**3.2 Comparison of charge/mass of electrospun and polarized PVDF fibers and yarns**

The plot in **Figure 7** compares the charges of the (a) as-spun mats and yarns, and (b) polarized mats and yarns. For comparison purposes the samples of polarized and nonpolarized mats and yarns are compared on equal mass basis. The labels A, B, C, D and E indicate the masses of fibers in the yarns and mats corresponding to 0.0058, 0.0124, 0.0196, 0.0278 and 0.0376 g respectively. The data reported in **Figure 7** are for electrospun mats of varying basis weights (not stacked layers of mats). For the given areas and masses of the mats the A, B, C, D and E mat samples correspond to 10, 20, 30, 40 and 50 g/m<sup>2</sup> basis weights.

In **Figure 7** the charges per mass of the mats were about 2 to 5 times the value for the yarns. The charge per mass of the as-spun and polarized mats increased as the mat mass increased with approximate slope of 17% (comparable to the 25% slope observed in the layered mats of **Figure 6**). Charges on the yarn samples did not vary as much with mass. Both the as-spun and polarized yarns tended to have a modest decrease in charge per mass as yarn mass increased. The difference in performance between the yarns and the mats is probably due to the way the yarn was folded to fit into the Faraday bucket. Increasing the mass of the yarn was obtained by increasing the length of the yarn hence the overall surface area per mass of the yarn was constant. But to fit the yarn into the Faraday bucket, the yarn was wound onto the U shaped metal wire which resulted in the first layers of the windings being covered by subsequent layers. Unlike the stacked fiber mats, the resulting charge/mass decreased with mass. This suggests that the measured charges per mass of the yarns were mostly proportional to the external area/mass ratio and may also give insight to the performance of the mats. This topic should be further explored in future work.

**Figure 8** shows plots comparing the as-spun to polarized mats and yarns. The comparison of the mats in **Figure 8a** shows the polarized treatments only marginally increased the charges on the mats. This contrasts with the increases in charges reported in literature [6]. There were some differences between the treatments in this work compared to reference [6] such as the heat cycle in [6] was at a controlled ramp rate and the electrical polarization was maintained until the mat had completely cooled, while in this work the ramp rate was not controlled and the electrical polarization was for a shorter time period. It is possible, though not verified here,

**Figure 7.**

*Charge/mass plot for mats and yarns (a) as-spun, (b) polarized. The respective masses of the samples were a = 0.0058 g, B = 0.0124 g, C = 0.0196 g, D = 0.0278 g, and E = 0.0376 g.*

**205**

the yarns.

**Acknowledgements**

tion of the Faraday bucket.

*Polarization of Electrospun PVDF Fiber Mats and Fiber Yarns*

that the beta phase content of the electrospun fibers was near its maximum in the as-spun fibers and hence the polarization treatment did not have much room to

*Charge/mass plot for as-spun and polarized samples (a) Mats, (b) yarns the respective masses of the samples* 

The comparison of yarns in **Figure 8b** similarly show a small increase in the charge in most of the cases. Overall, the charges on the yarns did not change significantly with mass. The polarized samples A, B, and E showed greater charge compared to the as-spun samples while C and D showed less charge. These variations may be within experimental error possibly due to the hand winding of the

Polymer PVDF was electrospun to form fiber mats and continuous twisted yarns. Samples of the mats and yarns were polarized by stretching, heating and poling. The as-spun and polarized mats and fibers were measured for their charge via a Faraday bucket. The results showed the mats had significantly higher charge per mass than the yarns at the same mass. The measured charge per unit mass of the mats increased as the mass of the mat increased. The measured charge per mass of the yarns slightly decreased as mass increased. The polarization treatments used in this work did not significantly increase the charge of the mats and yarns. Charge measurements of stacked layers of mats suggest that the charge measured by the Faraday bucket is a complicated combination of surface area and bulk mass. Changing the basis weights of fiber mats (instead of stacking layers) gave similar trends suggesting the same mechanisms may apply to both stacked and directly spun mats. The nearly constant measured charges of the yarns suggest that the charge per mass may be related to the surface area per mass of

This work was funded by Coalescence Filtration Fibers Consortium (CFNC): Parker Hannifin, Hollingsworth and Vose, and Donaldson. We acknowledge the assistance of technicians Steve Roberts and William Imes for fabrication and opera-

increase the beta phase content. This is left for future investigation.

