Radiopaque Polyurethanes Containing Barium Sulfate: A Survey on Thermal, Rheological, Physical, and Structural Properties

Abstract

Radiopaque polyurethanes are extensively used in biomedical fields owing to their favorable balance of properties. This research aims to investigate the influence of particle concentration on various properties, including rheological, radiopacity, structural, thermal, and mechanical attributes, with a thorough analysis. The findings are benchmarked against a commercial product (PL 8500 A) that contains 10% weight barium sulfate. Two more thermoplastic polyurethanes (TPU) were formulated with two different concentrations of barium sulfate (10 wt.% and 20 wt.%) and compared to the commercially available product. FTIR demonstrated similar absorption bands among all samples, indicating that the fabrication method did not impact the TPU matrix. DSC indicated a predominantly amorphous structure for PL 8500 A compared to the other samples, while the kinetic degradation was more influenced by the higher barium sulfate content. The rheological analysis showed a decrease in the complex viscosity and storage modulus with the radiopacifier and an increase in the radiopacity, as demonstrated by the X-radiography. X-ray microtomography showed a more spherical particle format with a heterogeneous particle structure for PL 8500 A compared to the other polyurethanes. These findings enhance the comprehension of the structure-property relationships inherent in these materials and facilitate the development of customized materials for targeted applications.

Keywords: barium sulfate; biomedical applications; polyurethane; radiopacity.

Figure 1

Different applications of nanoparticles and nanomaterials in biomedical products. The figure is based on [12].

Figure 2

FTIR spectra of PU sample and the nanocomposites. The gray circles highlight the regions with higher differences in the spectra.

Figure 3

DSC curves of PU sample and the nanocomposites: (A) cooling ramp; and (B) second heating rate.

Figure 4

Comparative curves for: (A) TPU; (B) TPU10%; (C) PL 8500 A-10%; and (D) TPU20% at some selected heating rates.

Figure 5

Conversion rate of the TPU at different heating rates: (A) 2 °C·min⁻¹; (B) 5 °C·min⁻¹; (C) 10 °C·min⁻¹; (D) 20 °C·min⁻¹; and (E) 40 °C·min⁻¹.

Figure 6

Friedman and Kissinger plots for: (A) TPU; (B) TPU10%; (C) TPU20%; and (D) PL 8500 A-10%, respectively.

Figure 7

Activation energy and preexponential factor dependency with the conversion degree for: (A) TPU; (B) TPU10%; (C) TPU20%; and (D) PL 8500 A-10%. The activation energy and preexponential factor plots represent the Friedman (red circle color) and Vyazovkin (blue line color) mathematical treatment. The gray line color of preexponential plot represent the R² while the red bar column in the activation energy factor represent the activation energy values concentration.

Figure 8

Combined kinetic analysis plots for: (A) TPU; (B) TPU10%; (C) TPU20%; and (D) PL 8500 A-10%. The same behavior was observed for runs 1 and 2, hence the curves are overlapped.

Figure 9

Master plots for (A) TPU, (B) TPU10%, (C) TPU20%, and (D) PL 8500 A-10%.

Figure 10

(A) Complex viscosity; and (B) storage and loss moduli of TPU, TPU10%, TPU20% and PL 8500 A-10%. The arrows are visual representations of the differences between the storage and loss moduli.

Figure 11

Radiopacity of the TPU and their nanocomposites: (A) TPU; (B) TPU10%; (C) PL 8500 A-10%; and (D) TPU20%.

Figure 12

X-ray microtomography of a longitudinal (top) and transverse (bottom) section of the: (A) bare polymer TPU; (B) PL 8500 A-10%; (C) TPU10%; and (D) TPU20%. 3D renderings of the distributions for: (E) PL 8500 A-10%; (F) TPU10%; and (G) TPU20% reveal injection streamlines, dispersion disparities and flow aggregation.

Figure 13

Volume–surface distributions of the three types of aggregates.