ACRYLONITRILE BUTADIENE STYRENE (ABS)

Acrylonitrile butadiene styrene is an amorphous terpolymer made from monomers: acrylonitrile, butadiene and styrene. These monomers are mixed in different proportions to achieve the desired properties of the final product. Typical composition is 15% to 35% acrylonitrile, 5% to 30% butadiene and 40% to 60% styrene.

acrylonitrile butadiene styrene chemical formula: (C₈H₈·C₄H₆·C₃H₃N)ₙ

Acrylonitrile butadiene styrene is a terpolymer, it’s made up of 3 different monomers. These monomers are:

• Acrylonitrile: This synthetic monomer gives chemical and thermal stability to ABS. It also gives strength, fatigue resistance, hardness and rigidity.
• Butadiene: This is a synthetic rubber and is responsible for the toughness and ductility of ABS especially in cold temperatures. However it makes the material less heat resistant and slightly less rigid.
• Styrene: This monomer gives ABS its glossy, impervious surface and contributes to hardness, rigidity and ease of processing.

The proportions of these 3 monomers can be varied to make different grades of ABS with different properties.

During the making of ABS, styrene and acrylonitrile monomers polymerize in the presence of polybutadiene. This results to long chains of polybutadiene linked to shorter chains of poly(styrene-co-acrylonitrile). The nitrile groups from the acrylonitrile being polar attracts each other and forms strong bonds between the chains. These attractions makes ABS stronger than pure polystyrene.

The combination of these 3 components makes ABS:

1. Strong and tough: ABS has a good balance of strength and toughness, impact resistant.
2. Heat resistant: ABS can be used from -20 to 80 °C.
3. Chemically resistant: ABS is resistant to many acids, alkalis and oils but can be affected by some solvents.
4. Easy to process: ABS can be moulded, sanded, shaped and dyed.

Note: The final properties of ABS can be affected by the processing conditions like moulding temperature.

ABS density varies with formulation but is generally in the following range:

• Density Range: 0.9 to 1.53 g/cm³, average 1.07 g/cm³.

Specific formulations can have densities:

• Standard ABS: 1.020 to 1.210 g/cm³
• High-impact ABS: 1.000 to 1.100 g/cm³

ABS has great strength properties for many demanding applications:

Tensile Strength:

• Ultimate tensile strength around 6020 psi (41.5 MPa)
• Yield tensile strength 6500 psi (44.8 MPa).
• Flexural Strength: 10,400 psi (71.7 MPa).
• Impact Resistance: ABS has high impact resistance even at low temperatures, due to the polybutadiene in its structure.

• Rigidity and Toughness: ABS is strong and rigid yet flexible enough for machining.
• Chemical Resistance: Good resistance to diluted acids and alkalis, for many environments.
• Thermal Stability: Keeps shape and mechanical properties from -20°C to 80°C (-4°F to 176°F)

ABS is a staple in the automotive world and is used for both interior and exterior parts. Its impact resistance and lightweight properties make it perfect for bumper bars, trim components and decorative interior car parts. It’s also used in dashboards, instrument panels, door panels, grilles, mirror housings and interior consoles.

ABS is found in the casings and components of many consumer electronics and household appliances. Its low conductivity and impact resistance plus ease of molding makes it a popular choice for products like computer keyboards, mice, phone cases, remote controls, audio/video equipment, vacuum cleaners, blenders and coffee makers. ABS is also used in computer cases and housings for small kitchen appliances.

ABS is used in piping and fittings for commercial and residential plumbing systems, especially in drain-waste-vent (DWV) applications. Its corrosion resistance plus its lightweight and easy to install makes it a popular choice in this sector.

ABS’s impact resistance and ability to be molded into intricate shapes makes it suitable for toys, games and sports/recreation equipment. Its use in LEGO bricks is well-known and it’s also used in helmets, protective gear and athletic equipment. The sources also mention golf club heads as an example of ABS being used for its good shock absorbance.

ABS has become a staple in 3D printing and rapid prototyping. Its strength, durability, affordability and ease of processing and post-processing makes it a popular choice for functional prototypes, models and small-batch production parts. Note that ABS is used in Fused Filament Fabrication (FFF) or Fused Deposition Modeling (FDM) 3D printers.

ABS is used in medical devices and equipment due to its durability, chemical resistance and sterilizability. It’s used in inhalers, nebulizers, tracheal tubes, medical instrument housings, equipment casings and drug delivery systems. One source mentions that ABS can be sterilized using gamma radiation or ethylene oxide but doesn’t specifically confirm its use in disposable medical devices.

In short, ABS is everywhere.

Acrylonitrile butadiene styrene (ABS) is a polymerisation of styrene and acrylonitrile in the presence of polybutadiene. This produces a terpolymer, a polymer made from three different monomer units.

ABS plastic production is usually an emulsification process or continuous mass polymerisation.

• Emulsification is a process where two or more substances that don’t mix are combined to form one product. This is used for ABS because it allows for controlled and uniform distribution of the three monomers.
• Continuous mass polymerisation, a patented process, is an alternative to ABS production.

The proportions of each monomer can be adjusted to produce ABS with different properties. For example:

1. More polybutadiene will increase the impact resistance of the final product.
2. More styrene will increase the gloss and heat resistance.

