe. Other vinyl products, including car interiors, shower curtains, flooring, etc., initially release chemical gases into the air. Some studies indicate that this outgassing of additives may contribute to health complications, but this information is preliminary and further study is needed.

According to some medical studies, the plasticizers added to PVC may cause chronic conditions such as scleroderma, cholangiocarcinoma, angiosarcoma, brain cancer, and acrosteolysis. PVC has been used for years and significant harms are being proven with regards to high levels or exposure to the chemical.

In 2004, a joint Swedish-Danish research team found a very strong link between allergies in children and the phthalates DEHP and BBzP, commonly used in PVC[1].

Alternative plasticisers are being developed but in many cases these alternatives remain significantly more expensive and their technical performance varies. IT is also worth noting that some, though not all, or the alternatives pose significant health risks.

One hospital network called the Catholic Healthcare West network, the 8th largest hospital network in the country, recently signed a contract with B.Braun for Vinyl free Intravenous(IV) bags and tubing.

Vinyl chloride monomer

In the late 1960s, Dr. John Creech and Dr. Maurice Johnson were the first to clearly link and recognize the carcinogenicity of vinyl chloride monomer to humans when workers in the polyvinyl chloride polymerization section of a B.F. Goodrich plant near Louisville, Kentucky, were diagnosed with liver angiosarcoma, a rare disease.[2] Since that time, studies of PVC workers in Australia, Italy, Germany, and the U.K. have all associated certain types of occupational cancers with exposure to vinyl chloride. The link between angiosarcoma of the liver and long-term exposure to vinyl chloride is the only one which has been confirmed by the International Agency for Research on Cancer. All the cases of angiosarcoma developed from exposure to vinyl chloride monomer, were in workers who were exposed to very high VCM levels, routinely, for many years.

According to the EPA, "vinyl chloride emissions from polyvinyl chloride (PVC), ethylene dichloride (EDC), and vinyl chloride monomer (VCM) plants cause or contribute to air pollution that may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible, or incapacitating reversible illness. Vinyl chloride is a known human carcinogen which causes a rare cancer of the liver."[3]

A front-page series in the Houston Chronicle claimed the vinyl industry has manipulated vinyl chloride studies to avoid liability for worker exposure and to hide extensive and severe chemical spills into local communities.[4]

Dioxins

The environmentalist group Greenpeace has advocated the global phase-out of PVC because they claim dioxin is produced as a byproduct of vinyl chloride manufacture and from incineration of waste PVC in domestic garbage. The European Industry, however, asserts that it has improved production processes to minimize dioxin emissions.

Vinyl chloride production is inherently a source of dioxins, a highly toxic substance that can cause cancer and other illnesses in humans even at very low exposure levels. Dioxins are a global health threat because they persist in the environment and can travel long distances. At very low levels, near those to which the general population is exposed, dioxins have been linked to immune system suppression, reproductive disorders, a variety of cancers, and endometriosis. According to a 1994 report by the British firm, ICI Chemicals & Polymers Ltd., "It has been known since the publication of a paper in 1989 that these oxychlorination reactions [used to make vinyl chloride and some chlorinated solvents] generate polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). The reactions include all of the ingredients and conditions necessary to form PCDD/PCDFs.... It is difficult to see how any of these conditions could be modified so as to prevent PCDD/PCDF formation without seriously impairing the reaction for which the process is designed." In other words, dioxins are an unavoidable consequence of making PVC. Dioxins created by vinyl chloride production are released by on-site incinerators, flares, boilers, wastewater treatment systems and even in trace quantities in vinyl resins.[5]

Dioxins are formed in virtually all combustion where the necessary atoms are available in the fuel. The formation of dioxins (and furans) requires presence of chlorine, heat, organic compounds and a catalyst. PVC can be a ready source for the chlorine in combustion for this process.

The largest well quantified source of dioxin in the US EPA inventory of dioxin sources is barrel burning of household waste.[6] Studies of household waste burning indicate consistent increases in dioxin generation with increasing PVC concentrations.[7] According to the EPA dioxin inventory, landfill fires, are likely to represent an even larger source of dioxin to the environment. A survey of international studies consistently identify high dioxin concentrations in areas affected by open waste burning and a study that looked at the homologue pattern found the sample with the highest dioxin concentration was “typical for the pyrolysis of PVC”. Other EU studies indicate that PVC likely “accounts for the overwhelming majority of chlorine that is available for dioxin formation during landfill fires.”[8]

The next largest sources of dioxin in the EPA inventory are medical and municipal waste incinerators. Studies have shown a clear correlation between dioxin formation and chloride content and indicate that PVC is a significant contributor to the formation of both dioxin and PCB in incinerators.[9]

Resin identification code

The symbol for polyvinyl chloride developed by the Society of the Plastics Industry so that items can be labelled for easy recycling is: File:Recycle-resin-logos-lr 03.png

The Unicode character for PVC is U+2675 (HTML ♵).

PVC is not typically recycled due to the prohibitive cost of regrinding and recompounding the resin compaired to the cost of virgin (unrecycled) resin.

References

  1. ^ Bornehag; et al. (2004). "The Association Between Asthma and Allergic Symptoms in Children and Phthalates in House Dust: A Nested Case-Control Study". Environmental Health Perspectives. 112 (14): 1393–1397. {{cite journal}}: Explicit use of et al. in: |author= (help)
  2. ^ Creech and Johnson (1974). "Angiosarcoma of liver in the manufacture of polyvinyl chloride.". Journal of occupational medicine. : official publication of the Industrial Medical Association. 16 (3): 150–1. {{cite journal}}: Unknown parameter |month= ignored (help)
  3. ^ National Emission Standards for Hazardous Air Pollutants (NESHAP) for Vinyl Chloride Subpart F, OMB Control Number 2060-0071, EPA ICR Number 0186.09 (Federal Register: September 25 2001 (Volume 66, Number 186))
  4. ^ Jim Morris, "In Strictest Confidence . The chemical industry's secrets," Houston Chronicle. Part One: "Toxic Secrecy," June 28 1998, pgs. 1A, 24A-27A; Part Two: "High-Level Crime," June 29 1998, pgs. 1,A, 8A, 9A; and Part Three: "Bane on the Bayou," July 26 1998, pgs. 1A, 16A.]
  5. ^ Pat Costner etal, "PVC: A Primary Contributor to the U.S. Dioxin Burden; Comments submitted to the U.S. EPA Dioxin Reassessment," (Washington, D.C. Greenpeace U.S.A., February 1995
  6. ^ The Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States: The Year 2000 Update, March 2005
  7. ^ Costner, Pat, (2005), ” Estimating Releases and Prioritizing Sources in the Context of the Stockholm Convention”, International POPs Elimination Network, Mexico.
  8. ^ Costner 2005
  9. ^ Katami, Takeo, et al (2002) “Formation of PCDDs, PCDFs, and Coplanar PCBs from Polyvinyl Chloride during Combustion in an Incinerator” Environ. Sci. Technol., 36, 1320-1324. and Wagner, J., Green, A. 1993. Correlation of chlorinated organic compound emissions from incineration with chlorinated organic input. Chemosphere 26 (11): 2039-2054. and Thornton, Joe (2002) “Environmental Impacts of polyvinyl Chloride Building Materials, Healthy Building Network, Washington, DC.

Films

  • Blue Vinyl (2002). Directed by Daniel B. Gold and Judith Helfand.

See also

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