What do uniaxial and biaxial mean in relation to piezoelectric film development?

[kaelibw]

Ok. I know this may sound like a stupid question but for the life of me i can't find definitions for these terms. I am working on developing a PVDF polymer based piezoelectric film and need to know what the terms Uniaxial and biaxial mean. I am using an electrospining method to make the fibers and need to know how these terms would change my methods.

 

[Space_Cowboy]

'Uniaxial' means exactly what it sounds like -- that your fibers are all parallel along a flat plane. 'Biaxial,' likewise, means the fibers are oriented in two directions (typically perpendicular - 90*) upon the same flat plane. The material known as 'triaxial' fiberglass laminate, used in snowboards, surfboards and longboards, typically has the axis of its main sheet oriented along the length of the deck, with two angled sheets crossing in the center of the deck and angled away from the main axis to the same degree on both sides in an 'X' pattern. The angles of any axes besides the first (which is assumed to be your 'length' direction') are arbitrary.

When it comes to a polymer film, the same general rules apply, i.e., the 'length' direction of each film layer is the fiber direction.

Just curious - what's your project? Are you building some kind of supercapacitor? ^_^

 

[kaelibw]

Actually my project Was to just create a piezoelectric fiber mat but we weren't able to get past the polarization step. couldn't find any clear way to do it.

regardless, this was a project we were doing in high school and the year ended a few months ago.

 

[Space_Cowboy]

"Actually my project Was to just create a piezoelectric fiber mat but we weren't able to get past the polarization step. couldn't find any clear way to do it. "

Sorry to jump on this train so late, then!

Polarization step... Since this stuff is a polymer I'm assuming it must also be polarizable to make an electret. That usually involves heating the plastic near its melting point, then cooling slowly while exposing it to a strong DC electrical field.

I haven't worked with PVDF so I'm not intimately familiar with its properties. That's pretty interesting though - it must have a combination of piezo and dielectric properties.

 

[kaelibw]

ok. I am back and i need help. though I am not doing this anymore, i would like to continue research and send my findings back to my teacher.

one of the biggest questions plagueing me was HOW do you expose it to dc electrical fields? what apparatus do you need to set up to acomplish this

 

[rexol]

i feel
PVDF due to 2 F on the same C atom will not polarizable to a huge extent. Also F will not be willing to orient the electrons so easily i nthe electric field direction. why can't u use some Cl based polymer instead?

 

[kaelibw]

The main reason I cannot use a Cl based polymer is because of two things. 1. From what I have read, PVDF has the strongest piezoelectric force of any polymer. 2. PVDF is the only thing we can afford right now in large quantities to perform these experiments