Stainless Steel
ID #1021
RAW MATERIALS FOR PLASTICS
Today, the plastics industry is heavily integrated with the oil industry
In fact a popular view is that it would not be able to produce plastics if oil were not available
This is very different from the situation 40-50 years ago when the plastics industry was being described as a ‘scavenger of raw materials’
Before World War I1 the most important class of thermoplastics, the cellulosics, were produced from vegetable sources, cellulose being an important constituent of vegetable matter
From waste oat husks were produced the furane plastics whilst routes to the nylons were also developed from this raw material
Henry Ford had experimented with soya bean plastics and several plastics had been derived from natural rubber
After the war IC1 produced a protein fibre, Ardil, from ground nuts whilst vegetable oils became a source for producing some of the acids used in nylon manufacture
Early grades of polyethylene were obtained from sugar cane via molasses, ethyl alcohol and ethylene
Some of these processes are still of importance but their relative significance has declined
On the other hand they could be revived and extended should the need arise
There is rather less scope for the re-emergence of the animal-based plastics such as casein, shellac and the blood albumin products
Until the mid-1950s the main raw material source for the European plastics industry was coal
On destructive distillation coal yields four products: coal tar, coke, coal gas and ammonia
Coal tar was an important source of aromatic chemicals such as benzene, toluene, phenol, naphthalene and related products
From these materials other chemicals such as adipic acid, hexamethylenediamine, caprolactam and phthalic anhydride could be produced, leading to such important plastics as the phenolic resins, polystyrene and the nylons
Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene
This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers
Furthermore, during World War IT, Reppe developed routes for many other monomers although these were not viable under normal economic conditions
The development of the petrochemical industry is probably the greatest single contributing factor in the growth of the plastics industry, the two industries today having a remarkable degree of interdependence
In the first instance the growth potential of plastics stimulated research into the production of monomers and other intermediates from petroleum
As a result there became available cheap and abundant intermediates which in turn stimulated further growth of the plastics industry in a way which would not have been possible if the industry had been dependent on coal alone
The petrochemical industry was founded shortly after the World War I to produce solvents from olefins which were then merely waste-products of ‘cracking’-the process of breaking down higher molecular weight petroleum fractions into lower molecular weight products, such as gasoline
By the advent of World War I1 petrochemicals were also being used to produce ethylene dichloride, vinyl chloride, ethylene glycol, ethylene oxide and styrene
During World War I1 the large synthetic rubber industry created in the United States used butadiene and styrene, the former entirely and the latter partly derived from petroleum
Whilst in its early days polyethylene was produced from molasses via ethyl alcohol and ethylene, today ethylene used for polymerisation, and for other purposes, is obtained almost entirely from petroleum
With each succeeding year in the 1950s and 1960s there was a swing away from coal and vegetable sources of raw materials towards petroleum
Today such products as terephthalic acid, styrene, benzene, formaldehyde, vinyl acetate and acrylonitrile are produced from petroleum sources
Large industrial concerns that had been built on acetylene chemistry became based on petrochemicals whilst coal tar is no longer an indispensable source of aromatics
There are three general routes for producing intermediates from petroleum: (1) Separation of individual saturated hydrocarbons from the petroleum fractions and subsequent conversion to more useful products
Important examples are n-butane to butadiene and cyclohexane to nylon intermediates
(2) Separation of olefins produced by cracking operations and subsequent conversion
This is the major route to aliphatic petrochemicals
(3) Formation of aromatic structures such as benzene and its homologues by ‘platforming’ and other processes
This route is of ever increasing importance in the production of aromatic materials
These three initial classes of product may then be converted to other chemicals by oxidation, halogenation, alkylation, hydration, carbonylation, telomerisation and many other reactions
There are nowadays few intermediates for plastics that cannot be produced more cheaply from petroleum than from other sources
During the 1960s and early 1970s the choice was not so much petroleum vel-sus coal but which petroleum route to use
However, there has now arisen a growing awareness of the fact that petroleum resources are not unlimited
This led to substantial increases in petroleum prices
Some idea of the spectacular growth in the plastics industry may be obtained from consideration of Table 1
1
Whilst growth in percentage terms was greatest before 1973, it has remained high in tonnage terms up to the present time
Table 1
