Global consumption of PVC reached a level of about 31 million tons in 2005. PVC is a matured polymer with average growth rate less than World GDP, but is seeing good growth in Asia due to more emphasis on infrastructure and construction. In fact, markets indicate that the power of business in PVC and related sectors are surely shifting to Asia, where PVC is growing at about 7% or almost at the same rate as Asia's GDP growth. North America as well as Europe are both matured markets for PVC. These regions are expected to grow at less than 3% in the coming five years. Asia is therefore expected to have a larger share in PVC consumption as compared to Europe and North America by 2010.
The global plastics additives market was about 9.9 million tons in 2004, valued at US$19 billion. Overall, the additives market is expected to grow at 4% AAGR from 2004 to 2009. While Europe, North America and Asia-Pacific (excluding China) are growing at about 3%, China is predicted to grow at 8-10%. The other smaller market regions are also poised to grow at 5-6% through 2009. India could be the next big growth area.
PVC consumes more than 65% of the total volume of 9 million tonnes of additives, with major portion of this volume arising from plasticizers. Additives for PVC excluding plasticizers, amount to a volume of over 2 million tons. The regional distribution of additives in 2005 has reached a level of 23% in Asia. Europe continues to be the largest region with almost 25% of the total global consumption currently.
Heat stabilizers contribute more than 30% of the global PVC additive demand. Heavy metal based stabilizers like lead based products - very widely used for stabilization of pipe in Europe and Asia (except Japan), are responsible for very large proportion of these products in the heat stabilizer group. Pipe constitutes almost 40% of the global PVC consumption. In pipes, lead content of about 1-1.5 % along with other metals, etc. at another 1% (called one pack system) is used.
PVC wire and cable sector also consumes lead stabilizers and will continue to use them because of inherent advantages offered by lead in terms of superior electrical resistance. While wire and cable sector constitutes only about 2-3% of the total PVC consumption, it requires heavy dosage of lead stabilizer at about 2-3% level. Lead stabilizers are being phased out in Europe. It is expected that by 2010, lead will be replaced by lighter metals like calcium or zinc, as well as organic stabilizers. Most of the replacement of lead will take place in pipe sector. The wire and cable sector is expected to stay with lead stabilizer longer until a suitable alternate is developed matching technical performance of lead. All the developments in this area still continue to be deficient.
Another group of additives called impact modifier/processing aids constitute another 30% of the PVC additive spectrum. More than 60% of PVC is in the form of unplasticized or rigid products. They are not soft and flexible because of the absence of plasticizers. To impart better flexibility impact strength without affecting rigidity, a group of polymeric additives called impact modifiers are used. They are used at the level of 2-10% depending upon the requirement of impact strength. The co-polymeric type of acrylates (MBS type) also retains inherent clarity of PVC and is used for films and sheets used for packaging. There are other impact modifiers (mainly acrylates and chlorinated PE) that also help in providing weather resistance due to better retention of impact strength over a long period of time and are used for window profiles etc.
Rigid PVC is quite difficult to process since it has high viscosity. To improve its processability without reducing mechanical properties appreciably, a group of polymeric additives (PMMA of specific molecular weight and particle size distribution) are used. While pipe may or may not use processing aids (only larger pipes require processing aids), profile, rigid film and sheet need processing aid for ease of processability. Higher dosing and larger volumes of PVC are responsible for higher usage of impact modifier/processing aid and heat stabilizer. They will continue to remain larger in future as well.
PVC melt gets stuck on hot metal during processing. It therefore requires higher level of lubricants that prevent sticking of PVC melt to hot metal. In addition, improving flow by addition of PVC compatible additives called internal lubricants are also used. Lubricants of all types are added at about 0.5-1% levels. Obviously 15% of the PVC additives comprise of lubricants.
PVC is inherently more flame retardant than the other commodity polymers. However, addition of plasticizers reduces flame resistance. For instance, limiting oxygen index of unplasticized PVC is 40 but plasticized PVC compositions can have oxygen index as low as 23 to as high as 27. These compositions therefore are required to be made more resistant to flame by incorporation of flame retardant additives. The flame retardant additives used are antimony trioxide, zinc borate or molybdenum oxide. While antimony trioxide increases oxygen index, both zinc borate and molybdenum oxide help in suppression of smoke after the fire is caught by PVC product. To further reduce smoke, additives (more like fillers) such as aluminum hydroxide are incorporated. These additives are required to be incorporated at much higher dosage compared to heat stabilizer, processing aid etc and therefore constitute 12% of additives.
PVC requires the largest dosage among all other polymers. Antioxidant is generally used by polyolefins, but PVC is quite resistant to oxidative degradation. However the dosage of antioxidant is lower than 0.2% compared to average 2-3% of heat stabilizer used in PVC. Antioxidant therefore has only has 1% share of the global additive consumption by volume.