Medical Design Briefs - November 2021 - 18

Biomedical Balloons
10
12
14
16
18
20
2
4
6
8
0.5
1
Fig. 6 - Puncture test for nylon and Pebax balloon.
50
60
70
40
30
10
20
Nylon Tube
Pebax Tube
Fig. 7 - Burst pressure of nylon and Pebax tube and balloons.
characterizations. The peaks at 904 and
946 cm-1 correspond to the γ-crystalline
phase, and the 936 cm-1 peak is associated
with the α-crystalline phase of the
polyamide. The measurements were performed
along axial (0°) and radial (90°)
directions to evaluate the effect of orientation
using a polarized beam.
The crystals in nylon tubes mostly consist
of γ phases, and some convert to α
phase when the tube is formed into the
balloon (see Figure 5). The Pebax tube
crystals have more α phases when compared
to nylon, and this becomes more
so when forming into a balloon. The
nylon 12 samples are more sensitive to
orientation when compared to Pebax.
For Pebax, the soft segments can be
identified using the peak at wavenumber
1100 cm-1.
Nylon exhibits a strong resistance to
puncture in comparison to other poly18
Cov
mers,
especially when it is biaxially
stretched. The puncture strength (penetration
force)
is
greater
for
Pebax
balloons. The nylon balloon sample
showed a good yield against puncture
but underperformed against the Pebax
sample both in penetration force and
deflection distance (see Figure 6).
Burst pressure is an important parameter
in medical applications of balloon
catheters and represents the strength of
balloon when pressurized.8 Burst pressure
tests were performed on the tube
and balloon samples in a ramp test (see
Figure 7).
Nylon tubes with a wall thickness of
0.355 mm passed the maximum capacity
of the burst pressure machine. The
lower burst pressure for Pebax tubes is
likely due to the presence of soft segments.
This contributes more to compliance
rather than strength.
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ToC
Nylon
Balloon
Pebax
Balloon
1.5
Pebax
Nylon
2
Penetration (mm)
2.5
3
Conclusion
The melt rheology and crystalline
structure of the nylon 12 and Pebax
6333 tubes and balloons were evaluated
using DMA, DSC, and FTIR measurements.
Among the physical and mechanical
properties noted, nylon 12 shows a
greater shear thinning behavior in a
melt state when compared to Pebax and
therefore the nylon tube dimension is
more sensitive to extrusion processing
parameters such as puller speed. The
Pebax balloon morphology revealed a
hybrid structure consisting of hard segments
dispersed with soft segments and
amorphous phases.
The glass transition temperature of the
nylon tube shifted to higher temperatures
(51-82 °C), which means nylon becomes
stiffer and less flexible when turned into a
balloon. The melting temperature shifted
to higher temperatures when the tubes
were formed into balloons; this shift was
more pronounced for the Pebax balloon
than the nylon. The Pebax balloons
showed a higher puncture resistance than
the nylon balloon. However, the burst
pressure was lower for Pebax (half of a
nylon balloon), which is in accordance
with the balloon tensile data.
References
1. Ro A. J. and Davé V., Mater. Sci. Eng. 2013,
C33, 909-915.
2. Sadeghi, F. and Le, D., " Characterization of
polymeric biomedical balloon: physical and
mechanical properties, " Journal of Polymer
Engineering, (2021): 000010151520210203.
https://doi.org/ 10.1515/polyeng-2021-0203.
3. Saab M. A., Med. Device Diagn. Ind. Mag.
2000, 86-96.
4. Warner J. A., et al., J. Biomed. Mater. Res. B
Appl. Biomater. 2016, 104b, 470-475.
5. Sadeghi F. and Ajji A., Int. Polym. Process.
XXVII 2012, 5, 565-573.
6. Dencheva N., et al., J. Appl. Polym. Sci. 2006,
32, 2242-2252.
7. Warner J. A., et al., J. Biomed. Mater. Res. B
Appl. Biomater. 2016, 104, 470-475.
8. Zhen L., et al., Appl. Mech. Mater. 2014, 528,
153-161.
9. Wagner J. R., et al., The Definitive Processing
Guide and Handbook (Plastics Design Library),
2nd ed.; Elsevier: MA, USA, 2014.
10. Money B.K. and Swenson J., Macromolecules
2013, 46, 6949-6954.
This article was written by Farhad Sadeghi,
Senior Staff Process Development Engineer,
and David Le, Process Development Engineer,
Confluent Medical, Laguna Niguel, CA. It is
a summary abstract of a paper that appeared
in the Journal of Polymer Engineering. The
authors wish to thank Frank Duran for help
in the fabrication of puncture test fixture, and
Sayeh Ghazyani with assisting in plotting the
graphs. For more information, visit http://
info.hotims.com/79419-340.
Medical Design Briefs, November 2021
Burst Pressure (atm)
Puncture Load (N)
https://www.doi.org/10.1515/polyeng-2021-0203 http://info.hotims.com/79419-340 http://www.medicaldesignbriefs.com
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