Plastics and the Environment / Edition 1

by R M Harrison, R E Hester

Overview

Plastic has become a ubiquitous part of modern life. A cheap, lightweight material, it is used in everything from food packaging to consumer electronics and microbeads in cosmetic products. However, we are becoming increasingly aware of the problems our reliance on plastic is causing in the environment. For example, recent campaigns have highlighted the build-up of microbeads in the marine environment and the damage this is doing to wildlife, and the problem of marine litter, often in very remote locations. There are also concerns over exposure to plasticisers and their possible consequences for health.

The plastics industry is under increasing pressure, not only from the government and environmental groups, but also from consumers, to improve the environmental impact of their products.

This book presents an introduction to the uses of plastics and an overview of how they interact with the environment. It is a valuable resource for students studying environmental science as well as researchers working in the plastics industry, and policy makers and regulators concerned with waste disposal and environmental planning and conservation.

Product Details

ISBN-13:	9781788012416
Publisher:	RSC
Publication date:	11/23/2018
Series:	ISSN , #47
Pages:	208
Product dimensions:	6.15(w) x 9.20(h) x (d)

About the Author

Roy Harrison OBE is Queen Elizabeth II Birmingham Centenary Professor of Environmental Health at the University of Birmingham. In 2004 he was appointed OBE for services to environmental science. Professor Harrison’s research interests lie in the field of environment and human health. His main specialism is in air pollution, from emissions through atmospheric chemical and physical transformations to exposure and effects on human health. Much of this work is designed to inform the development of policy.

Ron Hester is an emeritus professor of chemistry at the University of York. In addition to his research work on a wide range of applications of vibrational spectroscopy, he has been actively involved in environmental chemistry and was a founder member of the Royal Society of Chemistry’s Environment Group. His current activities are mainly as an editor and as an external examiner and assessor on courses, individual promotions, and departmental/subject area evaluations both in the UK and abroad.

Read an Excerpt

CHAPTER 1

The Nature of Plastics and Their Societal Usage

HERVÉ MILLET, PATRICIA VANGHELUWE, CHRISTIAN BLOCK, ARJEN SEVENSTER, LEONOR GARCIA AND ROMANOS ANTONOPOULOS

ABSTRACT

The purpose of this chapter is to review the history of plastics, describe the different kinds of plastics, their applications and their benefits, giving several examples of plastics found in our daily lives. The current chapter also provides deep insight into the qualitative characteristics of plastics, while describing their chemical nature in simple terms.

1 Plastics in a Nutshell

The term "plastic" is derived from the Greek words "plastikos", meaning "fit for moulding" and "plastos" meaning "moulded". Both terms refer to the material's malleability or plasticity during manufacture, that allows it to be cast, pressed, or extruded into a variety of shapes; such as films, fibres, plates, tubes, bottles, boxes and much more.

In addition, the wide range of possibilities to change their chemical structure or formulations and therefore their final properties allow them to be used in numerous and various applications. We can find them packaging the food that we eat, in the houses we live in, the cars we drive, clothes we wear, the toys we play with and in the televisions we watch. Plastics contribute to our convenience, as well as providing several solutions in our everyday lives, and help to improve the environmental impact of products in many applications.

When it comes to their chemical nature, plastics are synthetic or semisynthetic materials; they are organic materials, such as wood, paper or wool. Mostly derived from crude oil, they can also be produced from renewable raw materials.

In scientific terms, there are two main categories of plastic materials: thermoplastics and thermoset plastics. Thermoplastics can be heated up to form products, if these end products are re-heated the plastic will soften and melt again. Plastic bottles, films, cups, and fibres are some examples of thermoplastic products. On the other hand, thermoset plastics can be found in products such as electronic chips, dental fillings and the lenses of glasses, they will no longer melt after the "setting" process.

At the end of their useful life, plastic products can either be recycled back into new products or chemical raw materials or, where this is not possible or sustainable, used for energy recovery as a substitute for virgin fossil fuels.

