Piezotech films - technical informatioGO好姑娘n
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1. Piezoelectric and pyroele中文版姑娘ctric effects
Since the discovery in 1880, by姐姐直播 the brothers Jacques and Pierre Cu在线免费rrie, of the piezoelectric effect s高清美丽hown by the some simple asymmetric cryMV好姑娘stals, the phenomena has raised a 丁香花免费lot of interest. “Piezoelectricity” finds its roo视频在线ts in the Greek word “piezo” which means press中文版高清版ure. When certain materials are subjected 视频直播to mechanical stress, electricalTVTV charges proportional to the stress appear影院高清 on their surface. Conversely, wh丁香花影院en an electric potential diffe姐姐直播rence is applied to these materials, mech成全视频anical deformation occurs. This effect 影院丁香花is known as piezoelectricity. Similarly, w丁香花免费hen the temperature of the material is 飘雪资源changed, an electric potential appears between 姐姐艺术its terminals: it is called the高清版影院 pyroelectric effect. Quartz and some ceramics ar大地影院e widely used in the manufacture of mechanical an视频动漫d acoustic transducers taking advantage of t丁香花资源hese phenomena. The surfaces of these materi直播国语als are small and highly rigid.
2. Piezoelectric films
Kawai was the first one to discover on 1969 a h美丽TVighly noticeable piezoelectric effect on polyv飘雪TVinylidene fluoride (PVDF). This material is动漫GO the most studied and utilized piezoelec视频MVtric polymer. However, commercialized姑娘姐姐 piezo films only appeared on the world market动漫高清 in 1981.
Piezoelectricity can be obtained by orienting the免费中文版 molecular dipoles of polar polymers such a丁香花直播s PVDF in the same direction by subje姐姐国语cting appropriate films to an in影院成全tense electric field: this is poTV美丽larization. This polarization is mainly at免费TVtributable to the spatial arrangement of在线高清 the segments of the macromolecular chains, and直播高清版 the contribution of the injec美丽影院ted charges to the piezoelectric effec影院影院t is of secondary importance.
3. Characteristics properties of piezoelec高清姐姐tric films
The piezoelectric activity of pMV在线iezoelectric films is determined by the coefMV影院ficients of proportionality between the me动漫丁香花chanical causes and the electric在线免费al effects. The coefficients “d” ar影院直播e obtained by measuring the density of char高清版直播ge (Coulomb/m²) which appears on the surface高清高清s of the film (direction 3 = thickness) when a 美丽好姑娘mechanical stress of 1 Newton/m² is appli丁香花飘雪ed.
●&n高清版国语bsp;Depending on the thickness: d33
● 好姑娘GO;In the plane of the film, in the direction国语影院 of the machine: d31
●&nbs影院TVp;In the plane of the film, in the transverse d艺术姑娘irection: d32
In the first case, if the film ca直播好姑娘nnot be deformed freely in its p丁香花免费lane, the piezoelectric constant is动漫大地 called d33* or dT. The coefficients “d” are exp国语MVressed in Coulomb/Newton (C/N). If the variat姐姐直播ion in the electric field is meas美丽丁香花ured per unit of stress, coeffi影院视频cients “g” are obtained. These are connected 美丽艺术with coefficients “d” by the correlatiMV飘雪on g=d/ε, where ε is the dielectric大地美丽 constant depending on the thicTV在线kness of the film. Coefficients “美丽视频g” are expressed in V.m/N. Constant在线姐姐s “g” and “d” are most widely us高清版直播ed for the design of electromechanical 好姑娘GOtransducers. The conversion of mechanical energy 姐姐成全into electrical energy is represented视频GO by the electromechanical coupl直播飘雪ing coefficient KT expressed in %:
The pyroelectric constant “ρ” is the d成全成全ensity of the charge at the surface (C/m&supGO高清2;) when the film temperature is raised by 1 degr中文版丁香花ee Kelvin; “ρ” is expressed as C/m²K. The 影院高清版coefficient is used for designing thermal影院GO pick-ups. Furthermore, the films are characteri好姑娘国语zed by their mechanical properties: their modulus高清版飘雪 of elasticity, resistance and elon高清中文版gation at break.
4. Properties of piezoelectric films and sheets影院国语
The range of piezoelectric films pr动漫飘雪esents a unique combination of pr在线姐姐operties to the markets:
● Flexibility (possibility of application on non-高清版姐姐level surfaces)
● High mechanical strength
● Dimensional stability
● Balanced piezoelectric activity in the p在线大地lane of the film
● High and stable piezoelectric coeffic视频中文版ients
● Characteristic chemical inertness中文版高清
● Continuous polarization for grea影院GOt length spooled onto drums
● Thickness between 9µm and 1mm
● Acoustic impedance close to that of美丽影院 water with a flat response curve
The characteristic properties of o视频国语ur range of piezoelectric films and sheets, mono GO大地or bi-oriented are given in the tab美丽影院le and diagram below. Various type of metall免费MVization can be applied to thes成全美丽e films, depending on their application.
5. PVDF piezoelectric films properties
(1): Constants are given as indic视频大地ative value, it depends strongly on processi在线MVng conditions (annealing & poling) 高清版飘雪and on temperature.
(2): Excessive heating may destroy piezoelectric免费直播ity. It is advised not to heat above国语高清 90°C for more than 1 hour.
6. Properties of PVDF mono-orien飘雪艺术ted piezo sheets
(1): Constants are given as indicative好姑娘GO value, it depends strongly on proce成全成全ssing conditions (annealing & polin高清版国语g) and on temperature
7. Field of applications
The properties of PVDF piezoelectric fi丁香花影院lms suggest that they can be consider动漫艺术ed for developments in numerous MV大地fields of applications where experimenta免费影院tion shows encouraging results.
7.1 Example of application
7.2 Examples of Data Sheets of various 美丽中文版piezoelectric films
PVDF MONO-ORIENTED FILM – 25 &m动漫资源icro;m(1)
(1): Constants are given as indicativ动漫直播e value, it depends strongly on processing condit飘雪GOions (annealing & poling) and on te影院影院mperature
PVDF bi-oriented film – 9 µm
(1): Constants are given as indica影院GOtive value, it depends strongly on pr姑娘GOocessing conditions (annealing & p高清姐姐oling) and on temperature
P(VDF-TrFE) COPOLYMER 70/30 FILM – 20 &micr飘雪TVo;m
(1): Constants are given as in视频直播dicative value, it depends strongly on processingMV美丽 conditions (annealing & poling) and on tem中文版影院perature
P(VDF-TrFE) COPOLYMER 75/25 FILM – 20资源影院 µm
(1): Constants are given as ind成全视频icative value, it depends strong丁香花影院ly on processing conditions (ann国语中文版ealing & poling) and on temperature好姑娘GO
P(VDF-TrFE) COPOLYMER 80/20 FILM – 20姐姐姑娘 µm
(1): Constants are given as indicMVGOative value, it depends strongly on processing 中文版丁香花conditions (annealing & poling) and o飘雪国语n temperature
