Biodegradable nanocomposites based on poly(ester-urethane) and nanosized hydroxyapatite: Plastificant and reinforcement effects

Abstract

The processing and characterization of biodegradable nanocomposites based on poly(ester-urethane)s reinforced with different amounts (0.5, 1 and 3 wt %) of nanosized hydroxyapatite (nHA) are reported. The selected poly(ester-urethane) was synthesized starting from a tri-block copolymer based on poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLLA). The nanocomposites were prepared by extrusion and by press molding. Several techniques were applied to investigate the properties of the nanocomposites. Electron microscopy revealed that the poly(ester-urethane) matrix is able to phase separate and that the addition of well-dispersed nanofillers modifies the dimension of the segregated phase. The thermal stability of the PU matrix, regulated by the PLLA block, decreased when low contents of nHA (0.5 and 1 wt %) were added, even if the thermal stability of the PCL-block was increased for each nHA amount. The good mechanical response of the nanocomposites confirmed the absence of agglomerates in the dispersion of the nanofillers in the polymeric matrix. The nHA presence also increased the surface hydrophilicity. Furthermore, rheology measurements, mechanical and thermal tests demonstrated the different behavior induced by the addition of nHA in different amounts. In fact, nHA acts as plasticizer at low concentrations (0.5, 1 wt %) and as reinforcement at a higher nHA amount (3 wt %). In vitro degradation tests were performed using a phosphate buffer solution. The results reported here are relevant for the development of nanocomposites based on a biodegradable and biocompatible polymeric matrix reinforced with small amounts of biocompatible nanofillers for different applications, especially in the biomedical field.Keywords: mechanical properties; phase morphology; nanocomposite; poly(lactide); biodegradable; poly(ester-urethane) Abbreviations DMA: Dynamic-mechanical analysis; DSC: Differential scanning calorimetry; FE-SEM: Field emission electron microscopy; HA: Hydroxyapatite; HDI: hexamethylene diisocyanate; nHA: Nanosized hydroxyapatite; PU: poly(ester-urethane); PU+0.5 HA: Nanocomposite of poly(ester-urethane) with 0.5 wt % of HA; PU+1 HA: Nanocomposite of poly(ester-urethane) with 1 wt % of HA; PU+3 HA: Nanocomposite of poly(ester-urethane) with 3 wt % of HA; PCL: Poly(ε-caprolactone); PLLA: Poly(Llactic acid); TEM: Transmission electron microscopy; Tg: Glass transition temperature; 3 TGA: Thermogravimetric analysis; Tm: melting temperature; WCA: water contact angle.

Effect of pine resin derivatives on the structural, thermal, and mechanical properties of Mater‐Bi type bioplastic

“…The second major loss of G ′ is associated with a peak of tan δ at 60 °C, corresponding to the PCL and additives portion, which represents 10% of the Mater‐Bi polymeric matrix, as discussed before on FTIR and DSC analyses . Thus, in these dynamic mechanical analyses, it was observed a peak around 60 °C that coincides with the melting temperature of the PCL . Below the first T g ( T gPBAT and T g plasticized starch ), Mater‐Bi formulations with 15 wt % of UT, LF, and GR have a higher G ′ value than the neat Mater‐Bi.…”

“…As observed from DSC results, LF and UT act as cohesive agents, probably as a consequence of the chemical interactions between the functional groups of the polymer components and the functional groups of the modified resin derivatives commented in FTIR analysis . In fact, the peak of T gPBAT ‐ T gplasticized starch (between −20 and –25 °C) was well defined and separated from that corresponding to the melting of PCL (around 60 °C) . In contrast, the MaterBi‐GR‐based formulations exhibited a very different behavior: first, the peak corresponding to T gPBAT ‐ T g plasticized starch was shifted to higher temperatures (15 °C in the MaterBi‐15GR).…”

“…Mater‐Bi exhibited a thermal transition at −32 °C, corresponding mainly to the glass transition of the PBAT fraction ( T gPBAT ) with a combination of T g of the plasticized starch fraction ( T gplasticized starch ) of the Mater‐Bi . In addition, Mater‐Bi presents a thermal transition at 56.3 °C, attributed to the PCL melting . Since the PCL content in Mater‐Bi is estimated to be less than 10 wt %, this thermal transition is very trivial, and no melting peak is observed.…”

Multifunctional PLA Blends Containing Chitosan Mediated Silver Nanoparticles: Thermal, Mechanical, Antibacterial, and Degradation Properties

“…Interestingly, with the addition of 5 wt% of AgCH-NPs, the shape of the degradation curve changes significantly, with a temperature at maximum weight loss rate closer to the nanocomposites with 0.5 wt% of AgCH-NPs instead of the one with 3 wt% of AgCH-NPs. This phenomenon could be related with the high amount of AgCH-NPs that can affect the mass transport barrier, resulting in more intricate paths for the volatile products (i.e., low molecular weight OLA plasticizer) to scape during thermal decomposition and therefore, promoting slightly better thermal resistance for sample with AgCH-NPs loading of 5 wt% [44,45]. Thus, in general, TGA results show that the addition of low amounts of AgCH-NPs (0.5 wt%) did not significantly affect the thermal degradation of the PLA/OLA matrix, while amounts closer to 5 wt% of AgCH-NPs could even better prevent the thermal degradation of the matrix than the addition of 1-3 wt% of nanoparticles.…”

Influence of Poly(ε‐caprolactone) Molecular Weight and Coumarin Amount on Photo‐Responsive Polyurethane Properties

“…On the other hand, PUs are used in many industrial fields because they show very good chemical and physical properties, such as good elasticity and tensile strength, and a high working temperature range and resilience . Hydrolytic polyols, such as PCL‐diol, are also gaining interest for the development of PCL‐based PUs due to the fact that those PUs have low crystallinity, are biodegradable, and retain good physical properties, resulting in interesting systems for sustainable coating applications, mainly for the automotive and furnishing sectors. However, the main drawback of PUs based on PCL is their poor thermal resistance .…”