Polyvinyl chloride facts for kids

Quick facts for kids Polyvinyl chloride
IUPAC name	poly(1-chloroethylene)
Other names	Polychloroethene
Identifiers
Abbreviations	PVC
CAS number	9002-86-2
KEGG	C19508
MeSH	Polyvinyl+Chloride
ChEBI	CHEBI:53243
Properties
Molecular formula
Molar mass	0 g mol-1
Appearance	white, brittle solid
Odor	odorless
Density	1.4 g/cm3
Solubility in water	insoluble
Solubility in ethanol	insoluble
Solubility in tetrahydrofuran	slightly soluble
Magnetic susceptibility (χ)	−10.71×10−6 (SI, 22 °C)
Hazards
NFPA 704	1 1 0
U.S. Permissible exposure limit (PEL)	15 mg/m3 (inhalable), 5 mg/m3 (respirable) (TWA)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Polyvinyl chloride, often called PVC or simply vinyl, is a very common type of plastic. It is the third most produced plastic in the world. About 40 million tons of PVC are made every year.

PVC is special because it can be made in two main forms: rigid (hard) and flexible (soft). Rigid PVC is used in construction for pipes, doors, and windows. Flexible PVC is made by adding special ingredients called plasticizers. It is used in things like electrical cable insulation, flooring, and inflatable products.

How PVC Was Discovered

PVC was first made by accident in 1872 by a German scientist named Eugen Baumann. He found a white solid inside a flask of another chemical that had been left alone for a few weeks.

Later, in the early 1900s, other scientists tried to use PVC for commercial products. But it was too stiff and brittle to be useful. In 1926, Waldo Semon and the B.F. Goodrich Company found a way to make PVC softer and more flexible. They did this by mixing it with various additives, including a type of plasticizer. This discovery made PVC much more useful for many products.

How PVC is Made

PVC is produced from a smaller chemical unit called vinyl chloride monomer (VCM). Many VCM units link together in a process called polymerization to form long chains of PVC.

Most PVC is made using a method called suspension polymerization. In this process, VCM and water are introduced into a large container. Other chemicals, like a polymerization initiator, are also added. The mixture is kept under pressure and continually mixed. This helps create tiny PVC particles of a uniform size. The reaction creates heat, so the container needs to be cooled.

What Makes PVC Special?

The long chains of PVC are strong. About 57% of PVC's weight comes from chlorine. This chlorine gives PVC special properties. For example, PVC is denser than other similar plastics like polyethylene. Its density is about 1.4 g/cm³.

Who Makes PVC?

About half of the world's PVC production capacity is in China. The largest single producer of PVC, as of 2018, is Shin-Etsu Chemical from Japan. They make around 30% of the world's PVC.

Adding Ingredients to PVC

When PVC is first made, it's just a basic plastic. To turn it into useful products, other ingredients called additives are mixed in. These additives change how the PVC behaves. They can make it stronger, more flexible, or more resistant to heat and sunlight. Some common additives include:

• Heat stabilizers: These help PVC handle heat better during manufacturing and use.
• UV stabilizers: These protect PVC from damage caused by sunlight. Sunlight can make PVC turn yellow or become brittle over time.
• Plasticizers: These are very important for making PVC flexible.
• Fillers and pigments: These can add bulk or color to the PVC.

White PVC elements can turn yellow with age due to UV light exposure, which causes the plastic to degrade.

Making PVC Flexible with Plasticizers

PVC is unique because it can accept large amounts of plasticizers. These are special chemicals that make the plastic softer and more bendable. Without plasticizers, PVC is rigid and hard. With them, it can become as soft as a gel. Almost 90% of all plasticizer production is used to make flexible PVC. This flexible PVC is used in things like films and cable coverings.

Understanding Plasticizers: Phthalates

The most common plasticizers are called phthalates. There are different kinds of phthalates. Some, like bis(2-ethylhexyl) phthalate (DEHP), have raised health concerns. Because of these concerns, many companies now prefer to use safer, high-molecular-weight phthalates.

For example, in the US, certain phthalates were banned from children's products in 2008. In Europe, there are strict rules about labeling medical devices that contain certain phthalates. This helps ensure that healthcare professionals use equipment safely and take precautions for patients who might be at risk.

Bis(2-ethylhexyl) phthalate was a common plasticizer for PVC but is being replaced by higher molecular weight phthalates.

Keeping PVC Stable with Heat Stabilizers

PVC needs heat stabilizers to prevent it from breaking down when heated. In the past, some stabilizers contained heavy metals like lead and cadmium. However, in Europe, these have been phased out. By 2015, lead-based stabilizers were mostly replaced with safer calcium-based ones. This shows a commitment to making PVC products safer for everyone.

What Are PVC's Main Properties?

