Liquid Teflon™ vs. Parylene

Conformal coatings are applied to a wide array of products for various industries such as aerospace, automotive, biomedical, consumer goods, and military applications. These coatings aim to create a protective film that enhances the ease of use, functionality and longevity of the devices across different environments. Liquid Teflon™ (PTFE) and Parylene are two widely used hydrophobic coatings.

Comparing Liquid Teflon (PTFE) with Parylene

PTFE

Liquid Teflon’s corrosion resistant qualities are well documented; repelling nearly everything, the bond that exists between its carbon and fluorine atoms is so strong, the substance is nearly bullet resistant. Its lubricating properties greatly reduce friction and component wear during operation, particularly for machines with sliding parts, effectively lubricating bearings, gears, slide-plates and other moving components, more reliably than most competing covering materials.  Additionally, it also plays a role in surgical interventions as a grafting material.

Teflon displays resistance to chemical reaction, corrosion and stress-cracking. In addition, PTFE coatings:

• Demonstrate excellent electrically conductive capacities
• Repel virtually any other substance
• Provide reliable internal covering for ducts, pipeline and containers for chemicals that are highly corrosive or reactive

PTFE hydrophobic coatings enhance lubricity, a quality desirable for many applications, ranging from medical implants to aerospace/automotive mechanics, where decreased friction between components improves function and prolongs operational life. PTFE also has a lower co efficient of friction than Parylene, which normally would make it the coating of choice for applications where greater levels of lubricity are essential to enhanced performance.  However, in many cases application-specific considerations make Parylene a better choice.

While liquid Teflon offers benefits, it cures at temperatures and schedules that can impact the fundamental thermo-mechanical properties of components coated, especially those made of nitinol or similar alloys. Balancing the preservation of these alloys’ thermo-mechanical characteristics with maintaining adequate lubricity poses a significant obstacle for future liquid PTFE applications.

PTFE coatings can also produce particulates during prolonged operation.  When used for medical purposes, these minute particles of matter can become embedded in patients’ tissue or bloodstream, potentially endangering bodily function and health; particulates can interfere with the performance of non-medical components as well. In contrast, hydrophobic Parylene seldom dissociates or separates from the substrate during use, making it a superior option in cases where particulate development is a concern.  Parylene’s generally improved lubricity in these cases transforms “sticky” substrate surfaces into those that are smooth and non-resistant. These advantages in relation to PTFE are also transferred in many aerospace, automotive, consumer and military applications.

Parylene

An industry standard conformal coating material, Parylene is applied via a chemical vapor deposition (CVD) process, wherein the gaseous Parylene penetrates deeply into the substrate surface, covering even the most isolated or obscured regions of its topography. This quality makes Parylene very useful for adaptation to microelectricalmechanical systems (MEMS) and nanotechnology applications, as well as larger-scale product treatments. Like liquid PTFE, Parylene is noted for its durable lubricity, generating long-lasting and dependable barriers to biological, chemical, electrical and mechanical conditions that can endanger the performance of electronic components used both for specialized purposes and in everyday life.

Parylene also provides:

• Adhesion to an extensive range of substrate materials
• Micron-thin coating
• Minimal increase in weight and volume
• Pinhole-free coating
• Penetration of crevices and small nooks
• Tin whisker mitigation

Both PTFE and Parylene are adaptable to a wide range of product applications. Choosing between the two is always a function of the specific uses of the component and its operational context. For instance, although PTFE is a harder coating than Parylene, and is often a better option for many mechanical uses, it does tend to crack and wear. Thus, Parylene is a superior film choice in specific cases, such as laser welding. These considerations need to be analyzed in all cases before deciding between them.

Conclusion

Parylene and liquid PTFE each have their own performance benefits and disadvantages. Selecting the appropriate hydrophobic coating for biomedical, consumer or other products is essentially determined by the specific uses and operating conditions of each device. Quality control and cleanliness testing are supported by such methods and instruments as:

• Gauges and microscopes
• Product sampling
• Statistical control processing
• Thin film analysis

Evaluating the device’s performance in its intended application is crucial for making informed decisions. While liquid PTFE has a higher consumer profile, Parylene offers a broader range of product adaptations. To this extent, Parylene’s CVD process is often superior to Teflon’s liquid application methodologies for assuring reliable conformal coating. Typically applied by dipping or spraying, PTFE is prone to bridging, edge-effect or pooling, developments that limit the true conformity of the resultant protective film. Parylene CVD generates a micro-thin, authentically conformal film. Parylene emerges as the superior coating solution in scenarios where dimensional tolerances are tight (such as MEMS/nanotechnologies) and for components with intricate topographies that demand highly dependable conformal treatment.