2, based on Modern Plastics sources, provides USA consumption figures (based on sales data) for the main groups of plastics materials
The figures probably underestimate the global importance of the major tonnage thermoplastics since these are also manufactured in quantity in developing countries and OPEC countries
The similarity between USA and Western Europe data is quite striking
In recent years the dominance of these two areas, which traditionally accounted for at least two-thirds of the market, has decreased and by 1998 was closer to 50% of the market
This was as a result of growth in production in petroleumexporting countries, in Latin America and, particularly, in the Pacific Rim area
However, the economic turmoil which particularly affected the latter from 1997 is in early 1999 having an influence whose consequences are not yet clear
One recurring problem has been that a perceived shortage of a particular material has led to plans by more than one company to build large plants to produce that material, so that a shortage is then followed by a period of severe excess capacity and depressed polymer prices
As already mentioned, much of the use for plastics just after World War I1 was as a cheap substitute for traditional materials, and in other cases the material was used for its novelty value
In many instances the result was detrimental to the industry and it required several years of painstaking work by the technical service departments of the major plastics materials manufacturers before confidence was regained in the use of plastics
Even today the public image of plastics is not entirely positive and the significant contribution of plastics to raising the standard of living and quality of life is not fully recognised
In some outlets plastics materials have been long established
A prime example is in the electrical industries where the combination of excellent insulation properties with toughness, durability and, where desired, flame retardant characteristics have led to wide acceptance for plugs, sockets, wire and cable insulation
The ability of polyethylene to act as an excellent insulator at high frequencies was of great significance in the early development of radar
In this area three recent trends are discernible
Firstly there has been increasing acceptance of plastics for housing electrical and electronic equipment, leading to increased use of the more general purpose plastics
Secondly the development of microprocessors and the silicon chip has meant that components are becoming smaller and thus less plastics materials per part are used and in some cases even eliminated
Thirdly plastics are finding use in sophisticated techniques
For example, the photoconductive behaviour of poly(viny1 carbazole) is made use of in electrostatic copying equipment and in the preparation of holographs whilst the peculiar piezo-electric and pyro-electric properties of poly(viny1idene fluoride) are being utilised in transducers, loudspeakers and detectors
In the building industry there was much emphasis in the early 1960s on the allplastics house although the raw material suppliers who sponsored their design probably thought of them primarily as publicity exercises
As the plastics industry has matured it has been realised that it is better to emphasise those applications where plastics are preferable to traditional materials and this approach has led to widespread acceptance
Uses include piping, guttering and conduit, damp course layers, flooring, insulation, wall cladding and window frames
Quite rightly government organisations have been concerned about possible fire risks and although regulations have seemed unduly restrictive to some, others will feel that they have avoided unjustified excesses in the use of plastics
Plastics have been widely accepted as packaging materials
Plastics bottles have been particularly appreciated in the bathroom, where breakage of glass containers has led to many serious accidents
The ability of many materials to withstand the most corrosive chemicals has been of benefit to the chemical and related industries whilst the light weight compared with a glass bottle reduces the energy required for transportation
Small containers are also widely made from plastics and for medicines, particularly in tablet form, the use of closures that cannot be prised open by young children is particularly valuable
The wide use of plastics films for wrapping, for bags and sacks is almost too well known for comment
The sheer quantity of plastics used in this area nevertheless attracts critical comment, in particular that some goods are overpackaged and that waste plastics film left lying around is likely to be an all-too-durable eyesore
In many countries paper bag manufacturers have stressed the environmental desirability of using their products and in turn this has stimulated research into biodegradable plastics
The automotive industry is now a major user of plastics, with the weight of plastics being used per car increasing year by year
It has recently been stated that in the early 1990s the average car contained some 75 kg of plastics
For many years the main uses were associated with car electrical equipment such as batteries, flex, plugs, switches and distributor caps
Plastics then became established in light fittings, seating upholstery and interior body trim