The monomers are mixed with additives like antioxidants and pigments. These mixtures are then processed through:

• Extrusion: Melting and shaping the ABS into continuous forms like sheets, rods or tubes.
• Injection molding: To create complex shapes by injecting molten ABS into molds.

ABS resin is made from raw materials from natural gas and petroleum. PlasticsEurope, the European plastic trade association, estimates it takes an average of 95.34 megajoules of energy to produce one kilogram of ABS resin in Europe.

• ABS comes in many grades. When machining structural parts with ABS, use Machine Grade ABS.
• ABS can be machined with conventional methods: turning, drilling, milling, sawing.

• Joining ABS parts can be done with:
• Welding: ABS parts can be welded by applying heat to the joining surfaces until they melt. A thin ABS rod can be melted into the joint to reinforce the bond.
• Chemical bonding: Solvents can be used to bond ABS parts to each other or to other plastics.
• ABS can be machined and joined so easily.

• Cost: ABS is relatively cheap to produce, making it a great option for many applications. This is because the monomers are readily available and cheap: acrylonitrile, butadiene and styrene.
• Mechanical Strength and Durability: ABS has a good balance of mechanical properties: impact resistance, toughness and rigidity. It can take a beating and harsh conditions. The combination of acrylonitrile for chemical and thermal stability, butadiene for toughness and strength and styrene for surface finish makes it tough.
• Versatility in Processing: ABS is very versatile. It can be moulded, sanded and shaped. Its low melting point makes it suitable for injection moulding and 3D printing. It’s also machinable so you can create precise parts with turning, drilling and milling. ABS parts can be joined by welding or chemical bonding which makes it even more processable.
• Aesthetic Appeal: ABS can take colour so you have a wide range of colour options in your finished product. It can also have a glossy surface finish which makes it look good. This makes it suitable for applications where aesthetics are important like consumer products and automotive parts.
• Electrical Insulation: ABS has low heat and electrical conductivity so it’s great for applications that require electrical insulation. This is useful for electronic enclosures, housings for electrical components and other applications where electrical safety is critical.
• Recyclability: ABS being a thermoplastic can be melted and re-shaped multiple times without significant degradation. Although the sources say not all recycling facilities accept ABS, its recyclability is better than some other plastics.

• Low Melting Point: ABS has a relatively low melting point compared to other plastics so it’s not suitable for high temperature applications. This limitation means it can’t be used in environments where temperatures exceed 160°F (around 71 °C). Good for processing but a challenge for applications that require heat resistance.
• Susceptible to UV Degradation and Weathering: ABS is prone to degradation when exposed to ultraviolet (UV) radiation from sunlight. This can cause discolouration, brittleness and reduced mechanical strength. For outdoor applications, ABS needs to be protected from UV rays and harsh weather conditions to extend its life.
• Poor Solvent and Fatigue Resistance: ABS has poor resistance to some solvents, greases and fatigue stress. This limits its use in applications where it will be exposed to these substances or cyclic loading conditions.
• Toxic Fumes Upon Combustion: When burned ABS releases toxic fumes including carbon monoxide and hydrogen cyanide. This is a safety concern in fire situations as the fumes can be hazardous to health.
• Ultrafine Particle Emissions: Studies have shown that 3D printing with ABS can produce ultrafine particles (UFPs) even at lower temperatures. UFPs have been linked to health effects so this is a concern for 3D printing environments.

ABS plastic is generally safe for everyday use but there are some toxicity concerns with production, use and disposal especially at high temperatures. ABS is stable under normal use and processing conditions and exposure to carcinogens during these processes are below workplace exposure limits. But when ABS is heated to 400 °C (750 °F) it breaks down into its monomers: acrylonitrile, butadiene and styrene. Of these:

• Butadiene is a human carcinogen.
• Acrylonitrile is possibly carcinogenic to humans.
• Styrene is reasonably anticipated to be a human carcinogen.

The most toxic products released during combustion or pyrolysis of ABS are carbon monoxide and hydrogen cyanide. Combustion of pure ABS does not produce persistent organic pollutants as it doesn’t contain halogens.

Another concern is the release of ultrafine particles (UFPs) which can be produced at lower temperatures during processes like 3D printing. UFPs have been linked to adverse health effects, potentially due to accumulation in organs like kidneys, lungs and intestines causing tissue obstruction. So proper safety measures like good ventilation are necessary when working with ABS especially at high temperatures.

Acrylonitrile butadiene styrene (ABS) is a popular thermoplastic polymer that’s strong, durable and versatile. ABS is a terpolymer made from acrylonitrile, butadiene and styrene. Each one brings its own properties to the party. Acrylonitrile gives chemical and thermal stability, butadiene impact resistance and toughness, and styrene a glossy finish and ease of use. ABS can be moulded, sanded and coloured so it’s suitable for all sorts of applications, toys, automotive parts, construction materials and 3D printing.

ABS has many advantages, low cost, light weight and recyclable. But it has some downsides. Its low melting point means it’s not suitable for high temperature applications, it’s prone to UV degradation and weathering so you need to take measures for outdoor use. ABS also produces harmful fumes when burned. Overall ABS is a good material when used right, a balance of good properties and cost for all your manufacturing needs.