Polystyrene (PS) Plastic: Characteristics, Classification and Applications

PS plastic (Polystyrene plastic, plastic number 6) is a thermoplastic polymer with the chemical formula (C8H8)n, formed from Styrene through polymerization.

Eduard Simon, a Berlin pharmacist, discovered PS plastic in 1839 and the German corporation IG Farben began commercial production of this plastic in 1931.

PS plastic has 6 outstanding characteristics: high transparency, hardness, brittleness, non-toxicity, odorless and resistant to decomposition by many Acids and Bases.

With a density of 1.05 – 1.06 g/cm³, tensile strength of 35 – 59 N/mm² and good temperature resistance of 70 – 75°C, Polystyrene plastic can turn into a liquid at 100°C and return to a solid state when cooled, making it easy to shape by many methods.

PS plastic has 5 main types:

1. EPS plastic (Expanded Polystyrene)
2. XPS plastic (Extruded Polystyrene Foam)
3. OPS plastic (Oriented Polystyrene)
4. HIPS plastic (High Impact Polystyrene)
5. GPPS plastic (General Purpose Polystyrene).

Each type has its own properties and applications, of which EPS and XPS are often used as insulation materials, OPS for packaging, HIPS for equipment housings and GPPS for transparent food packaging.

Based on information provided by reliable sources, Kosmos found that PS plastic is widely used in four main areas: packaging (food containers, plastic cups), electronics (device housings), medical (syringes, test tubes) and construction (insulation panels, decorative materials).

“Polystyrene has remarkable mechanical properties with tensile strength ranging from 35 – 59 N/mm² and operating temperature stability in the range of 70 – 75°C, making this material suitable for many industrial applications.” according to the American Society for Testing and Materials (ASTM) International Report (2024).

What is PS plastic?

PS (Polystyrene) plastic is a thermoplastic polymer with the chemical formula (C₈H₈)n. This type of plastic has the SPI code (Society of the Plastics Industry, plastic symbol) number 6, so it is also called plastic number 6. It is formed from Styrene, through polymerization reaction. The chemical structure of PS plastic includes Styrene units linked together to form long Polymer chains.

Brief History of Polystyrene Plastic

Below is information about the discovery and production of Polystyrene plastic that Kosmos has compiled from many reputable sources.

The discovery process 

According to information verified by experts and reputable sources, Kosmos warehouse knows that the discovery of Polystyrene plastic has 4 main milestones:

1. In 1839, Eduard Simon (a Berlin pharmacist) was the first to discover the precursor of PS resin from the resin of the Oriental gum tree. Specifically, he distilled the resin into a viscous substance called Styrol (Styrene). After only a few days, the viscous substance solidified into a jelly form that is known today as Polymer.
2. In 1845, two chemists, John Buddle Blyth (Jamaican) and August Wilhelm von Hofmann (German) demonstrated the conversion of Styrene from liquid to jelly form without oxygen.
3. In 1866, French chemist Marcellin Berthelot correctly identified the process of forming the jelly form of Styrene as a polymerization process (polymerization reaction).
4. About 80 years later, German chemist Hermann Staudinger realized that heating Styrene would start a chain reaction that created macromolecules, eventually leading to the birth of Polystyrene plastic.

Production process

From 1931 to 1949, there were 4 main units producing Polystyrene plastic:

1. In 1931, IG Farben (a German chemical and pharmaceutical corporation) began producing PS in pellet form.
2. In 1944, Otis Ray McIntire (a chemical engineer) developed a process for producing foamed PS (Styrofoam).
3. In 1949, Fritz Stastny (a chemical engineer) developed pre-expanded PS granules for molding and extrusion (Styropor).
4. In 1954, Koppers Company (a chemical and materials company, USA) developed expanded polystyrene (EPS) foam under the trade name Dylite.

Features of Polystyrene resin

The main characteristics of polystyrene are that it is transparent, hard and brittle. Its impact resistance can be increased by combining it with other materials. It can turn into a liquid at 100℃ and return to a solid state when cooled. This feature makes PS plastic easy to shape by extrusion (foaming), vacuum forming (film forming) and casting.

Polystyrene is non-toxic, odorless and is a plastic used mainly in the food packaging industry. Polystyrene is relatively chemically inert, impermeable to water and resistant to degradation by many Acids and Bases. In particular, the molded shape of PS No. 6 plastic has a fairly high level of detail.

Mechanical properties of PS . resin

After collecting and evaluating information from reputable sources, Kosmos has summarized the mechanical properties of Polystyrene plastic in the following table:

Polystyrene plastic classification?

There are 5 main types of Polystyrene: EPS (Expanded Polystyrene), XPS (Extruded Polystyrene Foam), OPS (Oriented Polystyrene), HIPS (High Impact Polystyrene) and GPPS (General Purpose Polystyrene).

Expanded Polystyrene – EPS

EPS is a foamed PS plastic. EPS foam is produced by expanding small Polystyrene beads in a mold, through heat and steam. The uneven expansion process causes the EPS foam sheet to contain small voids. These voids will be the place for air and moisture to penetrate. Therefore, EPS foam is the ideal solution for humid environments. Common applications of EPS are:

• Food containers
• Fragile Box
• Insulation panels
• Make motorcycle helmets.

Extruded Polystyrene Foam – XPS

XPS is also a foamed polystyrene. However, XPS foam is produced by extruding polystyrene with other additives and cooling. XPS foam has no voids, so it is 100% water-resistant and air-tight. It can be said that XPS foam is the best solution for humid environments. Common applications of XPS foam are:

• Blue Board foam wall sticker manufactured by Dow Inc.
• Depron thin insulation board (Depron foam)
• Building materials for architectural models.

