The Role of ABS in Injection Molding

ABS Plastic is one of the most popular material choices in injection molding. It is an amorphous thermoplastic widely used in manufacturing through injection molding techniques.

This article provides an in-depth analysis of the role of ABS in injection molding. This article encompasses What is ABS plastic? Its properties, its applications and when you should consider ABS plastic for your projects.  

Table of Contents

What is ABS Plastic?

ABS, abbreviated for Acrylonitrile Butadiene Styrene, is a type of thermoplastic polymer.

ABS plastic is a polymer made up of three monomers: acrylonitrile, butadiene, and styrene.

ABS plastic monomers

Each of these three monomers has distinct properties and they combine their specific properties into the polymer to create a robust polymer that can resist impacts. Let’s understand more about each of the 3 monomers that combine to form the ABS plastic: 

  • Acrylonitrile: Acrylonitrile is the reason that ABS plastic has high chemical resistance and heat stability. It is produced by combining propylene and ammonia. 
  • Butadiene: Butadiene is responsible for the impact strength of the polymer. Butadiene is a byproduct that is formed during ethylene production from steam crackers.  
  • Styrene: Styrene is responsible for the rigidity & processability of ABS plastic. Styrene is made through the alkylation of benzene with ethylene to produce ethylbenzene which is then followed by dehydrogenation of ethylbenzene to styrene.
abs injection molding

ABS Plastic cannot only resist impacts, but it is also resistant to chemicals. It does get easily attacked by polar solvents but apart from that, it is strong and durable. 

ABS Plastic can be processed on almost every standard machinery. It can be injection-molded or blow-molded and since it has a low melting temperature (approximately 200°C or 392°F), it’s suitable for processing by 3D printing on an FDM machine. Thus, ABS plastic can be used in a wide array of applications.

Chemical Structure of ABS Plastic: (C₈H₈·C₄H₆·C₃H₃N)ₙ

ABS Plastic Properties

ABS plastic is a low-cost thermoplastic polymer whose properties enable it to be applied to various product designs. Let’s take a look at some of its properties: 

abs plastic properties

Can ABS Plastic be considered Strong and Safe?

As noted above in the properties, ABS plastic material has excellent resistance to stress, chemicals, heat and impact. It also offers a great balance of dimensional stability, tensile strength, and electrical characteristics. All these characteristics make it a strong and durable plastic material. 

Further, let’s understand how ABS plastic reacts to heat and its melting temperature: ABS plastic is a thermoplastic. As opposed to the thermoset plastic materials which allow only one-time heating during the injection molding process, thermoplastics do not burn. They do not undergo degradation through the process of heating to their melting point, cooling and reheating. 

Thus, ABS plastic does not undergo degradation. They instead become liquid, so they can be easily injection molded. This property also allows it to be recycled. Thermoplastic liquefies when it reaches a certain temperature level. In the case of ABS plastic, this temperature is 105°C /  221°F. ABS plastic thus, remains rigid and tough even at low temperatures. 

ABS plastic has various grades and is available in fire-retardant, heat-resistant and palatable grades. It is thus considered not only durable but also safe.

Advantages and Disadvantages of ABS Plastic

It’s established that ABS Plastic is a popular material choice for injection molding techniques but we must note that it has both advantages as well as disadvantages. 

abs plastic advantages and disadvantages

Let’s understand them in-depth:

Advantages

  • Energy Efficient: ABS plastic increases efficiency by delivering excellent performance. This helps to reduce the energy demand and improve overall cycle times. 
  • Flexibility in Applications: ABS plastic has excellent integration capabilities. It can be applied to various applications which is why it is one of the most flexible resins for manufacturing various components.  
  • Low Shrink Rate and High Dimensional Stability: Not only is ABS resin a rigid and impact-resistant plastic, but it also has a low shrink rate and high dimensional stability. All these characteristics make it a great choice for manufacturing lightweight, rigid products.  
  • Reproducibility: ABS plastic is a thermoplastic which means that very little degradation occurs when the resin is subjected to high temperatures. Since ABS plastic can maintain its characteristics through heating, cooling, and reheating, it can ensure reproducibility of results, especially when complex parts are concerned. 
  • Recyclability: Not only is ABS reproducible, but it can also be recycled. This advantage is also attributed to ABS resin being a thermoplastic. Since it maintains its characteristics through heating, cooling, and reheating, it can easily be recycled.
regrinder for plastic
This machine can recycle/regrind plastic scrap parts.

