Styrene monomer is a basic building block of the plastics industry, being one of the most important monomers produced by the chemical industry. Styrene undergoes polymerization by all the common methods employed in contemporary plastics technology to produce a wide variety of polymers and copolymers; it has a variety of uses due to its versatility. One of its polymers, polystyrene (PS), is a strong, malleable and inert plastic, being one of the most cost-effective and versatile available worldwide, with a full 59% of styrene produced being used in the polystyrene synthesis. One of the main advantages of PS is that it can be made clear and therefore is used to create consumer products such as Tupperware boxes and CD cases. If combined with colouring, other plastics or additional compounds it can be used to produce electronics as well as automobile parts, toys and even gardening pots. Expandable PS is light weight and is therefore often used as insulation in buildings and as packaging. The global demand for PS and expandable PS was around 14.9 million tonnes (2010) and the market for it is set to grow at a rate 5.6% from the year 2010 to 202021. However, this growth predicted may slow due to environmental restrictions placed on PS, such as bans on PS containers which have already gained legislative approval. For example, the EU have banned commercial use of single use plastics (including PS) with laws going into effect in 2021. Those bans are likely to cause market shrinkage in certain regions; however, the Chinese PS market will be largely safe from the predicted stagnation as China lifted its ban on expanded PS in 2013.

As part of this review, due to the current uncertainty facing the global disposable plastics market, an evaluation of alternative markets for styrene has been performed - this will largely be focused on ABS and SAN polymers, As stated, styrene can also be used to make Acrylonitrile butadiene styrene (ABS) and Styrene-acrylonitrile resin (SAN), which are used in refrigerator liners and food containers respectively; this makes up 20.6% of the styrene market. ABS is the largest-volume engineered thermoplastic resin and is used in a wide variety of injection-moulding applications. The ABS market demand is set to grow by 7.1% per year from 2012 to 202221, with China continuing to drive this market, with more than one-third of global production capacity and more than half of global consumption in 2017. However, this is set in stark contrast with slower predicted annual growth rates in more developed economies such as Western Europe, US and Japan. The market is currently oversupplied, as capacity has increased rapidly compared to consumption, but this is set to improve by 2022 due to increase in demand21. SAN polymers are brittle, optically clear resins with a variety of end uses including in packaging and in optical telecommunication fibres. SAN markets have continued to shift to Asia, as manufacturing industries also shift this way, with China alone accounting for 50% of global consumption; coupled with Western Europe, Japan and the US, these regions account for more than 3/4 of total global use. However, consumption is only set in increase in China, consumption in Japan, South Korea and Taiwan is expected to decline due to increased competition with other novel materials and tougher environmental regulations set to come into force in the near future. SAN consumption is forecast to grow an average of 1.6% annually between 2017-2022, lower than the growth rate of 2.4%23. Another derivative of styrene is Styrene-butadiene (SB Rubber), synthetic rubbers derived from styrene with the addition of butadiene. Increased toughness and resistance to abrasion vs natural rubber means SB is commonly used in the haulage industry (tires) and in applications requiring high impact resistance. SB Rubber constitutes 4.8% of the styrene application market. The choice between using natural rubber and SB rubber is often purely economic - as SB rubber can be produced at high quality relatively cheaply whereas natural rubber prices can be more variable. China is by far the largest styrene-butadiene elastomers consuming region in the world, followed by North America, Southeast Asia, and Western Europe22. A large proportion of SB rubber is consumed by the automotive industry, and with growing use of low-rolling resistance tires to reduce fuel consumption and decrease CO2 emissions will lead to an increase in the demand. The market is indicated to increase from 4.6 billion US$ in 2017 to 7.9 Billion US$ in 2025, with Asia being the largest market for SB Rubber23. The other form of styrene butadiene; SB latex is also a popular use of styrene occupying 4.8% of the styrene application market. It is an elastomer, with far greater elasticity than regular PS because of the higher degree of crosslinking within the macromolecular structure. It has a diverse range of uses such as electrical insulation, flooring, in footwear and in garment production24. The SB latex6 market is set to grow 3.3% per year in the period from 2015 to 2023, with the market in Asia being the largest at 40% and set to grow 3.6% per year in the same period. This growth is owed to the rise in demand of paper coatings market25. There are many different ways in which styrene can be produced, most of which involve the use of EB, as reported above. Although the primary use of EB is to produce styrene, less than 1% is used in solvent applications26. Over the last 5 years, global styrene production has been growing at a rate of 1.5% per year, with 27,180,000 tonnes produced per year and a market price of $1305 te/yr, equating to approx. 8695 Yuan/te. Due to the increasing demand for styrene and EB being the primary building block for styrene the future EB market demand will vary in tandem with the styrene market demand. The demand for EB is expected to grow at a compound annual growth rate of 3.7%, with the increasing market dominance of Asia-Pacific region27. As the use of EB in industry is primarily to create styrene, with very little sold directly to consumers, it is more practicable to recycle unreacted EB within the process rather than attempting to find a buyer for it. More than 99% of EB was produced by the alkylation of benzene and ethylene, with a small amount of EB being recovered from industrial xylene mixtures by super-fractionation. Benzene itself is one of the most important components in the petrochemical industry with a global demand of 46 million tonnes, and around 50% of benzene is used to produce EB. The market value of benzene is highly dependent upon global consumption rates in the petrochemical industries and these industries have become marginally weaker in recent times, not least within the Chinese market28. Ethylene is the other main component in EB production and also has a wide variety of uses including in surfactants and plasticisers as well as for EB formation. The market value of ethylene is dependent on the supply situation and for the Chinese market and with Japan being the biggest supplier. The market price of ethylene in China has remained fixed at around 9430 Yuan/te28 in recent years because the volume of supply is relatively stable. If in the future, Chinese industry increases its ethylene output rate, ethylene prices will likely stagnate, but if Chinese industry increases its reliance on foreign ethylene imports for future styrene production then the price of ethylene will most likely rise. In conclusion, because global and Asian market demand for styrene monomer is likely to remain high due to its versatility and plethora of uses, Bentham Corporation and GSM should aim to maximise conversion of its ethylbenzene product into styrene product directly. This styrene can be sold to a range of buyers in the chemical process industry, many producing different styrenederived polymers and other expedient products; EB, on the other hand, has a much smaller market share (as such a large proportion of EB produced is used to make styrene) and consequently future market demand for EB is much more uncertain in contrast to the strong predicted global growth patterns for styrene in the majority of major markets. If polystyrene demand declines in the future, styrene monomer can easily be fabricated into other commonly used polymers/copolymers, such as SAN, and so it is unlikely to lose its value as a commodity in the near short-term/medium-term future.