Polystyrene (PS): Production, Market, Price and its Properties
What is Polystyrene (PS)?
It is a synthetic polymer made of monomer styrene. PS is made by the polymerization of styrene which is a kind of building block material used to produce a variety of plastic products. It also occurs naturally (strawberries, cinnamon, coffee and beer).
This plastic polymer is a natural transparent thermoplastic that is available in both forms solid as well as a rigid foam material. Generally used PS material is clear, hard and brittle in properties.
It is commonly used plastic to produce a variety of end segment products. The solid form of plastic is widely used to produce products which require clarity. These are often used with a combination of colorants, additives and other forms of plastics to produce goods such as electronic appliances, automobile parts, gardening pots, equipment etc.
PS is made of foam material and is termed as Expanded Polystyrene (EPS) or Extruded Polystyrene (XPS) which is known for its insulating and cushioning properties.
The solid form of this material is commonly used for medical device applications (test tubes, Petri dishes etc) or for day to day items like smoke detectors, CDs, food containers, coffee cups etc. The foam form of the polymer is commonly used for as a packaging material for a variety of products.
Polystyrene Pricing Trend
Production of Polystyrene
It is produced like other plastic polymers through a polymerization process. This polymer result when the styrene monomers interconnect with each other during polymerization.
In this process the carbon IT bond of the vinyl group breakdown and form a new carbon bond, further attaching to the carbon of another styrene monomer in the chain. The newly formed bond is much stronger than the last one that is why it becomes difficult to de-polymerize the polymer.
It is produced primarily in two different forms:
This is commercially an important form of PS produced. To produce atactic PS phenyl groups are randomly distributed on both sides of the polymer chain. This random positioning prevents chains from aligning and provide sufficient amount of regularity to achieve the desired crystallinity. This plastic polymer has a glass transition temperature of 90° C and polymerization process is strongly initiated by free radicals.
To produce syndiotactic PS “Ziegler-Natta polymerization” process is used. In this process of polymerization, phenyl groups are positioned on the alternate sides of the hydrocarbon backbone. This is a highly crystalline form of PS polymer produced with a transition temperature of 270° C. These types of PS are currently produced under the brand name of XAREC by Idemitsu Corporation by using metallocene catalyst for the polymerization reaction.
In the production of polymer generally, four polymerization process and three foaming methods are brought into use. The initially used three processes are Mass Suspension, Emulsion and Solution Polymerization. The latter is- closed mold foaming of EPS, extrusion of EPS and direct injection extrusion of GPPS.
Global Production Capacity of Polystyrene
Global PS capacity in 2016 was 14.7 million tons. China was the leading countries with highest production capacity. Asia is the leading region accounting for the largest share of global production capacity of the polymer. It occupied 55.1% of the production capacity.
The Asian region is the largest market for the PS plastics is also responsible for more than half of the global production capacity. The second largest region is North America accounting for 17% followed by Europe with 16.3%.
Global Market Forecast for Polystyrene
The market for PS is forecasted to grow more than US$28 bn by 2020. The market was around US$ 24bn in 2016 and will cross US$ 28bn by 2020 as per the industry analysis. PS plastic market has been growing rapidly since last few years and is also expected to increase in coming years also.
PS is a versatile plastic with a number of uses in different end segment markets. PS is widely used to produce daily use consumer products such as refrigerators, air conditioners, televisions, computers and disposable utensils (foamed cups, plates and bowls).
The major factors driving PS market are population growth, increasing urbanization and industrialization, increased middle-class income.
Packaging and electronics sector are two major prominent sectors which have witnessed the growth in demand for PS in recent years and are also anticipated to further fuel the growth of global PS market.
China is expected to be the largest market for PS for the year (2016-17) which is followed by other emerging economies in Asian- Pacific regions.Even though the Asia-Pacific countries are largest consumers of PS worldwide but still other countries such as Africa, Europe, and South America are also expected to have increased demand in coming years.
It is also subjected to certain restrains in the forecasted period such as fluctuating raw material prices (benzene, styrene monomer etc). Disposal problems related to this material and its negative scrap value may also hamper the growth of the market.
Topmost players of PS in the global market are BASF SE (Germany), Styrosolution Group (Germany), Videolar S/A. (Sao Paulo), SABIC (Saudi Arabia), and Formosa Plastic Corporation (Taiwan) among all other manufacturers.
