Copper-Polyurethane Composite Materials: Particle Size Effect on the Physical-Chemical and Antibacterial Properties

Abstract

In this work, thermoplastic polyurethane (TPU) composites incorporated with 1.0 wt% Cu particles were synthesized by the melt blending method. The effect of the incorporated copper particle size on the antibacterial, thermal, rheological, and mechanical properties of TPU was investigated. The obtained results showed that (i) the addition of copper particles increased the thermal and mechanical properties because they acted as co-stabilizers of polyurethane (PU) (ii) copper nanoparticles decreased the viscosity of composite melts, and (iii) microparticles > 0.5 µm had a tendency to easily increase the maximum torque and formation of agglomerates. SEM micrographics showed that a good mixture between TPU and copper particles was obtained by the extrusion process. Additionally, copper-TPU composite materials effectively inhibited the growth of the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus. Considering that the natural concentration of copper in the blood is in the range of 0.7-0.12 mg/L and that the total migration value of copper particles from TPU was 1000 times lower, the results suggested that TPU nanocomposites could be adequately employed for biomedical applications without a risk of contamination.

Keywords: antibacterial; composite; copper particle; particle size; polyurethane.

Figure 1

Torque variation as a function of time for samples.

Figure 2

The thermal stability of thermoplastic polyurethane (TPU) and composites evaluated by TGA: (a) TGA and (b) DTG.

Figure 3

SEM micrographs of neat TPU and CPC materials: (a) Neat polyurethane; (b) 0.05 µm; (c) 0.2 µm; (d) 0.5 nm; (e) 1 µm; (f) 5 µm; (g) 10 µm;(h) 15 µm; (i) 20 µm.

Figure 4

Biofilm formation on a copper-polyurethane composite of (a) Escherichia coli ATCC 25922, (b) Staphylococcus aureus ATCC 25923, and (c) a negative control (materials in tryptic soy broth (TSB) with no inoculum).

Figure 5

Bacterial death kinetics exhibited by copper-polyurethane composites: (a) E. coli ATCC 25922; (b) S. aureus ATCC 25923; PU was used as control.

Figure 6

Mechanical properties obtained from the traction test of all CPC samples: (a) tensile strength, (b) elongation at break and (c) tensile modulus.

Figure 6

Mechanical properties obtained from the traction test of all CPC samples: (a) tensile strength, (b) elongation at break and (c) tensile modulus.

Figure 7

Representative tensile stress versus strain of the prepared sample with different particle sizes (tensile rate of 10 mm/min).