A Tribute to Plastics

Eulogising synthetic polymers

0
45

“Plastics” is the general term used to refer to synthetic polymers. They have been around for almost exactly 100 years and have established such a stranglehold in our everyday lives, especially in packaging applications, that it is almost inconceivable to think what we would do without them. Most people would say. “Imagine, if you can, a world without plastics!” I would extend that to ask, “Can you dare imagine a world without them?”
Some time in the mid 1980’s, plastics overtook metals as the world’s most widely used basic materials and the gap between them has been growing at exponential rates ever since. This is actually more remarkable than what is suggested by mere basic figures because of the following factors:

–  Plastics are much lighter and lower density materials than metals (or, indeed, any other basic materials) and, so, the non-plastic applications that they substitute actually consume much less quantum or value than the materials they replace.

–  There is a conscious, and usually successful, effort going on all the time to reduce the plastic usage in practically every application by reducing the thickness of material used (called downgauging), design modifications, usage of stronger and newer custom-developed grades, improvements in converting and processing technologies and optimisation in general. The overall growth in plastics consumption is, therefore, even higher than that indicated by just basic statistics. With more and more stress today on “sustainable” technologies and practices, where light-weighting of materials used in any application has emphatically proved itself to be the most suitable and desirable way forward, the importance of this can hardly be re-iterated often enough.

–  If properly handled, no other material is as perfectly and endlessly recyclable or recoverable.

–  They are so versatile that they can be tailor-made or customised for almost any application, no matter how exacting the requirement. The range of applications that use plastics far outweighs that of all other materials put together.

–  Although Bakelite, the synthetic polymer that really ushered in the plastics age, was developed in 1909, it was a thermosetting resin and was largely used for a variety of industrial and non-packaging applications. The real growth of plastics came when thermoplastic resins started being used for packaging. The first of the major commodity thermoplastics (that constitute the bulk of plastics usage) that was commercially developed was Polyethylene and this happened only in 1935. This means that, within 50 years of the introduction of the first thermoplastic polymer, plastics went on to become the world’s most widely used raw material. This is a truly remarkable achievement.

–  Plastics are by far the most cost-effective materials ever developed by man and there is nothing else on the horizon that even remotely approaches them in terms of utility or potential.

Let us trace the phenomenal progress made by this wonder material.
History of Polymer Developments
The  most important pioneering work on polymers was done by German chemist Hermann Staudinger in the 1920’s. The prevailing theory at that time was that polymers were aggregates of small molecules. He disproved this by demonstrating that they are actually gigantic long-chain molecules and by developing methods for joining monomers to create polymer chains. His work firmly establishes him as the founder of polymer science and provides the foundation for the modern plastics industry. Staudinger was awarded the Nobel Prize for chemistry in 1953.

The first synthetic plastic developed was actually cellulose nitrate although purists dispute its “synthetic” tag; it was based on natural materials (wood pulp or cotton) and not on totally man-made raw materials. It was popularised as Celluloid but was hazardous since it was highly inflammable and melted when subjected to heat. (A safer version – cellulose acetate – was developed later but this came on the scene only after Bakelite.)

Bakelite was invented by Belgian scientist Leo Baekeland in 1907 (he was granted a patent in 1909). It was a phenolic thermosetting resin that was moulable and provided excellent insulation against heat and electricity. It was the first plastic made from truly man-made synthetic raw materials. (Incidentally, Baekeland was already famous for co-inventing Velox photo-printing paper; Velox was bought by George Eastman in 1899.) Baekeland’s original intention was to develop a substitute for shellac varnish. The first commercial grade of Bakelite was introduced in 1909 and the rest is history. There was even a time when the U.S. government considered moulding one-cent coins out of Bakelite due to shortages of metals. Baekeland eventually sold his Bakelite Corporation to Union Carbide in 1939.

Between 1928 and 1932, German and British researchers separately developed polymethyl methacrylate, popularly known as acrylic, which was commercialised by Rohm and Haas in 1933. Around 1930, I. G. Farben started commercial production of polystyrene. At around the same time, injection moulding – the first commercial processing technology for thermoplastics – was developed.

