Rubber and PVC (polyvinyl chloride) are two popular materials used in the production of moulded parts across a wide range of industries, from automotive to construction and consumer goods. Each material has distinct properties that make it suitable for specific applications. Understanding the differences between rubber and PVC moulded parts can help customers choose the best material for their needs.
Composition and Structure
Rubber: Rubber can be either natural or synthetic. Natural rubber is derived from the latex sap of rubber trees, while synthetic rubber is produced from petrochemical feedstocks. Rubber molecules are elastomers, meaning they can stretch and return to their original shape. Common types of synthetic rubbers include EPDM (Ethylene Propylene Diene Monomer), SBR (Styrene-Butadiene Rubber), and NBR (Nitrile Butadiene Rubber).
PVC: Polyvinyl chloride is a synthetic plastic polymer. It is produced by polymerising vinyl chloride, a petrochemical. PVC is versatile and can be made rigid (e.g., for pipes) or flexible (e.g., for insulation) by adding plasticisers. Flexible PVC is more commonly used in moulded parts.
Physical Properties
Elasticity and Flexibility
Rubber: Rubber can be either natural or synthetic. Natural rubber is derived from the latex sap of rubber trees, while synthetic rubber is produced from petrochemical feedstocks. Rubber molecules are elastomers, meaning they can stretch and return to their original shape. Common types of synthetic rubbers include EPDM (Ethylene Propylene Diene Monomer), SBR (Styrene-Butadiene Rubber), and NBR (Nitrile Butadiene Rubber).
PVC: PVC, especially in its rigid form, lacks the elasticity of rubber. While flexible PVC can offer some degree of bendability, it does not have the same ability to stretch or recover from deformation. This limits its use in dynamic applications requiring frequent movement.
Durability and Wear Resistance
Rubber: Rubber is highly resistant to wear and tear, which makes it suitable for long-term use in harsh environments. It can withstand repeated stress and extreme temperatures without cracking or breaking down, particularly in its synthetic forms like EPDM and silicone.
PVC: PVC is durable but tends to become brittle over time, especially when exposed to direct sunlight (due to UV degradation) or very cold temperatures. It is less capable of withstanding long-term mechanical stress compared to rubber.
Chemical Resistance
Rubber: Different types of rubber vary in their chemical resistance. For example, nitrile rubber (NBR) is highly resistant to oils and fuels, while EPDM excels in resisting weathering, ozone, and UV exposure. However, rubber is less resistant to certain solvents and chemicals than PVC.
PVC: PVC offers excellent resistance to a wide range of chemicals, including acids, alkalis, and salts. It is commonly used in chemical handling applications due to this resistance. However, it is susceptible to degradation when exposed to certain organic solvents and prolonged UV exposure without additives.
Applications
Rubber Moulded Parts
Rubber is often used in applications that require flexibility, elasticity, and resistance to dynamic stresses. These include:
- Seals and gaskets: Rubber’s elasticity allows it to form tight seals under compression.
- Vibration dampers: Its ability to absorb shock and vibration makes it ideal for automotive parts and industrial machinery.
- Tires and belts: Rubber’s durability and wear resistance make it the go-to material for these high-stress applications.
PVC Moulded Parts
PVC is widely used where rigidity, chemical resistance, and cost-effectiveness are key considerations. Common applications include:
- Piping and fittings: Rigid PVC is commonly used in plumbing and irrigation systems.
- Electrical insulation: Flexible PVC is often used for cable insulation and protective coverings due to its good electrical properties.
- Consumer goods: PVC is also found in everyday items like footwear, raincoats, and inflatable products.
Benefits of Rubber Over PVC
While both rubber and PVC have their strengths, rubber offers several distinct advantages over PVC in certain applications:
- Superior Elasticity and Flexibility: Rubber’s natural elasticity outperforms PVC in applications requiring flexibility and stretch. Its ability to recover from deformation is essential in products like seals, hoses, and vibration dampers, where continuous movement and stress are present. This makes rubber a better choice for dynamic environments where flexibility is crucial.
- Higher Temperature Tolerance: Rubber can withstand a broader range of temperatures than PVC. While PVC softens at relatively low temperatures (around 60-80°C) and becomes brittle in cold conditions, rubber maintains its integrity in extreme heat and cold. Silicone rubber, for instance, can perform well in temperatures ranging from -100°C to 300°C, making it ideal for automotive, aerospace, and industrial applications.
- Better Wear and Tear Resistance: Rubber’s natural resilience makes it resistant to abrasion, impact, and mechanical wear. In applications where parts are exposed to continuous friction or stress—such as conveyor belts, tires, and gaskets—rubber outlasts PVC, which may crack or degrade over time under similar conditions.
- Long-Term Durability in Harsh Environments: Rubber is particularly suited for outdoor applications where exposure to the elements (UV, ozone, moisture) is a concern. EPDM rubber, for example, is highly resistant to environmental degradation and outperforms PVC in outdoor sealing and insulation applications. PVC, when exposed to UV rays, tends to degrade and lose flexibility, requiring the use of additives or UV stabilisers.
- Enhanced Shock Absorption: Rubber’s excellent damping properties allow it to absorb shock and vibrations much more effectively than PVC. This makes rubber the preferred choice for automotive bushings, vibration mounts, and other components where cushioning and impact absorption are critical.
- Biocompatibility and Safe Handling: For applications involving human contact, especially in the medical or food industries, rubber can be more biocompatible than PVC. Some types of PVC contain plasticizers and additives that can leach out over time, raising concerns about health and environmental impacts. Rubber, particularly silicone rubber, is often preferred in food-grade and medical-grade applications due to its inertness and biocompatibility.
In Conclusion
Both rubber and PVC are valuable materials for moulded parts, but their properties make them suitable for different environments and uses. Rubber’s flexibility, durability, and resistance to wear and extreme temperatures make it the superior choice for dynamic, high-stress applications, especially in industries such as automotive, aerospace, and heavy machinery. PVC, on the other hand, excels in chemical resistance, cost-effectiveness, and rigid applications like piping or cable insulation.
In summary, when selecting between rubber and PVC for moulded parts, the choice should be based on the specific requirements of the application, with rubber offering clear advantages in flexibility, longevity, and performance under challenging conditions.inertness and biocompatibility.