1.1 The History of Plastics

For more than a century, plastics have been providing significant solutions for humans. The development of plastic materials started with the use of natural materials with plastic properties (e.g., chewing gum, shellac), they then evolved with the development of chemically modified natural materials (e.g. rubber, nitrocellulose, collagen, galalith). Finally, the wide range of completely synthetic materials that we would recognise as modern plastics started to be developed around 100 years ago. The first was discovered by Alexander Parkes in 1862 and is commonly known as celluloid today.

The development of plastic materials passed through various historical phases, becoming today the most widely used material globally. In particular, global plastics production ramped up from 1.5 million tonnes in 1950 to 335 million tonnes in 2016.

1.1.1 19th Century: The First Polymers. Although it is largely known that plastics are a modern invention, 'natural polymers', such as amber, tortoiseshell and horn, are abound in nature. These materials have a similar structure to manufactured plastics and they were often used to replace glass (amber) in the 18th century.

The original breakthrough for the first semisynthetic plastics material – cellulose nitrate – occurred in the late 1850s and involved the modification of cellulose fibres with nitric acid.

Cellulose nitrate had many false starts and financial failures until a Briton, Alexander Parkes exhibited the so-called "Parkesine" as the first world's man-made plastic, in 1862. However, the failure of this product, due to its high manufacturing costs, led to the creation of Xylonite by Daniel Spill. This new material started finding success in the production of objects such as ornaments, knife handles, boxes and more flexible products such as cuffs and collars.

It was in 1869 that an American, John W. Hyatt, made a revolutionary discovery, a process to produce celluloid, a product that could be used as a substitute for natural substances such as tortoiseshell, horn, linen, and ivory. This product entered mass production in 1872.

1.1.2 20th Century: The Revolution of Plastics Starts. Up until the early 1900s, it was impossible to use cellulose nitrate at very high temperatures, because it was flammable. The development of cellulose acetate brought about a solution to this problem, as it started being used as a nonflammable 'dope' to stiffen and waterproof the fabric wings and fuselage of early airplanes and was later widely used as cinematographic 'safety film'. In the meantime, casein formaldehyde was developed, based on fat-free milk and rennin, and used for shaping buttons, buckles and knitting needles. The next years saw a revolution in plastics, making them an integral part of our daily lives.

1.1.3 Beginning of the 20th Century: The Discovery of Bakelite. In 1907, Belgian Leo Baekeland (who coined the term plastic later on), discovered Bakelite, which was largely used in the expanding automobile and radio industries at that time.

In 1912, polyvinyl chloride (PVC) and polyvinyl acetate (PVA) were discovered by a German chemist, Fritz Klatte. The following year, Jacques E. Brandenbergen, a Swiss engineer, invented Cellophane, a clear, flexible and waterproof packaging material.

1.1.4 1920s: Staudinger and Polymers. In 1921, the first injection moulding press appeared, invented by Arthur Eichengrün.

Meanwhile, a revolution came in 1922, when a German, Herman Staudinger, father of macromolecular chemistry, claimed molecules could join to form long chains and therefore become 'macromolecules' or polymers. Staudinger provided enough evidence for his macromolecular concept and promoted it, despite the strong opposition of several chemists.

Staudinger provided the theoretical basis for polymer chemistry and significantly contributed to the rapid development of the polymer and plastic industry – which are the reasons why he was awarded with Nobel Prize for chemistry in 1953.

Another important scientific breakthrough occurred in 1927, when Waldo Semon, an American researcher, found a way to plasticise PVC, which had been discovered more than a decade before. PVC was thus converted into a flexible material that could be used for flooring, electrical insulations and roofing membranes. Thanks to this, its real development could start.

1.1.5 1930s: Plexiglas™ and Nylon™ First Appear. In 1930, the commercial production of polystyrene started. In the meantime, Otto Röhm invented a great product in 1933, Plexiglas™, "a crystal-clear, shatter-proof polymethyl acrylate sheet", which found an important market in the aircraft industry.

In 1935, Wallace Carothers from the company DuPont was the first to synthesized Nylon™ (polyamide), which became very famous in stockings. The first commercial PVC products were introduced onto the market in 1934 and 1935, these were flooring and pipes, respectively.