*were a = 0.0058 g, B = 0.0124 g, C = 0.0196 g, D = 0.0278 g, and E = 0.0376 g.*

*DOI: http://dx.doi.org/10.5772/intechopen.96305*

yarns onto the U-shaped wire holder.

**4. Conclusions**

**Figure 8.**

*Polarization of Electrospun PVDF Fiber Mats and Fiber Yarns DOI: http://dx.doi.org/10.5772/intechopen.96305*

**Figure 8.**

*Nanofibers - Synthesis, Properties and Applications*

correspond to 10, 20, 30, 40 and 50 g/m<sup>2</sup>

be further explored in future work.

**yarns**

**3.2 Comparison of charge/mass of electrospun and polarized PVDF fibers and** 

The plot in **Figure 7** compares the charges of the (a) as-spun mats and yarns, and (b) polarized mats and yarns. For comparison purposes the samples of polarized and nonpolarized mats and yarns are compared on equal mass basis. The labels A, B, C, D and E indicate the masses of fibers in the yarns and mats corresponding to 0.0058, 0.0124, 0.0196, 0.0278 and 0.0376 g respectively. The data reported in **Figure 7** are for electrospun mats of varying basis weights (not stacked layers of mats). For the given areas and masses of the mats the A, B, C, D and E mat samples

basis weights.

In **Figure 7** the charges per mass of the mats were about 2 to 5 times the value for the yarns. The charge per mass of the as-spun and polarized mats increased as the mat mass increased with approximate slope of 17% (comparable to the 25% slope observed in the layered mats of **Figure 6**). Charges on the yarn samples did not vary as much with mass. Both the as-spun and polarized yarns tended to have a modest decrease in charge per mass as yarn mass increased. The difference in performance between the yarns and the mats is probably due to the way the yarn was folded to fit into the Faraday bucket. Increasing the mass of the yarn was obtained by increasing the length of the yarn hence the overall surface area per mass of the yarn was constant. But to fit the yarn into the Faraday bucket, the yarn was wound onto the U shaped metal wire which resulted in the first layers of the windings being covered by subsequent layers. Unlike the stacked fiber mats, the resulting charge/mass decreased with mass. This suggests that the measured charges per mass of the yarns were mostly proportional to the external area/mass ratio and may also give insight to the performance of the mats. This topic should

**Figure 8** shows plots comparing the as-spun to polarized mats and yarns. The comparison of the mats in **Figure 8a** shows the polarized treatments only marginally increased the charges on the mats. This contrasts with the increases in charges reported in literature [6]. There were some differences between the treatments in this work compared to reference [6] such as the heat cycle in [6] was at a controlled ramp rate and the electrical polarization was maintained until the mat had completely cooled, while in this work the ramp rate was not controlled and the electrical polarization was for a shorter time period. It is possible, though not verified here,

*Charge/mass plot for mats and yarns (a) as-spun, (b) polarized. The respective masses of the samples were* 

*a = 0.0058 g, B = 0.0124 g, C = 0.0196 g, D = 0.0278 g, and E = 0.0376 g.*

**204**

**Figure 7.**

*Charge/mass plot for as-spun and polarized samples (a) Mats, (b) yarns the respective masses of the samples were a = 0.0058 g, B = 0.0124 g, C = 0.0196 g, D = 0.0278 g, and E = 0.0376 g.*

that the beta phase content of the electrospun fibers was near its maximum in the as-spun fibers and hence the polarization treatment did not have much room to increase the beta phase content. This is left for future investigation.

The comparison of yarns in **Figure 8b** similarly show a small increase in the charge in most of the cases. Overall, the charges on the yarns did not change significantly with mass. The polarized samples A, B, and E showed greater charge compared to the as-spun samples while C and D showed less charge. These variations may be within experimental error possibly due to the hand winding of the yarns onto the U-shaped wire holder.
