What is Polystyrene?
Polystyrene is a naturally transparent and synthetic thermoplastic extracted from a styrene monomer. It is typically available in two forms – Solid Plastic and rigid foam material. Its main characteristic includes softening when applied heat and its films and sheets can be transformed into various products used in different applications. It is one of the largest commodity plastic in terms of the market size(holding approximately 7% of the global thermoplastic market).
The solid plastic form of PS is mostly used in medical and healthcare applications like Petri-dishes, test tubes, consumer appliances, containers, CDs, smoke detectors, etc.
Talking about the foam form of PS, It also has a wide array of packaging and consumer goods applications. You must have noticed a white foam custom packaging whenever you bought a new television or any other sizable electronic product(That foam packaging is made from polystyrene foam).
How is PS Made?
Like other thermoplastics, PS is made by filtration of hydrogen fuels into lighter groups called “fractions”. Some of those fractions are blended with certain catalysts to though polystyrene; the process is called polymerization. PS foams are made by “Blowing agents” that enlarge or lengthen and shape the foam so that it can trap air.
Polystyrene Manufacturers –
Here are the largest and most prominent PS manufacturers in the world:
Country of Origin
|Chi Mei Corporation||Taiwan|
|Kumho Petrochemical||South Korea|
History of PS Plastic –
Polystyrene was invented in 1839 by Edward Simon, a medical professional from Berlin, Germany. He started by filtering an oily substance, a monomer made from Styrol(derived from storax).
I. G. Farben started the commercial production of styrene monomer in Ludwigshafen by the year 1931. They used it in many applications by successfully developing a reactor vessel that extruded polystyrene through a heated tube and cutter, producing PS in pellet form.
Fast-forward to 1954, the Koppers Company in Pittsburgh, Pennsylvania, developed a prototype foam under the trade name Dylite. That same prototype is now famously known as Expanded-polystyrene(EPS)
Fun Fact – The First polystyrene-made product order was shipped by Dart Container Corporation, the largest manufacturer of foam cups and containers, in 1960.
Fundamental Properties of PS Plastic –
Adding additives and certain chemical agents with PS is a normal practice to enhance some of its weaker properties. For example – PS can be blended with methyl methacrylate to achieve higher clarity and better chemical and UV stability. However, one should keep a note that the blend makes yellow products.
Anoter good example is poly(styrene-co-butadiene) (SBR, SBS) and poly(styrene-co-acrylonitrile-co-butadiene) (ABS). All the blends boast high impact and stress strength.
To specifically increase polystyrene’s heat resistance, os is often copolymerized with a monomer with an alternating structure.
- Lack of crystallinity makes PS optically transparent.
- PS is an excellent electrical insulator and boasts good chemical resistance against diluted acids and bases.
- Poor resistivity towards hydrocarbon solvents, oxygen, and UV
- Meager impact strength due to firmness in the polymer’s backbone
- The maximum temperature limit for prolonged r continuous use is limited due to lack of crystallinity and low glass transition temperature (Tg = 373 K (100°C))
- Medium to high tensile strength and low impact strength
Below are the typical properties of PS Plastic and foam:
53 MPa (7700 PSI)
210-249 °C (410-480 °F)
|Heat Deflection Temperature (HDT)||
95 °C (284 °F) at 0.46 MPa (66 PSI)
83 MPa (12000 PSI)
|Typical Injection Molding Temperature||
38 – 66 °C (100 – 150 °F)
|Molecular Weight of Repeat unit||104.15 g mol-1|
|Molar Cohesive Energy||
J mol-1 34200 – 37100
g mL-1 1.05 – 1.06
|Entanglement Molecular Weight||
g mol-1 13600 – 17500
|Solubility Parameter||18.5 – 19.4 MPa|
Disadvantages of Polystyrene –
- High Flammability. Should be handled carefully
- Recycling is possible but is very expensive
- Harmful to environment
- EPS, due to its low density, fills a large amount of space in the landfills.
Interesting Read – How is Plastic Made? A Simple and Detailed Explanation.
Commerical Polystyrenes –
There are three main grades of polystyrene used worldwide.
High-impact polystyrene is a thermoplastic boasting high impact strength. It is comprised of 5 to 10 rubber. HIPS is a graft copolymer with polystyrene sidearms. The grafting takes place when some of the radicals start reacting to double bonds of the polybutadiene.
General-purpose polystyrene is a crystal clear polymer, and it is rigid and rather brittle in its nature and an in-expensive thermoplastic extracted from styrene monomer. GPPS is solid form plastic that is usually manufactured in the form of 2-5 mm pellets.