History of PS Polymer
It was initially discovered by Eduard Simon, an apothecary of Berlin. From storax, the resin of Turkish sweet gum tree Liquidambar a distilled an oily kind of substance named as styrol. After few days of discovery, Simon found that the styrol produced from monomer has thickened due to oxidation into a jelly form which he named “Styroloxyd”.
In 1845 chemist John Blyth and another German chemist August Wilhelm Von Hofmann represented the same transformation of styrol in absence of oxygen. This substance was termed as “metastyrol”. Later, analysis depicted that the chemical properties of both the substance produced are same.
Further in 1866 Marcelin Berthelot rightly analyzed the formation of metatyrol/dining from styrol by the process of polymerization.
After 80 years of the time gap, on the basis of the thesis of German organic chemist “Hermann Staudinger (1881-1965),” it was discovered that the heating of styrol results in a chain reaction that produces several macromolecules named as PS plastics.
Properties of PS Plastics
It is a versatile form of plastic used to make a variety of end segment plastic products. PS polymer is a clear, amorphous, non-polar kind of material that can be easily processed and converted to a large number of semi-finished goods such as foams, films, and sheets. In terms of volume, it is one of the largest used plastic due to its properties such as:
- It has high impact and heat resistance.
- These polymers are a good electric insulator with excellent optical clarity.
- PS has strong chemical resistance to diluted acids and bases.
- It is a viscous liquid above its glass temperature which allows easy fabrication into a large number of finished goods.
- They are easily expandable and allow good flow.
- These materials are strongly flame retardant in nature.
Physical Properties of PS
- Chemical formula used for PS is (C8H8)n
- Density- 0.96–1.04 g/cm3
- Melting point is ~ 240 °C (464 °F; 513 K)  For Isotactic PS
- Solubility in water-insoluble
- Solubility-Non soluble in acetone 
- Thermal conductivity of polymer is 0.033 W/ (M·K) (foam, ρ 0.05 g/cm3) 
- Refractive index is 1.6; dielectric constant 2.6 (1 kHz – 1 GHz) 
Different Grades of PS Plastics
PS is counted among one of the most important and widely used commodity plastic in the market. The production volume of PS and styrene copolymers are at several million tons per year globally.
It has been selling under different trade names such as (Styrofoam, Styropor, Styron, Carinex, Styro-Flex, Cellofoam, Depron XPS, Fostarene, Styraclear, Lustrex1, SABIC PS, and INEOS Styrenics ) globally.
In general, these polymers are available in three important different grades which are:
GPPS also termed as Crystal-clear PS. This form of plastics is fully transparent, rigid and is usually low-cost PS made from styrene monomer. GPPS is a solid form of PS manufactured in form of 2-5 mm PS pellets.
High impact PS contains usually 5 to 10% of rubber (butadiene) and is for producing products which require higher impact resistance. HIPS PS is usually a kind of graft copolymer having PS as side arms. The grafting process occurs when some radical reacts with the double bond of poly-butadiene.
This grade of plastics consists of micro-pellets or beads containing blowing agent (usually pentane). EPS or Foamed PS is thermally insulating with high impact resistance and easy processing.
Applications of PS Plastics
It is a cheap and easily available form of the polymer. It is used for many applications such as electronics, medical, optical, automotive parts, and packaging of consumables. A large number of goods produced using PS are formed by injection molding including dining utensils, cups, CD cases, cosmetic containers and covers etc.
It is majorly used for producing two kinds of semi-finished products- PS Sheet and PS Foam. This semi-finished good is widely used to produce final products for a variety of end market segments.
PS is widely used to produce high impact styrene sheets which are further used for producing models, prototypes, signs, displays, enclosures and more. These sheets are low-cost material and used for general purpose uses. PS sheets are preferred over another form of sheets for a variety of products as they are:
- Water Resistant to high density
- Light Weight
- Temperature sensitive
- Non-toxic and odorless
- Excellent forming properties
- Dimensionally stable & low water absorption
- Heat & electronically sealable
PS Sheets – Physical properties
- Forming temperature: 325°F to 350°F
- Maximum temperature: 180°F
- Meets FDA standards
- Opaque with matte finish
- Standard size of sheets sold- 40″ x 72
PS foam is another form of the semi-finished good of the polymer which is further used to produce end segment consumer products. PS foams comprise 95-98% of air. They are good thermal insulators, therefore, are widely used as building insulation material.
