Poly(lactic acid)

Definition

Poly(lactic acid) is a biodegradable and bioactive thermoplastic made from renewable resources, particularly corn starch or sugarcane. It's widely used in various applications, from packaging materials to medical devices, due to its environmental friendliness and favorable mechanical properties. Its ability to degrade under certain conditions makes it a focus in studies of hydrolytic degradation, which refers to the breakdown of polymers by the reaction with water.

5 Must Know Facts For Your Next Test

1. Poly(lactic acid) can undergo hydrolytic degradation through the cleavage of ester bonds when exposed to moisture, leading to the formation of lactic acid monomers.
2. The rate of hydrolytic degradation of poly(lactic acid) can be influenced by factors such as molecular weight, crystallinity, and the presence of additives.
3. Due to its biodegradability, poly(lactic acid) is often considered an eco-friendly alternative to conventional petroleum-based plastics.
4. In medical applications, poly(lactic acid) is used for sutures and drug delivery systems because it can degrade in the body without causing harm.
5. Research into modifying poly(lactic acid) with other biodegradable materials is ongoing to enhance its properties and broaden its applications.

Review Questions

• How does hydrolytic degradation affect the properties of poly(lactic acid) over time?
  • Hydrolytic degradation leads to the gradual breakdown of poly(lactic acid), resulting in changes to its physical properties such as mechanical strength and ductility. As the polymer degrades, the molecular weight decreases due to the cleavage of ester bonds in the presence of water. This process can make poly(lactic acid) more suitable for applications where controlled degradation is desired, such as in temporary medical implants that dissolve after fulfilling their purpose.
• Discuss how factors such as molecular weight and crystallinity influence the hydrolytic degradation rate of poly(lactic acid).
  • The rate of hydrolytic degradation in poly(lactic acid) is significantly affected by its molecular weight and crystallinity. Generally, lower molecular weight polymers degrade more quickly because they have fewer entanglements and less resistance to water penetration. Higher crystallinity can slow down the degradation process since crystalline regions are more ordered and less accessible to water molecules, making it more difficult for hydrolysis to occur within those areas. Understanding these factors is crucial for tailoring poly(lactic acid) for specific applications.
• Evaluate the implications of using poly(lactic acid) as a biodegradable material in packaging compared to traditional plastics.
  • Using poly(lactic acid) as a biodegradable material in packaging has significant implications for reducing environmental impact compared to traditional plastics. Traditional plastics often persist in landfills for hundreds of years, contributing to pollution and harming wildlife. In contrast, poly(lactic acid) can degrade into harmless byproducts under proper conditions, minimizing waste accumulation. However, challenges remain in ensuring that enough infrastructure exists for effective composting or recycling of these materials, making further innovation essential in promoting sustainable packaging solutions.

Related terms

Biodegradation: The process by which organic substances are broken down by living organisms, typically microorganisms, into simpler, non-toxic compounds.

Hydrolysis: A chemical reaction involving the breaking of a bond in a molecule using water, often leading to the breakdown of larger molecules into smaller ones.

Thermoplastic: A type of plastic that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling, allowing for easy processing and recycling.