Toxicity of Building Materials (eBook)

Aleksandra Fucic, S Jalali, Fernando Pacheco-Torgal (Herausgeber)

eBook Download: PDF | EPUB

2012 | 1. Auflage
512 Seiten
Elsevier Science (Verlag)
978-0-85709-635-7 (ISBN)

Infos

From long-standing worries regarding the use of lead and asbestos to recent research into carcinogenic issues related to the use of plastics in construction, there is growing concern regarding the potential toxic effects of building materials on health. Toxicity of building materials provides an essential guide to this important problem and its solutions.Beginning with an overview of the material types and potential health hazards presented by building materials, the book goes on to consider key plastic materials. Materials responsible for formaldehyde and volatile organic compound emissions, as well as semi-volatile organic compounds, are then explored in depth, before a review of wood preservatives and mineral fibre-based building materials. Issues related to the use of radioactive materials and materials that release toxic fumes during burning are the focus of subsequent chapters, followed by discussion of the range of heavy metals, materials prone to mould growth, and antimicrobials. Finally, Toxicity of building materials concludes by considering the potential hazards posed by waste based/recycled building materials, and the toxicity of nanoparticles.With its distinguished editors and international team of expert contributors, Toxicity of building materials is an invaluable tool for all civil engineers, materials researchers, scientists and educators working in the field of building materials. - Provides an essential guide to the potential toxic effects of building materials on health - Comprehensively examines materials responsible for formaldehyde and volatile organic compound emissions, as well as semi-volatile organic compounds - Later chapters focus on issues surrounding the use of radioactive materials and materials that release toxic fumes during burning

Textauszug

2

Plastic materials: polyvinyl chloride (PVC)

G. Akovali,     Middle East Technical University (METU), Turkey

Abstract:

PVC is a ‘contested’ versatile material used in the construction industry. There is always a controversy about whether or not there are significant health risks associated with its use, because a number of toxic additives are involved, and hence there remains the question of whether the health risks of the use of PVC outweigh its many benefits. In the text, the applications of PVC in construction are reviewed and health concerns are briefly summarized. A brief discussion of the replacement possibilities is presented.

Key words

PVC

VCM

plasticizers

additives

safety

2.1 Introduction

Polyvinyl chloride (PVC), or vinyl for short, or using the IUPAC name ‘chloroethane’ or ‘poly(chloroethanediyl)’, with 57% of mass by chlorine, is an ‘infrastructure thermoplastic’ material. PVC is one of the most important plastic materials used worldwide in various phases of the construction industry, such as pipes, fittings and gutters, window profiles and doors, ceiling tiles, various furniture and upholstery applications, coatings for electrical cables, etc., mainly because of its economy, in addition to its durability and ease of assembly. PVC is also a much used ‘commodity plastic’ in our everyday life, e.g. in clothing, synthetic leather, car seat covers, inflatable structures, etc. PVC with its predicted annual production of around 40 million tons (Ebner, 2009) is second only to polyethylene (PE), the number one commodity plastic. The global market for PVC is expected to continue to grow at about 3–5% per year, with the strongest demand predicted to be in Asia, e.g., China and India, and the EU representing about a fifth of the world market.

2.2 Polyvinyl chloride (PVC – CAS number: 9002-86-2)

PVC is a ‘contested’ versatile material, that is, there is a controversy about whether or not there are significant risks to human health associated with its use. Over its life cycle, a number of by-products and additives, most of which are known to be human toxicants, are involved with PVC materials and hence there remains the question of whether the health risks of PVC use outweigh its many benefits. Controversy extends to both research findings and their interpretation, as well as to the regulatory policy. Green certifying boards have already been asked to award credit for buildings that reduce or eliminate PVC use. Government regulations for the use of PVC in the US and EU have been focused mostly on medical and consumer products, but not on building materials. While this review certainly will not intend to resolve these controversies, it is intended to outline the science relevant to understanding them for the use of PVC as a building material.