PVC is a thermoplastic polymer. This means it can be melted and reshaped multiple times. Its properties vary depending on whether it's rigid or flexible.

How PVC Reacts to Heat and Fire

The raw PVC material doesn't handle high temperatures very well. It starts to change shape around 60°C (140°F). This is why heat stabilizers are added. As a thermoplastic, PVC has a natural insulation. This helps reduce condensation and resist temperature changes for hot and cold liquids.

Everyday Uses for PVC Plastic

PVC Pipes for Water and Waste

PVC is used extensively in sewage pipes due to its low cost, chemical resistance and ease of jointing

Roughly half of the world's PVC resin made each year is used for pipes. These pipes are used in cities and industries for water and sewage systems. In homes, PVC pipes are very common for drains and sewers. They are popular because they are affordable, resist chemicals, and are easy to connect. Buried PVC pipes are often joined with a special gasket-sealed connection.

PVC for Electrical Cable Insulation

PVC is often used as the insulating covering on electrical cables. It is chosen because it insulates electricity well, is easy to shape, and resists burning. In a fire, PVC can form hydrogen chloride fumes. The chlorine in PVC helps to stop the fire from spreading, making PVC-coated wires fire retardant. While hydrogen chloride fumes can be irritating, they dissolve in moisture and settle on surfaces, especially in cooler air.

PVC in Buildings and Homes

"A modern Tudorbethan" house with uPVC gutters and downspouts, fascia, decorative imitation "half-timbering", windows, and doors

PVC is widely used in the construction and building industry.

• Vinyl siding is a popular, low-maintenance material for the outside of houses. It is used extensively in places like Ireland, the United Kingdom, the United States, and Canada. It comes in many colors and can even look like wood.
• Window frames and sills are often made from PVC. It is used when installing insulated glazing in new buildings or replacing older windows. PVC doesn't rot and stands up well to weather.
• It has almost entirely replaced cast iron for plumbing and drainage. It is used for waste pipes, drainpipes, gutters, and downspouts. PVC is known for its strong resistance to chemicals, sunlight, and water damage.

Double glazed units

PVC for Signs and Creative Graphics

Polyvinyl chloride is formed into flat sheets of various thicknesses and colors. These sheets are often expanded to create voids inside. This makes them thicker without adding much weight or cost. The sheets are cut using saws and rotary equipment.

Flexible PVC is also used to produce thin, colored, or clear films with adhesive backs, often called "vinyl." These films are typically cut on a computer-controlled plotter or printed on a wide-format printer. These sheets and films are used to create many different products:

• Commercial signage
• Vinyl wraps or racing stripes on vehicles for looks or advertising
• General purpose stickers

PVC in Fashion and Protective Gear

Black PVC trousers

PVC fabric is water-resistant. It is used for its weather-resistant qualities in coats, skiing equipment, shoes, jackets, and aprons. The shoulders of some work jackets are traditionally made out of PVC. Early high visibility clothing was also made of PVC.

PVC in Medical Devices and Hospitals

PVC is used in many single-use medical items. These include flexible containers for blood and other liquids, and tubing for blood transfusions, catheters, and dialysis. Almost one-third of plastic-based medical devices are made from PVC. In Europe, about 85,000 tons of PVC are used in medical devices each year.

Due to past concerns about certain plasticizers, many healthcare providers are now choosing alternative materials for some devices. This is especially true for items that come into direct contact with patients for long periods. This ensures the highest level of safety for patients.

PVC for Keeping Food Fresh

PVC has been applied to various food packaging items. These include bottles, packaging films, blister packs, cling wraps, and seals on metal lids.

PVC Coatings for Wire Ropes

PVC may be extruded under pressure to encase wire rope and aircraft cable. This is used for general purpose applications. PVC-coated wire rope is easier to handle, resists corrosion and abrasion, and can be color-coded for better visibility. It is found in many industries and environments, both indoors and outdoors.

Other Cool Uses for PVC

A vinyl record.

• Molded PVC is used to produce phonograph records, often called "vinyl records."
• PVC piping is a cheaper alternative to metal tubing for making musical instruments. It is often used for fun or for rarer instruments like the contrabass flute.
• The thongophone, a percussion instrument, is almost exclusively built from PVC tubes.
• PVC is also used as a raw material in automotive underbody coating.

Stronger PVC: Chlorinated PVC (CPVC)

PVC can be usefully modified by chlorination. This process increases its chlorine content to or above 67%. Chlorinated polyvinyl chloride (CPVC), as it is called, is produced by chlorinating an aqueous solution of suspension PVC particles. This is followed by exposure to UV light, which starts the chlorination process. CPVC is known for its increased resistance to heat and chemicals compared to regular PVC.