Three years later, a Swiss researcher, Pierre Castan, patented the synthesis of epoxide resins, which were initially used in dentistry (for dental fixtures and castings), as well as medicine. Their properties were also useful as a constituent of glue.

1.1.6 1940s: Large Use of Plastics in World War II. World War II meant a boost for the production and further development of plastics, which took on a key role in the military supply chain. Plastics were used to make almost everything: for example, nylon could be found in parachutes, ropes, body armour and helmet liners, while Plexiglas™ replaced glass in aircraft windows.

A wide variety of pioneering materials, which are still used today, were invented during the wartime period, such as polyethylene, polystyrene, polyester, polyethylene terephthalate, silicones and many more.

1.1.7 1950s: The Spread of Plastics for Domestic Usages. The 1950s saw the growth of plastics for domestic use. Decorative laminates were invented, such as Formica™ tables, which were very popular particularly in the US, and were used in espresso bars and diners. In the same period, plastics also became a major force in the clothing industry. Polyester, Nylon™ and Lycra™ fabrics were easy to wash, needed no ironing and often were cheaper than their natural alternatives.

In 1953, an American chemist named Daniel Fox discovered polycarbonate, a new type of thermoplastic that was very durable and almost bulletproof. Today, it can be found in several modern products, such as smartphones.

1.1.8 1960s: Plastics in the Fashion Industry. The 1960s are known as a decade of mass distribution of stylish, innovative and impressive plastic products in the fashion world, such as soft and hard foams with a protective skin, wet-look polyurethane, transparent acrylic and artificial leather.

Home decoration was also enriched, where unconventional designer furniture such as inflatable chairs and acrylic lights became important for fashion-conscious consumers.

Moreover, plastic materials played an important role in the production of spacecraft components, its lightness and versatility made it irreplaceable for the success of space exploration.

1.1.9 1970s: Plastics Become the Most Used Materials Worldwide. The technological advances during this period would have been impossible without plastics. In engineering and in the computer industry, the new polymers started to replace the use of metals. In healthcare, the hygienic nature of plastics meant that they became extremely important.

1.1.10 1980s: Plastics and the Development of Communication and Transport. The rise of global communications had a direct impact on the production and use of plastics, which provided raw material for the production of personal computers, fibre optic cables and portable telephones.

In transport, the demand for plastics in cars also increased. In the 1980s, the first flight tests of an all-plastic-aircraft took place. Moreover, plastic packaging became very important in shopping, because it helped in the distribution and preserving the quality of the products we buy from supermarkets.

1.1.11 1990s and 2000s: Plastics' Key Role in Society. Consumer demands for longer product shelf lives and freshness retention led to the development of plastic packaging that has superior barrier properties. Raised awareness in society of the necessity to save fossil fuels increased the need for plastic products, enabling improvement in the energy efficiency of buildings and a reduction in fuel consumption in transportation.

In the 2000s, plastics became key components for meeting challenging societal demands. Used in several applications, plastics are currently essential in the design of structural elements such as insulation, life support systems, space-suit fabric, food packaging, guidance and communication systems, solar panels, and so forth.

2 How Is Plastic Made?

Derived from organic materials, plastics today are mainly made from fossil raw materials. However, the production of plastics only accounts for 4–6% of global oil consumption.

The production of plastic from crude oil begins in the distillation process of an oil refinery, involving the separation of heavy crude oil into lighter fractions. Each fraction is a mixture of hydrocarbon chains (chemical compounds made up of carbon and hydrogen), which differ in terms of the size and structure of their molecules. One of these fractions, naphtha, is the crucial raw material for the production of plastics. Naphtha is used to generate, through cracking, the different monomers needed (ethylene, propylene, styrene, etc.).

These monomers are the building blocks to produce plastics, through the so-called polymerisation process. The two major polymerisation processes are called polyaddition and polycondensation, and they both require specific catalysts. In a polyaddition process, monomers like ethylene or propylene simply join to form long polymer chains. Polycondensation is the process through which the polymer originates from successive bonds between monomers, with the elimination of a small molecule (water, ammonia, etc.) during the bonding process. Each plastic has its own properties that depend on the various types of basic monomers used, its structure and formulation.

