25 September 2023

How to Induce Elasticity in Polystyrene?

Polystyrene is a widely used polymer known for its rigid and brittle nature. It is a widely used polymer in various custom machining industries due to its low cost, easy processability, and excellent electrical insulating properties. 

However, its inherent brittleness has limited its applications in scenarios that require flexibility and resilience.  Thus, there are various techniques and methods available to induce elasticity in polystyrene, making it more flexible and versatile for different applications. 

In this article, we'll explore some effective ways to enhance the elasticity of polystyrene making it suitable for a broader range of uses in custom CNC machining services.

Factors Influencing Elasticity in Polystyrene

Many factors can influence the elasticity of polystyrene. Understanding and manipulating these factors enable the tailoring of polystyrene's mechanical properties to meet specific application requirements.

Molecular Structure and Chain Flexibility

The molecular structure of polystyrene plays a pivotal role in determining its elasticity. Polystyrene is made up of long chains of repeating styrene monomer units. The arrangement and length of these chains influence the material's flexibility and ability to return to its original shape after deformation. 

Long, linear chains can hinder movement and reduce elasticity, while introducing branches or incorporating more flexible monomers can enhance chain mobility and increase elasticity.

Temperature and Thermal Properties

Temperature has a significant impact on the elasticity of polystyrene. At higher temperatures, the kinetic energy of polymer chains increases, allowing them to move more freely and making the material more elastic. 

However, extreme temperatures can lead to thermal degradation, reducing elasticity. The glass transition temperature (Tg) is a critical point for polystyrene. Above Tg, the material transitions from a rigid, glassy state to a rubbery state, increasing its elasticity.

Elasticity Inducing Techniques for Polystyrene

1. Annealing and Heat Treatment Techniques

Annealing and heat treatment are techniques commonly used to induce elasticity in polystyrene. By manipulating its molecular arrangement and reducing internal stresses you can get better quality for custom machining.


Annealing involves subjecting a material to controlled heating and controlled cooling cycles in order to alter its internal structure and relieve stresses. In the case of polystyrene, annealing can help increase its elasticity by allowing the polymer chains to relax and reorganize themselves.

1. Heating Phase: Polystyrene samples are heated to a temperature slightly below its glass transition temperature (Tg). This allows the polymer chains to become more mobile and enables them to move and rearrange.

2. Holding Phase: The material is held at this temperature for a specific period, allowing the polymer chains to adjust their positions and relieve internal stresses that may have developed during processing or deformation.

3. Cooling Phase: After the holding phase, the samples are gradually cooled to room temperature. During this cooling process, the polymer chains become locked in a more relaxed and organized state, which contributes to improved elasticity.

Heat Treatment

Heat treatment involves subjecting polystyrene to higher temperatures for a specific duration to induce changes in its molecular structure, crystallinity, and mechanical properties. 

This process can lead to improved elasticity by promoting the rearrangement of polymer chains and increasing chain mobility.

1. Heating Phase: Polystyrene samples are heated to a temperature above its glass transition temperature or even slightly above its melting temperature. This allows the polymer chains to move more freely.

2. Holding Phase: The material is held at the elevated temperature for a specific period to ensure sufficient molecular rearrangement and relaxation of stresses.

3. Cooling Phase: The samples are gradually cooled down to room temperature or below. The slow cooling helps maintain the changes induced during the heat treatment.

Both annealing and heat treatment help reduce internal stresses and allow the polymer chains to regain a more relaxed and organized state, resulting in improved elasticity. Also, these processes can lead to increased ductility and toughness, making the material more resistant to deformation and better able to recover its original shape.

2. Incorporation of Elastomers or Rubber Modifiers

Elastomers are polymers with a high degree of flexibility and the ability to return to their original shape after deformation. When these elastomers or rubber modifiers are blended with polystyrene, they create a sophisticated composite material. This material combines the rigidity of polystyrene with the elasticity of rubber, resulting in improved overall elasticity for custom CNC machining.

1. Selection of Elastomer: Choose an appropriate elastomer or rubber modifier that complements the desired mechanical properties of the final material. Common elastomers used with polystyrene include polybutadiene and styrene-butadiene rubber.

2. Blending: Mix the chosen elastomer with polystyrene through a process such as melt blending. This can be done using techniques like extrusion or compounding, ensuring thorough distribution of the elastomer throughout the polystyrene matrix.

3. Processing: The blended mixture is then processed using conventional methods like injection molding, extrusion, or compression molding to shape the material according to the desired form and application.

The presence of elastomers imparts greater flexibility and elastic behaviour to the polystyrene matrix, allowing it to deform under stress and recover its original shape upon release. Besides, elastomers can significantly increase the material's impact resistance and ability to absorb energy, making it less prone to fracture or breakage.

3. Copolymerization with Other Monomers

Copolymerization involves the simultaneous polymerization of two or more different monomers to create a polymer chain that combines the properties of both. By copolymerizing polystyrene with a more flexible monomer, the resulting copolymer can exhibit increased elasticity. It also leads to retaining some of the polystyrene's other desirable properties for custom cnc service.

1. Monomer Selection: Choose a suitable monomer to copolymerize with styrene. Monomers that introduce flexibility and elasticity, such as butadiene, can be selected.

2. Copolymerization: The selected monomer is polymerized alongside styrene using suitable catalysts and reaction conditions. The resulting polymer chain consists of alternating segments of both monomers.

3. Tailoring Properties: The ratio of styrene to the flexible monomer can be adjusted to control the degree of elasticity and other mechanical properties in the final copolymer.

By adjusting the monomer ratio and polymerization conditions, it's possible to fine-tune the material's mechanical properties to match specific application requirements. The copolymer can still retain some of the inherent strength and rigidity of polystyrene while gaining elasticity.

4. Plasticization and Utilization of Plasticizers

Plasticization involves incorporating specific additives called plasticizers into the polystyrene matrix. These plasticizers interact with the polymer chains, reducing the forces between them and promoting greater mobility. This results in improved flexibility and elasticity of the material used in producing cnc machining parts.

1. Plasticizer Selection: Choose a suitable plasticizer based on its compatibility with polystyrene and its ability to reduce intermolecular forces. Common plasticizers include phthalates, adipates, and citrates.

2. Addition and Mixing: The chosen plasticizer is added to polystyrene and thoroughly mixed. This can be done through processes like melt blending or solution mixing.

3. Plasticization: Plasticizers penetrate between the polymer chains, creating space and reducing intermolecular forces. This enables the chains to move more freely, increasing the material's flexibility and elasticity.

The amount and type of plasticizer added can be adjusted to achieve the desired level of elasticity while maintaining other mechanical properties. Plasticized polystyrene gains improved toughness and impact resistance due to its enhanced ability to absorb energy.


Incorporating elasticity into polystyrene opens up a world of possibilities for its applications across various industries including custom machining. Annealing, heat treatment, elastomer incorporation, copolymerization, and plasticization are effective methods to enhance the polymer's flexibility and resilience. By carefully selecting and combining these techniques, manufacturers can tailor polystyrene properties to meet specific requirements.