Introduction to Polystyrene

Welcome to the fascinating world of polystyrene! In this blog post, we’ll explore this extraordinary material’s definition, characteristics, types, and applications. Beyond that, we’ll delve into its interesting historical background and main ingredients. On the other hand, we’ll address some frequently asked questions about polystyrene.

The picture on the left shows some polystyrene products used in daily life.

What is polystyrene?

Polystyrene is an amorphous plastic widely used in the manufacture of a variety of consumer products. It has no obvious melting point and a wide melting temperature range. This means it can be combined with other plastic polymers of the same type to form new plastic parts with improved properties. Poly styrene is a polymer composed of polystyrene molecules connected by multiple styrene monomers, with the chemical formula (C8H8)n. where n represents the number of repeating units in the polymer; polystryne is produced by the polymerization of styrene monomer, in which individual styrene monomer units are linked together to form a polystyrene polymer chain.

When polystyrene is in its solid, rigid plastic state, products such as auto parts, appliances, flower pots, and toys can be made. As a foam material, commonly known as polystyrene foam, it is used in electrical insulators, protective packaging, and food packaging. When used as food packaging, it can often extend the shelf life of food at a lower cost than other options.

How is polystyrene made?

Polystyrene is typically produced through a process called suspension polymerization. Here is a general overview of how polystryne is made:

Monomer Preparation: The first step in polystyrene production involves preparing the monomer, styrene. Styrene is derived from petroleum or natural gas through various refining processes.

Polymerization: The polymerization of styrene is initiated by adding a polymerization initiator, typically a free radical initiator, to a suspension of styrene monomer in water. The suspension also contains small amounts of other substances, including dispersants and stabilizers.

Heating and Stirring: The mixture is heated and stirred to maintain uniformity and promote the dispersion of monomer droplets throughout the water phase.

Polymerization Reaction: The initiator molecules decompose, generating free radicals that initiate the polymerization reaction. The styrene monomers react with the free radicals, causing them to join together and form long chains of polystyrene.

Formation of Beads: As the polymerization progresses, the polystyrene chains grow and aggregate, forming solid particles or beads suspended in the water. These beads contain numerous interconnected polystyrene chains.

Washing and Drying: After the desired level of polymerization is achieved, the poly-phenylethene beads are separated from the reaction mixture. They are typically washed and then dried to remove residual water and any unreacted monomer.

Processing Into Final Forms: The dried polystyrene beads can be further processed into various forms depending on the desired application. The beads may undergo processes like extrusion, molding, or foaming to create products such as sheets, films, molded objects, or expanded polystyrene foam.

What are the properties of polystyrene?

Polystryene has a range of physical and chemical properties. The following are the specific physical and chemical properties of polystyrene:

Physical properties:

Transparency: Polysterene is a transparent material that allows light to pass through easily.
Lightweight: Polystyrene is a lightweight material that is easy to handle and transport.
Rigidity and Stiffness: Polysterene has rigidity and rigidity, providing structural integrity to products made from it.
Low thermal conductivity: Polystyrene has a low thermal conductivity and is an effective insulating material.
Electrical Insulation: Polysyrene is a good electrical insulator and prevents the flow of electrical current.
Dimensional stability: Polysyrene has good dimensional stability, which means it maintains its shape and size under normal conditions.
Moisture resistance: Polsytrene has a low affinity for water and therefore does not absorb moisture easily. This means that polyethylene products do not need to be dried during molding and have low molding shrinkage.

Chemical properties:

Chemically Inert: Polystyrene is chemically inert, which means it is resistant to many chemicals and does not easily react with them.
Solubility: Polyestyrene is soluble in a variety of organic solvents, such as benzene, toluene, ethyl acetate, etc.
Flammability: Polsytrene is flammable and can easily ignite. However, flame retardants can be added to improve its fire resistance.
Stability: Polystyrene is stable under normal conditions and will not significantly degrade over time.
Acid and alkali resistance: Polyestyrene is generally resistant to weak acids and weak alkali, but can be corroded by strong solvents or concentrated acids.

