Polyvinyl chloride

Elongation at break	20–40%
Notch test	2–5 kJ/m²
Glass Transition Temperature
Melting point	to
Effective heat of combustion	17.95 MJ/kg
Specific heat	0.9 kJ/
Water absorption	0.04–0.4
Dielectric Breakdown Voltage	40 MV/m

Polyvinyl chloride is the world's third-most widely produced synthetic polymer of plastic. About 40 million tons of PVC are produced each year.
PVC comes in rigid and flexible forms. Rigid PVC is used in construction for pipes, doors and windows. It is also used in making plastic bottles, packaging, and bank or membership cards. Adding plasticizers makes PVC softer and more flexible. It is used in plumbing, electrical cable insulation, flooring, signage, phonograph records, inflatable products, and in rubber substitutes. With cotton or linen, it is used in the production of canvas.
Polyvinyl chloride is a white, brittle solid. It is soluble in ketones, chlorinated solvents, dimethylformamide, THF and DMAc.

Discovery

PVC was synthesized in 1872 by German chemist Eugen Baumann after extended investigation and experimentation. The polymer appeared as a white solid inside a flask of vinyl chloride that had been left on a shelf sheltered from sunlight for four weeks. 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 thwarted their efforts. Waldo Semon and the B.F. Goodrich Company developed a method in 1926 to plasticize PVC by blending it with various additives, including the use of dibutyl phthalate by 1933.

Production

Polyvinyl chloride is produced by polymerization of the vinyl chloride monomer, as shown.

About 80% of production involves suspension polymerization. Emulsion polymerization accounts for about 12%, and bulk polymerization accounts for 8%. Suspension polymerization produces particles with average diameters of 100–180 μm, whereas emulsion polymerization gives much smaller particles of average size around 0.2 μm. VCM and water are introduced into the reactor along with a polymerization initiator and other additives. The contents of the reaction vessel are pressurized and continually mixed to maintain the suspension and ensure a uniform particle size of the PVC resin. The reaction is exothermic and thus requires cooling. As the volume is reduced during the reaction, water is continually added to the mixture to maintain the suspension.

Microstructure

The polymers are linear and are strong. The monomers are mainly arranged head-to-tail, meaning that chloride is located on alternating carbon centres. PVC has mainly an atactic stereochemistry, which means that the relative stereochemistry of the chloride centres are random. Some degree of syndiotacticity of the chain gives a few percent crystallinity that is influential on the properties of the material. About 57% of the mass of PVC is chlorine. The presence of chloride groups gives the polymer very different properties from the structurally related material polyethylene. At 1.4 g/cm³, PVC's density is also higher than structurally related plastics such as polyethylene and polymethylmethacrylate.

Producers

About half of the world's PVC production capacity is in China, despite the closure of many Chinese PVC plants due to issues complying with environmental regulations and poor capacities of scale. The largest single producer of PVC as of 2018 is Shin-Etsu Chemical of Japan, with a global share of around 30%.

Additives

The product of the polymerization process is unmodified PVC. Before PVC can be made into finished products, it always requires conversion into a compound by the incorporation of additives such as heat stabilizers, UV stabilizers, plasticizers, processing aids, impact modifiers, thermal modifiers, fillers, flame retardants, biocides, blowing agents and smoke suppressors, and, optionally, pigments. The choice of additives used for the PVC finished product is controlled by the cost performance requirements of the end use specification. Previously, polychlorinated biphenyls were added to certain PVC products as flame retardants and stabilizers.

Plasticizers

Among the common plastics, PVC is unique in its acceptance of large amounts of plasticizer with gradual changes in physical properties from a rigid solid to a soft gel, and almost 90% of all plasticizer production is used in making flexible PVC. The majority is used in films and cable sheathing. Flexible PVC can consist of over 85% plasticizer by mass, however unplasticized PVC should not contain any.