Oriented Polystyrene – OPS

OPS is Polystyrene that is stretched to form a film. When stretched, OPS film reduces opacity and improves stiffness. OPS is an environmentally friendly packaging material. OPS film is relatively cost-effective and is used for packaging deli products.

OPS film is often used to allow visibility of the contents inside the film. However, this film is prone to cracking or tearing.

High Impact Polystyrene – HIPS

HIPS is a polystyrene plastic with high impact strength and good dimensional stability. HIPS plastic is naturally white with a matte surface. We can enhance the aesthetics of this plastic by painting and gluing.

A typical application of HIPS plastic is yogurt containers. Typically, HIPS plastic is used for items that require resistance to cracking due to high environmental pressure.

General Purpose Polystyrene – GPPS

GPPS is a type of PS plastic that is brittle and has poor impact resistance. GPPS does not have good dimensional stability like HIPS. However, GPPS plastic has the transparency of glass, so it is commonly used to make food packaging. Manufacturers can easily mold this plastic into different shapes, so it is often used to make children's toys.

What are the applications of PS plastic?

Polystyrene plastic has many applications in life due to its outstanding properties. Below are 5 main areas where PS plastic is commonly used:

Applications in packaging

PS plastic is one of the most popular materials for packaging, especially in the food industry. 5 popular packaging products made from plastic number 6 include:

1. Food containers: Styrofoam boxes for fast food, fruit, vegetable boxes, etc.
2. Cups, glasses: Disposable plastic cups, coffee cups, tea cups, etc.
3. Bottles: Bottles for drinking water, cooking oil, milk, etc.
4. Egg tray: Styrofoam egg trays in various sizes.
5. Cosmetic packaging: Box for powder, lipstick, cream, etc.

The advantages of PS plastic in packaging production are low cost, light weight, transparency, easy to print and decorate.

Applications in electronics

PS plastic, especially impact-resistant PS plastic (HIPS), is widely used in the electronics industry to produce:

1. Computer case: Desktop computer case, laptop,…
2. Phone case: Mobile phone cases, power bank cases,…
3. Electronic components: Printed circuit boards, transistor bases, buttons, etc.
4. Insulating material: PS plastic sheet for insulation in transformers, switches, etc.

Polystyrene plastic has good impact resistance, high insulation, fire resistance, helping to protect internal electronic components.

Medical applications

PS plastic is also used in the medical field to produce 5 product lines such as:

1. Syringe: Disposable plastic syringes in various sizes
2. Test tube: Plastic test tubes used in testing, microbial culture, etc.
3. Medicine tray: Plastic tray for pills, capsules, etc.
4. Medical equipment: Box for cotton, bandages, surgical instruments, etc.
5. Pharmaceutical packaging: Bottles, boxes, blister packs containing tablets, powders, etc.

PS plastic used in medicine must meet strict standards for safety and sterility.

Applications in construction

PS plastic is a popular material in the construction industry with many applications such as:

• Insulation foam board: EPS foam panels are used to insulate walls, ceilings, floors, etc.
• Interior decoration materials: PS plastic wall and ceiling panels with many colors, patterns,...

PS 3 wave plastic wall panel collection

PS 5 wave plastic wall panel collection

PS 2 wave plastic wall panel collection

Frequently Asked Questions about PS Thermoplastic

Is PS plastic toxic?

PS plastic is considered safe when used properly. However, when heated above 100°C, Polystyrene can release Styrene, a potential carcinogen. Therefore, PS plastic utensils should not be stored in a microwave or heated.

Is PS plastic recyclable?

PS plastic can be recycled, however the recycling process is more difficult and expensive than other plastics such as PET or HDPE.. The main reason is that PS plastic is easily deformed when heated and is difficult to classify because it comes in many different forms such as EPS foam, XPS, hard PS plastic, and OPS film.

The difference between PS plastic and PVC plastic

PS plastic and PVC plastic are both thermoplastic polymers and are both used in the production of decorative materials: plastic panels, molding, etc. However, PVC plastic is more durable, heavier and more flexible than PS plastic..

How much is PS plastic granules?

According to reliable sources collected by Kosmos, the price of PS resin is about 35.000 VND/kg updated in February 2. This is only a reference price that may change depending on the unit and time.

What is the lifespan of products made from PS plastic?

The lifespan of polystyrene plastic products depends on the conditions of use and storage. Typically, products such as food packaging and disposable plastic cups have a short lifespan of only a few months. Long-term products such as construction insulation panels and plastic number 6 household items can be used for 10-20 years.

How has Kosmos applied PS plastic material to its products?

Kosmos PS plastic products have high aesthetics, good durability and reasonable price, suitable for many interior design styles. Typically:

• PS fluted panel: Used for wall and ceiling cladding, creating accents for interior spaces with 2-wave, 3-wave, 5-wave designs, etc. The highlight is its ability to be water-resistant, moisture-proof, light weight, easy to transport and construct.
• PS plastic cornice: Used to decorate corners, create borders for ceilings and walls. Impressive with its light weight, easy to cut, termite-proof, bringing delicate beauty to the space.

>>> Instructions for Korean molding construction | PS plastic molding.

PS plastic (Polystyrene plastic) is widely used in the field of interior decoration materials production. It is popular not only because of its beautiful shape but also because of its water resistance, heat insulation, electrical insulation, etc.