What is PVC

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What is PVC (Polyvinyl Chloride) ?

PVC is Polyvinyl Chloride. This is a plastic that has the following chemical formula: CH2=CHCl (see picture on the right).

Plastic covers a wide rage of synthetic or semi-synthetic polymerization products (i.e. long-chain carbon-based "organic" molecules) which name refers to the fact that in their semi-liquid state they are malleable, or have the property of plasticity. PVC is a thermoplastic material.Thermoplastic materials are those that can be melted again and again. These materials can be heated to a certain temperature and will harden again as they cool.

After the First World War, there were a boom in new forms of plastics due to the improvements in the chemical technology sector, including "polystyrene (PS)" and "polyvinyl chloride (PVC)", developed by the I.G. Farben company of Germany.

Nowadays, PVC is commonly used in the construction sector, for example in window frames and shutters, pipe cabling and coating, etc.. Vinyl is also used in gramophone records, and that is why we use the term vinyl records to refer to them. PVC can be used for tons of other applications from industrial ware and widely used in the healthcare sector, to car spare parts, toys factory, food packaging, raingear, etc.

PVC can be clear or colored, rigid or flexible, depending on the added compounds and final application that needs to be achieved; For example there exists different PVC grades such as coast or blow film, high impact, wire and cable grade, thermoforming, injection molding, rotational molding, etc.

For example rigid PVC like the one which is used in windows frames is normally PVCU ("unplasticized"). On the other hand flexible PVC is achieved by adding plasticizers such as phthalates.

Furthermore, pure poly-chloroethene is unstable when exposed to visible light or UV. In order to modify this disadvantage and make it suitable for different applications antioxidants are added. Some other additives comprise:

 

 

 

 

Additives

Properties achieved

 

Anti-oxidants & other stabilizers

Slow down the rate at which the polymer will be degraded by oxygen, heat, visible light or UV radiation

 

Compatibilizers

Enable PVC to be mixed with other plastics and helps plastic recycling

 

Flame retardants

Reduce flammability of plastic

 

Pigments

To colour the plastic

 

 

Plasticisers

To produce flexible and manageable plastic

 

Impact modifiers

To absorb shock without damage

 

Fillers

Inexpensive, inert materials that simply add bulk to the plastic

Environmental impact and occupational health and safety aspects of PVC

Manufacture of PVCThe manufacturing plastics often creates large quantities of toxic chemical pollutants such as dioxin, hydrochloric acid, and vinyl chloride. This poses a severe health risks to humans during the PVC life cycle. These toxins can produce sever illness like cancer, diabetes, neurological damage, reproductive and birth defects. Dioxin is a persistent Organic Pollutants (POPs), this are chemical substances that persist in the environment, bio-accumulate through the food chain, and pose a risk of causing adverse effects to human health and the environment.

In addition, the chloro-ethene monomer is also a carcinogen released during PVC manufacture. This un-reacted monomer can also be present in the final PVC and released during its life cycle.

Plasticizers added to make PVC flexible, may leach out (ex. group phthalates) which are also toxic.

DisposalPlastic was almost too good, as it was durable and degraded very slowly. On the other hand this same properties is what makes plastic a dangerous material. Due to the quantity and different additives added to PVC (the PVC product may consist up to 60% of additives) and also due to its chlorine contain, the final disposal or recycling of PVC is a issue to be closely examine.

The options for disposal are recycling, landfill or incineration:

For example, a recyclable plastic container using this scheme is marked with a triangle with three arrows inside of it (see picture on the left), which enclose a number giving the plastic type as follows:

 

1. PETE or PET (i.e. polyethylene terepthalate: termoplastic material used in plastic soft drink and rigid containers)2. HDPE (i.e. high density polyethylene: the plastic commonly used to make milk and water jugs and two liter soda bottle bases)3. PVC (i.e. polyvinyl chloride)4. LDPE (i.e. low density polyethylene: the plastic used in cellophane wrap, diaper liners, and some squeeze bottles)5. PP (i.e. a light, thermoplastic resin used in packaging, coating, pipes, and tubes)6. PS (i.e. polystyrene)7. Others- IncinerationThe incineration of PVC causes the release of dioxins and other toxic chemicals. - LandfillLandfill of PVC has other environmental and social impacts. This is due to the not biodegradability of PVC which stays in place indefinitely; besides, attention should be taken to the fact that PVC may leach out toxic chemicals and contaminate the soil and water. There are some "biodegradable" plastics that break down with exposure to sunlight but it still doesn't lead to complete breakdown of the plastic. In addition, some researchers have genetically engineered bacteria that synthesize a completely biodegradable plastic.

 

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ronnie raj

Wednesday, October 24, 2007 1:38 PM

Re: [HealthyIndia] Urban legend - John Hopkins Article

 

 

 

 

what is the full form of PVC.

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