How to Glue PVC Together

Flexible PVC can be glued with special adhesives often called solvent cement. Solvents are the main ingredients in these glues. PVC or polyurethane resin may be added to make the glue thicker, help it fill gaps, speed up setting, and reduce shrinkage. Since the solvents mobilize the molecules and PVC polymers link together at the joint, this process is also called welding or cold welding.

PVC can be made with various plasticizers. Sometimes, plasticizers can move from the PVC part into the adhesive, which might weaken the joint. If this is a concern, adhesives should be tested for their resistance to the plasticizer. Nitrile rubber adhesives are often used with flexible PVC film because they are known to resist plasticizers. Some epoxy adhesives can also provide good adhesion to flexible PVC.

Keeping PVC Safe for Everyone

Plasticizers: Safety and Regulations

Plasticizers, especially phthalates, are added to plastics like PVC to make them flexible. These chemicals are not permanently bonded to the plastic, so they can sometimes move out of the product. Because of this, there have been concerns about their potential health effects. For example, some studies have looked at how these chemicals might affect indoor air quality.

To address these concerns, strict regulations are in place. As mentioned earlier, certain phthalates are no longer used in children's toys or some medical devices in many parts of the world. This ensures that products are safe for everyone.

Why Lead is No Longer Used in PVC

In the past, lead compounds were sometimes added to PVC to improve how it could be worked with and its stability. However, it was found that lead could leach out of PVC pipes into drinking water. Because lead is harmful, its use in PVC stabilizers has been completely stopped in Europe and many other regions. The VinylPlus program, which started in 2000, saw European manufacturers complete the replacement of lead-based stabilizers by 2015. This is a great example of how industries change to protect public health.

Ensuring Safety with Vinyl Chloride Monomer

The chemical used to make PVC, vinyl chloride monomer (VCM), needs to be handled with great care in factories. In the early 1970s, it was discovered that VCM could cause serious health problems, including certain types of cancer, in workers who were exposed to it without proper protection. Since that time, very strict safety rules and regulations have been put in place worldwide to protect workers in PVC factories. These rules ensure that VCM is handled safely and that workers are not exposed to harmful levels.

What Happens When PVC Burns?

When PVC burns, it produces HCl gas, water, and carbon dioxide. The chlorine in PVC actually helps to make it fire retardant. This means it resists burning and can help stop fires from spreading. While hydrogen chloride fumes can be irritating, they dissolve in moisture and settle on surfaces, especially in cooler air.

PVC and Dioxins

Burning any type of waste, including plastics, can sometimes release chemicals called dioxins into the environment. There have been discussions about whether PVC contributes to dioxin formation when waste is burned. Modern waste management facilities, like incinerators, are designed with advanced technologies. These technologies burn waste at very high temperatures and filter emissions, which helps to minimize the release of dioxins and other harmful substances. Studies have shown that the way waste is burned (temperature and oxygen levels) is more important for dioxin formation than just the presence of PVC.

The PVC industry in Europe, through initiatives like VinylPlus, is actively working on sustainable waste management, including recycling. This helps to reduce any potential environmental impact.

Industry Efforts for PVC Recycling

In Europe, developments in PVC waste management have been monitored by Vinyl 2010, established in 2000. This initiative aimed to recycle a large amount of post-consumer PVC waste. Since June 2011, it has been followed by VinylPlus, which set new goals for sustainable development. Its main target was to recycle 800,000 tonnes of PVC per year by 2020. In 2020, over 731,000 tonnes of PVC were recycled, showing strong progress despite challenges like the COVID-19 pandemic.

One special recycling process called Vinyloop uses a solvent to separate PVC from other materials. This solvent is then recycled and reused. Recycled PVC is used in many new products, like coatings for swimming pools, shoe soles, and hoses. Using recycled PVC helps save energy and reduces the environmental footprint.

Medical Gloves: Vinyl vs. Other Materials

Vinyl gloves

Plasticized PVC is a common material for medical gloves. However, vinyl gloves have less flexibility and elasticity compared to gloves made from latex or nitrile rubber. Because of this, several guidelines recommend using latex or nitrile gloves for clinical care and procedures that require a lot of hand movement or involve patient contact for more than a brief period. Vinyl gloves also show poor resistance to many chemicals. Some additives in PVC are also known to cause skin reactions in sensitive people.

PVC and Sustainability Efforts

According to Vinyl 2010, the life cycle and sustainability of PVC have been extensively discussed and addressed within the PVC industry. In Europe, a 2021 VinylPlus Progress Report indicated that 731,461 tonnes of PVC were recycled in 2020. This shows a strong commitment to reducing waste and reusing materials.

Images for kids

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  The polymerisation of vinyl chloride

See also

In Spanish: Policloruro de vinilo para niños