Main Difference – PLA vs ABS
PLA and ABS are two types of polymer material. Therefore, they are macromolecules that are composed of many repeating units. PLA is polylactic acid. The monomer that is used to form PLA is lactic acid. ABS is acrylonitrile butadiene styrene. It is made from three monomers: acrylonitrile, butadiene, and styrene. These polymer materials are used in different applications depending on their chemical and physical properties. One of the most common applications of both these compounds is as filaments in 3D printing. The main difference between PLA and ABS is that PLA is a biodegradable thermoplastic polymer whereas ABS is a non-biodegradable thermoplastic polymer.
Key Areas Covered
1. What is PLA
– Definition, Production, and Properties
2. What is ABS
– Definition, General Properties and Uses
3. What is the Difference Between PLA and ABS
– Comparison of Key Differences
Key Terms: ABS, Acrylonitrile, Acrylonitrile Butadiene Styrene, Butadiene, Lactic Acid, PLA, Polylactic Acid, Styrene, Thermoplastic
What is PLA
PLA is polylactic acid. It is a biodegradable thermoplastic polyester. It is an aliphatic polymer. PLA is derived from renewable sources such as corn starch, cassava roots, sugarcane, etc. PLA is the most common bioplastic that is in use today due to its biodegradability and biocompatibility.
The earliest method of producing PLA was by condensation polymerization, which gives low molecular weight products. But nowadays, ring-opening polymerization is used for the production of high molecular weight PLA.
The monomer used for the production of PLA is lactic acid. This monomer is produced from the fermentation or by chemical means. However, fermentation is the most favorable method because of fewer limitations. The production of PLA can be done mainly in three major ways.
- Condensation polymerization
- Polycondensation in an azeotropic solution
- Polymerization through lactide formation
Condensation polymerization includes the formation of an ester which then undergoes condensation reactions. This method removes water molecules during the polymerization process. However, this method is not very favorable because we cannot obtain high molecular weight polymer material from this method. The second method polycondensation in an azeotropic solution which is more practical. This method uses various catalysts. But polymerization through lactide formation is the most efficient method for the production of PLA. It gives high molecular weight PLA. Lactide is a cyclic dimer formed from a condensation reaction. This method of production of PLA is also known as ring-opening polymerization because lactide is a cyclic molecule.
Figure 1: Obtaining PLA from Lactic Acid and Lactide
PLA can be processed into fiber forms and films. The most common application of PLA is as filaments used in 3D printing. These filaments are less prone to twist and has a lower flexibility. Generally, these filaments are less durable. The melting point is lower. However, PLA is generally thermally unstable and exhibit rapid loss of molecular weight when treated thermally. This is because the ester linkages tend to degrade when heat is provided. This thermal degradation occurs at lower temperatures than the melting point of PLA. PLA has a good appearance, high mechanical strength, and low toxicity. The glass transition temperature of PLA is low. It limits the use of PLA in thermally processed packages.
What is ABS
ABS is acrylonitrile butadiene styrene. It is an amorphous, thermoplastic polymer. This polymer is produced from three types of monomers: styrene, acrylonitrile, and butadiene. Here, styrene and acrylonitrile are subjected to undergo polymerization in the presence of polybutadiene.
Acrylonitrile is a synthetic monomer. It is made from propylene and ammonia. Butadiene is obtained from petroleum refining as a byproduct. Styrene is also a synthetic monomer. Therefore, ABS is not a biopolymer. It is an opaque thermoplastic. The method of production of ABS is known as emulsion process. The mixture of reactants is in the form of an emulsion. The continuous mass polymerization is another process which will eventually form ABS.
Figure 2: Monomers used in the Production of ABS
Since ABS is a thermoplastic material, it can be easily recycled. This is because they can be heated to their melting point, cooled, and re-heated again without significant degradation. This means the most common method of producing ABS is by recycling the pre-existed ABS material.
One of the most common applications of ABS includes its use filaments in 3D printing. Using ABS for this purpose results in a burning plastic scent during the process of printing. These filaments are more prone to twist. They are somewhat flexible when compared to other types of filaments used in 3D printing. Since they are chemically resistant, ABS is more durable.
ABS has a higher melting point. Since it is an amorphous polymer, its true melting point cannot be calculated. The glass transition temperature is about 105oC. Due to the properties of ABS, it is used in automotive applications such as wheel covers, mirror, and headlight housing.
Difference Between PLA and ABS
Definition
PLA: PLA is polylactic acid.
ABS: ABS is acrylonitrile butadiene styrene.
Nature
PLA: PLA is an aliphatic, thermoplastic polymer.
ABS: ABS is an amorphous, thermoplastic polymer.
Monomers
PLA: PLA is made from lactic acid monomers.
ABS: ABS is made from acrylonitrile, butadiene and styrene monomers.
Occurrence in Nature
PLA: PLA is a biodegradable polymer.
ABS: ABS is a non-biodegradable polymer. But it can be recycled.
Raw Material
PLA: PLA is a plant-based material.
ABS: ABS is a petroleum-based material.
Durability
PLA: PLA is comparatively less durable.
ABS: ABS is more durable.
Flexibility
PLA: PLA is less flexible.
ABS: ABS is more flexible than PLA.
Melting Point
PLA: PLA has a lower melting point.
ABS: ABS has no defined melting point due to its amorphous structure.
Conclusion
PLA and ABS are important polymer materials. PLA is polylactic acid. ABS is acrylonitrile butadiene styrene. Both these materials are commonly used as filaments for 3D printing. There are many differences between PLA and ABS when the chemical composition and the properties are considered. The main difference between PLA and ABS is that PLA is a biodegradable thermoplastic polymer whereas ABS is a non-biodegradable thermoplastic polymer.
References:
1. Jamshidian, Majid, et al. “Poly‐Lactic Acid: Production, Applications, Nanocomposites, and Release Studies.” Comprehensive Reviews in Food Science and Food Safety, Blackwell Publishing Inc, 26 Aug. 2010, Available here.
2. Rogers, Tony. “Creative Mechanisms Blog .” Everything You Need to Know About ABS Plastic, Available here.
3. “Acrylonitrile butadiene styrene.” Wikipedia, Wikimedia Foundation, 13 Oct. 2017, Available here.
Image Courtesy:
1. “PLA from lactic acid & lactide” By Rifleman 82 – Own work (Public Domain) via Commons Wikimedia
2. “ABS resin formula” By H Padleckas at English Wikipedia – Own work (Public Domain) via Commons Wikimedia
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