Expanded Polystyrene is comprised of beads commanded by pentane( the blowing agent). EPS is widely utilized in packaging applications and boasts good processability, high impact resistance, and thermal insulation.
Styrofoam is a Dow chemical company trademarked brand of closed-cell extruded polystyrene foam (XPS). It is also known as “Blue Board,” manufactured as a foam continuous building insulation board extensively used in walls, foundations for thermal insulation, and a water barrier.
The material is usually light blue in color. It is most popular in terms of applications in the United stated and Canada. It comprises 95% air, making it unsinkable and capable of marinating its form for a prolonged time.
Styrofoam is mostly utilized for manufacturing containers, packaging materials, and coffee cups. The branded polystyrene foam is categorized by its roughness and the type of “crunch” it makes while being cut. It has moderate soluble properties, mixing with many organic solvents, cyanoacrylate, and propellents.
PS plastic and foams come with many applications making our day-to-day life very easy. Here are they:
Thermoplastics utilization of automotive has increased substantially over the years; Polystyrene is no different. Both foam and solid variation are used for manufacturing knobs, instrument panels, trims, sound dampening foams, energy-absorbing door panels, and child protective seats.
For insulation uses, good thermal insulation properties are a must, and lightweight polystyrene is provided fabulous insulation properties making it apt for applications like refrigerators, freezers, building walls & roofing, cold storage facilities, etc. Polystrene insulation moves less, resistant to water damage, and durable in its nature.
As PS foam and solid form doesn’t react with materials and are cost-effective is used in electronic appliances like air-conditioners, coolers, ovens, blenders, vacuum cleaners, etc.
Polystyrene foam and plastic can play an integral role in a product’s aesthetic integrity; thus, it is also used in appliances like computers, television, routers, and printers.
The packaging is the largest PS foam consumer thanks to numerous food industry options – egg cartons, meat packaging, poultry trays, and container packaging for vegetables. Additionally, CD and DVD cases and other types of foam packagings are also used in the market.
Owing to its clarity and good sterilization properties, it is quite popular within the medical sector for being used in products like Petri dishes, diagnostic components, culture trays, test tubes, and medical devices.
Polystyrene Plastic Processing Conditions –
PS is best suited for the injection molding process due to its mechanical and physical properties. However, drying is not necessary but should be done if stored improperly before processing. Here are the available processing conditions:
If drying is required, the advisable conditions are 2 – 3 hours before professing at 80 C (176 F).
20 – 70 C (68 – 158 F)
180 – 280 C (356 – 536 F)
|Material Injection Pressure||20 – 60 MPa|
Recommended speed is fast
|Screw L/D Ratio||20:1|
The Future of Polystyrene –
According to a study conducted by Intrado GlobalNewsWire in 2019, polystyrene will register a CAGR of 4.87% from 2018 to 2023. PS plastic and foam will have a market value of over USD 33 Billion by the end of 2023.
Global Extruded Polystyrene Market, by region, 2018
the packaging industry is the largest and fastest-growing contributor to the PS market. The growing number of packaging applications and rapid growth in the E-commerce sector will continue the growth momentum up for PS.
As you can see in the above chart, Asia-pacific (thanks to china) is the market leader and, according to several analyses, will remain the market leader for the near future.
1. Why is polystyrene useful?
Ans. Polystyrene is the go-to packaging material thanks to its high compression, It is also light and cool. It is more suspective snapping or collapsing, but still, protects delicate objects if dropped. It is also a strong insulator, meaning it can flow and accumulate electrical charge with ease.
2. Is Polystyrene toxic to humans?
Ans. Polystyrene is long been caused for being toxic and unhealthy for humans. It contains two harmful substances called benzene and styrene. It has been proven that hot ad liquid food can go through a partial break down leaching certain impurities or toxins in your body.
3. What is the chemical name for polystyrene resin?
Ans. The chemical name – C 8 H 8. It is often regarded as the most used plastic.
4. Is Polystyrene polar or non-polar?
Ans. It is non-polar and can be only mixed with non-polar solvents. Because it is comprised of only carbon dioxide bonds.
5. What is the history of polystyrene?
Ans. The commercial production started back in 1938 and within no time it became extremely popular with manufacturers thanks to its low-cost production for large quantities, great processability with injection molding, good mechanical, physical, and optical properties.
The Takeaway –
Polystyrene plastics have high applicability, readily available in the market, and inexpensive, so choosing them for your next product can be quite profitable.
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