	Plasticizer content	Specific gravity	Shore hardness	Flexural stiffness	Tensile strength	Elongation at break	Example applications
Rigid	0	1.4		900	41	<15	Unplasticized PVC : window frames and sills, doors, rigid pipe
Semi-rigid	25	1.26	94	69	31	225	Vinyl flooring, flexible pipe, thin films, advertising banners
Flexible	33	1.22	84	12	21	295	Wire and cable insulation, flexible pipe
Very Flexible	44	1.17	66	3.4	14	400	Boots and clothing, inflatables,
Extremely Flexible	86	1.02	< 10				Fishing lures, polymer clay, plastisol inks

Phthalates

The most common class of plasticizers used in PVC is phthalates, which are diesters of phthalic acid. Phthalates can be categorized as high and low, depending on their molecular weight. Low phthalates such as Bis phthalate and Dibutyl phthalate have increased health risks and are generally being phased out. High-molecular-weight phthalates such as diisononyl phthalate and diisodecyl phthalate are generally considered safer.
While DEHP has been medically approved for many years for use in medical devices, it was permanently banned for use in children's products in the US in 2008 by US Congress; the PVC-DEHP combination had proved to be very suitable for making blood bags because DEHP stabilizes red blood cells, minimizing hemolysis. However, DEHP is coming under increasing pressure in Europe. The assessment of potential risks related to phthalates, and in particular the use of DEHP in PVC medical devices, was subject to scientific and policy review by the European Union authorities, and on 21 March 2010, a specific labeling requirement was introduced across the EU for all devices containing phthalates that are classified as CMR. The label aims to enable healthcare professionals to use this equipment safely, and, where needed, take appropriate precautionary measures for patients at risk of over-exposure.

Metal stabilizers

BaZn stabilisers have successfully replaced cadmium-based stabilisers in Europe in many PVC semi-rigid and flexible applications.
In Europe, particularly Belgium, there has been a commitment to eliminate the use of cadmium and phase out lead-based heat stabilizers such as liquid autodiachromate and calcium polyhydrocummate by 2015. According to the final report of Vinyl 2010, cadmium was eliminated across Europe by 2007. The progressive substitution of lead-based stabilizers is also confirmed in the same document showing a reduction of 75% since 2000 and ongoing. This is confirmed by the corresponding growth in calcium-based stabilizers, used as an alternative to lead-based stabilizers, more and more, also outside Europe.

Heat stabilizers

Some of the most crucial additives are heat stabilizers. These agents minimize loss of HCl, a degradation process that starts above 70 °C and is autocatalytic. Many diverse agents have been used including, traditionally, derivatives of heavy metals. Metallic soaps are common in flexible PVC applications.

Properties

PVC is a thermoplastic polymer. Its properties are usually categorized based on rigid and flexible PVCs.

Property	Unit of measurement	Rigid PVC	Flexible PVC
Density	g/cm³	1.3–1.45	1.1–1.35
Thermal conductivity	W/	0.14–0.28	0.14–0.17
Yield strength	Pounds per square inch\|	4,500–8,700	1,450–3,600
Yield strength	Pascal \|	31–60	10.0–24.8
Young's modulus	psi	490,000	—
Young's modulus	Pascal \|	3.4	—
Flexural strength	psi	10,500	—
Flexural strength	MPa	72	—
Compression strength	psi	9,500	—
Compression strength	MPa	66	—
Coefficient of thermal expansion	mm/	5×10⁻⁵	—
Vicat B	°C	65–100	Not recommended
Resistivity	Ohm\| m	10¹⁶	10¹²–10¹⁵
Surface resistivity	Ω	10¹³–10¹⁴	10¹¹–10¹²

;Notes

Thermal and fire

The heat stability of raw PVC is very poor, so the addition of a heat stabilizer during the process is necessary in order to ensure the product's properties. Traditional product PVC has a maximum operating temperature around 60 °C when heat distortion begins to occur.
As a thermoplastic, PVC has an inherent insulation that aids in reducing condensation formation and resisting internal temperature changes for hot and cold liquids.