Put bluntly, PVC smells like sick. It is inexpensive and is often used as a cheap replacement for natural materials, such as imitation leather, but it is one of the most widely used plastics in the world. It’s found in everything from credit cards to roof membranes and has come to define cheapness, and in recent years has been considered a generally unhealthy plastic.
One of the reasons for its widespread use is that, like polyurethanes, PVC is extremely versatile and can be produced as thermosets, thermoplastics and in elastomeric forms. These range from a powdery, dry feeling PVC to the rubbery stickiness of a child’s swimming inflatable. Another reason for the popularity of PVC is its low cost and the stability of its price, due to 50 per cent of its make-up coming from non-petroleum based sources. This and ease of processing means that it was one of the most widely used plastics in the world until the 1980s, when it became the poster boy for how bad plastics are.
Industry is still divided regarding the health and environmental damage that PVC causes, but the concerns are detailed in the box on the right. The PVC industry’s defence lays in what they claim is the low level of risk and likely exposure to these substances and the fact that PVC has been used in the medical industry for many years for blood bags, where the use of plasticizers have actually been shown to extend the shelf life of blood.
Image: PVC soap dish
•Versatile processing
•Inexpensive
•Easy to colour
•Blends well with other materials
•Good chemical resistance
•Good electrical resistance
•Multiple forms/grades
•Not naturally UV resistant
•Environmental concerns
•Recyclable
Sources
Widely available from multiple global suppliers.
Cost
£0.65 ($1) per kg.
Sustainability issues
Dioxins are emitted when PVC is produced, melted for recycling and incinerated, largely because of a chlorine compound that is a large part of its composition. Unlike many other plastics, PVC is based on approximately 50% petrochemicals, the rest is made of a chlorine-based compound. This means PVC is more stable price wise.
Production
The variety of processing techniques is one the reasons that PVC is so widely used. Apart from extrusion, rotational moulding, injection moulding, blow moulding and calendering, it is also used for dip moulding. Varying the amount of plasticizer gives flexibility in moulding, with stretch PVC sheet containing large amounts of plasticizer. In sheet form it is also conducive to being ultrasonic and high frequency welded.
The second environmental issue is the use of stabilizers and plasticizers in the production of the material. In terms of function, stabilizers are used to impede degradation and plasticizers to increase flexibility. Both of these additives have problems. Stabilizers use heavy metals like lead and barium and the plasticizers contain hormone disrupters. There are moves to reduce these problems by the manufacturers who, through various means, can reduce the amount of dioxins being produced and also use organic stabilizers.
PVC is identified by the number 3 on the recycling symbol.
Typical applications
It is difficult to summarize the versatility of this material. However, applications include dip-moulded bicycle handles, fake leather, garden hoses, drain pipes, flooring, electrical cabling, ‘artificial skin’ used in burns treatment, sun visors, raincoats, credit cards and inflatable toys. Unplasticized, or rigid, PVC (PVC-U) is used extensively in building applications such as window frames.
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–Extremely versatile –Good chemical resistance –Widely available –Low cost –Hard wearing –Recyclable |
–Health concerns over its production and disposal –Negative associations of cheapness –Poor UV resistance |