Polystyrene, widely utilized in injection molding, offers numerous advantages, making it a favored material in diverse manufacturing realms. Its cost-effectiveness stands out, providing an economical option for high-volume production. The ease of processing, characterized by its smooth melting and flowing properties, facilitates faster cycle times and efficient production, also contributing to lower energy consumption.

What is Polystyrene?

Polystyrene, a synthetic aromatic hydrocarbon polymer, is made from the monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum. At room temperature, polystyrene is a solid thermoplastic, which can be transparent or can have various colors. Its molecular structure comprises a long chain of styrene units, which is the key to its properties.

Chemical Properties

Polystyrene’s chemical composition lends it several notable properties. It is non-reactive under normal conditions, which makes it resistant to acids and bases. However, it can be dissolved in organic solvents, oils, and esters. This property is particularly important in the recycling and reshaping of polystyrene products.

Physical Properties

The physical properties of polystyrene include:

  • Lightweight: Polystyrene is very light, with a density ranging from about 10 to 50 kilograms per cubic meter for expanded polystyrene.
  • Insulation: It is an excellent insulator, which makes it ideal for use in building insulation materials, refrigerators, and coolers.
  • Durability and Flexibility: Polystyrene is quite durable. It can be rigid or foamed, which is a versatile feature for various applications. Its flexibility can be adjusted by adding different additives during the manufacturing process.

Types of Polystyrene

There are primarily two types of polystyrene:

  • General Purpose Polystyrene (GPPS): Known for its clarity and rigidity, GPPS is often used in products like plastic models, CD cases, and other items where a clear, hard plastic is desired.
  • High Impact Polystyrene (HIPS): This is a rubber-modified version of polystyrene, which is less brittle and more impact-resistant. It is used in products that require a higher level of impact resistance, such as in appliance housings and toys.

Properties of Polystyrene: GPPS vs HIPS

Polystyrene, a versatile and widely used plastic, comes in various forms, each with unique properties suited for different applications. Below is a comparative table highlighting their key material properties:

Property General Purpose Polystyrene (GPPS) High Impact Polystyrene (HIPS)
Chemical Type Synthetic aromatic hydrocarbon polymer Synthetic aromatic hydrocarbon polymer
Monomer Styrene Styrene with polybutadiene rubber
Density 1.04 – 1.07 g/cm³ 1.03 – 1.07 g/cm³
Melting Point 240°C – 260°C 180°C – 270°C
Tensile Strength 46-60 MPa 25-35 MPa
Flexural Strength 80-100 MPa 40-70 MPa
Impact Strength 2-3 kJ/m² 10-20 kJ/m²
Thermal Conductivity 0.033 W/m·K 0.033 W/m·K
Heat Resistance Moderate, deforms at high temperatures Better than GPPS, but still limited
Transparency Transparent Opaque
Chemical Resistance Resistant to acids and bases, soluble in organic solvents Similar to GPPS, slightly better impact resistance to chemicals
Electrical Properties Good electrical insulator Good electrical insulator
Water Absorption Low Low
Biodegradability Non-biodegradable, can be recycled Non-biodegradable, can be recycled

The presence of numerical ranges in the table for properties like density, melting point, tensile strength, and others, reflects the variability in these properties due to several factors:

Manufacturing Variations: Different manufacturing processes and conditions can lead to slight variations in the properties of polystyrene. Factors such as temperature control, pressure settings, and the purity of the raw material can influence the final properties of the polymer.

Material Grades: Both General Purpose Polystyrene (GPPS) and High Impact Polystyrene (HIPS) come in various grades, each designed for specific applications. These grades can have slightly different compositions, leading to variations in their physical and mechanical properties.

Versatile Uses of Polystyrene in Injection Molding: From Packaging to Automotive Components

Polystyrene, a synthetic thermoplastic polymer, has emerged as a crucial material in various industries, primarily due to its unique properties. Known for its ease of molding and cost-effectiveness, polystyrene is extensively used in a multitude of products that form part of our everyday lives. Here are some of the primary applications:


Food Containers: Polystyrene is widely used in making food packaging containers like yogurt pots, egg cartons, and fast-food trays. Its lightweight and insulating properties make it ideal for these uses.

Protective Packaging: Expanded Polystyrene (EPS) is used in protective packaging for electronics, appliances, and other fragile items due to its shock-absorbing qualities.

Consumer Products

Disposable Cutlery and Tableware: Polystyrene is used to make disposable knives, forks, spoons, and plates. Its low cost and ease of molding make it suitable for these single-use items.

CD and DVD Cases: The rigidity and durability of polystyrene make it ideal for protecting media like CDs and DVDs in cases.

Toys and Models

Model Kits and Toys: Polystyrene is a favorite material for model kits and various types of toys due to its ease of molding and painting.


Housings and Casings: Electronic housings, such as for computers and televisions, are often made with polystyrene because it can be easily molded into complex shapes and sizes.

Automotive Components

Interior Parts: Polystyrene is used for various interior components of vehicles, such as knobs, instrument panels, and trim parts, due to its lightweight and molding capabilities.


Stationery Items: Items like rulers, pen casings, and plastic folders are often made from polystyrene.

Horticulture: EPS trays are used for seedling starting and hydroponic systems.

Injection Molding Services

Senses is an ISO 9001:2015 certified plastic injection molding company, offering a comprehensive array of services including mold and part designprototyping, small-batch production, and full-scale manufacturing. We serve a diverse range of industries, encompassing automotive, medical, and consumer electronics. Our focus is on ensuring each product we deliver meets the highest standards of quality and functionality.

For personalized solutions and expert consultation, reach out to us today at info@senseschina.com.