Disadvantages

  • UV Sensitive: ABS Plastic degrades upon continuous exposure to sunlight which is why it needs to be coated with a UV resistant material.  
  • Low Fatigue Resistance: It has a low fatigue resistance and can degrade if subjected to continuous exposure or strain thus, it is not a suitable plastic of choice for projects with high-stress applications.

ABS Plastic in Injection Molding Techniques

How is ABS Plastic injection molded?

ABS plastic in its pellet form is melted into a moldable state which is then injected into the cavity of the mold where it forms a part. The molten plastic solidifies as soon as the mold is filled which then cools to take the shape of the mold. Once it has fully cooled, the mold sides open to eject the part. The mold parts are then reset to begin the process again.

Factors to Comprehend during the manufacturing process

Uniform Wall Thickness in ABS Plastic Parts Design

If the thickness of the wall isn’t uniform, then the ABS plastic may be under stress which is why the wall of the plastic parts design must be uniformly thick. Your manufacturer can also implement extra ribs or radii to enhance the strength of the mold.

Radius Size

It’s essential to pay attention to the radius size as it is inversely proportional to the stress and strain on ABS plastic. The more the radius, the less the stress.

The wall thickness also determines the radius size, thus, it should be ensured by the manufacturer that the ratio of the radius to the wall thickness is not less than 0.3. You should also avoid using an excessively large radius as shrinkage of the resin can occur when the radius is too big.

Pre-treatment of Dry ABS Resins

It is imperative to ensure that ABS resins are dried before proceeding for processing and manufacturing. This is because dry ABS resins tend to absorb water which can result in various issues. They can lead to increased operating costs and cycles. You must also note that the presence of water often leads to cloudy molded parts.

Injection Molding Temperature Control

Overheating ABS resins can lead to thermal decomposition which is why it is essential to ensure optimum injection molding temperature controls. If manufacturers apply excessive heat to the plastic, the chemical bonds will break which often results in brown granules on the injected molded part. This is generally unavoidable if your manufacturer uses old equipment with poor temperature control.

The molding temperature needs to be high when the injected molded ABS parts contain high gloss and ensure not to damage the material in the process. Thus, the temperature for ABS plastic is higher than other injection molding materials. 

The recommended temperature range is between  200 – 238°C / 392°F – 460.4°F. You must also ensure that if the temperature is higher, the resins should not be exposed for a longer time. This will prevent degradation of the ABS resins.

High Injection Pressure

In case of ABS plastic resins, high injection pressure is necessary due to its viscosity but your manufacturer needs to ensure that even though the injection pressure is high, it’s not excessively high as it can increase friction and cause sticking of the molded parts. These molded parts can be separated but separating the molded parts causes the production cost to increase. It is also essential to ensure that the injection pressure isn’t low as low pressure leads to an increase in mold shrinkage, which results in inferior quality parts. 

Injection Molding Speed

The next factor that your manufacturer should ensure is the injection molding speed. If the injection molding speed is high, it can cause burning or thermal decomposition of the plastic material. It can also cause poor glossiness, discoloration and weld lines in the plastic material.  

On the other hand, if the injection molding speed is too slow, insufficient mold filling will occur which can result in other types of defects in the injection molded part.  

Processing Conditions of ABS Plastic in Injection Molding Techniques

ABS plastic pre-treatment: ABS resins in dry form tend to absorb moisture. Thus, it is essential that they are dried prior to processing. It is recommended that ABS resins are treated between 80 to 90°C for at least 2 hours. This pretreatment restricts the moisture content of the resin to less than 0.1%. The moisture absorption rate of ABS plastic is between 0.2% – 0.8%.

abs dryer

Melting Point: The melting point temperature is between 200 to 280°C.

