What Is Styrene Acrylonitrile?: Styrene Acrylonitrile resin is a copolymer plastic containing styrene and acrylonitrile.
Formula of Styrene Acrylonitrile:
The chemical formula of styrene acrylonitrile is (C8H8)n-(C3H3N)m
Properties of Styrene Acrylonitrile:
• Material: SAN
• Chemical Name: Styrene Acrylonitrile
• Structure: Amorphous
• Opacity: Transparent
• Strength: Brittle
• Specific Gravity: 1.08
• Shrinkage: 0.3%-0.7%
• Melting Point: 239°F
• Deflection temperature: 183.2°F – 204.8°F
• Service Temperature: 131°F
Polystyrene and styrene acrylonitrile are similar in use. Like polystyrene, styrene acrylonitrile is optically transparent and brittle in mechanical behavior. This copolymer has a glass transition temperature greater than 100 °C owing to the acrylonitrile units in the chain and this makes the material resistant to boiling water. Styrene Acrylonitrile is structurally related to ABS plastic, where polybutadiene is copolymerised with SAN to give a much stronger material. The rubber chains form separate phases which are 10-20 micrometers in diameter. When the product is stressed, crazing from the particles helps to increase the strength of the polymer. Other polymers such as PMMA and nylon are strengthened using the method of rubber toughening.
Production of Styrene Acrylonitrile:
The copolymerization of styrene and acrylonitrile produces styrene-acrylonitrile copolymer (SAN), a rigid, transparent plastic. SAN combines the hardness, strength, clarity and rigidity of polystyrene and also the heat and solvent resistance of polyacrylonitrile. It is employed in automotive parts, furniture, appliances, battery cases, kitchenware, and medical supplies.
Styrene units and acrylonitrile units in a ratio of approximately 70:30 make up SAN. The two compounds are mixed in a water-based emulsion or suspension or in bulk-liquid form, and polymerization takes place under the action of free-radical initiators. The resultant plastic material shows a better resistance to solvents and heat than the polystyrene alone. The impact resistance of the copolymer is not good enough for many engineering applications, and styrene and acrylonitrile are therefore often copolymerized
with admixtures of butadiene rubber to get a more shatter-proof product called ABS, or acrylonitrile-butadiene-styrene copolymer.
Applications of Styrene Acrylonitrile:
Styrene Acrylonitrile is used for the following:
1. In place of Polystyrene, Styrene Acrylonitrile resin, a copolymer is used due to its greater thermal resistance.
2. SAN copolymers are gotten from the polymerization reaction of styrenes and acrylonitrile. The properties rely on the acrylonitrile content. Different acrylonitrile molecular masses are offered by commercial grades of SAN.
3. Due to it’s transparency, SAN is one of the few plastics that can be used in clear applications. It is a preferred type of plastic in the housewares market because of it’s glass-like clarity.
4. Styrene Acrylonitrile is used in food containers, water bottles, kitchenware, computer products, packaging material, battery cases and plastic optical fibers.
5. Styrene Acrylonitrile is used in dishwasher-safe containers.
6. Styrene Acrylonitrile is used in disposable lighters.
7. Styrene Acrylonitrile is used in brush bristles.
8. Styrene Acrylonitrile is used in auto gauge covers.
9. Styrene Acrylonitrile is used in cosmetic cases.
10. Styrene Acrylonitrile is used in medical syringes.
11. Styrene Acrylonitrile is used in reflectors.
12. Styrene Acrylonitrile is used in doors.
13.Styrene Acrylonitrile is used in battery cases.
Advantages of Styrene Acrylonitrile:
Here are some of the advantages of Styrene Acrylonitrile:
1. Styrene Acrylonitrile has an excellent rigidity/stiffness.
2. Styrene Acrylonitrile has an excellent load-bearing capacity.
3. Styrene Acrylonitrile resin has an excellent chemical resistance.
4. Styrene Acrylonitrile has a high flexural strength.
5. Styrene Acrylonitrile has a good appearance.
6. Styrene Acrylonitrile has a good color-ability.
7. Styrene Acrylonitrile has a good clarity.
8. Styrene Acrylonitrile has a good thermal resistance.
9. Styrene Acrylonitrile has a good dimensional stability.
10. Styrene Acrylonitrile has good heat resistance.
11. Styrene Acrylonitrile is easily processed.
Disadvantages of Styrene Acrylonitrile:
Here are some of the disadvantages of Styrene Acrylonitrile:
1. Styrene Acrylonitrile has a low max service temperature.
2. Styrene Acrylonitrile is hygroscopic.
3. Styrene Acrylonitrile yellows with age.
4. Styrene Acrylonitrile is flammable with a high smoke generation.
Health risks of Styrene Acrylonitrile:
The acrylonitrile present in the SAN containers has been found to migrate to content in variable amounts. The Agency for Research on Cancer (IARC) has carried out a research on acrylonitrile and has classified it to be a Class 2B carcinogen (Possibly carcinogenic). Acrylonitrile increases the rates of cancer appearance in high dosage tests in both male and female rats and mice.