2.2.1 Production, structure and properties of PVC

PVC, with chemical formula C2H3Cl, is a vinyl polymer composed of repeating vinyl groups (ethenyls), having one hydrogen atom replaced by chlorine on alternate carbon atoms per repeat unit:

PVC production and processing consists of five major steps (Titow, 1984):

1. Ethylene (C2H4) and chlorine gas production

2. Vinyl chloride monomer (VCM) production

3. Polymerization of VCM into polymer

4. Formulation of polymer product with additives

5. Direct molding or end product processing.

VCM is polymerized into the polymer product by an exothermic free-radical reaction at 40–70°C in the liquid state under pressure (in batch reactors) with continual mixing of the ‘suspension’ to obtain a uniform particle size. After degassing, stripping, centrifuging and drying of the resulting slurry, it is sieved to obtain the powdered ‘suspension PVC’ product with sizes of 120–150 μm. There are other production methods for PVC as well, e.g. the ‘emulsion’ technique, which produces smaller sizes (e.g., 10 μm). Suspension and emulsion type PVCs have somewhat different properties and are used for different applications, suspension being the more commonly used. Normally, any PVC product is expected to have less than 1 ppm (parts per million) of monomer (VCM) content left unreacted:

[2.1]

PVC is a white, amorphous, odorless powder, which is stable under normal temperatures and pressures up to 70–80°C, after which it begins to decompose with evolution of hydrochloric acid (HCl) gas and discoloration (yellowing).

PVC was first made in 1872 by the German chemist Eugen Baumann, who did not apply for any patent. In 1912, the German chemist Fritz Klatte working for Greisheim-Electron, Germany, decided to try to react acetylene with HCl (which apparently produced the monomer VCM), and he left the product on the shelf, where it apparently polymerized over time by sunlight. Hence Klatte was the first inventor to receive a patent for PVC (in 1913), using mercuric chloride as a catalyst; this patent expired in 1925. This original method was widely used during the 1930s and 1940s, but has since been superseded by more economical advanced processes, at least in the Western hemisphere.

The importance of PVC and its use was not realized until 1926 when Waldo Semon, an American chemist working at B.F. Goodrich, invented PVC independently. Semon quickly understood that this new material would have a big potential to produce brand-new objects, and he first produced a shower curtain.Semon and B.F. Goodrich immediately patented PVC for the USA (Semon, 1926a, 1926b). Later, Semon tried to produce golf balls and shoe heels from PVC. A great many new uses for this wonderful waterproof material then followed, and PVC was a real success in the world.

Being a thermoplastic, PVC softens if heated and hardens as it cools; and it can be processed by the use of any conventional plastics processing techniques, such as extrusion (specifically for complex-shaped extrusion profiling for housing materials), calendering (wide films and sheets such as agricultural films and PVC leather), injection and blow molding (except injection molding, because its melt viscosity is high). PVC materials have rather low densities, hence they offer relatively low material costs on a volume basis and hence are cost-effective. PVC is one of the major low-cost, high-volume commodity resins used today due to its economy and the excellent chemical and mechanical properties it provides.

Two main types of PVC resins are produced and processed:

1. Rigid PVC resins (unmodified PVC, uPVC), which have considerable strength and hardness; they are processed mainly by extrusion or molding to make pipes and conduits, fittings, window profiles, roof tiles, fences and various rigid automotive parts. Rigid PVC sheets can be welded easily to produce tanks, trays and troughs.

2. Flexible PVC resins, which contain various additives, mainly plasticizers, usually in high proportions to make them soft and flexible and heat and UV stable.

When plasticizers are added, flexible plasticized PVC (pPVC) is obtained with rubber-like elasticity, high tensile and fatigue strengths, which can be used specifically for industrial hoses, gaskets, elastic automotive parts and electrical cable covers, where elasticity is a must. pPVC also finds applications in film and sheets, flooring, shower curtains and synthetic leather products. In the 1970s pPVC was often used to make ‘vinyl car tops’, and it was also used to make vinyl records. PVC-based materials also have a key role in the production of medical and clinical devices; however, similar arguments are arising with regard to its safety issues (Latini et al., 2010). Table 2.1 summarizes some characteristics of PVC.

Table 2.1

Some characteristics of (rigid) uPVC

Density (at 25°C)

0.5–1.45 g/cm3

Specific gravity

1.3–1.7

Hardness durometer

R 90–115

Tensile strength

30–65 MPa (flexible: 7–25 MPa)

Tensile (Young’s) modulus

2–4 × 102 MPa

Tensile elongation

20–190%

Compressive strength

50–90 MPa

Fatigue strength

17 MPa (after application of repeated stress by 107 times)

Impact strength (notched)

2–6 kJ/m2

Service temperatures

− 13°C (min.) to 70–80°C (max.)

Tg (glass transition temperature)

80°C

Tm (melting temperature)

240°C (decomposes)

Ignition...

Produkt-Details

• Erscheint lt. Verlag: 13.8.2012
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Gesundheitsfachberufe
• Themenwelt: Studium ► 2. Studienabschnitt (Klinik) ► Pharmakologie / Toxikologie
• Themenwelt: Technik ► Bauwesen
• ISBN-10: 0-85709-635-4 / 0857096354
• ISBN-13: 978-0-85709-635-7 / 9780857096357