Decoding PU and PVC: Characteristics, Distinctions, and How to Identify Them

August 31, 2023

1. What is PU?


PU, or polyurethane, is a versatile polymer that was invented in the late 1930s by German chemist Dr. Otto Bayer. This synthetic material is formed through the reaction of isocyanates and polyols. PU exhibits a wide range of properties that make it a popular choice for various applications.


Chemical Characteristics: Polyurethane is highly flexible and resistant to abrasion, chemicals, and solvents. It can be formulated to exhibit varying degrees of hardness, from soft and flexible to rigid and durable.


Physical Characteristics: PU is known for its exceptional load-bearing capacity, tear strength, and elongation. It offers excellent resilience and can return to its original shape after deformation.


Applications: PU finds applications in industries such as automotive, furniture, footwear, and healthcare. It is used to create a variety of products, including seat cushions, wheels, medical devices, footwear soles, and even coatings for fabrics.


2. What is PVC?


PVC, or polyvinyl chloride, is a widely used thermoplastic polymer. It was first discovered in the 19th century by French chemist Henri Victor Regnault, and its commercial development began in the early 20th century. PVC is produced through the polymerization of vinyl chloride monomers.


Chemical Characteristics: PVC is known for its chemical resistance and flame retardancy. It is also resistant to moisture, making it suitable for applications where exposure to water is a concern.


Physical Characteristics: PVC is a lightweight and rigid material with good electrical insulating properties. It can be formulated to have varying levels of hardness, from flexible to rigid.


Applications: PVC is used in various industries, including construction, automotive, healthcare, and packaging. It is commonly used in pipes, electrical insulation, window frames, flooring, and even clothing.


3. How to Distinguish between PU and PVC?

Identifying whether a wheel is made of PU or PVC is essential, as using the wrong material could lead to significant consequences. Here are three methods to help you distinguish between the two:


a. Flexibility Test: PU is typically more flexible than PVC. Gently bending the wheel can give you a sense of its flexibility and whether it exhibits the characteristic "softness" of polyurethane.


b. Weight Test: PU is generally denser than PVC, so PU wheels tend to be heavier for a given size. Comparing the weight of the wheel to its size can provide a clue about the material.


c. Appearance Test: PU often has a slightly translucent appearance, while PVC is usually more opaque. Observing the color and translucency of the wheel's surface can help differentiate between the two materials.


4. The Cost Difference between PU and PVC:


The cost difference between PU and PVC can vary depending on factors such as formulation and manufacturing processes. Generally, PU tends to be more expensive than PVC due to its superior performance and versatility. Accurately identifying the material is vital to avoid unnecessary expenses and ensure optimal performance.


5. Temperature Resistance of PU and PVC:


PU typically has a temperature resistance range of around -30°C to 80°C (-22°F to 176°F). To enhance its resistance to extreme temperatures, additives or modifiers can be incorporated into the formulation.


PVC offers a broader temperature range, approximately -10°C to 60°C (14°F to 140°F). For applications requiring greater temperature resistance, specialized formulations or additives can be used to expand its capabilities.

6. Defining PU and PVC by Burning Test:


An additional method to distinguish between PU and PVC is through a burning test. When subjected to heat, PU and PVC exhibit different behaviors that can help identify the material:


a. PU Burning Test: Polyurethane burns with a blue flame that produces thick, dark smoke and a sweet, chemical smell due to its chemical structure. After burning, PU will leave behind a fine ash or residue.


b. PVC Burning Test: PVC burns with a yellowish-green flame that produces dense, dark smoke with a strong, acrid odor of chlorine. It may drip or produce charred fragments. The resulting ash will be darker and more substantial compared to PU.


Performing a controlled burning test in a well-ventilated area can provide valuable insights into the material composition of a wheel or component.




In conclusion, understanding the distinctions between PU and PVC is crucial when selecting materials for specific applications. While PU offers exceptional flexibility, resilience, and chemical resistance, PVC is favored for its flame retardancy, rigidity, and electrical insulating properties.


Distinguishing between PU and PVC can be accomplished through flexibility, weight, and appearance tests. This knowledge empowers you to choose the right material, avoiding unnecessary expenses and optimizing your applications for performance and longevity.


Given the cost difference between PU and PVC, accurately identifying the material can save you money and prevent potential operational issues.


Both PU and PVC have distinct temperature resistance ranges, and incorporating additives or modifiers can tailor their properties to meet specific temperature requirements.


Next time you encounter a wheel or component of a caster, you can confidently determine whether it's made of PU or PVC. Armed with this knowledge, you can make informed decisions to ensure the success of your projects while optimizing costs and performance.

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