What types of polystyrene are there?

There are five main types of polystyrene commonly used in life: expanded polystyrene (EPS), extruded polystyrene (XPS), high impact polystyrene (HIPS), crystalline polystyrene (GPPS), flame retardant (FR) polystyrene. Here is a brief description of each type:

Expanded polystyrene (EPS): EPS is a lightweight, rigid polystyrene. It is produced by expanding polyestyrene beads using steam and blowing agents. The expansion process creates a honeycomb structure, and the beads fuse together to form the foam. EPS foam is known for its excellent insulation properties, buoyancy, and cushioning capabilities. It is commonly used in packaging materials, insulation panels, disposable food containers, and as a core material in construction applications.

Extruded polystyrene (XPS): XPS is another type of rigid foam insulation made from polystrene. It is made by extruding molten polystyrene through a die, followed by a cooling process. The extrusion process creates a closed-cell structure with smooth, dense skin. XPS foam has higher compressive strength than EPS and has good thermal insulation properties. It is commonly used in applications such as insulation on roofs, walls, foundations, and under concrete slabs.

High Impact Polystyrene (HIPS): High-impact polystyrene is a modified form of polystrene that has a rubber component added to it. The addition of rubber enhances its toughness and impact resistance, making it less brittle than standard polystyrene. HIPS are commonly used in applications where impact resistance is important, such as packaging, toys, appliances, and automotive parts.

Crystalline Polystyrene (GPPS): Crystalline polystyrene, also known as general purpose polystyrene (GPPS), refers to the standard, clear, rigid form of polystyrenen. It is clear and has a high gloss finish. GPPS is commonly used in applications that require transparency and clarity, such as food packaging, cosmetic containers, and disposable tableware.

Flame-retardant (FR) polystyrene: Flame-retardant grades of polystyrene contain additives to increase their fire resistance. These additives reduce flammability and slow the spread of flames when heated or ignited. Flame retardant polystyrene is used in applications where fire safety is a concern, such as electrical and electronic equipment, construction materials, and transportation components.

What are the uses of polystyrene?

Polystyrene(PS) is a versatile material with a wide range of uses. They are found in most areas of our daily lives, and some common uses of polystyrenen include:

Packaging: Polystyrene is widely used in packaging materials due to its lightweight, insulating, and protective properties. It is used to package electronics, appliances, fragile items, food, and disposable containers such as foam cups, trays, and clamshells.

Insulation: Expanded and extruded polystyrene foam (EPS and XPS) are widely used as insulation materials. They provide insulation for buildings, roofs, walls, and foundations, as well as insulation for pipes and other industrial applications.

Construction: Polystyrene has many uses in the construction industry. It is used in the production of lightweight concrete blocks, insulating boards, and panels. Polystyrene sheets are also used as formwork material to create voids in concrete structures.

Food Service Industry: Polystyrene foam products are commonly used in the food service industry due to their insulating properties, lightweight nature, and affordability. Foam cups, plates, bowls, and food containers help keep food and drink hot or cold and are commonly used in the takeout, fast food, and restaurant industries.

Consumer Products: Polystyrene is used to make a variety of consumer products, including toys, home appliances, audio and video equipment, office supplies, and consumer electronics.

Medical and Laboratory Applications: Polystyrene is used in medical and laboratory fields. Because of its transparency, chemical resistance, and ease of sterilization, it can be used on petri dishes, test tubes, vials, and other disposable labware.

Craft and Hobby Materials: Styrofoam sheets and balls are popular materials for craft projects, model making, and DIY hobbies. They can be cut, shaped, and painted easily.

Soundproofing: Due to its sound-absorbing properties, polystryrene can be used in soundproofing and acoustic applications such as recording studios, home theaters, and noise barriers.

What is the origin and nickname of polystyrene?

