Integrated Understanding of ABS materials through the ABS injection molding process

ABS injection molding is one of today’s most commonly used plastic product processing methods. ABS materials offer superior mechanical strength and exhibit good overall performance, making them highly suitable for a wide range of applications. The processing of this material holds a significant position in various industries, including electronics, machinery, automotive, aerospace, toy manufacturing, and many others. Its versatility, durability, and desirable properties make ABS a preferred choice for manufacturing various components and products.

Features of ABS Materials

What is ABS?

ABS materials are terpolymers consisting of acrylonitrile, butadiene, and styrene. The abbreviation ABS stands for the three monomers, with “A” representing acrylonitrile, “B” representing butadiene, and “S” representing styrene. Each component contributes specific properties to the ABS resin, resulting in a well-rounded material with desirable characteristics. Acrylonitrile provides chemical stability, oil resistance, stiffness, and hardness to the ABS resin. Butadiene enhances toughness, impact resistance, and cold resistance. Styrene contributes to good dielectric properties and the overall processability of the material.

Characters of ABS Materials

Most ABS Materials are non-toxic and have excellent water resistance. While it is impervious to water but slightly permeable to water vapor. ABS has low water absorption, with a water absorption rate of no more than 1% when immersed in water at room temperature for one year, and its physical properties do not change significantly. Besides, ABS resin products can be polished to achieve a high-gloss surface finish.

ABS exhibits excellent physical and mechanical properties, including exceptional low-temperature impact resistance and dimensional stability. It is resistant to water, inorganic salts, alkalis, and acids. ABS is insoluble in most alcohols and hydrocarbon solvents but readily soluble in aldehydes, ketones, esters, and certain chlorinated hydrocarbons. However, ABS has a low heat deflection temperature and is combustible. It also has poor weather resistance. The melting temperature of ABS is typically between 217°C and 237°C, and its thermal decomposition temperature is above 250°C.

Modified ABS In Injection Molding

ABS can be blended with other plastics or additives to modify its properties and create different grades with specific characteristics. By incorporating various additives or blending ABS with other polymers, it is possible to achieve additional performance attributes such as high-impact ABS, heat resistance ABS, flame retardant ABS, transparent ABS, reinforced ABS, conductive ABS, and more. Different industries can tailor ABS for a wide range of applications by making these modifications. The specific combination of additives or blended polymers determines the resulting properties and performance of the ABS material.

Standard ABS

This grade of ABS material offers a balance of mechanical properties, impact strength, and processability. It is commonly used for general-purpose applications like consumer products, toys, and automotive interior parts.

Flame Retardant ABS

This ABS grade contains additives to enhance its flame retardancy. It meets specific fire safety regulations and is suitable for applications requiring fire resistance, such as electrical enclosures and automotive components.

High Impact ABS

This grade of ABS material has superior impact strength compared to standard ABS. It finds frequent usage in applications that demand toughness and resistance to impact loading, such as protective equipment, automotive exterior parts, and tool handles.

Heat-Resistant ABS

This ABS grade exhibits improved resistance to high temperatures. It can withstand elevated temperatures without significant deformation or loss of properties. Heat-resistant ABS is used in automotive under-the-hood components, electrical connectors, and appliances.

Conductive ABS

This ABS grade contains conductive additives, typically carbon fibers or carbon black, which impart electrical conductivity to the material. Conductive ABS is used in applications requiring static dissipation or electromagnetic shieldings, such as electronic housings and industrial equipment.

Reinforced ABS

ABS materials can be supported with additives like glass fibers or mineral fillers to enhance their mechanical properties. The addition of these reinforcements improves stiffness, strength, and dimensional stability. Reinforced ABS is commonly used in applications that require higher strength and rigidity, such as automotive components, structural parts, and industrial equipment.

Transparent ABS

ABS is inherently opaque, but transparent or translucent grades of ABS are achieved by modifying its composition. Transparent ABS materials are typically formulated with special additives or modifiers that improve light transmission and reduce haze. These grades find applications in products where both transparency and impact resistance are desired, such as display panels, light covers, and consumer electronics.

Various kinds of modified ABS

ABS/PC

This blend combines ABS with polycarbonate to create a material that exhibits the impact resistance and processability of ABS with the high heat resistance and dimensional stability of polycarbonate. It is commonly used in automotive interior and exterior components, electronics, and industrial equipment.

ABS/PMMA

This blend combines ABS with polymethyl methacrylate (PMMA) to create a transparent or translucent material with improved impact resistance compared to pure PMMA. It finds applications in automotive lighting, display panels, and consumer electronics.

ABS/ASA

ABS can be blended with ASA to enhance weather ability and UV resistance. The resulting material is suitable for outdoor applications that require resistance to fading, discoloration, and weathering, such as automotive exterior trims, signage, and outdoor equipment.

