| Polyvinyl Chloride |
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Polyvinyl chloride, ( IUPAC Polychloroethene) commonly abbreviated '''PVC''', is a widely used Thermoplastic Polymer . 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 Material s such as Wood , Concrete and Clay in many areas. Despite appearing to be an ideal building material, concerns were raised about the costs of PVC to the Natural Environment and Human Health . There are many uses for PVC. As a hard plastic, it is used as Vinyl Siding , Magnetic Stripe Card s, window profiles, Gramophone Record s (which is the source of the name for Vinyl Record s), Pipe , Plumbing and Conduit fixtures. The material is often used in Plastic Pressure Pipe Systems for Pipelines in the Water and Sewer industries because of its inexpensive nature and flexibility. PVC pipe plumbing is typically white, as opposed to ABS , which is commonly available in grey as well as white. It can be made softer and more flexible by the addition of Plasticizer s, the most widely used being Phthalates . In this form, it is used in Clothing and Upholstery , and to make flexible Hose s and tubing, Flooring , to roofing membranes, and electrical cable insulation. PREPARATION Polyvinyl chloride is produced by polymerization of the Monomer Vinyl Chloride , as shown. Since a significant proportion of its mass is Chlorine , creating a given mass of PVC requires less petroleum than many other polymers. 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 (Polyvinyl Chloride) 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 the insulation on electric wires; the plastic used for this purpose needs to be (low-smoke, zero-halogen) cable insulation is used. The applicable Building Code should be consulted to determine the type of electrical wires approved for the intended use. Pipes Polyvinyl chloride is also widely used for producing pipes. In the water distribution market it accounts for 66 percent of the market in the US, and in sanitary sewer pipe applications, it accounts for 75 percent.(http://www.vinylbydesign.com/site/page.asp?CID=14&DID=15) In February 2007, the California Building Standards Code was updated to approve the use of Chlorinated Polyvinyl Chloride (CPVC) pipe for use in residential water supply piping systems. CPVC has been a nationally accepted material in the US since 1982; however, California has only permitted its use on a limited basis since 2001. The Department of Housing and Community Development prepared and certified an Environmental Impact Report resulting in a recommendation that the Commission adopt and approve the use of CPVC. The Commission's vote was unanimous and CPVC will be placed in the 2007 California Plumbing Code.(http://www.bsc.ca.gov/documents/PR07-02_final__pics.pdf) Signs In flat sheet form, Polyvinyl chloride is formed in a variety of thicknesses and colors. As flat sheets, PVC is often expanded to create voids in the material, providing additional thickness without additional weight and cost. Sheets are cut using saw and rotary cutting equipment (see CNC ). PVC is also used to produce thin, colored, adhesive backed films referred to simply as vinyl. These films are typically cut on a computer controlled Plotter . These sheets and films are used to produce a wide variety of Commercial Signage products. Unplasticized polyvinyl chloride (uPVC) " house with uPVC gutters and downpipes, fascia, decorative imitation " Half-timber ing", windows and doors.]] uPVC or Rigid PVC is often used in the building industry as a low maintenance material, particularly in the s and Sill s when installing Double Glazing in new buildings or to replace older single glazed windows. It has many other uses including Fascia , and Siding or Weatherboarding . The same material has almost entirely replaced the use of Cast Iron for Plumbing and Drainage , being used for waste pipes, drainpipes, Gutter s and downpipes. Fascia, Guttering, Fascias, PVCu Soffits, Roofing, Cladding Due to and The Netherlands . This only concerns PVC rather than uPVC as it is the plasticizers in PVC that are the problem. uPVC does not contain these plasticizers. It is important to note that the PVC used by USA manufacturers of building components such as vinyl siding and vinyl windows use what the European community refer to as uPVC. They are one and the same when discussing these product groups. The use of modern impact modifiers offer great stability. The issues of migration and brittleness of the PVC compound are overcome. 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 Additive s can leach out of vinyl products. Plasticizer s which must be added to make PVC flexible have been an additive of particular concern. 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. In January 2006, the European Union placed a ban on six types of phthalate softeners, including DEHP (, 2007 ) In April 2006, the European Chemicals Bureau of the European Commission published an assessment of DINP which found risk "unlikely" for children and newborns.http://www.dinp-facts.com/upload/documents/document2.pdf Vinyl IV bags used in neo-natal Intensive Care units have also been shown to leach DEHP. 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 {Link without Title} . 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. 