Polyvinyl chloride (PVC)

(C2H3Cl)n

 

There can be few materials that have the capacity to generate debate and polarise opinion quite as much as PVC. From its origins in the 1830s, technological development in the 1920s, through to mass production in the 1960s, PVC along with Nylon has characterised the triumph of 20th Century plastics technology and engineering. Today the world market demand is for around 40 million tonnes, 70% of which is used in construction. PVC's characteristics of durability and resistance to corrosion make it very suitable for above and below ground piping; its near-ubiquity as a window frame material is well known, even notorious, and, with the addition of plasticisers, PVC-based floor coverings have effectively marginalized the once dominant linoleum industry.

Yet in the last couple of decades there has gathered a strong reaction to the material. Though there had been questions asked of PVC before the mid 90s, particularly over associations between production and illness of workers, it was the entering of Greenpeace into the debate that brought doubts to many who thought that PVC was inherently 'safe'. Greenpeace in its introduction to the monograph 'What's wrong with PVC?'6, looked forward to its eventual phasing-out: 'We all stand to gain as the environmental burden of toxic, persistent, bio accumulative chemicals, of hormone disrupters and of heavy metals would be significantly reduced.'

Further research began to confirm much that Greenpeace had alleged. Though sometimes confused and contradictory, findings have led public bodies non-the-less to question their use. In some cases, particularly in medical applications, a policy of substituting other polymers and materials for PVC has been put into effect.

The initial reaction of the PVC industry was denial, but after a period of further research-based and persistent criticism, reaction became more complicit. With the help of external sanctions and a drive to make itself more accountable, the industry has striven to remedy both the toxic elements of PVC product composition and the more dangerous aspects of its production and disposal.

The PVC industry has done much to reduce its overall environmental impact, but critics stand firm in pointing out that the manufacture and some methods of disposal are inherently dangerous, and, as their argument goes, however low the risk of release to the environment of toxic chemicals, it is a risk that society need not, and should not, take.

 

The argument for PVC:

 

Pro

Durable

Pro

Cost effective

Pro

Corrosion resistant

Pro

Versatile

Pro

Rigid PVC is recyclable

Pro

Production is highly regulated in Europe

Pro

Generally inexpensive

 

The argument against PVC:

 

Con

The production of PVC can result in the release of toxins including dioxins

Con

The burning of PVC can result in the release of dioxins

Con

Additives to PVC can be toxic to users

Con

Production in China, the biggest producer, is relatively unregulated

 

The PVC life cycle

 

1 Feedstock production


Conversion of raw chemicals into vinyl chloride (VC):

* Ethylene is produced from petroleum or natural gas; Chlorine is synthesised from sea salt by electrolysis.

* Chlorine is reacts with ethylene to produce 1,2-dichloromethane (ethylene dichloride)

* 1,2-dichloromethane is then pressurised under heat to form VC, a gas, with HCl as a by-product.

Chlorine, ethylene, ethylene dichloride, hydrogen chloride, vinyl chloride monomer and chlorinated by-products including dioxins.

The greatest risk of exposure is to workers in production facilities though there is also risk to the environment through accidents occurring during transportation.

 

2 Manufacturer of PVC

 

Polymerization


Gaseous VC monomers are linked together to produce complex long chain solid PVC polymers. Pure PVC polymer is typically found as a white solid powder that is inert and non-toxic.

pvc polymerisation

 

Formulation


PVC can be mixed with other chemicals to yield a wide variety of plastic products. Additives, sometimes in excess of 50 percent by weight, are blended with the PVC polymer to yield the end product plastic characteristics.

Additives will typically include stabilisers, lubricants, fire retardants and for flexible PVC, plasticisers.

 

Moulding


Once PVC has been formulated to meet certain end-use specification, the pellets are heated so that they melt together into a molten form. Once molten, the formulated PVC can be forced through various moulds and dies to achieve the product forms. The moulded forms are then cooled to produce the desired solid end-use products.

Emission potential

Vinyl chloride monomer and solvents have the potential to be released into the air during the PVC manufacturing polymerization step.

