Acrylonitrile butadiene styrene (ABS): These materials are complex blends and copolymers of acrylonitrile, but Adrienne and styrene. These resions for its widespread appetence are high impact resistance, good stiffness, and excellent surface quality. Chemical formula (C8H8)x· (C4H6)y·(C3H3N)z) is a common thermoplastic.
- These materials are complex blends and copolymers of Acrylonitrile, butadiene and styrene.
- In most types, Acrylonitrile and styrene are grafted onto a polybutadiene backbone. The product also contain unreacted polybutadiene and some acrylonitrile styrene copolymer.
- The reasons for its widespread acceptance are high impact resistance, good stiffness, excellent surface quality, high dimensional stability at elevated temperatures.
- Its main disadvantages are lack of transparency, poor weathering resistance, poor flame resistance.
These materials are complex blends and copolymers of Acrylonitrile, butadiene and styrene.
In most types, Acrylonitrile and styrene are grafted onto apolybutadiene backbone. The product also contain unreacted polybutadiene and some acrylonitrile styrene copolymer.
The reasons for its widespread acceptance are high impact resistance, good surface quality, high dimensionalstiffness, stability at excellent elevated temperatures.
Its main disadvantages are lack of transparency, poor weathering resistance, poor flame resistance.
ABS Preparation
- Styrene and Acrylonitrile are added to polybutadiene latex and the mixture is warmed to about 50°C to allow absorption of the monomers.
- Water soluble initiator is added to polymerize styrene and Acrylonitrile.
- The resultant materials will be a mixture of Polybutadiene, polybutadiene grafted with Acrylonitrile and Styrene, and Styrene-Acrylonitrile copolymer.
Processing Considerations
- May absorb upto 0.3% moisture and therefore must be stored under dry condition.
- Greater tendency to degradation than PS during processing so important not to overheat. Avoid too high screw speed and back pressure during moulding.
- Generally less free flowing than PS particularly with heat resistance grades.
- Being an amorphous, the materials have a low moulding shrinkage.
Processing Techniques
Injection Moulding
Typical Injection Moulding conditions
- Recommended melt temperatures 220-280 °C.
- Typical mould temperature is 40–90 °C.
- Injection pressures of 69-138 MPa.
- L/D ratio is 20:1 and Compression ratio of 2:1 to 3:1.
Extrusion
Typical extrusion conditions
- Melt temperatures 205-250 °C.
- Temperature profile 192-250°C.
- Recommended screw L/D ratio 20:1 to 36:1.
- Recommended Compression ratio 2.5:1 to 3:1.
Thermoforming
- ABS can be thermoformed over a temperature range of 130 to 190°C.
- The optimum conditions depend on material grade,part design, draw ratio, sheet thickness and forming technique.
Electroplating
- ABS is the best material for electroplating.
- The polymer is treated by an acid etching process which dissolves out some of the rubber particles at or near the polymer surface. After sensitization and activation electroless metal deposition processes are carried out .
Properties of ABS
1. Good combination of mechanical, thermal and chemical properties
2. Low cost of all engineering thermoplastics
3. High impact strength
4. Low continuous use temperature
5. High thermal expansion
6. Limited weather resistance
7. Poor solvent resistance
8. Low water absorption
9. Easy processable by injection, extrusion and vacuum forming
10. Electroplatable
11. Opaque
12. Glossy surface finish
13. Very low dust attraction
14. Rigid
15. Very good shock and fracture resistance
16. Good Chemical resistance
17. Heat resistance up to 105 °C
18. High Dimensional accuracy and stability
19. Good Electrical insulation
20. Good flowability
21. Readily electroplated
Chemical and Solvent resistance
Generally resistant to alkalis and acids but not concentrated oxidizing acids.
Dissolved by many aromatic and chlorinated hydrocarbons, esters and ketones.
Maximum Service temperature
UL temperature index 60-75°C.
Alloy with Polycarbonate may be as high as 95°C.
Flammability
Standard grades are considered as slow burning and usually meet the UL HB requirement.
The material burns with a smoky yellow flame emitting a pungent gas.
Processing Considerations of ABS
1. May absorb upto 0.3% moisture and therefore must be stored under dry condition.
2. Greater tendency to degradation than PS during processing so important not to overheat. Avoid too high screw speed and back pressure during moulding.
3. Generally less free flowing than PS particularly with heat resistance grades.
4. Being an amorphous, the materials have a low moulding shrinkage.
Typical Injection Moulding conditions
1. Recommended melt temperatures 220-280 °C.
2. Typical mould temperature is 4090 °C.
3. Injection pressures of 69-138 MPa.
4. L/D ratio is 20:1 and Compression ratio of 2:1 to 3:1.
Extrusion
1. Typical extrusion conditions
2. Melt temperatures 205-250 °C.
3. Temperature profile 192-250°C.
4. Recommended screw L/D ratio 20:1 to 36:1.
5. Recommended Compression ratio 2.5:1 to 3:1.
Thermoforming
1. ABS can be thermoformed over a temperature range of 130 to 190°C.
2. The optimum conditions depend on material grade,part design, draw ratio, sheet thickness and forming technique.
Electroplating
1. ABS is the best material for electroplating.
2. The polymer is treated by an acid etching process which dissolves out some of the rubber particles at or near the polymer surface. After sensitization and activation electroless metal deposition processes are carried out .
APPLICATIONS OF ABS
1. Telephone casings
2. Housing for domestic appliances eg. Vaccum cleaners, TV cabinets, etc.
3. Luggage cases
4. Safety helmets
5. Car fascia and instrument panels
6. Toys
7. Furniture
8. Food mixture housings
9. Automobile radiator grills
10. Refrigerator door and tank liners
11. Automotive front and assembly
Automobile
- Radiator grills, head light housing, seat belt, head lamp fixtures, door knobs, two wheeler front noise, water panel, helmet, electroplated parts, mirror housing and wheel covers. In the vehicle construction industry.
Agriculture
- Drinking water system, water vent systems and irrigation systems.
Household
- Plumbing fixtures, table edging, sliding doors, window trucks, refrigerators liners, refrigerator door handles, pipe fittings, ventilator system components, picnic boxes, food processors, coffee maker leads, microwave oven tops.
Medical
- IV fluid monitoring controllers, blood glucose meter, surgical clips, emergency intravenous infusion pump, scanner body, ECG / EEG body frames, cabinets for medical kit, breathing exerciser.
ABS/PC BLENDS
1. High impact strength and hardness
2. Improved HDT compared to ABS
3. Dimensional stability
4. Electrical properties independent of moisture and temperature
APPLICATIONS
1. Electrical and Electronics appliances, Automotive parts
ABS/PVC BLENDS
1. Flame resistance
APPLICATIONS
1.Electrical appliance housing, Automotive instrument panels
ABS/TPU BLENDS
1. Very high impact strength
2. TPU contributes lubricity, wear resistance, toughness, low temperature impact strength
3. ABS provides increased stiffness and improved processability
ABS/PC
- Increase in HDT up to 130°C.
ABS/PVC (80:20)
- Fire retarding ABS type material.
ABS/PVC (10:90)
- Impact modified form of unplasticised PVC.
ABS/Acrylic material
- A reasonable transparent ABS-type polymer.
No comments:
Post a Comment