In recent times there has been increased use in under-the-bonnet (under-the-hood) applications such as radiator fans, drain plugs, petrol tubing and coolant water reservoirs
In many applications the weight of material used is small
For example, it has been stated that in one small European car there were 450 different parts made from polyacetal plastics but which had a total weight of only one kilogram
The requirements of fuel economy demanding lighter cars and of increased occupant safety have led to a substantially increased use of plastics materials for bumpers, radiator grilles and fascia assemblies
Indeed if it were not for the trend towards fabric rather than leathercloth upholstery most parts of the car within reach of the driver other than the windows would be made from rubbers and plastics, and even then the fabric and the glass are polymeric! Plastics also find increasing use in vehicles for both water and air transport
Glass-fibre-reinforced plastic boats are widely used as a result of their economy in manufacture, ease of maintenance, lightness of weight and, for military purposes, antimagnetic characteristics
The non-corrosive nature of plastics also leads to their widespread use in boat fixtures and fittings
In aircraft, plastics are particularly useful on account of their low density
Domestic and commercial furniture and fittings form another important market
Uses include stacking chairs, armchair body shells, foam upholstery and desk and cupboard drawers, whilst chipboard and decorative laminates are very widely used
The variety of finishes possible at a relatively low cost compared to traditional materials as well as ease of maintenance are important in raising standards of living around the world
As with other applications the use of plastics in furniture is not without its detractors and in particular there is concern about the inflammability of those plastics that are used in a form which has a high surface-to-volume ratio, such as polyurethane foams
Whilst most of the problem appears to lie in the correct choice of covering fabric the matter continues to require attention
Industrial equipment is a continuing area of development for plastics
Pipes, pumps, valves and sight glasses, made from such materials as PVC, PTFE and poly-4-methylpent-l-ene, have become well established on account of their corrosion resistance
The nylons are used for such diverse applications as mine conveyor belts and main drive gears for knitting machines and paper-making equipment
These and other materials are widely used where such features as toughness, abrasion resistance, corrosion resistance, non-stick properties, electrical insulation capability and transparency are of importance
In the general area of medicine uses range from spare-part surgery, such as hip joints and heart valves, through catheters, injection syringes and other sterilisable equipment, to more mundane but nevertheless desirable uses such as quietrunning curtain rails
In agriculture and horticulture plastics are most widely known in film form but they also find use for water piping containers, automatic watering equipment and potato chitting trays to name but a few uses
What may loosely be described as the leisure industries are widespread users of plastics
The photographic industry was of course one of the earliest users of plastics, for photographic film
There has also been widespread use of plastics in darkroom equipment for many years
More recently there has been increasing acceptance of plastics in cameras, both inexpensive and expensive
It is now recognised that well-designed camera bodies made from the correct plastics materials are more able to withstand rough usage than metal camera bodies, particularly in resistance to denting
In the audio field use of plastics for tapes and compact discs is well-established whilst plastics are now almost standard for the housings of reproduction equipment
Sports equipment makes increasing use of glass- and even carbon-fibre-reinforced materials for such diverse articles as fishing rods, canoes, racquets and so on
Toys and games (both for children and adults!) make wide use of the materials that form the subject of this book
The widespread use of plastics film for printing paper appears to be only a remote possibility in the near future
There is, however, the prospect of the establishment of polyethylene film for use in service manuals, maps and other printed articles which are required to be resistant to water, oils and other liquids
Whilst natural and synthetic fibres will no doubt remain the major materials for clothing, plastics will be more widely employed
Footwear will provide the major outlet; not only are plastics likely to be used in soles and uppers but there is an increasing use of the all-plastics moulded shoe, which although unacceptable for general wear in Britain is in high demand in under-developed regions of the world
In rainwear, plastics and rubbers will continue to be used for waterproof lining and in the manufacture of the all-plastics packable mackintosh
Polyurethane foam will find increased use as the insulation layer in cold-weather apparel and for giving ‘body’ to clothing, whilst other plastics will be widely used for stiffening of light fabrics
The above paragraphs indicate some of the major uses of plastics materials, but these materials also find applications in a variety of other areas
In addition, closely related materials such as rubbers, fibres, surface coatings and adhesives are of considerable importance