Research and innovation is ongoing to diversify the raw material base to produce plastics. In particular, biomass can be used for the production of so-called bio-based plastics. There are two possible categories of plastics that can be derived from renewable resources. The first one includes similar polymers to those produced from crude oil, but with their monomers being produced from biomass: for instance, sugar cane can serve for the production of ethylene and consequently, polyethylene. The second category includes new polymers derived from new monomers. For example, starch can be used to produce lactic acid and consequently polylactic acid (PLA). In 2017, the global production of bio-based plastics was around 2 million tonnes.

2.1 The Different Kinds of Plastics

There are different types of plastics that can be grouped into two main polymer families, thermoplastics and thermosets.

Thermoplastics are a family of plastics that can be melted when heated and hardened when cooled. These characteristics, which lend the material its name, are reversible. That is, it can be reheated, reshaped, and hardened repeatedly. This quality also makes them mechanically recyclable.

Thermosets: Thermoset, or thermosetting, plastics are synthetic materials that undergo a chemical change when they are treated, creating a three-dimensional network. After they are heated and formed, these molecules cannot be re-molten and reformed.

2.1.1 Thermoplastics. Thermoplastics can be categorised according to their chemical structural organization and the level of their properties and performances (Figure 1). They represent almost 80% of the plastics demand.

2.1.1.1 Standard Plastics

Standard plastics are the most widely used plastics and account for more than 85% of the global thermoplastics demand (Figure 2).

Polyolefins: They represent the largest family of thermoplastics (55%), which includes all types of polyethylene (LDPE, LLDPE, HDPE) and polypropylene. They are produced mainly from oil and natural gas by a process of polymerisation of ethylene (PE) and propylene (PP) respectively. Thanks to their versatility, polyolefins are used in a very wide range of applications ranging from packaging, automotive, building and construction, medical, sports to consumer goods.

– LDPE: is used in cling film, carrier bags, agricultural films, milk carton coatings, electrical cable coatings, and heavy duty industrial bags.

– LLDPE: is used in stretch film, industrial packaging film, thin walled containers, and heavy-duty, medium- and small bags.

– HDPE: is used in crates and boxes, bottles (for food products, detergents and cosmetics), food containers, toys, petrol tanks, industrial wrapping and film, pipes and houseware.

– PP: is used in food packaging, including yoghurt and margarine pots, sweets and snack wrappers, microwave-proof containers, carpet fibres, garden furniture, medical packaging and appliances, luggage, kitchen appliances, and pipes.

Polyvinyl chloride: PVC is the third largest thermoplastic and one of the earliest plastics. It is derived from salt (57%) and oil or gas (43%). It can be either in rigid form, used mainly for the production of pipes and fittings or window-frames, or in soft form such as in flooring or cable applications.

Polystyrene: Polystyrene (PS) is a thermoplastic polymer which can be solid or foamed. It is made from the monomer styrene. It is widely used in packaging, cosmetic packs, toys and refrigerator trays, as well as in many other applications.

Expanded polystyrene: Expanded polystyrene (EPS) is a solid foam with a unique combination of characteristics, such as lightness, insulating properties, durability and an excellent processability. EPS is used in thermal insulation board in buildings, in packaging, cushioning of valuable goods, and in food packaging.

Polyethylene terephthalate: Polyethylene terephthalate (PET) consists of polymerised units of ethylene terephthalate monomers. It is used in fibres for clothing and in containers for foods and beverages.

(Continues…)

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Table of Contents

The Nature of Plastics and Their Societal Usage;
Plastic in Marine Litter;
Microplastics in the Environment;
Nanoplastics in the Environment;
Plasticisers and Their Impact on Wildlife;
Plastics Additives and Human Health: A Case Study of Bisphenol A (BPA);
Plastics Recycling;
Plastics, the Environment and Society: Current Consensus and Future Directions