The damping property of PS foam makes it highly suitable for the packaging industry. PS is used on a very large scale in the packaging industry.
Suitable properties and low cost of plastics foam prove to be a strong competition for other forms of polymers used in packaging industry. PS foams ate also used in the construction sector for construction of non-weight bearing architectural sectors such as ornamental pillars.
General Properties of PS Foam
- Lightweight and portable,
- Easily recyclable,
- Can be easily laminated with epoxy resin,
- PS foams have high thermal insulation,
- It is ideal for outdoor/indoor works,
- Resistant towards moisture and compression,
- Low price and highly durable
- Manufactured into different shapes, sizes, and compression materials.
PS foams are commonly produced in two different forms:
A. Expanded Polystyrene (EPS)
EPS is a kind of rigid, tough and closed foam. It is usually white in appearance and produced from pre-expanded PS beads. EPS is one of the most commonly used PS foam in everyday life. The white foam is commonly used for hot beverages, in refrigerators, insulation, and packaging etc.
EPS material is inexpensive and lightweight (15-30 kg per cubic meter) It does not lose its fundamental property with time and is completely recycled and being reused to maintain environmental balance.
Due to its favorable technical and physical properties such as low weight, rigidity, and formability, EPS is brought into use for wide range of applications. It is even used for producing molded sheets which are used for building insulation and packaging materials
B. Extruded Polystyrene (XPS)
XPS is another form of a foam which offers improved surface roughness and higher stiffness with reduced thermal conductivity. The density range is about 28-45 kg/m3. It has almost same kind of chemical composition as of the EPS but produced with a different kind of technology. EPS comes in three basic colors pink, blue and green etc. It is commonly used for manufacturing demonstration panels and in the construction area.
General Uses of Polystyrene
It is applicable to a variety of end-user industries for producing a number of goods in different forms. It has become the most commonly used polymer in various industries such as:
Appliance – It is used in a number of appliances like refrigerators, air conditioners, oven, microwaves, vacuum cleaners, and blenders etc. It is used in solid or foam form widely for manufacturing these appliances as it is inert (does not react with materials), cost-effective and long-lasting.
Automotive – PS (solid and foam) is used in the production of many automotive parts including knobs, instrument panels, trim, energy absorbing door panels and even sound dampening foam.
Electronics – It is used for the housing and also in other parts of televisions, computers and different types of IT equipment, where combination of form, function, and aesthetics are required
Food Service – PS holds a major share in packaging sector as compared to its competitors. It is widely used in food packaging as it insulates better, keeps food fresh for a long time and is cost-effective.
Insulation – Lightweight PS foam proves to be excellent thermal insulation in a number of applications such as building wall, roofing, refrigeration, freezers and even in industrial cold storage facilities. It is preferred for insulation as it is more inert, durable and resistant to water damage.
Medical – Due to its clarity and ease of sterilization, PS is used for a wide range of medical uses including tissue culture trays, test tubes, petri dishes, diagnostic components and other testing medical devices.
Packaging- It is highly used and preferred material in the packaging sector. It is widely used to protect consumer products like CD and DVD cases, foam packaging peanut for shipping goods, consumables packaging, meat and poultry trays and also egg cartons etc. They are a suitable material for packaging as protect goods against damage and spoilage.
Disadvantages Of PS Plastics
Though it is the most widely used thermoplastic and also preferred over other competitors for a number of uses, still has certain limitations in usage which are:
- It is flammable, but retarded grades are also available.
- They are poor solvent resistance and might be attacked by many chemicals.
- Homo-polymers are brittle in nature.
- Subjected to stress and environmental cracking.
- They have poor thermal stability.
Recycling of PS Plastics
Usually, it is not accepted in the curbside collection at the recycling centers. Different centers and techniques are utilized for recycling of PS. In certain countries such as Germany, there is a law that requires the manufactures to completely take the responsibility of recycling or disposing of any PS packaging material they sell.
Recycling of this plastic products requires a high amount of investment to set up compactors and logistical systems to carry out the process. The recycled form of material is used with new produced PS materials to produce PS sheets and foams.
Individually recycled PS scrap can be used to produce products such as clothes, hangers, park benches, flower pots, toys, rulers, stapler bodies, seedling containers, picture frames and architectural moldings from etc.