for purposes of this invention , high temperature thermal stability is defined as the ability of a material to retain substantially its piezoelectric properties at high temperatures . the present invention relates to a polarized material that provides increased piezoelectric properties with high temperature stability . the polarized material of this invention includes a blend of at least one vinylidene - containing polymer such as poly ( vinylidene fluoride ) ( pvdf ) and poly ( vinylidene fluoride / vinyl trifluoride ) copolymer ( poly ( vf 2 - vf 3 )) and at least one odd - numbered nylon such as nylon - 3 , nylon - 5 , nylon - 7 , nylon - 11 , or an odd - odd numbered nylon such as nylon 5 - 7 or nylon 3 - 5 . the polarized material may alternatively include a blend of pvdf and poly ( vf 2 - vf 3 ) as well as a blend of more than one odd - numbered or odd - odd numbered nylon . the polarized material can be prepared without the use of a polarization solvent and is thermally stable up to at least about 160 ° c . the components may be mixed in various amounts , preferably with more than 10 % by weight odd - numbered or odd - odd numbered nylon , and most preferably a 50 : 50 by weight blend . the blended polarized material of the present invention produces a significant increase in piezoelectric properties , i . e . remanent polarization , as compared to the component materials individually . a polarized material that includes a 50 : 50 by weight blend of nylon - 11 and poly ( vf 2 - vf 3 )( 80 / 20 mol %) displays a remanent polarization that is 100 % greater than that of the poly ( vf 2 - vf 3 )( 80 / 20 mol %) and 50 % greater than that of nylon - 11 . when the polarized material includes a 50 : 50 by weight blend of nylon - 11 and pvdf , it displays a remanent polarization that is 70 % larger than that of either component . a desired method of preparing a single - layered piezoelectric film is shown in fig1 . the method includes preparing a powder blend of nylon - 11 and pvdf , melting the blend , pressing the melted blend into a film 10 , quenching the film , stretching the film , and poling the film . the direction of stretching is perpendicular to the placement of electrodes 11 on either side of the blended film 10 . the polarized material may be formed into a single - layered film capable of substantially retaining its piezoelectric properties at high temperatures . the film is prepared from a fine powder blend of at least one vinylidene - containing polymer and at least one odd - numbered or odd - odd numbered nylon as described above , and is desirably prepared without the use of a solvent . the fine powder blend may be prepared by first preparing a powder of the odd - numbered or odd - odd numbered nylon by impacting pellets of the nylon or a combination of different nylons in a freezer / mill at liquid nitrogen temperature , adding the pvdf or poly ( vf 2 - vf 3 ) powder ( or a mixture of both ), and mixing the blend in the freezer / mill for a sufficient time to achieve a uniform mixture , e . g . about a half hour . the prepared powder blend can then be formed into a film by melting the powder at temperatures up to about 210 ° c . and pressing . the thickness of the film can vary depending on its intended application . generally , the thickness may vary from about 10 μm to about 35 μm , desirably from about 20 μm to about 30 μm . the melted film may then be quenched in an ice water bath . the film may then be drawn , which increases the piezoelectric properties . the films are preferably uniaxially cold - drawn at room temperature at about a 3 : 1 draw ratio . the films can then be placed in an electric field to induce polarization . fig2 demonstrates an apparatus useful for poling . the blended film 10 may be placed in an oil bath 12 to reduce corona discharge during poling . electrodes 11 placed on either side of the film 10 , provide an electric field supplied by a power supply 15 . the voltage and current are measured by a volt meter 14 and current meter 16 , respectively . a computer 17 is provided for analysis and recordation of data . the temperature may be controlled by a heating / cooling device 13 as desired . the poling may be carried out at room temperature in a field of up to about 220 mv / m , preferably in a field above 160 mv / m . after poling , the film may additionally be annealed . annealing is performed at temperatures up to the melting temperature of the material . preferably , the annealing will be conducted in a vacuum at 160 ° c . for a sufficient time , e . g . about two hours . a multi - layered film may also be produced by laminating two or more films produced by the above process . nylon - 11 pellets and pvdf powder were obtained from rilsan corporation and sotex polymer corporation , respectively . nylon - 11 powder was obtained by impacting the pellets in a spex mill at liquid nitrogen temperature . the nylon powder was then mixed with the pvdf powder in the spex mill , also at liquid nitrogen temperature for approximately a half hour . the mixed powder was vacuum dried at 100 ° c . for twelve hours , then sandwiched between aluminum foils in a hot press at 210 ° c . it was then melted and quenched in an ice water bath . the melt - quenched films were uniaxially drawn from 1 : 1 to 3 . 5 : 1 in steps of 0 . 5 with a draw speed of 2 . 56 cm / min at room temperature . the thickness of the films varied from ˜ 30 μm to 18 μm for the undrawn film , respectively . gold electrodes were then evaporated under high vacuum on opposing sides of the films . the shape of the electrodes were rectangular and the area was 40 mm 2 ( 4 mm × 10 mm ). poling was carried out at room temperature by application of a triangular shaped field at a very low frequency of { fraction ( 1 / 640 )} hz . the samples were immersed in a silicone oil bath during poling to reduce corona discharge . the silicon oil was continuously purged using dried air to decrease the conductivity and increase the maximum dielectric strength of nylon - 11 which decreases with adsorbed water . a maximum poling field of 220 mv / m was used for the blend . as a comparison , blends of pvdf and nylon - 11 were prepared using a solution method for mixing as opposed to the powder blend . the table below shows a comparison of several piezoelectric properties of films prepared with only nylon - 11 , only pvdf , solution blends , and the powder blends of the present invention . the properties listed are as follows : remanent polarization ( p r ), coercive field ( e c ), young &# 39 ; s modulus , piezoelectric stress constant ( d 31 ), piezoelectric strain constant ( e 31 ), and the dielectric constant . solution blend nylon - 11 / powder blend nylon - 11 pvdf pvdf nylon - 11 / pvdf p r ( mc / m 2 ) 51 52 65 87 e c ( mc / m 2 ) 69 64 75 75 young &# 39 ; s modulus 4 . 5 2 . 2 2 . 96 3 . 15 c ( gpas ) d 31 2 . 8 25 . 2 4 . 28 6 . 96 e 31 6 . 2 71 . 0 12 . 65 22 . 43 dielectric constant 2 . 8 12 . 0 5 . 68 5 . 76 [ 0031 ] fig3 a and 3b show a comparison of both d 31 and e 31 , respectively , for films made of only nylon - 11 , only pvdf , and blends of the materials at ratios of 20 : 80 , 50 : 50 , and 80 : 20 by weight of the blend . the above table and fig3 both show the improvement in piezoelectric properties with the blends as opposed to the component materials separately . fig3 also shows that the properties are maintained as the temperature approaches 160 ° c . while there have been described what are presently believed to be the preferred embodiments of the invention , those skilled in the art will realize that changes and modifications may be made thereto without departing from the spirit of the invention , and it is intended to include all such changes and modifications as fall within the true scope of the invention .