Injection Molding Pressure: The plastic molding injection pressure is between 50 – 100 MPa

Gate & Vent Design: The gate and vent design needs to be optimally designed according to the plastic. In the case of ABS plastic, following parameters should be paid attention to: 

  • The gate length of the mold should be less than 1mm 
  • Vent width should be set between 4 and 6mm. 
  • The thickness should be set between 0.025 – 0.05mm. 
  • The channel diameter should be 3mm 

Back Pressure: A high back pressure is able to ensure uniform mixing but to avoid wear, back pressure should be as minimum as possible. The expected back pressure is usually 5 bar.

Applications of ABS molded plastic parts

As we have discussed above, ABS plastic is impact and chemical resistant which makes it ideal for a wide array of applications. It is also a popular choice in injection molding techniques because of its low melting point and low cost. It has been thus implemented in various industrial and commercial industries. Let’s take a look at some of the sectors ABS Plastic can be applied to: 

Automotive Industry
ABS Plastic is widely used in the automotive industry when the project details require the products to be lightweight. It is very often implemented as an alternative to metals. Some of the examples include instrument panels, dashboard components, handles, and seat belt parts.
Commercial Industry
The next industry where ABS plastic is widely applied in the commercial sector. It is especially used for manufacturing home appliances. The product applications in this industry range from vacuum cleaners, and control panels, to food processors and more.
Electrical Industry
ABS plastic is a popular choice in the electrical industry and is often used to manufacture computer keyboards and electronic enclosures.
Construction Industry
ABS plastic has high impact resistance which is why it can withstand chemical and physical changes and is thus, a popular choice in the construction industry for pipes and fittings.
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*Pictures from Unsplash

When Should You Consider ABS Plastic?

ABS Plastic can be applied to a wide array of products but it is particularly used when the project details require rigidity and durability from a product while ensuring that it is lightweight as well. Some of its popular applications include home appliances, musical instruments, computer parts and more.

Purchase ABS Plastic

ABS Plastic is available in the form of resins, rods and sheets. We have listed some of the leading suppliers for ABS Plastic:

  • Chimei: Chimei is a Taiwan based company that provides ABS resins to manufacturing companies in various industries. Along with ABS, they also manufacture ASA, PMMA and ABS alloys.  
  •  LG Chemicals: LG Chemicals was founded in 1947 in Korea. It is a pioneer plastic company that specializes in a variety of products. In addition, LG chemical is a top global provider of ABS plastics. 
  • GE Plastics: GE Plastics continually adds high-tech materials and high-performance resins so that they can cater to global industries. In the case of ABS resins, they have various grades that the manufacturers can buy to develop their products. 
  • Lanxess: Lanxess is a german based company that specializes in manufacturing lightweight plastics for various manufacturing companies across the globe.  
  • Cheil: Cheil, the parent company of Samsung is a Korean based company that includes a high-value engineering plastic division. Cheil produces synthetic resins such as ABS and more that can be used to produce quality products for the automotive, consumer and electrical industries. 
  • Formosa Plastics: Formosa plastics is a USA based company headquartered in Taiwan. The brand name for Formosa ABS is TAIRILAC and there, are more than 30 types of ABS products that the manufacturers can choose from to develop their products.  
  • Dow: Dow is a US-based based company that provides innovative materials to manufacturing companies. Dow has around 10 types of ABS resins and the brand name for ABS resin is Paraloid.  
  • Grand Pacific: Grand Pacific Petrochemicals is a Taiwan based company. They primarily manufacture ABS resins, styrene monomer, and styrene-acrylonitrile resin. 
  • Techno Polymer: Techno Polymer is a Japanese based company and they are known for developing high-quality ABS resins. 

Contact Us for ABS Injection Molding?

VEM Tooling has the expertise and the team that is required for your ABS plastic injection molding techniques. At VEM Tooling, we offer quick quotes, fast, and dependable service.

VEM Tooling team encompasses experts that can provide you with ABS injection molding guidance. We ensure that you have a great experience and a seamless manufacturing process from prototype to production. You can contact us to further understand how ABS Injection Molding can be implemented for your project and solve your manufacturing needs. 

To better understand how VEM tooling can serve you, contact us or request a quote today.