In fact a popular view is that it would not be able to produce plastics if oil were not available
This is very different from the situation 40-50 years ago when the plastics industry was being described as a ‘scavenger of raw materials’
Before World War I1 the most important class of thermoplastics, the cellulosics, were produced from vegetable sources, cellulose being an important constituent of vegetable matter
From waste oat husks were produced the furane plastics whilst routes to the nylons were also developed from this raw material
Henry Ford had experimented with soya bean plastics and several plastics had been derived from natural rubber
After the war IC1 produced a protein fibre, Ardil, from ground nuts whilst vegetable oils became a source for producing some of the acids used in nylon manufacture
Early grades of polyethylene were obtained from sugar cane via molasses, ethyl alcohol and ethylene
Some of these processes are still of importance but their relative significance has declined
On the other hand they could be revived and extended should the need arise
There is rather less scope for the re-emergence of the animal-based plastics such as casein, shellac and the blood albumin products
Until the mid-1950s the main raw material source for the European plastics industry was coal
On destructive distillation coal yields four products: coal tar, coke, coal gas and ammonia
Coal tar was an important source of aromatic chemicals such as benzene, toluene, phenol, naphthalene and related products
From these materials other chemicals such as adipic acid, hexamethylenediamine, caprolactam and phthalic anhydride could be produced, leading to such important plastics as the phenolic resins, polystyrene and the nylons
Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene
This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers
Furthermore, during World War IT, Reppe developed routes for many other monomers although these were not viable under normal economic conditions
The development of the petrochemical industry is probably the greatest single contributing factor in the growth of the plastics industry, the two industries today having a remarkable degree of interdependence
In the first instance the growth potential of plastics stimulated research into the production of monomers and other intermediates from petroleum
As a result there became available cheap and abundant intermediates which in turn stimulated further growth of the plastics industry in a way which would not have been possible if the industry had been dependent on coal alone
The petrochemical industry was founded shortly after the World War I to produce solvents from olefins which were then merely waste-products of ‘cracking’-the process of breaking down higher molecular weight petroleum fractions into lower molecular weight products, such as gasoline
By the advent of World War I1 petrochemicals were also being used to produce ethylene dichloride, vinyl chloride, ethylene glycol, ethylene oxide and styrene
During World War I1 the large synthetic rubber industry created in the United States used butadiene and styrene, the former entirely and the latter partly derived from petroleum
Whilst in its early days polyethylene was produced from molasses via ethyl alcohol and ethylene, today ethylene used for polymerisation, and for other purposes, is obtained almost entirely from petroleum
With each succeeding year in the 1950s and 1960s there was a swing away from coal and vegetable sources of raw materials towards petroleum
Today such products as terephthalic acid, styrene, benzene, formaldehyde, vinyl acetate and acrylonitrile are produced from petroleum sources
Large industrial concerns that had been built on acetylene chemistry became based on petrochemicals whilst coal tar is no longer an indispensable source of aromatics
There are three general routes for producing intermediates from petroleum: (1) Separation of individual saturated hydrocarbons from the petroleum fractions and subsequent conversion to more useful products
Important examples are n-butane to butadiene and cyclohexane to nylon intermediates
(2) Separation of olefins produced by cracking operations and subsequent conversion
This is the major route to aliphatic petrochemicals
(3) Formation of aromatic structures such as benzene and its homologues by ‘platforming’ and other processes
This route is of ever increasing importance in the production of aromatic materials
These three initial classes of product may then be converted to other chemicals by oxidation, halogenation, alkylation, hydration, carbonylation, telomerisation and many other reactions
There are nowadays few intermediates for plastics that cannot be produced more cheaply from petroleum than from other sources
During the 1960s and early 1970s the choice was not so much petroleum vel-sus coal but which petroleum route to use
However, there has now arisen a growing awareness of the fact that petroleum resources are not unlimited
This led to substantial increases in petroleum prices
Some idea of the spectacular growth in the plastics industry may be obtained from consideration of Table 1
1
Whilst growth in percentage terms was greatest before 1973, it has remained high in tonnage terms up to the present time
Table 1
2, based on Modern Plastics sources, provides USA consumption figures (based on sales data) for the main groups of plastics materials
