Polyvinyl Chloride- Plastjoo

Polyvinyl Chloride

Polyvinyl chloride is also known as PVC, vinyl, Chlorethylene homo polymer, and Chlorethene homo polymer. It was first discovered accidentally in 1835 by the French physicist and chemist Henry Victor Regnault (1810–1878). Polyvinyl chloride remained a subject of little or no interest to chemists for almost a century. In the 1920s, Waldo Lonsbury Semon (1898–1999), a chemist at B. F. Goodrich, found new ways of adapting the compound for applications by discovering properties of the material. By the 1931, the company had begun to turn out a full line of polyvinyl chloride products in most of the forms currently available. It is easily colored and manufactured in a variety of forms, including sheets, films, fibers, and foam

 

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How It Is Made

Polyvinyl chloride is produced by breaking the double bond of monomer vinyl chloride (CH2 = CHCl) during suspension or emulsion polymerization and in the presence of an initiator. In the original experiments carried out by Regnault, that initiator was sunlight. Chemists have long since learned, however, that a variety of chemicals known as peroxide initiators with an oxygen-oxygen bond (-O-O-) are more effective at breaking double bonds. One of the most widely used initiators is benzoyl peroxide (C6H5CO-O-O-C6H5CO)

 

PVC 

 

:PVC comes in two basic forms

Rigid (sometimes abbreviated as RPVC-

Flexible-

  

Properties

Polyvinyl chloride is resistant to moisture, weathering, most acids, fats and oils, many organic solvents, and attack by fungi

 

Rigid PVC

Flexible PVC

Properties

1.3–1.45

1.1–1.35

Density [ g/cm3]

0.14–0.28

0.14–0.17

Thermal Conductivity [W/(m·K)]

4,500–8,700 psi (31–60 MPa)

1,450–3,600 psi (10.0–24.8 MPa)

Yield Strength

490,000 psi (3.4 GPa)

-

Young’s Modulus

1500- 3000

1.5-15

Elastic Modulus  (Mpa)

10,500 psi (72 MPa)

-

Flexural Strength ( Yield)

9,500 psi (66 MPa)

-

[psi]      Compression Strength

5×10−5

-

Coefficient of thermal expansion (linear) [mm/(mm °C)]

1016

1012–1015

Resistivity [Ωm]

1013–1014

1011–1012

Surface resistivity [Ω]

  

Applications

It is the third most commonly produced plastic in the United States, exceeded only by polyethylene and polypropylene. An estimated 7 billion kilograms (15.7 billion pounds) of polyvinyl chloride were produced in the United States in 2006. About three-quarters of that amount was made in a rigid format that is hard and inflexible. The remaining one-quarter was made in a flexible form, produced by adding plasticizers such as phthalates (diisononyl phthalate (DINP), diisodecyl phthalate (DIDP) and di-2-ethylhexyl phthalate (DEHP)). About 75 percent of all rigid polyvinyl chloride (half of all the compound made in the United States) goes to the construction industry. It has replaced older building materials such as clay, concrete, and wood because it is inexpensive, lightweight, resistant to damage by the sun, and easy to assemble. The compound is used to make vinyl siding, windows, plumbing pipes, flooring, electric cables, roofing materials, and insulation for cables and wires

 

Flexible polyvinyl chloride is used to make fibers and films for applications such as clothing, upholstery, plastic bottles, medical equipment, lightweight toys, shower curtains, and packaging films. Some of the medical equipment produced from polyvinyl chloride include bags to hold blood and other fluids, artificial heart valves, and tubes used in kidney dialysis. Automobile manufacturers use polyvinyl chloride in body side moldings, interior upholstery, engine wiring, floor mats, adhesives, dashboards, arm rests, and coatings under the vehicle

 

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Hazards

The commercial and household products containing polyvinyl chloride are generally regarded as posing no threat to human health. However, a number of questions have been raised about possible health hazards and risks to the environment as a result of the process by which polyvinyl chloride is made, some of its applications, and its eventually disposal. For example, polyvinyl chloride is made from vinyl chloride, which itself is toxic and a carcinogen. People who work with vinyl chloride in production facilities are at risk for developing a form of liver cancer that may be related to exposure to vinyl chloride. Vinyl chloride, in turn, is made from chloride, a very toxic gas that poses health risks to people who work with it

 

Some environmental health experts point out that products made of polyvinyl chloride such as automobile upholstery may release toxic or carcinogenic gases into the air for short periods of time after they have been put into use

 

Finally, the disposal and destruction of compounds containing polyvinyl chloride may create environmental problems by releasing hydrogen chloride gas, a suffocating and toxic gas, into the atmosphere. Enough concern about the health and environmental hazards has arisen that some governmental bodies in Europe have placed limitations on the uses to which PVC products can be put

 

The environmental group Greenpeace has called for a global ban on the production of polyvinyl chloride because the toxic substance dioxin is released (albeit, in very small amounts) as a byproduct of the compound's production

 

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