by Polyvinylidene fluoride or PVDF is a versatile fluoropolymer material that has found widespread applications due to its combination of properties such as chemical inertness, thermal stability, and piezoelectric behavior. In this article, we will discuss in detail the structure, properties, and applications of PVDF.
Chemical Structure and Properties
PVDF is a semi-crystalline fluoropolymer whose chemical structure consists of polymeric chains made of repeating units of -CH2-CF2-. This chemical structure gives PVDF its unique combination of properties. Due to the strength of carbon-fluorine bonds, PVDF exhibits high chemical inertness and resistance to corrosion from acids, bases, and solvents. It also has excellent thermal stability and can withstand temperatures up to 150°C without degradation. PVDF is lightweight and has high impact strength over a wide temperature range due to its flexible polymer chains.
Piezoelectric Behavior
One of the remarkable properties of PVDF is its piezoelectric behavior. The semi-crystalline structure of Polyvinylidene Fluoride allows molecular dipoles to align along the polymer chains when an external electric field or mechanical stress is applied. This alignment of molecular dipoles induces an electric charge, making PVDF piezoelectric. The piezoelectric effect in PVDF can be attributed to its repeated -CH2-CF2- units which act as molecular dipoles able to reorient themselves under applied force or electric field. PVDF’s ability to generate electric potential has led to its use in sensor and transducer applications.
Polymorphism and Applications
PVDF can exist in various crystalline phases called polymorphs that impact its properties and applications. The most common crystalline phases exhibited by PVDF are alpha, beta, and delta phases. The piezoelectric beta phase, which has all-trans planar conformation of its monomers, exhibits the strongest piezoelectric effect compared to the other two phases. PVDF finds use in applications that leverage its piezoelectricity and other properties:
Pressure and Flow Sensors
Due to its piezoelectric effect, PVDF is widely used to develop reliable and robust pressure and flow sensors for industries. Thin PVDF films are capable of generating electric signals proportional to applied pressure or flow which can then be analyzed. PVDF pressure sensors are highly compatible with harsh chemical environments.
Ultrasonic Transducers
PVDF’s ability to quickly generate and receive high-frequency sound waves make it suitable for fabricating lightweight and durable ultrasonic transducers for medical imaging and non-destructive testing. Large-area PVDF transducers are used in medical ultrasonography and underwater sonar applications.
Energy Harvesting Devices
PVDF exhibits reverse piezoelectric effect where application of external electric field causes it to deform mechanically. This property is leveraged in developing energy harvesting devices that can convert ambient mechanical vibration or stress into electric energy. Piezoelectric PVDF nanogenerators are being researched as a possible power source for self-powered sensors.
Seismic Sensors
Due to high sensitivity and suitability for outdoor use, PVDF-based seismic sensors are preferred over geophones for monitoring seismic activities and earthquake early warnings. Their lightweight and simple design makes them an economic option for large-scale seismic networks.
Membrane Filters and Coatings
Outstanding chemical inertness and strength of PVDF membranes enable their use as reliable filters for separating compounds and particles in industries. PVDF coatings provide protective non-stick layers on utensils and equipment handling aggressive chemicals. Its non-reactivity also makes PVDF suitable for food packaging applications.
The versatile fluoropolymer PVDF, including its chemical structure, piezoelectric behavior, polymorphism, and widely varied applications leveraging its impressive combination of properties. Owing to its stability, biocompatibility, and piezoelectric response, research on PVDF is ongoing to utilize its potential for advanced applications in sensors, transducers, biomedical implants, clean energy, and more. PVDF’s future appears promising as science and technology continue to progress.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