The figures probably underestimate the global importance of the major tonnage thermoplastics since these are also manufactured in quantity in developing countries and OPEC countries
The similarity between USA and Western Europe data is quite striking
In recent years the dominance of these two areas, which traditionally accounted for at least two-thirds of the market, has decreased and by 1998 was closer to 50% of the market
This was as a result of growth in production in petroleumexporting countries, in Latin America and, particularly, in the Pacific Rim area
However, the economic turmoil which particularly affected the latter from 1997 is in early 1999 having an influence whose consequences are not yet clear
One recurring problem has been that a perceived shortage of a particular material has led to plans by more than one company to build large plants to produce that material, so that a shortage is then followed by a period of severe excess capacity and depressed polymer prices
As already mentioned, much of the use for plastics just after World War I1 was as a cheap substitute for traditional materials, and in other cases the material was used for its novelty value
In many instances the result was detrimental to the industry and it required several years of painstaking work by the technical service departments of the major plastics materials manufacturers before confidence was regained in the use of plastics
Even today the public image of plastics is not entirely positive and the significant contribution of plastics to raising the standard of living and quality of life is not fully recognised
In some outlets plastics materials have been long established
A prime example is in the electrical industries where the combination of excellent insulation properties with toughness, durability and, where desired, flame retardant characteristics have led to wide acceptance for plugs, sockets, wire and cable insulation
The ability of polyethylene to act as an excellent insulator at high frequencies was of great significance in the early development of radar
In this area three recent trends are discernible
Firstly there has been increasing acceptance of plastics for housing electrical and electronic equipment, leading to increased use of the more general purpose plastics
Secondly the development of microprocessors and the silicon chip has meant that components are becoming smaller and thus less plastics materials per part are used and in some cases even eliminated
Thirdly plastics are finding use in sophisticated techniques
For example, the photoconductive behaviour of poly(viny1 carbazole) is made use of in electrostatic copying equipment and in the preparation of holographs whilst the peculiar piezo-electric and pyro-electric properties of poly(viny1idene fluoride) are being utilised in transducers, loudspeakers and detectors
In the building industry there was much emphasis in the early 1960s on the allplastics house although the raw material suppliers who sponsored their design probably thought of them primarily as publicity exercises
As the plastics industry has matured it has been realised that it is better to emphasise those applications where plastics are preferable to traditional materials and this approach has led to widespread acceptance
Uses include piping, guttering and conduit, damp course layers, flooring, insulation, wall cladding and window frames
Quite rightly government organisations have been concerned about possible fire risks and although regulations have seemed unduly restrictive to some, others will feel that they have avoided unjustified excesses in the use of plastics
Plastics have been widely accepted as packaging materials
Plastics bottles have been particularly appreciated in the bathroom, where breakage of glass containers has led to many serious accidents
The ability of many materials to withstand the most corrosive chemicals has been of benefit to the chemical and related industries whilst the light weight compared with a glass bottle reduces the energy required for transportation
Small containers are also widely made from plastics and for medicines, particularly in tablet form, the use of closures that cannot be prised open by young children is particularly valuable
The wide use of plastics films for wrapping, for bags and sacks is almost too well known for comment
The sheer quantity of plastics used in this area nevertheless attracts critical comment, in particular that some goods are overpackaged and that waste plastics film left lying around is likely to be an all-too-durable eyesore
In many countries paper bag manufacturers have stressed the environmental desirability of using their products and in turn this has stimulated research into biodegradable plastics
The automotive industry is now a major user of plastics, with the weight of plastics being used per car increasing year by year
It has recently been stated that in the early 1990s the average car contained some 75 kg of plastics
For many years the main uses were associated with car electrical equipment such as batteries, flex, plugs, switches and distributor caps
Plastics then became established in light fittings, seating upholstery and interior body trim
In recent times there has been increased use in under-the-bonnet (under-the-hood) applications such as radiator fans, drain plugs, petrol tubing and coolant water reservoirs
