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Polycaprolactone (PCL) is a distinctive type of polyester renowned for its biodegradable properties and versatile applications. The molecular structure of Polycaprolactone is unique, consisting of long chains of caprolactone units. Notably, PCL possesses biodegradability, allowing it to be widely used in environmentally friendly applications. EuroPlas' article will provide you with more information about Polycaprolactone-related topics.

1. What is polycaprolactone?

Polycaprolactone (PCL) is a type of biodegradable polyester with a low melting point of approximately 60°C and a glass transition temperature of about -60°C. Its primary application is often in the production of specialized polyurethanes.

PCL provides excellent resistance to water, oil, solvents, and chlorine for the resulting polyurethanes. Additionally, it is commonly used as an additive for plastics to enhance their processing properties and final use, such as impact resistance.

Polycaprolactone also exhibits compatibility with various other materials. It can be combined with starch to reduce costs and improve biodegradability or employed as a plasticizer for polyvinyl chloride (PVC).

Furthermore, Polycaprolactone finds applications in modeling, molding, and serves as a material for rapid prototyping systems like 3D printing and fused filament fabrication for creating consolidated hair strands.

What is polycaprolactone?

2. Polycaprolactone structure

Polycaprolactone (PCL) is a biodegradable polyester with a chemical formula of (C6H10O2)n. It is synthesized from crude oil or through the ring-opening polymerization of ε-caprolactone with a catalyst (e.g., octanoic tin).

The structure of PCL consists of caprolactone monomers linked together by ester bonds. Each caprolactone monomer unit comprises a six-membered lactam ring. Caprolactone is a hexameric ring with a chemical formula of C6H10O2.

The chemical formula of PCL's structure is [-OC(O)C6H10-]n, where n represents the number of monomer units in the polymer chain.

The caprolactone monomers are connected through ester bonds between the carboxyl (-COOH) group of one monomer and the hydroxyl (-OH) group of another.

PCL is a semi-crystalline polymer, meaning it has a structure that includes both crystalline and amorphous regions. The crystalline regions are tightly arranged, while the amorphous regions have a random arrangement.

The ratio of crystalline to amorphous regions in PCL can be adjusted by varying polymerization conditions. PCL with a higher ratio of crystalline regions will have higher tensile strength and stiffness, whereas PCL with a lower ratio of crystalline regions will exhibit greater flexibility and elasticity.

Polycaprolactone structure

3. Polycaprolactone density

Polycaprolactone has an average density of 1.145 g/cm³ at 25°C. The density of PCL depends on the molecular structure and the purity of the material. PCL has a lower density compared to other synthetic plastics, such as polypropylene (PP) and polyethylene (PE). The lower density of PCL makes it lighter and easier to handle than other synthetic plastics.

The density of polycaprolactone is slightly higher than that of water (1 g/cm³). This means that polycaprolactone will float on water.

Polycaprolactone density can be determined using various methods, including:

• Hydrostatic weighing: This method is based on Archimedes' principle, where a sample of PCL is weighed in both air and water.
• Pycnometry: This method involves weighing a sample of PCL in a pycnometer containing a known liquid with a known density.
• Mass spectroscopy method: This method is based on the difference in molecular weight of PCL molecules.
  Light scattering method: This method is based on the light scattering by PCL molecules.

Polycaprolactone density

4. Is polycaprolactone biodegradable? 

The answer is yes. Polycaprolactone (PCL) is a biodegradable polyester. It can be broken down by microorganisms in soil, water, or composting environments. The rate of PCL degradation depends on factors such as moisture, temperature, and pH.

During degradation, PCL is metabolized by bacteria into smaller molecules, such as fatty acids and carboxylic acids. These molecules can then be used as a source of nutrients by plants.

PCL has a slower degradation rate compared to other biodegradable plastics like polylactic acid (PLA). Under normal conditions, it may take several years for PCL to completely degrade. However, in composting conditions, PCL can break down within a few months.

Is polycaprolactone biodegradable? 

5. Polycaprolactone applications

Polycaprolactone (PCL) is a biodegradable polyester widely applied in various fields, including:

5.1. Medical applications

PCL is a biocompatible and safe biomaterial that can biodegrade in the human body over a period of 18-24 months, depending on its molecular structure. Some medical applications of PCL include:

• Self-absorbing surgical sutures: PCL is used as self-absorbing surgical sutures, replacing traditional sutures like nylon or polyester. PCL sutures are flexible and have a longer self-absorption time, reducing pain and discomfort for patients.
• Skin grafts: PCL is utilized as a skin graft to cover wounds or skin defects. PCL grafts exhibit good durability and elasticity, protecting underlying tissues from environmental factors.
• Bone grafts: PCL is employed as a bone graft to regenerate damaged or lost bone tissue. PCL grafts can be used to treat bone fractures, joint inflammation, or other bone disorders.
• Drug delivery systems: PCL serves as a drug delivery system to control the rate and location of drug release within the body. PCL drug delivery systems can be used to treat chronic diseases such as cancer or diabetes.

Polycaprolactone medical applications

5.2. Industrial applications

PCL is used as an additive for various plastics to enhance processability and impact resistance. PCL is also employed as a plasticizer for PVC, making PVC more pliable and flexible. Some specific applications include:

• Plastic additives: PCL is used as an additive for plastics such as polypropylene, polyethylene, and polystyrene. PCL improves the processability and impact resistance of these plastics.
• PVC plasticizer: PCL serves as a plasticizer for PVC, making PVC more pliable and flexible. PVC is used in construction materials, electronics, and toys.

Polycaprolactone industrial applications

5.3. Consumer applications

PCL is used as a material for packaging, toy manufacturing, sports equipment, and more, including:

• Packaging material: PCL is employed as a packaging material, such as for food and beverage packaging. PCL's water and oxygen resistance properties help protect food and beverages from spoilage.
• Toy manufacturing: PCL is used as a material for toy manufacturing, including children's toys and sports equipment. PCL's durability and impact resistance make toys safe for children.
• Sports equipment: PCL is utilized in sports equipment production, such as golf clubs and tennis rackets. PCL's strength and impact resistance qualities contribute to durable and effective sports equipment.

PCL is a versatile material with numerous potential applications across various fields. With advancements in technology, PCL is expected to find even broader applications in the future.

Polycaprolactone consumer applications

6. Some related questions

What are the mechanical properties of polycaprolactone?

Polycaprolactone is a material with high strength and hardness, along with an elongation of 30-50%. It also exhibits good resistance to bending and impact.

What are the chemical properties of polycaprolactone?

• Polycaprolactone is a material that is impermeable to water, gases and is resistant to common chemicals. It also has the ability to resist bacteria and mold.
• PCL has excellent chemical resistance and can be used in applications involving contact with chemicals. It is not corroded by water, oil, solvents, or chlorine.
• Polycaprolactone also has the capability to resist ultraviolet radiation, but it cannot withstand ionizing radiation.

What are the physical properties of polycaprolactone?

Polycaprolactone is typically white or pale yellow and has a specific gravity of 1.11 g/cm^3. It has a melting point of around 60°C and a glass transition temperature of approximately -60°C. PCL can be used in applications that require resistance to both high and low temperatures.