Polymer Data File:

Acrylonitrile Butadiene Styrene
- ABS 

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Introduction

Advantages and Limitations

Typical Applications

Processing

Physical and Mechanical Properties

Finishing

Thermal, Electrical and Optical Properties

Health and Safety

Chemical Resistance Properties

Other Information


Introduction

ABS (Acrylonitrile - butadiene - styrene terpolymer) is a member of the styrene family of polymers and shares many properties with the PS type of polymer. The actual properties of a particular ABS material depend on the blend ratio of the three major constituents (Acrylonitrile, butadiene and styrene). The material properties can be tailored to give specific desired properties: the acrylonitrile component gives chemical resistance and heat stability, the butadiene gives toughness and impact strength and the styrene gives rigidity and processability. Varying the A-B-S ratios will change the properties significantly and the number of grades available is almost limitless.

The ABS material itself can also be 'alloyed' with other materials such as PC, PMMA, PBT, PA and even PVC. This creates an even greater choice of properties and processing opportunities and many ABS materials are created for a single application (mainly automotive).

The material can be readily processed by most of the common processing methods.

Typical Applications

Mechanical: Office machine housings that are colour fast and fire retardent, pipes and fittings.

Consumer goods: Food containers, luggage shells, household equipment such as vacuum cleaners and hair driers, vacuum formed refrigerator liners, internal trays for refrigerators, telephone handsets.

Automotive: Safety helmets, electroplating possibilities give applications in fascia panels, body fittings, instrument clusters and radiator grilles. ABS is effectively the 'material of choice' for automotive interior applications.

Electrical: Computer housings and fascias.

Miscellaneous: Dinghy hulls thermoformed from sheets give stiff, impact resistant hull that is unaffected by sea water. Plumbing fittings when electroplated.

Physical and Mechanical Properties

ABS is hard and tough even at temperatures as low as -40oC. It has a high resistance to temperature fluctuations but has very limited weathering resistance and the mechanical properties tend to degrade quickly in outdoor exposure. It has low water absorption.

Property

Approximate Value

ABS

Tensile strength

55 - 80 MN/m2

Tensile Modulus

2 - 3 GN/m2

Elongation at Break

10 - 50 %

Flexural Strength

<50 - 150 MN/m2

Notched Impact Strength

10 - 20 kJ/m2

Specific Heat

1.25 - 1.70 kJ/kgoC

Glass Transition Temperature

110 oC

Heat Deflection Temperature

<100oC

Coefficient of Thermal Expansion

5 - 10 x 10-5 / oC

Long Term Service Temperature

<100 oC

Specific Gravity

1.0 - 1.2

Mould Shrinkage

0.001 - 0.005 m/m

Water Absorption

0.1 - 0.5 % (50% rh)

Transparency

Opaque

Thermal, Electrical and Optical Properties

Thermal properties

ABS has good high temperature performance and the softening point is generally higher than standard PS. The heat deflection temperature can be increased by several methods to between 120 to 130oC.

ABS can be used down to about -40oC.

Fire behaviour

Most ABS variants are flammable and will burn freely (giving off typical styrene odours). The flame and fire properties of ABS can be improved by blending bromine compounds at 15 - 20 pts phr - an expensive solution that seriously compromises the toughness of the material.  Another method is to create an ABS/PVC blend and to let the chlorine on the PVC act as a fire retardent.

Electrical properties

ABS has relatively good electrical insulating properties and products are suitable for secondary insulating applications.

Optical properties

Natural ABS is milky-opaque but can be easily coloured in a wide variety of colours. Special glass clear versions are available.

Chemical Resistance Properties

ABS is resistant to most acids and alkalis, hydrocarbons, oils and fats. It is not resistant to acetone, ether, ethyl benzene, ethyl chloride and ethylene chloride.

ABS has a low water absorption.

Weathering resistance: Most ABS blends have poor weathering resistance. 

ABS Chemical Resistance Chart

Advantages and Limitations

Advantages

Limitations

1. Good stain resistance

1. Poor weathering resistance.

2. Good impact resistance even at low temperatures.

2. Must be dried before processing.

3. Good electrical insulator and the electrical properties are unchanged by changes in humidity.

3. Ordinary grades burn easily and continues to burn once the flame is removed.

4. Low water absorption.

4. Poor heat resistance.

5. Easily electroplated to give good finish.

5. Poor transparency but can be mixed with PMMA to improve.

6. Good scuff or abrasion resistance.

6. Scratches easily.

7. Tough and stiff.

7. Attacked by strong adds and alkalis, chlorinated solvents and can suffer from stress cracking in the presence of some greases.

8. Wide colour range possible (natural is ivory colour).

 

Processing

ABS is an amorphous material and softens over a range of temperatures rather than melting quickly as do the crystalline materials. The materials have a broad processing window and can be processed on most standard machinery. ABS is available in standard and easy-flow grades and the easy flow grades are very good for complex mouldings. 

Pre-drying is not always needed for injection moulding with a vented cylinder but if drying is needed then 4 hours at 80oC is generally sufficient. Signs of moisture are stripes, streaks or bubbles in the moulding and if any of these are seen then the material should be pre-dried.

Injection moulding

Mould temperature is usually between 30 and 80oC and the higher the mould temperature the better the surface quality. Weld lines may also become less prominent with increasing mould temperature.

Moulding is carried out with an injection pressure of 1000 to 1500 bar and using a follow-up pressure of relatively short length but in the region of 30 - 60% of the injection pressure.

Back pressure using a normal cylinder is 100 - 250 bar and should be kept high to avoid air scorching of the material, a vented cylinder uses 20 - 50 bar and if this is too high then the easy flow grades will ooze from the vent port.

Screw speeds can be high but should be set to ensure complete plastification.

Injection speeds can be high but it is best to start slowly and then to inject rapidly.

Extrusion

Screws should be chrome plated, single lead, full flighted constant pitch screws. Compression ratio should increase from around 2:1 to 2.5:1. In the absence of special ABS screws, low-compression PVC or shallow flighted PS screws can be used at low production rates.

Reprocessing of up to 30% can be used provided the regrind has not been subjected to previous thermal degradation.

Processing Method

Applicable

Injection Moulding

Yes.

Extrusion

Yes

Extrusion Blow Moulding

No

Injection Blow Moulding

No

Rotational Moulding

Yes

Thermoforming

Yes

Casting

Yes

Bending and joining

Yes

Finishing

Machining

ABS can be easily machined using most conventional methods. The chips formed during machining will tend to melt unless coolants are used. Tools should be sharp and have good clearance and cutting angle.

Surface treatment

ABS can be electroplated and can easily be polished to an excellent surface finish.

Welding

All processes suitable for thermoplastics can be used e.g. high frequency, hot gas, ultrasonic, friction, hot plate and heat impulse welding.

Bonding

ABS can be readily bonded with solvent cements such as MEK, tetrahydofuran, and methylene chloride. Bonds should use the minimum amount of solvent and be held under slight pressure until complete.

Health and Safety

Health and Safety

ABS does not constitute a health hazard.

Other Information

Identification

  • ABS is flammable and continues to burn when the source of ignition is removed.

Last edited: 11/03/10

© Tangram Technology Ltd. 2001

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