It was in 1933 that polyethylene (PE) and polyvinyl chloride (PVC), two of today’s major plastics, were invented. PE was discovered accidentally by Reginald Gibson and Eric William Fawcett of ICI and Waldo Semon was granted the original U.S. patent for PVC.

In 1935, Wallace Carothers discovered nylon (polyamide) at DuPont and it went on to become one of the most successful synthetic fibres of all time. It was in 1957 that Hoechst AG began the production of polypropylene (PP) – today’s most widely used plastic – based on catalysts pioneered by Karl Ziegler and Giulio Natta (who shared the Nobel Prize for chemistry in 1963). By 1969, PP production just in the U.S. had exceeded 1 billion pounds (453.6 million metric tones).

The Growth of Plastics
So phenomenal has been the growth of plastic usage that it is expected that the global demand for thermoplastic polymers, which constitute the bulk of plastics applications, will exceed 200 million metric tones by 2010. As of 2005, the polymer-wise break-up was as follows:

According to projections, the demand for all polyethylenes (PE’s) and polypropylene (PP) will be 82 million metric tonnes and 52 million metric tonnes respectively by 2010.

Going by statistics from Frost & Sullivan, the total polymer usage during 2004-5 was over 195 million metric tones valued at over US$ 130 billion and the break-up of polymer usage in the different end-use sectors as of 2005 was as follows:

The processing technologies used for converting plastics are dominated by extrusion since it is the preferred process in the flexible packaging and building and construction segments. The process-wise break-up is as follows:

Plastics and Packaging
Plastics have been an absolute boon for packaging. Thanks to their unique properties, there has been a major trend in packaging to move from traditional rigid systems like glass jars, metal cans/barrels and wooden cases to flexible plastic-based systems or plastic bottles. Flexible packaging is growing world-wide at over 6 per cent per annum and the growth of plastics in packaging is at least 50 per cent higher than those of packaging materials. Of all basic materials used in packaging, plastics rule the roost even though paper-based corrugated fibreboard cartons have a virtual stranglehold on intermediate and transport packaging.

Not only is the packaging segment’s share of overall polymer usage increasing, plastics are also increasing the gap between themselves and other packaging materials despite the constant downgauging and optimisation that takes place in reducing the use of plastics in most applications. I remember that in the beginning of the 1980’s, packaging applications accounted for just under 22 per cent of total polymer demand; today that figure is estimated to be over 33 per cent in spite of significant developments in the establishment of several non-packaging applications in segments like automotives/transportation, building/construction and medical devices.

The growth of plastics in packaging started from the mid-1950’s. Not only did they provide water-proofing, moisture resistance and chemical resistance but they provided excellent heat-seal properties which made them the ideal component of structures that required hermetic sealing. The first PE Baggies and sandwich bags on a roll were introduced in 1957 and they rapidly penetrated the market for bags. By 1974, major retail chains like Sears, JCPenney and Montgomery Ward started switching to plastic bags from kraft paper bags.

In 1969, the New York Sanitation Department started a shift to plastic bags used as trash can liners by proving that they were much cleaner, safer and quieter than metal can pick-up. This became a major trend and, by the 1980’s, the trash bag business became the largest end-use segment for LDPE/LLDPE films accounting for close to half a million metric tonnes annually. 1973 saw the advent of the first commercial system for manufacturing plastic grocery bags and they made rapid inroads into supermarkets by replacing paper bags. The development of feedblock coextrusion in the late 1970’s drastically brought down costs and production times for producing multilayered plastic structures and even complex high-barrier combinations could now be produced in a single operation. Combined with the development of barrier metallisation that significantly boosted barrier properties, this led to exponential growth in flexible plastic packaging with high-volume applications switching from rigid systems and non-plastic flexible structures. The development of stretch-blown PET bottles was another major landmark in plastics packaging.

Conclusion
What more can one say than to reiterate that plastics have really been miracle materials for all applications in general and packaging in particular. They have become truly indispensable in our daily lives in less than a century of existence and this itself is testimony to their usefulness, versatility and impact. On the centenary of the appearance of the first plastic, one can only sit back and thank the Lord for them. Long may plastics thrive and continue to astonish us.