In many applications the weight of material used is small
For example, it has been stated that in one small European car there were 450 different parts made from polyacetal plastics but which had a total weight of only one kilogram
The requirements of fuel economy demanding lighter cars and of increased occupant safety have led to a substantially increased use of plastics materials for bumpers, radiator grilles and fascia assemblies
Indeed if it were not for the trend towards fabric rather than leathercloth upholstery most parts of the car within reach of the driver other than the windows would be made from rubbers and plastics, and even then the fabric and the glass are polymeric! Plastics also find increasing use in vehicles for both water and air transport
Glass-fibre-reinforced plastic boats are widely used as a result of their economy in manufacture, ease of maintenance, lightness of weight and, for military purposes, antimagnetic characteristics
The non-corrosive nature of plastics also leads to their widespread use in boat fixtures and fittings
In aircraft, plastics are particularly useful on account of their low density
Domestic and commercial furniture and fittings form another important market
Uses include stacking chairs, armchair body shells, foam upholstery and desk and cupboard drawers, whilst chipboard and decorative laminates are very widely used
The variety of finishes possible at a relatively low cost compared to traditional materials as well as ease of maintenance are important in raising standards of living around the world
As with other applications the use of plastics in furniture is not without its detractors and in particular there is concern about the inflammability of those plastics that are used in a form which has a high surface-to-volume ratio, such as polyurethane foams
Whilst most of the problem appears to lie in the correct choice of covering fabric the matter continues to require attention
Industrial equipment is a continuing area of development for plastics
Pipes, pumps, valves and sight glasses, made from such materials as PVC, PTFE and poly-4-methylpent-l-ene, have become well established on account of their corrosion resistance
The nylons are used for such diverse applications as mine conveyor belts and main drive gears for knitting machines and paper-making equipment
These and other materials are widely used where such features as toughness, abrasion resistance, corrosion resistance, non-stick properties, electrical insulation capability and transparency are of importance
In the general area of medicine uses range from spare-part surgery, such as hip joints and heart valves, through catheters, injection syringes and other sterilisable equipment, to more mundane but nevertheless desirable uses such as quietrunning curtain rails
In agriculture and horticulture plastics are most widely known in film form but they also find use for water piping containers, automatic watering equipment and potato chitting trays to name but a few uses
What may loosely be described as the leisure industries are widespread users of plastics
The photographic industry was of course one of the earliest users of plastics, for photographic film
There has also been widespread use of plastics in darkroom equipment for many years
More recently there has been increasing acceptance of plastics in cameras, both inexpensive and expensive
It is now recognised that well-designed camera bodies made from the correct plastics materials are more able to withstand rough usage than metal camera bodies, particularly in resistance to denting
In the audio field use of plastics for tapes and compact discs is well-established whilst plastics are now almost standard for the housings of reproduction equipment
Sports equipment makes increasing use of glass- and even carbon-fibre-reinforced materials for such diverse articles as fishing rods, canoes, racquets and so on
Toys and games (both for children and adults!) make wide use of the materials that form the subject of this book
The widespread use of plastics film for printing paper appears to be only a remote possibility in the near future
There is, however, the prospect of the establishment of polyethylene film for use in service manuals, maps and other printed articles which are required to be resistant to water, oils and other liquids
Whilst natural and synthetic fibres will no doubt remain the major materials for clothing, plastics will be more widely employed
Footwear will provide the major outlet; not only are plastics likely to be used in soles and uppers but there is an increasing use of the all-plastics moulded shoe, which although unacceptable for general wear in Britain is in high demand in under-developed regions of the world
In rainwear, plastics and rubbers will continue to be used for waterproof lining and in the manufacture of the all-plastics packable mackintosh
Polyurethane foam will find increased use as the insulation layer in cold-weather apparel and for giving ‘body’ to clothing, whilst other plastics will be widely used for stiffening of light fabrics
The above paragraphs indicate some of the major uses of plastics materials, but these materials also find applications in a variety of other areas
In addition, closely related materials such as rubbers, fibres, surface coatings and adhesives are of considerable importance
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