ABS/TPU

By blending ABS with thermoplastic polyurethane (TPU), a material with enhanced flexibility, impact resistance, and abrasion resistance is obtained. ABS/TPU blends are used in applications such as protective cases, sporting goods, and flexible automotive components.

ABS/FR

ABS can be modified with flame retardant additives to meet specific fire safety requirements. The resulting ABS/FR material exhibits improved flame resistance. It is used in applications such as electrical enclosures, housing for electronics, and transportation components.

ABS/Carbon Fiber

Adding carbon fiber as a reinforcement to ABS results in a material with improved stiffness, strength, and dimensional stability. ABS reinforced with carbon fiber finds applications in industries like automotive, aerospace, and sporting goods, where high-performance and lightweight materials are desired.

ABS/PP

Blending ABS with polypropylene (PP) can enhance chemical resistance, impact strength, and dimensional stability. ABS/PP blends, such as interior trims and panels, are commonly used in automotive applications.

ABS/Nylon

Combining ABS with nylon (polyamide) results in a material that combines the impact resistance and processability of ABS with the strength, toughness, and wear resistance of nylon. This blend is suitable for applications that require both durability and dimensional stability, such as gears, bearings, and industrial components.

ABS/PVC

Blending ABS with PVC can improve chemical resistance, flame retardancy, and weatherability. ABS/PVC blends find applications in building and construction, electrical enclosures, and piping systems.

ABS/PE

Combining ABS with polyethylene (PE) can improve impact strength and toughness while maintaining processability. ABS/PE blends are used in various applications, including automotive parts, packaging, and consumer goods.

ABS/PBT

ABS can be blended with PBT to achieve a material with improved heat resistance, dimensional stability, and chemical resistance. ABS/PBT blends are commonly used in automotive components, electrical connectors, and appliance housings.

ABS/TPV

When ABS is blended with a thermoplastic vulcanizate (TPV), it combines the toughness and impact resistance of ABS with the flexibility and weather resistance of TPV. ABS/TPV blends are utilized in applications such as automotive seals, gaskets, and weatherstripping.

Mold Design When choosing the ABS materials

Wall Thickness of products in ABS injection molding

The wall thickness of a product in ABS injection molding is related to various factors such as flow length, production efficiency, and usage requirements. The ratio of the maximum flow length of melted ABS plastic to the product’s wall thickness is commonly around 190:1. However, the specific grade of ABS being used may cause variations in this value. The recommended wall thickness for ABS products typically falls within the 1.5 to 4.5 mm range.

Uniformity ensures consistent performance. In the case of products that will undergo plating or coating, a flat surface without bumps is desirable to prevent dust adherence, which could compromise the coating adhesion. Sharp corners should be avoided to prevent stress concentration, and it is often preferable to use rounded corners and transitions in areas where thick and thin sections meet. These design considerations help to optimize the structural integrity and overall quality of ABS-molded products.

Draft Angle Design in ABS injection molding

The draft angle in injection molding is related to material shrinkage, which can vary between 0.3% to 0.6% (or even higher) depending on the ABS grade, product shape, and molding conditions. A draft angle of 31′ toward the mold core and 1°20′ toward the mold cavity is commonly recommended for ABS products. Complex-shaped products may require increased draft angles. Draft angles compensate for material shrinkage and facilitate easy part ejection from the mold.

Ejecting Requirements in ABS injection molding

The ejecting requirements are crucial in ABS injection molding to achieve a high-quality finish, especially for plating applications. ABS products should have a scar-free mold cavity and a large effective ejecting area. Synchronization of multiple ejector bars and uniform ejection force is essential to prevent surface imperfections that may affect the plating performance.

Venting Design in ABS injection molding

In ABS injection molding, proper venting is essential to prevent issues like burned plastic and visible weld lines. To facilitate the release of gases generated by the melted ABS, it is necessary to incorporate venting holes or exhaust slots with a depth of around 0.04mm. Adequate venting ensures smooth plastic flow and helps maintain the quality of ABS products during molding.

Runner and Gate design in ABS injection molding

In ABS injection molding, the runner and gate design is important for efficiently filling the mold cavity and achieving high-quality parts. Here are the key points:

Runner Diameter: The diameter of the runner, which is the channel that delivers melted ABS plastic to the mold cavity, should typically be at least 5mm. This ensures an adequate flow of material throughout the mold.

Gate Thickness: The gate is the narrowest part of the runner system and connects it to the mold cavity. The gate thickness is recommended to be more than 30% of the thickness of the product. This helps facilitate material flow and reduces the potential for gate-related issues.

Gate Length: The length of the straight part of the gate, the section that enters the cavity, is generally around 1mm. This length is selected to balance efficient filling and minimize gate marks on the final part.

Gate Location: The location of the gate should be determined based on product requirements and material flow considerations. For parts that require plating, having the gate on the plating surface is generally not desirable. This helps to avoid visible gate marks or potential adhesion issues during the plating process.