Polystyrene’s history dates back to the early 20th century. In 1839, German apothecary Eduard Simon discovered styrene, the monomer from which polystyrene is derived. However, it wasn’t until 1922 that polystyrene was first synthesized by German chemist Hermann Staudinger. Throughout the years, advancements in polymer chemistry and manufacturing processes have led to the widespread adoption of polystyrene in various industries.

Polystyrene is commonly referred to as “Styrofoam,” which is actually a brand name for a specific type of polystryrene foam. This misnomer has become widely used to describe expanded polystyrene foam in general.

Which processing technologies are suitable for polystyrene products?

At Ruitai, we handle a variety of technologies depending on the product and application required. Generally, polystyrine can be processed using some common processing techniques:

Injection Molding: Injection molding is a process widely used to produce complex polystyrene parts. Molten polystyrene is injected into a mold under high pressure, where it cools and solidifies, forming the shape of the mold cavity. It is commonly used in the manufacture of a variety of products, including consumer products, automotive parts, electronic casings, and home appliances.

Extrusion: Extrusion is a continuous process in which molten polystyrene is forced through a die to form long, uniform profiles or sheets. The extruded polystyrene is then cooled and cut into desired lengths or rolled into sheets. Extrusion is used to produce items such as plastic sheets, films, tubes, rods, and profiles.

Foam extrusion: Polystyrene foam products, such as expanded polystyrene (EPS) and extruded polystyrene (XPS), are manufactured using a foam extrusion process. Molten polystyrene is mixed with a blowing agent and the mixture is extruded through a die. Blowing agents expand polystyrene to create a porous structure with low density and excellent insulating properties.

Thermoforming: Thermoforming involves heating a flat sheet of polystyrene until it becomes pliable and then using a mold or vacuum to shape it into the desired shape. The process is commonly used to produce food packaging containers, disposable cups, trays, and other similar products.

Blow Molding: Blow molding is used to produce hollow polystyrene products such as bottles, containers, and cans. In this process, a molten polystyrene tube or parison is formed, which is then inflated using pressurized air within the mold to form the shape of the mold cavity.

Cutting and Fabrication: Polystyrene sheets and blocks can be easily cut, shaped, and fabricated using techniques such as sawing, milling, laser cutting, and hot wire cutting. This allows customization and the creation of specific shapes and designs. This cutting technique is called CNC machining, and our online CNC machining services can help you produce various types of prototype projects.

What are the advantages and disadvantages of polystyrene?

Like any material, polystyrene has its pros and cons. Here are some of the main advantages and disadvantages of polystyrene:


Thermal insulation properties: Polystyrene foams such as expanded polystyrene (EPS) and extruded polystyrene (XPS) have excellent thermal insulation properties and are suitable for a wide range of applications in the construction and packaging industries.

Lightweight: Polystyrene is a lightweight material, making it easy to handle, transport, and use in a variety of applications. This feature is particularly advantageous in packaging and industries where weight reduction is important.

Versatility: Polystyrine is a versatile material that can be molded, extruded, and formed into a variety of shapes and sizes. Due to the flexibility of its manufacturing process, it is used in a wide range of products from disposable containers to automotive parts.

Cost-Effectiveness: Polystyrene is relatively cheap compared to many other materials, which contributes to its widespread use in the packaging and consumer goods industries.

Chemical resistance: Polystyrene has good resistance to many chemicals, making it suitable for applications that require contact with certain substances.


Environmental Impact: One of the major disadvantages of poly styrene is its impact on the environment. Traditional polystyrene is not biodegradable and can persist in the environment for long periods of time. Improper disposal and littering of polystyrene products can lead to environmental pollution.

Recycling Challenges: While polystyrene can be recycled, its lightweight and bulk present challenges in the recycling process. The lack of polystyrene recycling infrastructure in some areas may limit its recyclability.

Brittleness: Polystyrene can be brittle and prone to cracking under certain conditions, especially in its standard form. However, modifications such as high-impact polystyrene (HIPS) can improve its impact resistance.

Flammability: Polystyrene is a flammable material and can easily ignite. However, flame-retardant versions of polystyrene can solve this problem in certain applications.