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 an article on FOXNews.com, "PVC plastic has been used safely for more than 70 years in a variety of medical and commercial applications and humans. No reports of adverse human health effects have been reported from intravenous (IV) bags and medical tubing made with PVC, according to a 2002 report by the Food and Drug Administration." In February 2007, the Technical and Scientific Advisory Committee of the US Green Building Council (USGBC) released its report on a PVC-related materials credit for siding, drain/waste/vent pipe, resilient flooring and window frames for the LEED Green Building Rating system.https://www.usgbc.org/ShowFile.aspx?DocumentID=2372 The report concludes that "no single material shows up as the best across all the human health and environmental impact categories, nor as the worst." Vinyl chloride monomer A 1997 U.S. Centers for Disease Control and Prevention (CDC) report concluded that the development and acceptance by the PVC industry of a closed loop polymerization process in the late 1970s "almost completely eliminated worker exposures" and that "new cases of hepatic angiosarcoma in vinyl chloride polymerization workers have been virtually eliminated."Epidemiologic Notes and Reports Angiosarcoma of the Liver Among Polyvinyl Chloride Workers – Kentucky, Centers for Disease Control and Prevention Web site. 1997. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/00046136.htm According to the EPA, "vinyl chloride emissions from polyvinyl chloride (PVC), 2001 (Volume 66, Number 186)]) EPA's 2001 updated Toxicological Profile and Summary Health Assessment for VCM in its Integrated Risk Information System (IRIS) database lowers EPA's previous risk factor estimate by a factor of 20 and concludes that "because of the consistent evidence for liver cancer in all the studies...and the weaker association for other sites, it is concluded that the liver is the most sensitive site, and protection against liver cancer will protect against possible cancer induction in other tissues."EPA Toxicologica Review of Vinyl Chloride i Support of Informaiton on the IRIS. May 2000 A 1998 front-page series in the 1998 , pgs. 1A, 16A.] Retesting of community residents in 2001 by the U.S. Agency for Toxic Substances and Disease Registry (ATSDR) found dioxin levels similar to those in a comparison community in Louisiana and to the U.S. population.“ATSDR Study Finds Dioxin Levels in Calcasieu Parish Residents Similar to National Levels,” available at: http://www.atsdr.cdc.gov/NEWS/calcasieula031506.html; “ATSDR Study Finds Dioxin Levels Among Lafayette Parish Residents Similar to National Levels,” available at: http://www.atsdr.cdc.gov/NEWS/lafayettela031606.html; ATSDR Report: Serum Dioxin Levels In Residents Of Calcasieu Parish, Louisiana, October 2005, Publication Number PB2006-100561, available from the National Technical Information Services, Springfield, Virginia, phone: 1-800-553-6847/1-703-605-6244 Cancer rates in the community were similar to Louisiana and US averages."Calcasieu Cancer Rates Similar to State/National Averages." News Release, State of Louisiana Dept. of Health and Hospitals. January 17, 2002 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. 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 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 undesirable byproduct of polymerizing PVC and eliminating the production of dioxins while maintaining the polymerization reaction may be difficult. 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.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 The US EPA estimate of dioxin releases from the PVC industry was 13 grams TEQ in 1995, or less than 0.5% of the total dioxin emissions in the US; by 2002, PVC industry dioxin emissions had been further reduced by 23%.US EPA, The Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States: The Year 2002 Update, May 2007 The largest well-quantified source of dioxin in the US EPA inventory of dioxin sources is barrel burning of household waste.US EPA2005 Studies of household waste burning indicate consistent increases in dioxin generation with increasing PVC concentrations.Costner, Pat, (2005), "Estimating Releases and Prioritizing Sources in the Context of the Stockholm Convention" , International POPs Elimination Network, Mexico. 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 identifies 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."Costner 2005 The next largest sources of dioxin in the EPA inventory are medical and municipal waste incinerators.Beychok, M.R., ''A data base of dioxin and furan emissions from municipal refuse incinerators'', Atmospheric Environment, Elsevier B.V., January 1987 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.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. RECYCLING The symbol, or ' SPI Code ', for polyvinyl chloride developed by the Society Of The Plastics Industry so that items can be labelled for easy recycling is: The Unicode character for this symbol is U+2675 (HTML ♵). Post-consumer PVC is not typically recycled due to the prohibitive cost of regrinding and recompounding the resin compared to the cost of virgin (unrecycled) resin. Some PVC manufacturers have placed vinyl recycling programs into action, recycling both manufacturing waste back into their products, as well as post consumer PVC construction materials to reduce the load on landfills. The Thermal Depolymerization process can safely and efficiently convert PVC into fuel and minerals, according to the company that developed it. It is not yet in widespread use. A new process of PVC Recycling is being developed in Europe and Japan called texiloop® . This process consists of recovering PVC plastic from composite materials through dissolution and precipitation. It strives to be a closed loop system, recycling its key solvent and hopefully making PVC a future Technical Nutrient . REFERENCES MOVIES
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