Drying of ABS resins

Drying of resins, including ABS, is necessary to remove moisture and ensure optimal processing conditions. Here are the key points:

Water Absorption: ABS has a water absorption rate of about 0.2% to 0.8%. Moisture absorption can negatively impact the quality and properties of the molded parts, such as causing surface defects or reducing mechanical strength.

Drying Temperature and Time: For general grade ABS, it is recommended to dry the material by either baking it at 80-85°C for 2-4 hours or using a drying hopper at 80°C for 1-2 hours before processing. These drying conditions help to remove moisture effectively.

Heat-Resistant ABS: When ABS is blended with polycarbonate (PC) components to create a heat-resistant grade, the drying temperature should be adjusted to a higher value, typically up to 100°C. The increased temperature helps remove moisture effectively from the heat-resistant ABS material.

Drying Time Determination: The presence of air bubbles or “squeezing out the air” from the material can determine the specific drying time. This ensures that the ABS resin is thoroughly dried and ready for processing.

Melt temperature setting in ABS injection molding

The melt temperature of ABS can be determined using the air injection method, and it varies based on the specific grade of ABS being used. The recommended melt temperature settings for different ABS grades are as follows:

Impact Resistant Grade: The recommended range is 220°C to 260°C, with 250°C being a preferred setting.

Heat-Resistant Grade: The recommended range is 240°C to 280°C, with 265°C to 270°C being preferable.

Flame Retardant Grade: The recommended range is 200°C to 240°C, with 220°C to 230°C being preferable.

Transparent Grade: The recommended range is 230°C to 260°C, with 245°C preferred.

Glass Fiber Reinforced Grade: The recommended range is 230°C to 270°C.

For products with high surface requirements, it is generally recommended to use higher melt temperatures and mold temperatures. These higher temperatures can help achieve better surface quality and reduce the likelihood of surface defects.

ABS Molding Temperature and Mold Temperature

Molding Temperature: The molding temperature varies depending on the ABS grade and processing requirements. ABS’s recommended molding temperature range is typically between 200°C and 280°C, with the specific temperature determined by grade, part thickness, and desired properties.

ABS Grade	Molding Temperature Range (°C)
General Purpose	200-230
High Impact	210-240
Heat Resistant	220-260
Flame Retardant	200-230
Transparent	220-250
Glass Fiber Reinforced	230-260

Mold Temperature: It affects the cooling and solidification of the melted ABS resin inside the mold cavity. Proper mold temperature control is crucial for achieving consistent part dimensions, minimizing deflection, and improving surface finish. Typically, the recommended mold temperature for ABS ranges from 40°C to 80°C. However, the optimal mold temperature depends on part design, wall thickness, and the specific ABS grade used. Adjustments to the mold temperature may be necessary to achieve the desired balance between cooling time, cycle time, and part quality.

ABS Grade	Mold Temperature Range (°C)
General Purpose	40-70
High Impact	40-80
Heat Resistant	50-80
Flame Retardant	40-70
Transparent	50-80
Glass Fiber Reinforced	60-80

Post-treatment for ABS products

Post-treatment for ABS products is not typically required. Still, post-treatment techniques can be employed in cases where ABS parts have specific requirements or are subject to internal stress. Here are some key points:

Internal Stress: ABS products, like other plastics, can develop internal stress due to factors such as molding conditions, part design, or cooling rates. The presence and magnitude of internal pressure can be evaluated by immersing the part in a glacial acetic acid solution and observing for cracks. However, stress cracking is generally rare with ABS.

Hot Air Circulation Drying: In situations where ABS products have more stringent requirements or exhibit internal stress, placing them in a hot air circulation drying oven at temperatures between 70°C and 80°C for 2 to 4 hours can help alleviate or reduce internal stress. The parts are then cooled gradually to room temperature.

Limited Need for Post-Treatment: In most cases, ABS products can be utilized without post-treatment. ABS has good dimensional stability and mechanical properties, allowing for immediate use after molding. However, additional post-treatment processes like annealing or stress-relieving techniques may be considered for critical applications or parts with specific requirements.

Advices to buyers of ABS injection molded products

Some modified ABS materials in the market can contain recycled content. Using recycled materials in plastics, including ABS, has become more prevalent as sustainability and environmental concerns have grown. However, the impact on the performance and stability of molded products can vary depending on the quality and consistency of the recycled material used.

The use of recycled content can introduce variations in the material properties, such as melt flow, impact strength, and dimensional stability. The performance and stability of the molded product can be influenced by controlling the recycled content correctly or ensuring consistent quality of the recycled material. The impact will be dependent on how the percentage of recycled content, the quality of the recycled material, and the specific requirements of the application are considered.

To ensure consistent and stable performance, manufacturers must work closely with their suppliers and carefully select the materials used in their manufacturing processes. Quality control measures, including rigorous testing and material certifications, can help mitigate potential variations and ensure the desired performance of the molded product.

It is recommended to communicate your specific requirements and concerns regarding material stability with your injection molding service suppliers.