Research into the toxic effect on workers reveals contradictory opinion. However, according to the United States 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 that causes a rare cancer of the liver.' 1

 

3 Use


Potential health and environmental hazards during the use phase could include the release of toxic substances from largely plascticised PVC products into the indoor or outdoor environment .

PVC without additives is inert, but risks become and issue when it is combined with additives. The salient concern is with the phthalate family of plasticers, and, in particular DHEP (diethylhexyl phthalate), which has historically been the main plasticiser by volume. DHEP can be released to air from plastic materials, coatings, and flooring and can lead to high indoor concentrations which are considered highly toxic. DHEP has recently become effectively proscribed in Europe as a result of its being added to the REACH 'Authorisation List' along with other phthalates BBP and DBP.

Alternative plasticisers are now finding there way into PVC, primarily the phthalates DINP and DEDP, but their potential health risks of are largely unknown, due to the lack of toxicological data publicly available.

 

4 Disposal


Disposal of PVC occurs in four ways:

1 To landfill
2 Incineration and fires
3 Recycled
4 Dumped illegally

Each method of disposal attracts its own set of issues:

 

Landfill


The destination for most redundant PVC in the UK is landfill. Around 380,000 tonnes is disposed of in this way every year - a sum representing in its own right a substantial environmental impact. 4

The concern is that additives including plasticisers and metal-based stabilisers will leach from the PVC into the environment. The recognised potential is greatest for flexible PVC products, such as floor coverings, that carry the greater amount of additives by weight. Research 5 , however, would suggest that leaching of chemicals of concern in landfill settings does occur but in most cases is minimal. In those cases where releases of chemicals of were increased, high temperatures and acidic conditions were required.

 

Incineration and fires


Burning PVC whether in incinerators, accidental open fires or casual burning is associated with the potential for hazardous substances to be released to air. 2 Though numerous toxic chemicals released

 

Recycling PVC


An obvious route to minimising the overall potential environmental impact of PVC is through recycling pre- and post-consumer waste. Rather than heading for landfill or incineration, waste PVC is returned to manufacturers as raw material for forming into new products. The 'loop' avoids the dangers associated with the creation of VC at the outset and the impacts of disposal at end-of-life.

Grabbing the headlines is the recycling of uPVC window frames stripped from properties undergoing refurbishment. Less advanced is the recycling of elasticised PVC where additives can easily confound the process. Tests have been performed recently on recycling PVC flooring through WRAP which show that at least some of the estimated 50,000 7 tonnes currently sent to landfill might be recoverable.

 

 

Vinyl 2020


Following on from Vinly 2010, Vinyl 2020 is a European PVC industry 10-year plan, a voluntary commitment '… to enhance sustainability of its product and production over the full life cycle. This means continually improving production processes and products, investing in technology, minimising emissions and waste, and boosting collection and recycling.' 3 Results from the first 10 year plan show that the industry ran very close to achieving its commitment to recycle some 240,000 tonnes of post consumer waste.

 

 

References


1 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)

2 Jay et al. 1995, Lemiuex 1997, EPA 1987a, EPA 1987b, EPA 1989, and EPA 1998.

3 Vinyl 2010 website

4 The Behaviour of PVC in Landfill, European Commission DGXI.E.3, 2000

5 Mersiowsky, I., R. Brandsch, J. Ejlertsson, 2001. “Screening for Organotin Compounds in European Landfill Leachate.” Journal of Environmental Quality #30:1604-1611.
Mersiowsky, I., M. Weller, J. Ejlertsson, 2001. “Fate of Plasticised PVC Products under Landfill Conditions: A Laboratory-Scale Landfill Simulation Reactor Study.” Water Research #35:3063-3070.
Mersiowsky, I., 2002. “Fate of PVC Polymer, Plasticizers and Stabilizers in Landfilled Waste.” Journal of Vinyl Additive Technology # 8(1) March 2002.

6 What's wrong with PVC? Unidentified authors, Greenpeace, 1997

7 WRAP

 

 

 

 


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