Styrene monomer: The production of polystyrene involves the use of styrene monomer, which is classified as a potential human carcinogen. However, styrene monomers are chemically bound into the polymerized form of polystyrene, reducing the risk of exposure.


This article introduces polystyrene, explains its definition, and discusses its properties and various applications. In addition to this, we’ve picked out some frequently asked questions to answer, so if you’d like to find out more about polystyrene, get in touch with our team.

As we conclude our description of polystyrene, we hope you have gained a deeper understanding of this fascinating material. Its history, diverse applications, and unique properties make it an important part of modern society. Whether you use it for packaging, insulation, or everyday items, remember polystyrene’s incredible versatility and contributions.

Ruitai is a prototype parts manufacturer offering a wide range of manufacturing services for all your prototyping and production needs. You can contact us anytime for a free quote.

The content provided in this article is for reference only, and Ruitai Mould makes no representations or warranties, express or implied, as to the completeness, accuracy, or validity of the information.

Addressing Common Polystyrene Questions:

Q1: Is polystyrene recyclable?
A1: Yes, polystyrene can be recycled. However, the process can be challenging due to its lightweight nature and low density. Mechanical recycling and thermal processes, such as pyrolysis, are employed to recycle polystyrene.

Q2: Is polystyrene harmful to the environment?
A2: Polystyrene is a subject of environmental concern due to its persistence in the environment and potential for littering. However, advancements in recycling and the development of bio-based alternatives are helping mitigate its environmental impact.

Q3: Can I microwave polystyrene containers?
A3: It is generally not recommended to microwave polystyrene containers unless they are labeled as microwave-safe. High temperatures can cause the material to melt or release chemicals into the food.

Q4: Is polystyrene the same as plastic?
A4: Polystyrene is a type of plastic, specifically a thermoplastic polymer. It belongs to the broader family of polymers widely used in manufacturing various plastic products.

Q5: What is the melting point of polystyrene?
A5: The melting point of polystyrene is typically about 240 to 260 degrees Celsius (464 to 500 degrees Fahrenheit). It is worth noting, however, that the melting point may vary depending on the grade of polystyrene and the specific formulation.

Polystyrene is an amorphous thermoplastic, which means it does not have a distinct melting point like crystalline materials. Instead, it gradually softens as it is heated, eventually transforming into a molten state. When heated, polystyrene has a glass transition temperature (Tg) of approximately 90 to 105 degrees Celsius (194 to 221 degrees Fahrenheit). Above the glass transition temperature, polystyrene becomes soft and rubbery and continues to soften until it reaches a molten state.

Q6: Is polystyrene foam a polymer?
A6: Yes, polystyrene foam is a type of polymer. This foam structure provides the material with its lightweight and insulating properties, making it suitable for packaging, insulation, and other applications.

Q6: What is the abbreviation for polystyrene?
A6: The common abbreviation for polystyrene is “PS.” It is derived from the first letter of “polystyrene” followed by the first letter of “styrene,” the monomer from which polystyrene is derived. The abbreviation “PS” is widely used in scientific literature, industry, and product labeling to refer to polystyrene.

Q7: Is polystyrene toxic?
A7: Polystyrene itself is considered non-toxic, but there are concerns about potential health and environmental impacts associated with certain additives or chemicals used in its production.

Q8: Is polystyrene waterproof?
A8: Polystyrene itself is not inherently waterproof, but certain forms of polystyrene exhibit water-resistant properties. Expanded polystyrene (EPS) and extruded polystyrene (XPS) foam, which are commonly used for insulation and packaging, have inherent water resistance due to the closed-cell structure of the foam. The closed-cell structure prevents the penetration of liquid water, making EPS and XPS foam effectively waterproof in practical applications.

Q9: Why is polystyrene soluble in acetone but not in water?
A9: Polystyrene is soluble in acetone but not in water due to the differences in their molecular interactions. Polystyrene is a nonpolar polymer composed of hydrocarbon chains, while both acetone and water are polar solvents.